RP-Taiwan - Rushurgent Working Group

Transcription

Relative vertical deformations in La Union,
Philippines revealed by Holocene coral
microatolls
M.I. Abigania1,2, F.P. Siringan2,3*,
G.M. Besana-Ostman1,4* and Y.
Yokoyama5
1
Geology and Geophysics R&D Division,
Philippine Institute of Volcanology and
Seismology – Department of Science
and Technology (PHIVOLCS-DOST),
Philippines
2
National Institute of Geological
Sciences, University of the Philippines,
Diliman, Quezon City, Philippines
3
Marine Science Institute, University of
the Philippines, Diliman, Quezon City,
Philippines
4
Department of Geological Sciences,
University of North Carolina at Chapel
Hill, NC, USA
5
Department of Earth and Planetary
Sciences, University of Tokyo, Japan
*present address
Abstract
Coral microatolls have long been
used as good indicators of relative
sea level change especially in an
actively deforming region. Relative
vertical
deformations
possibly
associated with paleoseismic events
are
reconstructed
from
the
morphology of living and emergent
coral
microatolls
in
Paraoir,
Balaoan, La Union facing Manila
Trench in the Philippines. The living
microatolls
exhibit
emergence
throughout their life history by
having a domal raised center and
down-stepping terraces towards the
rim. The highest level of survival
(HLS) of the annual growth rings
seen in x-radiograph of the sampled
living microatoll showed short
periods of gradual submergence (24 mm/yr) in between abrupt
relative sea-level falls. These are
possibly periods of relaxation phase
corresponding
to
interseismic
adjustments. Two episodes in the
coral’s band pattern are marked by
a decrease in the extension rate of
the growth bands. One took place
in ca. 1938 and another in ca.
1963. Incidentally, a Ms 7.0
earthquake occurred offshore of
Ilocos
associated
with
Manila
Trench in 1938. The decrease in
growth rate might be due to
increased turbidity brought by
elevated sediment load from rivers
due
to
landslides
upstream
triggered by the earthquake. Rapid
submergence of ~2cm ca.1938 is
possibly tectonic as a Ms 7.6 and
7.0 earthquake events in offshore
northwest Luzon occurred in 1934
and 1938 respectively. Whereas,
the growth rate pattern and rapid
submergence noted in ca. 1963
might be correlated with two
earthquake events offshore of
Pangasinan in 1963 and offshore of
northwest Ilocos in 1964. can be
correlated with the growth pattern
in ca.1964. Oceanographic effects
on sea level like the sea surface
temperature changes in the South
China Sea was also recorded in the
coral, marked by a 2-3 cm gradual
submergence and emergence in the
growth rings from 1989 to 2006.
EARTH SCIENCES INTERNATIONAL CONFERENCE, PHILIPPINES | 36
Emerged microatolls 1km south of
the
sampled
living
coral
predominantly exhibit a “cup-like”
morphology having two exterior
raised rims with gentle outward
slopes and abrupt down-steps
toward the center. One of the
sampled microatoll less than 1 m in
diameter
shows
an
initial
hemispherical growth for 23 years
which then experienced a possible
sudden emergence of 6 cm followed
by a relative sea level stability for
about
4
years.
An
abrupt
submergence of 6.5 cm followed
that allowed for a catch-up growth
band pattern for 9 years before its
final emergence of ~1 m. More
complex topography can be seen in
larger microatolls of more than one
meter in diameter indicating other
earlier events of relative sea level
changes. The final emergence of
the reef at about 1.4 kyBP lead to
the demise of the microatolls . This
sea level fall is also recorded in
other places in the Philippines. The
study can most probably identify
other events older than the known
historical record
along
Manila
Trench.
Electromagnetic, geochemical and thermal
studies on Taal Volcano (Philippines) from
2005 to present
P.K.B. Alanis1, J. Zlotnicki2, J.P.
Sabit1, Y. Sasai3, J. M. Cordon1,
M. Harada4, J.P. Toutain5, E.U.
Villacorte1, A. Bernard6, H.
Hase7, J.T. Punongbayan1, T.
Nagao8 and R.U. Solidum Jr1.
1
Seismology, C. P. Garcia Avenue, U. P.
Campus, Diliman, Quezon City,
Philippines
2
CNRS, UMR6524, UMS 833-UBP
Observatoire de Physique du Globe de
Clermont-Ferrand, 24 avenue des
landais, 63177 Aubiere Cedex, France
3
Disaster Prevention Division, Tokyo
Metropolitan Government, NishiShinjuku, 2-8-1, Shinjuku-ku, Tokyo
163-8001, Japan
4
Centre for Frontier Electronics and
Photonics, Chiba University, 1-33
Yayoi-cho, Inage-ku, Chiba 263-8522,
Japan
5
Laboratoire des Mecanismes de
Transfert en Geologie, UMR5563,
Observatoire Midi-Pyrenees, 14 avenue
Edouard Belin, 31400 Toulouse, France
6
Laboratoire de Geochimie et
Mineralogie Appliquee, Universite Libre
de Bruxelles, CP160/02, avenue FD
Roosevelt 50, 1050 Brussels, Belgium
7
Geological Survey of Japan, AIST,
Tsukuba, Ibaraki 305-8567, Japan
8
Earthquake Prediction Research
Centre, Tokai University, 3-20-1, Orido,
Shimizu-ku, Shizuoka 424-8610, Japan
Abstract
Taal Volcano is one of the most
active volcanoes in the Philippines.
Its first recorded eruption was in
1573. It has since erupted 33 times
resulting in hundreds of casualties
and large damages to property. In
1995, it was declared one of the 15
Decade Volcanoes. Beginning in the
early 1990s it has experienced
several phases of abnormal activity,
including seismic swarms, episodes
of ground deformation, ground
fissuring
and
hydrothermal
activities. In January 2005, several
felt earthquakes drove inhabitants
living near the volcano to evacuate.
Joint self-potential (SP), total
magnetic
field
(TMF),
ground
temperature, and carbon dioxide
(CO2) soil degassing surveys along
with satellite thermal imaging were
begun in Taal Volcano in 2005,
which aims to study the geothermal
activity occurring in the volcano.
These
surveys
are
repeated
regularly and several permanent
and continuous TMF and SP stations
were also established on the
northern part of the volcano, as
well as on the northeastern shore
of the Main Crater Lake (MCL). The
results
from
these
combined
studies indicate strong thermal
transfers and degassing in the area
of Daang Kastila on the northern
flank of the volcano along E-W
trending fissures. These fissures
may be linked to the Main Crater
Lake at its northern border as well
as to thermal sources near the Main
Crater Lake shoreline. This latter
thermal source is a possible
location of future eruptive activity.
In order to identify the centre of
the
geothermal
activity,
we
conducted measurements of the
lake topography, TMF, surface water
temperature as well as CO2
concentrations on the surface of
MCL in March, 2008. A new mound,
which appeared between the years
1986 and 2008, was found near the
NNE coast of MCL. The mound (a
topographic high at a depth of 40
m) is non-magnetic and coincides
with the position of thermal
anomaly
emerged
during
the
volcanic crisis in the early 2005.
This area could be the outlet of
magmatic fluids, which is connected
to the vent from the magma
reservoir at depth.
Harnessing ICT and high performance
computing for environmental monitoring
and hazard mitigation
The Philippine e-Science Grid Program,
Department of Science and Technology
- Advanced Science and Technology
Institute, Diliman, Quezon City,
Philippines 1101
Abstract
The
Advanced
Science
and
Technology Institute (ASTI), a
research and development institute
under the Department of Science
and
Technology
(DOST),
is
mandated to conduct research and
development in the advanced fields
of Information and Communications
Technology
(ICT)
and
Microelectronics.
Over the years, ASTI's programs
and projects have focused on
providing
more
significant
contributions
to
national
development through ICT and
Microelectronics. ASTI has been
involved
with
a
number
of
collaborations with government,
academe, and industry to carry out
high-impact projects that contribute
to agriculture, distance education,
weather forecasting, education,
environmental monitoring, disaster
mitigation, among others.
Environment stands as one of the
priority research areas of ASTI. The
Institute’s activities on the area are
to conduct R&D and develop
technologies and products that will
have useful and critical applications
in disaster and hazard mitigation,
as
well
as
in
monitoring
environmental health and safety.
Among the focus areas include:
weather
notification
system;
remote data monitoring/ sensing/
acquisition
for
research
and
disaster mitigation; and, real-time
environmental data monitoring and
acquisition.
ASTI continues to build and
strengthen its capabilities in the
areas of Sensor and Warning
Systems
Development
and
Deployment, and High-Performance
Computing, among others. ASTI is
currently
implementing
the
Philippine Real-time Environment
Data Acquisition and Interpretation
for
Climate-related
Tragedy
(PREDICT)
Prevention
and
Mitigation.
PREDICT
aims
to
improve weather forecasting using
a system of automated weather
stations (AWS) that can remotely
send weather parameters to a
central server using the nationwide
cellular network. The received data
is then processed and analyzed to
come up with weather bulletins for
general information.
ASTI also initiated the Philippine eScience Grid (PSciGrid) Program,
which
was
conceptualized
in
response to the emerging need of
the Filipino scientific community for
a
national
high-performance
computing facility. PSciGrid aims to
establish
a
grid
computing
infrastructure in the Philippines that
will provide internet-accessible eScience solutions to a diverse
community of researchers and
scientists in the academe and
government. Through the PSciGrid
Program, ASTI has set up a highperformance
computing
(HPC)
facility with installed applications
for meteorology.
ASTI’s future activities in relation to
geoscience include the following:
1. Development of a web-based
federated geospatial information
system (FedGIS) for use in
hazard
mapping
and
assessment. The FedGIS is
envisioned to be a collection of
geospatial databases and other
databases
brought
and
integrated together for disaster
risk
management
using
a
collection of networking and
computing
technologies
for
high-availability and real-time
access. Essentially, FedGIS aims
to provide a tool for scientists
and decision-makers to make a
more precise forecast of events,
better allocate resources, and
save lives.
2. Participation
in
a
regional
initiative
on
earthquake
monitoring that simulates global
and regional (continental-scale)
seismic wave propagation. The
data that will be generated will
be critical in understanding the
earth’s inner structure.
Caught off guard: the January 2009
flooding of Mindanao, Philippines
L.T. Armada1, D.V. FaustinoEslava1, G.P. Yumul, Jr.1,2, R.C.
Viado3 and C.B. Dimalanta1
1
2
Department of Science and
Technology, Bicutan, Taquig City, Metro
Manila, Philippines
3
Philippine Council for Industry and
Energy Research and Development,
Department of Science and Technology,
Bicutan, Taquig City, Metro Manila,
Philippines
attributed to Tropical Depression
Auring and the existence of a cold
front in the region. The total
amounts of precipitation exceed
160% of the thirty-year average for
most areas in Mindanao. As a
consequence, catastrophic floods
and
landslides
devastated
numerous communities in the
region. This report presents an
account of the series of disasters
that affected the cities of Cagayan
de Oro, Gingoog, Bislig and the
township of Maco in Compostela
Valley.
Abstract
Popularization of global climate
change
issues
has
led
to
international, national and local
government initiatives aimed at
combating its effects. However,
despite
efforts
at
preparing
communities for the many geologic
hazards that are projected to
become more frequent with the
changing climatic conditions, local
communities remain ill prepared for
the dangers that face them.
In January 2009, unexpectedly
heavy precipitation accompanied an
otherwise
ordinary
weather
phenomenon which affected nearly
the
entire
country.
However,
abnormally larger amounts of rain
fell on the island of Mindanao in the
southern Philippines. This elevated
amount
of
precipitation
was
Deformational styles of sedimentary
packages in offshore south Bondoc
Peninsula, Luzon, Philippines
M. Aurelio1, E. Cutiongco2, J.
Foronda3, K.J. Taguibao1, Z.
Calucin1 and M. Forbes3
1
2
Pearl Energy Limited, 80 Raffles Place,
UOB Plaza 2, #12-20, Singapore
3
Philippine National Oil Company –
Exploration Corporation, Energy Center,
Fort Bonifacio, Taguig, Philippines
Abstract
Recently acquired 2-D seismic
profiles and gravity data in the
offshore area between Bondoc
Peninula and Burias Island, South
Luzon, Philippines, are interpreted
in the context of known structural
styles observed onshore and in
relation to paleo- and neo-tectonic
regimes in the region.
Keywords
Seismic horizons, sedimentary
packages, basin formation, tectonic
inversion
gravity and magnetics gathered
through air-borne techniques (e.g.
Pineda and Aurelio 1990, Bischke et
al. 1990). In 1986, the then Bureau
of Energy Development of the
Philippines
published
a
comprehensive summary of the
sedimentary features of Philippine
basins,
based
primarily
from
regional data. Detailed studies have
been confined to areas surveyed by
independent workers, mostly from
the petroleum industry. In 1989,
studies more specific to the Visayan
Sea area were published in Porth
and Von Daniels.
This paper presents recent and
detailed data (primarily seismic
profiles, magnetic and gravity data)
gathered in the offshore area south
of Bondoc Peninsula in Southern
Luzon, Philippines. The offshore
data is integrated with onshore
observations
to
gain
a
comprehensive understanding of
the structural geology and tectonic
character
of
the
region.
A
preliminary effort to understand the
implications of this structural and
tectonic
nature
to
petroleum
exploration is attempted.
Methodology
Introduction
Published materials in studies of
offshore areas in inter-island seas
of Luzon in the Philippines are
generally few and sporadic. If any,
these studies have been based on
regional geophysical data such as
Offshore data (seismic profiles and
bathymetry) gathered in 2007
(complimented with older profiles)
were processed and interpreted.
Among others, seismic processing
involved
signal
deconvolution,
stacking and velocity migration.
Software-aided
interpretation
allowed 2D and 3D appreciation of
interpreted
stratigraphy
and
structures. Seismic profiles were
interpreted along with topographic
contours and bathymetry, and
compatible
available
map
information from other works. The
relationship
between
offshore
seismic data and stratigraphy was
established using onshore data as
well as from few offshore wells.
Summary of Onshore Geology:
Southern Bondoc Penisula –
Burias Island
The study area is located between
Bondoc Peninsula and Burias Island
in Southern Luzon (Figure 1).
Bondoc Peninsula is a large
anticlinorium with an anticlinorial
axis oriented roughly N-S in the
south and bends NWesterly to the
north (Aurelio et al. 1990, Aurelio
et al. 1991, Aurelio 1992). It is
underlain by a pre-Tertiary volcanoophiolitic basement topped by
several sedimentary packages aged
Eocene to Recent. The older
sequences, including portions of the
volcano-ophiolitic basement and
Eocene-Oligocene
volcanoclastics
and limestones form the core of the
anticlinorium and are exposed
mostly at the northern and central
sections of the peninsula as
structural windows. Younger clastic
sequences starting from OligoMiocene turbidites but passing into
younger and generally shallower
and more calcareous deposits cover
the rest of the peninsula. The
degree of deformation in these
younger sedimentary sequences
intensifies towards the southern
half of the peninsula.
similar stratigraphy, with indurated
Eocene volcanoclastics forming the
structural core and exposed in
Sombrero Island and on the NW
coasts of the the main island
(Aurelio 1992). This core is topped
by
carbonates
and
clastic
sequences
generally
showing
shallower
depositional
features
towards younger deposits and
exposed widely over the island.
In Bondoc and Burias, three major
unconformities since the Eocene are
observed
to
separate
several
structurally-distinct
sedimentary
packages (Aurelio 1992). The
oldest
unconformity
(~NP21)
separates Eocene limestones from
Oligo-Miocene turbidites while the
middle unconformity (~NN5) marks
the contact between these stronglydeformed E. Miocene turbiditic
sequences with L. Miocene shallow
marine clastics and carbonates. The
youngest unconformity (~NN11)
separates the L. Miocene clastics
from the youngest sedimentary
sequences.
Burias Island, located to the SE of
Bondoc
Peninsula,
presents
a
Figure 1. Summarized geology of the Bondoc Peninsula – Burias Island area (Marinduque
Island also shown) based from Aurelio (1992). Bathymetry is from GEBCO, topography is from
SRTM. Offshore structures (red lines) in the Sibuyan Sea area are from Sarewitz and Lewis
(1991). Approximate location of seismic profile presented in Figure 2 is shown. See text for
discussion.
Summary of Observations from
Seismic Profiles
Figure 2 shows a seismic profile in
the study area and its structural
interpretation. A strong seismic
reflector (Horizon 1 – H1) believed
to be the equivalent of Late
Oligocene
–
Early
Miocene
limestone and carbonate sequences
exposed in Bondoc peninsula,
appears as a folded and faulted
horizon. The longer fold axis is
generally
oriented
NNW-SSE,
expressed in an anticline-syncline
sequence plunging to the NNW. The
shorter fold axis orients subperpendicular to the longer fold
axis on an ENE-WSW direction. The
NNW plunge allows the reflector to
emerge
on
the
seabed
southeastwards in the direction of
Burias Island, where the same midTertiary limestones are exposed.
Faulting
is
in
the
form
of
compressive faults but which show
indications of initial normal faulting.
Above the H1 horizon is a package
generally
characterized
by
incoherent reflections on its lower
half but by strong to moderately
folded and truncated reflectors on
its upper half. This sequence,
together with the upper section of
the H1 horizon, is affected by
thrust-fold style deformation with
the thrust plane – fold axis striking
almost parallel to the longer fold
axis of H1.
The truncation of the sequence
overlying
the
H1
horizon
is
represented
by
a
faintly
to
moderately visible horizon (H2)
characteristic
of
an
angular
unconformity. Above H2 is a
generally coherent seismic package
occasionally
affected
by
moderatelyto
steeply-dipping
normal faults forming half-grabens
and horsts biased towards a
westerly basinal dip. The blocktilted unit is capped by a thin,
generally undeformed sequence.
Figure 2 Seismic profile (top) between Bondoc Peninsula and Burias Island (location shown on
Figure 1) and its interpretation (bottom). Vertical scale is two-way travel time in seconds. See
text for discussion.
The H1 and H2 horizons correspond
to
the
two
most
recent
unconformities discussed in the
summarized geology of the study
area.
On the SW flank, a rugged seabed
slope falls abruptly to the WSW
suggesting instability. Reflectors are
highly disturbed, often truncated by
steeply
dipping
faults
cutting
through seabed.
Concluding Remarks
Burias Island is the result of
multiple tectonic events known to
have affected the region and
nearby areas. These tectonic events
involved
basin
deposition
at
different depths and time intervals,
punctuated
by
compressional
periods in between. The alternance
of extensional (basin formation)
and compressional (as in the case
of collision) tectonic regimes often
brings about tectonic inversion
processes, which may generate
geologic structures favourable for
hydrocarbon accumulation.
The complex deformational style
observed
in
the
sedimentary
packages in the offshore area
between Bondoc Peninsula and
Acknowledgements
M. Aurelio, holder of a Pearl Energy
Professorial Chair in Energy Research, wishes
to thank Pearl Energy Limited and PNOC-EC
for allowing use of part of their data in this
paper.
References
[1] Aurelio, M.A., Rangin, C., Barrier, E. and
Müller, C. Tectonique du segment central de la
faille
Philippine.
Comptes
Rendues
Academie de Science t310, SII (1990), 403410.
[2] Aurelio, M.A., Barrier, E., Rangin, C. and
Müller, C. The Philippine Fault in the late
Cenozoic evolution of the Bondoc-Masbate-N.
Leyte area, central Philippines. Journal of
Southeast Asian Earth Sciences 6, 3/4 (1991),
221-238.
[3] Aurelio, M.A. Tectonique du segment
central
de
la
faille
philippine:
etude
structurale,
cinématique
et
evolution
géodynamique.
Thèse
de
doctorat
de
l'Université de Paris 6, Université Pierre et
Marie Curie, Académie de Paris, T 92-22,
France (1992) 500 p.
[4]Bischke, R. E., Suppe, J. and Del Pilar, R. A
new branch of the Philippine Fault system as
observed from aeromagnetic and seismic
data. Tectonophysics, 183, 1-4 (1990), 243264.
[5] Bureau
of
Energy
Development,
Philippines. Sedimentary basins of the
Philippines: their geology and hydrocarbon
potential. Bustamante Press, Inc., Manila,
Philippines (1986).
[6] Pineda, M.J.Y. and Aurelio, M.A. New
insights on the tectonics of the Southern
Luzon-Northern
Visayas
region
(from
aeromagnetic data): a preliminary report. In:
The Third Annual Geological Convention,
December 5-7, 1990, Q.C. Philippines.
Abstracts, p. 54.
[7] Porth, H. and Von Daniels, C.H., Eds.,
1989. The sedimentary formations of the
Visayan Sea Basin. Geologisches Jarbuch, 70,
B, (1989), 428 p.
[8]
Sarewitz, D.R. and Lewis, S.D. The
Marinduque intra-arc basin, Philippines: Basin
genesis and in-situ ophiolite development in a
strike-slip setting. Geological Society of
America Bulletin, 103 (1991), 597-614.
Sibuyan Sea Fault, Marinduque Fault and
Philippine Fault (Ragay segment): New
insights from GPS data
T. Bacolcol1,3, S.-B. Yu2 and R.
Solidum Jr.1
1
Seismology – Department of Science
and Technology, PHIVOLCS Bldg., C.P.
Garcia Ave., University of the
Philippines Campus, Diliman, Quezon
City, Philippines 1101
2
Institute of Earth Sciences, Academia
Sinica, Nankang, Taipei, Taiwan
3Département de Géotectonique,
Université Pierre et Marie Curie, 4 place
Jussieu, T26, E1, Paris, France
Abstract
Data gathered in October 2005 and
in June 2008 from the 11-point GPS
network in Ragay-Bondoc were
combined with other survey data
from 22 other nearby points to
calculate for the surficial velocity
rates and to determine patterns of
deformation for the three major
crustal
structures
straddling
Southern Luzon namely: Sibuyan
Sea Fault, Central Marinduque Fault
and the Philippine Fault along the
Ragay-Bondoc.
also probable that the on-land
extension of the Sibuyan Sea Fault
is the 30-km, northwest-trending
Central
Marinduque
Fault
in
Marinduque Island. The gathered
data also showed that Central
Marinduque
Fault
is
probably
creeping at 15 mm/yr, which would
explain for the sparse seismicity
recorded along its length. Another
major information gathered from
these GPS data is the recognition of
a significant NW movement (about
33 mm/yr) between Palawan and
the group of islands on the east
(Marinduque, Banton and Sibuyan).
This would imply that the suture
zone between Palawan and the
Philippine Mobile Belt is located still
further west of Marinduque and
Romblon.
As expected, calculations with
respect to Palawan showed NWdirected movements for all the
points included in the network.
Surficial velocities range from 33
mm/yr in Sibuyan Island to about
90 mm/yr in Virac. Based on the
vector magnitude and direction and
as complemented by seismicity
data, it appears that the Philippine
Fault in Ragay Gulf is locked. It is
Mid-Holocene sea-level changes in Poro
Point, La Union using morphostratigraphic
indicators
N.P. Baluda1, F.P. Siringan2 and
A.M.F.A. Lagmay1
1
2
Philippines
Abstract
Vertical land motions during the
mid-Holocene along the coast of
Poro Point, San Fernando, La Union
(Northwestern Luzon, Philippines)
were
delineated
from
the
stratigraphy of uplifted coral reef
sequence,
micromorphology
of
Porites sp. microatolls, and overall
geomorphology of the area. Four
14
C dates from corals within the
raised reef sequence yielded ages
ranging between 6605 and 6220 yr
bp. The topographic profile and
elevation of the uplifted landforms
as well as 28 flat-topped Porites sp.
microatolls, with 11 being eroded,
were determined using an EDM.
Age-elevation relationships indicate
(1) the presence of faults across
the study area and (2) multiple
episodes of sea level change with
magnitudes of rise and fall in the
order 50 to 70 centimeters within
this 385-year interval.
Terrane characteristics and configuration
in Northwestern Mindoro and their
implications
A.P.B. Canto1, R. Tamayo Jr.1, C.
Dimalanta1, D. Faustino-Eslava1,
G. Yumul Jr.1,2, K.L. Queaño3 and
E. Marquez4
1
Rushurgent Working Group, National
Institute of Geologic Sciences,
University of the Philippines, Diliman,
Quezon City, Philippines
2
Technology, Bicutan, Taguig Metro
Manila, Philippines
3
Mines and Geosciences BureauDepartment of Environment and
Natural Resources, North Avenue,
Quezon City, Philippines
4
2009 Centennial Faculty Grant
Awardee, Department of Physical
Sciences and Mathematics, University
of the Philippines Manila, Padre Faura
St., Ermita, Manila, Philippines
Abstract
Mindoro represents a tectonically
complex
island
in
central
Philippines; the evolution of which
and its importance to arc –
continent
collision
along
the
western Philippines remain unclear.
On northwestern Mindoro including
the offshore islands of Lubang and
Ambil,
remnants
of
multiple
collision events appear as NW-SE
oriented tectonic slices that are
separated by southwest verging
thrust faults, essentially parallel to
the trend of the currently active
Manila Trench. A profile from the
trench to Central Mindoro indicates
the presence of distinct terranes:
the
Middle
Oligocene
Amnay
Ophiolite and the Mesozoic Halcon
Metamorphics. A Late Pliocene to
Early Pleistocene dated sequence
consisting
of
sandstone
and
limestone with minor mudstone and
conglomerate (Balanga Formation)
unconformably overlies the two
terranes.
Aside from the age variance, the
Amnay
Ophiolite
and
Halcon
Metamorphics differ in petrological
and geochemical characteristics and
origin,
as
well.
The
former
corresponds to an exhumed piece
of the South China Sea crust,
whereas the latter correlates to a
metamorphosed continent derive
fragment. Isolated ophiolitic blocks
previously identified to compose
the Mangyan and Lubang – Puerto
Galera Ophiolites are enclosed by
schists of the Halcon Metamorphics.
Preliminary results suggest these
peridotite and volcanic blocks have
affinity with mid-oceanic ridge
materials, which contrast with the
chemistry of the Amnay Ophiolite.
We propose the Mangyan and
Lubang – Puerto Galera Ophiolite
represent
megaclast
materials,
which were incorporated into the
Halcon Metamorphics protolith. As
such, the Halcon Metamorphics
could well be the metamorphosed
equivalent of the accretionary
complexes currently exposed in
northern Palawan and northwest
Panay. Metamorphism must have
occurred prior to the Late Eocene
as constrained by the Lasala
Formation sedimentary package
that unconformably overlies the
Halcon Metamorphics.
These preliminary results support
the presence of two terranes in
northwestern Mindoro, the ages of
which increase toward the interior
of the island. The older terrane
could
represent
the
metamorphosed edge of the microcontinental block that rifted from
the East Asian margin at this site of
arc – continent suturing in western
Philippines. Active movement along
the Manila Trench and the Central
Mindoro
Fault
enhances
the
exhumation of the basal units of
the terranes thereby promoting
higher susceptibility of the island to
mass wasting processes.
A plate tectonic mechanism fluid migration
in the convergent margin, southwestern
Taiwan
W.-B. Cheng1, S.-K. Hsu2 and C.H. Chang3
1
Department of Environment and
Property Management, Jinwen
University of Science and Technology,
Taiwan
2
Institute of Geophysics, National
Central University, Taiwan
3
Central Weather Bureau, Taiwan
Abstract
In a subduction zone, the most
likely source of the fluid would be
water contained in the hydrous
minerals of the subducting oceanic
crust, because dehydration of clay
minerals in sediments is completed
at depths shallower than 10 km.
Therefore,
the
sources
and
pathways of upward expelled fluid
flow on the accretionary prism of
southern Taiwan have been the
subjects of intense debate. This
paper
investigates
velocity
structure of the active plate
boundary in southwestern Taiwan
by joint analysis of gravity anomaly
and seismic arrival time data. P and
S-P arrival time data from 3,238
earthquakes. In addition to CWBSN
permanent networks, seismic data
include the Central Weather Bureau
permanent
networks
and
a
temporary network consisting of 11
ocean bottom seismometers (OBSs)
that was deployed to detect the
aftershocks of the 2006 (ML7.1)
Henchun
earthquake
occurred
beneath southern Taiwan. The total
available OBS data set consists of
~700 detected earthquakes, from
which around 500 could be well
located where about 450 events
have been used in simultaneous
inversion for hypocenters, threedimensional Vp and Vp/Vs models
for the study area. Gravity data are
used to improve the model for the
offshore area, where it is poorly
sampled by local earthquakes. This
study
found
three
crustal
anomalies: (1) two prominent high
velocity/high
Poisson's
ratio
anomalies in the mid to lower crust
beneath the eastern coastal and
offshore area; (2) several volumes
of
relatively
high-velocity/high
Poisson's ratio rocks in the upperto mid-crust beneath the Central
Range; (3) a thin low-velocity zone
is detected above the subducting
Eurasian slab in the mantle wedge
and earthquakes are distributed
along the transition zone between
this thin low-velocity zone and the
high-velocity Eurasian slab. Based
on gravity modeling and our
resulting velocity and Poisson's
ratio models suggest that the
subduction decollement, which is
characterized
beneath
the
continental shelf can be traced
landward into a duplex structure in
the lower crust near southern
Taiwan. This study also suggested
that the geochemical and geologic
setting in a convergent plate
boundary exerts specific controls on
the
formation
of
a
bottom
simulating reflections and the
inferred
distribution
of
gas
hydrates. This crustal thickening
occurred above the locked plate
boundary
and
uplifts
the
continental margin should raising
stored gas hydrate out of the
stability zone and thus destabilizing
them to release methane in the
region east to the deformation
front. Continuous sedimentation
could
ensure
carbon
supply
according
to
the
very
high
sedimentation rate despite the
dissociation of gas hydrates due to
uplift in active margin.
Rapid seismic tsunami warning for the
South China Sea Region
P.-F. Chen
Central University
Abstract
The widespread tsunami hazards of
the 2004 Sumatra-Andaman Is.
Earthquake prompted us to build a
tsunami warning system for the
South China Sea Region. We adopt
the principle that tsunami waves
can be expressed as a linear
combination of unit tsunamis and
then divide the potential source
region (the Taiwan-Luzon trench)
into sub-regions of squares, called
unit tsunami event (Lee et al.,
2005). The propagation of each unit
tsunami event is simulated using
the COMCOT package (Liu et al.,
1998). We store the resulting unit
tsunami waveforms of selected tidal
stations in database for further
uses. In a real tsunamigenic
earthquake, the predicted tsunami
waveform of a certain tidal station
is then synthesized by linear
combinations of unit tsunamis form
the database, similar to the concept
of green function. The coefficients
of unit tsunamis are determined by
on-site
seafloor
displacements
which are usually calculated by the
earthquake parameters (longitude,
latitude, depth and seismic moment
tensor). We will also implement the
fast
seismic
source
inversion
method using W phase to retrieve
the seismic source in a near real
time fashion (Kanamori and Rivera,
2008). W phase is a long period
phase arriving before S wave,
which make the W phase source
inversion method effectively for
rapid and robust tsunami warning
purposes (Kanamori and Rivera,
2008). The purpose of this study is
to build a seismic tsunami warning
system for the South China Sea
region by combining the W phase
source inversion method and the
unit tsunami method.
References
[1] Lee, H.-J., Y.-S. Cho and S.-B. Woo,
Quick tsunami forecasting based on database,
Tsunamis:
Case
Studies
and
Recent
Developments, K. Satake (ed.), 231-240,
2005.
[2] Liu, P. L.-F., S.-B. Woo and Y.-S. Cho,
Computer programs for tsunami propagation
and inundation, Cornell University, 1998.
[3] Kanamori, H., and Rivera. L, Source
inversion of W phase: speeding up seismic
tsunami warning, Geophys. J. Int., 175, 222238 doi:10.1111/j.1365-246X.2008.03887.x
Applications of 2-D resistivity surveys in
characterizations of active faults in Luzon:
Implications for fault occurrence beneath
the Bataan Nuclear Power Plant
M. Collado1 and C.A. Arcilla2
1
Department of Agriculture
2
Sciences
Abstract
Resistivity surveys have found wide
applications
in
determining
groundwater levels and, when used
with
other
geophysicial
and
geological
parameters,
provide
imaging of the subsurface. Given
the presence of active segments of
the Marikina Valley Fault system in
Metro Manila, we conducted several
resistivity profiles across areas
where there were visible surface
ruptures due to the fault. The
intention was to test the usefulness
of
the
resistivity
method
in
detecting the continuation of the
fault beneath the surface. We
present 2-D inverted resistivity
profiles
across
active
fault
segments and demonstrate that
there are enough geophysical
contrasts
to
distinguish
the
subsurface fault signature with that
of
the
bedrock.
Since
the
controversial Bataan Nuclear Power
Plant is thought to be built on top
of a fault, we employed four
resistivity lines around the building,
using closely-spaced electrodes in
a Wenner array, in an attempt to
image the fault if it existed.
Comparing results of the BNPP
resistivity
survey
with
our
numerous surveys on active faults,
we conclude that there are no
anomalies that indicate faults or
fractures underneath and along the
vicinity of the nuclear building. This
study, however, DOES NOT preclude
the existence of fault/s close to the
vicinity of the nuclear building that
may be outside the range of the
resistivity profile lines. The data
presented, however, arguably rules
out the existence of a fault beneath
the nuclear plant. It must be noted
that the “existence” of such a fault
was one of the main reasons why
the BNPP was never operated.
Petrographic and geochemical data from
the Klondyke and Zigzag Formations:
Implications on the oceanic to island arc
evolution of the Baguio Mineral District,
Philippines
C.B. Dimalanta1, G.P. Yumul Jr.1,2
and R.A. Concepcion1
1
Rushurgent Working Group - Tectonics
and Geodynamics Group, National
Institute of Geological Sciences,
College of Science, University of the
Philippines, Diliman, Quezon City,
Philippines 1101
2
Technology, Bicutan, Taguig, Metro
Manila, Philippines
Abstract
Cataguintingan Formation samples
were derived from a mafic source
whereas samples from the Zigzag
Formation indicate derivation from
intermediate to felsic igneous
rocks. These results suggest that
the Zigzag Formation was derived
from an active continental margin
setting whereas the Klondyke,
Amlang
and
Cataguintingan
Formations are associated with an
oceanic island arc environment.
Introduction
This study presents a petrographic
and geochemical examination of
the clastic rock units that underlie
the Baguio Mineral District and the
nearby areas. The results obtained
from this investigation will offer
clues on the evolution, not only of
northern
Luzon,
but
of
the
Philippine island arc system as well.
Petrographic
examination
of
samples
collected
from
the
sedimentary units in the Baguio
Mineral District show that the
Zigzag Formation samples have
more quartz but less plagioclase
compared to the Klondyke, Amlang
and
Cataguintingan
Formation
samples. Lithic fragments are more
abundant
in
the
Klondyke
Formation sandstone samples.
The major and immobile trace
element data suggest that the
Klondyke,
Amlang
and
The
amount
of
literature
documenting the application of
petrography and geochemistry to
the study of sedimentary rocks has
increased over the last years.
These techniques are now being
applied to investigations of the
sedimentary units capping the
basement rocks in the Philippines.
The
Cretaceous
to
Eocene
sandstone sequence in Palawan was
investigated by Suzuki et al.
(2000).
A significant amount of
quartz grains and lithic acidic
fragments was noted during the
petrographic examination of the
sandstone samples. In terms of
the geochemical characteristics,
high SiO2 and low FeO plus MgO
values were obtained for the
samples. This suggests derivation
from a continental source region
which is consistent with existing
models that Palawan is a fragment
derived from the southern margin
of mainland Asia.
This work presents the petrographic
and geochemical compositions of
clastic units from the Baguio
Mineral District and nearby areas
(Figure 1). The results are used to
constrain the composition and
tectonic setting of the source rocks.
This, in turn, will give insights into
the geologic evolution not only of
Northern Luzon but also of the
whole Philippine island arc system.
The results contained herein will
also help build up the database on
the petrographic and geochemical
compositions of sedimentary units
in the Philippine island arc system,
which, at the moment, is almost
lacking.
Clastic units in the Baguio
Mineral District
Zigzag Formation
The
Zigzag
Formation,
best
exposed along Kennon Road, is
subdivided into the Early to Middle
Miocene
Upper
Zigzag
and
Oligocene Lower Zigzag members
which
are
separated
by
an
unconformity (Peña and Reyes,
1970). The alternating layers of
red and green sandstones and
siltstones comprise the Lower
Zigzag member. Upper Zigzag, on
the other hand, is made up of
massive,
well
indurated
and
oligomictic
conglomerates
consisting dominantly of basalt to
basaltic andesite clasts.
Klondyke Formation
A thick sequence of coarse clastic
rocks, polymictic conglomerate,
conglomeratic
sandstones,
sandstones, flow breccias, vitric
tuffs, with minor shales and
siltstones
characterize
this
formation (Leith, 1938).
This is
best
observed
along
Marcos
Highway, Naguilian Road, Asin Road
and the lower portion of Kennon
Road.
Previous studies revealed
that the Klondyke Formation has
well-defined proximal, midfan and
distal slope portions. A Middle to
Late Miocene age was assigned to
this unit based on calcareous
nannofossil assemblage (De Leon et
al., 1991).
Other clastic units
Aside from the Zigzag and Klondyke
Formations, samples were also
collected from sedimentary units in
the nearby La Union area. These
include
the
Amlang
and
Cataguintingan Formations.
The
Amlang Formation is a “flysch-type”
sequence of thin, rhythmically
interbedded sandstones, shales and
minor
conglomerates
(Lorentz,
1984).
A gradational contact
separates the basal portion of the
Amlang
Formation
from
the
Klondyke Formation. A Middle to
Late Miocene age is assigned to this
unit based on the calcareous
nannofossil assemblage (Catinaster
sp., Discoaster pentaradiatus and
Sphenolithus abies) (De Leon, pers.
comm.).
A
sequence
of
tuffaceous
sandstones
interbedded
with
siltstones,
shales
and
conglomerates with some limestone
lenses
makes
up
the
Cataguintingan Formation (Lorentz,
1984). An unconformity serves as
the
boundary
between
the
Cataguintingan Formation and the
Amlang Formation. This formation
has been given a Late Pliocene age
based on the molluscan shell
fragments,
echinoid
spines,
ostracods and red algae (Maleterre,
1989).
Petrographic results
Twenty-two
fineto
mediumgrained sandstone samples were
petrographically
examined
and
point counted. Angular to subangular
grains
comprise
the
sandstone samples and these are
embedded in <15% clay matrix.
The cement, on the other hand, is
usually in the form of calcite and
quartz overgrowth.
The samples from the Zigzag
Formation are mainly composed of
quartz (60-80%).
The quartz
crystals are mostly monocrystalline,
non-undulatory and devoid of
inclusions.
These characteristics
commonly imply that the quartz
might have been derived from the
surrounding volcanic rocks as a
result of weathering and erosion
(Tucker, 2001).
A
considerable
amount
of
plagioclase minerals (17-30%) are
also present in the Zigzag samples
but this is much less than the
number
of
plagioclase
grains
observed in the Amlang (45-58%)
and
Klondyke
(25-50%)
Formations. Abundant plagioclase
crystals
are
indicative
of
a
compositionally
immature
sandstone since plagioclase is a
labile
mineral.
Compositional
maturity reflects the weathering
process in the source area and the
degree and extent of reworking and
transportation (Tucker, 2001). It is
also evident that some of the
plagioclase grains of the Klondyke
samples exhibit zoning while some
are almost completely altered into
calcite.
Lithic fragments, which are mostly
in the form of volcanic clasts, are
common in the Klondyke (15-30%)
samples.
Provenance
setting
and
tectonic
An examination of the geochemical
compositions of sedimentary rocks
can offer useful information on the
composition of its source area or
source rocks. When plotted on the
discrimination
diagram
for
provenance
using
the
major
elements, most of the Klondyke,
Amlang
and
Cataguintingan
samples plot in the mafic igneous
provenance field.
The Zigzag
samples show derivation from both
intermediate igneous rock sources
and mafic igneous provenance (e.g.
Yan et al., 2007).
Some workers are not too eager to
use the Rb versus K2O diagram
arguing that these elements are
quite mobile during diagenesis or
metamorphism.
But when the
diagram is used along with other
plots, some useful information may
still be derived. The samples from
the Baguio Mineral District can be
divided into two groups based on
the K and Rb contents. Low K, Rb
and K/Rb ratios exhibited by the
Klondyke,
Amlang
and
Cataguintingan samples suggest
derivation from basic igneous rocks
(Figure 2). The Zigzag samples, in
contrast, are characterized by high
K, Rb and K/Rb ratios typical of
rocks derived from intermediate to
felsic igneous rocks.
To determine the tectonic setting of
the provenance region, Roser and
Korsch (1986) proposed plotting
the SiO2 versus K2O/Na2O values
(Figure
3).
This
diagram
differentiates oceanic island arc
environments from more evolved
arcs (i.e. active continental margins
or continental island arcs).
The
K2O/Na2O ratios of the Zigzag
Formation samples are generally
higher compared to the ratios of
the
Klondyke,
Amlang
and
Cataguintingan Formation samples.
This suggests that the sediments
that make up the Zigzag Formation
samples were derived from an
evolved arc.
Conversely, the
Klondyke,
Amlang
and
Cataguintingan Formation samples
have lower K2O/Na2O and indicates
that their sediments were derived
from oceanic island arcs.
Conclusions
The clastic units from the Baguio
Mineral District and the nearby
areas were analyzed in terms of
their
petrography
and
geochemistry.
The results show
that the sediments of the Zigzag
Formation were sourced from
intermediate to felsic igneous rocks
within an active continental margin
setting. Mafic source rocks from an
oceanic island arc setting comprise
the sediments of the Klondyke,
Amlang
and
Cataguintingan
Formations.
Acknowledgements
This work was supported by the National
Research
Council
of
the
Philippines,
Department of Science and Technology,
Commission on Higher Education and National
Institute of Geological Sciences. Our thanks
also go to T.A. Tam III, E.G.L. Ramos, A. Imai
for help in the fieldwork and in the processing
of samples.
References
[1] De Leon, M.M., Tamesis, E.V. and
Militante-Matias, P.J. 1991.
Calcareous
nannofossil study of the Klondyke Formation
section along km posts 278-251, Marcos
Highway, Baguio City – Pugo, La Union
Province, Philippines.
Journal of the
Geological Society of the Philippines 47, 3592.
signatures of the Klondyke and Zigzag
Formations and its implication on the oceanic
to island-arc setting evolution of the Baguio
Mineral District, Philippines. Terminal Report,
National Research Council of the Philippines,
36pp.
[4] Leith, A. 1938. Geology of the Baguio
gold district.
Philippine Department of
Agriculture and Communication Technology
Bulletin 9, 38.
[5] Lorentz, R.A.Jr. 1984. Stratigraphy and
sedimentation of the Late Neogene sediments
on the southwest flank of Luzon, Central
Cordillera, Philippines.
Journal of the
Geological Society of the Philippines 38, 1-24.
[6] Maleterre, P. 1989. Histoire sedimentaire,
magmatique, tectonique et metallogenique
d'un arc cenezoic deforme en regime de
transpresion: La Cordillere Centrale de Luzon,
a l'extremite de la faille Philippine, sur les
transects de Baguio et de Cervantes-Bontoc,
Contexte structural et geodynamique des
mineralisations
epithermales
auriferes.
Universite de Bretagne Occidentale, Brest,
France. Doctoral thesis. 304pp.
[7] Peña, R.E. and Reyes, M.V. 1970.
Sedimentological study of a section of the
“Upper Zigzag” Formation along Bued River,
Tuba, Benguet.
Journal of the Geological
Society of the Philippines 24, 1-19.
[8] Roser, B.P. and Korsch,
Determination
of
tectonic
sandstone-mudstone suites using
and K2O/Na2O ratio. Journal of
635-650.
R.J. 1986.
setting
of
SiO2 content
Geology 94,
[9] Suzuki, S., Asiedu, D.K., Takemura, S.,
Yumul, G.P.Jr., David, S.D.Jr. and Asiedu D.K.
2000. Composition and provenance of the
Upper Cretaceous to Eocene sandstones in
Central Palawan, Philippines: Constraints on
the tectonic development of Palawan. Island
Arc 9, 611-26.
[10] Tucker,
M.E.
2001.
Sedimentary
Petrology: An Introduction to the Origin of
Sedimentary Rocks. 3rd edition.
Blackwell
Science Ltd, USA, 262 pp.
[11] Yan, Y., Xia, B., Lin, G., Cui, X., Hu, X.,
Yan, P. and Zhang, F. 2007. Geochemistry of
the sedimentary rocks from the Nanxiong
Basin, South China and implications for
provenance,
paleoenvironment
and
paleoclimate
at
the
K/T
boundary.
Sedimentary Geology 197, 127-140.
[2] Dimalanta, C.B. and Yumul, G.P.Jr. 2009.
A geochemical approach on the provenance
Figure 1. The sedimentary formations in the Baguio Mineral District and nearby areas were
sampled for petrographic and geochemical analyses (Dimalanta and Yumul, 2009).
Figure 2. Binary diagram using K
and Rb to characterize the source
rocks of the Baguio Mineral District
sedimentary units (Dimalanta and
Yumul, 2009).
Figure 3.
Discrimination diagram
from Roser and Korsch (1986) shows
the Zigzag Formation samples mostly
occupying the active continental
margin (ACM) field whereas the other
samples plot within the oceanic island
arc (ARC) field. PM is passive margin
(Dimalanta and Yumul, 2009).
Liquefaction potential assessment of
Malabon & Navotas cities, Philippines
J.R. Dungca
De La Salle University-Manila
2401 Taft Ave., Malate,
Manila, Philippines
Abstract
The geotectonic setting of the
Philippines makes it prone to
various types of seismic related
hazards. The devastating Luzon
earthquake of 1990 is one of the
most recent manifestations of this
phenomenon and it has also
opened opportunities to better
understand
the
liquefaction
phenomenon. Many areas in the
Philippine
archipelago
including
Malabon and Navotas are believed
to have deposits of potentially
liquefiable sand exist and are
presently used for residential,
commercial or industrial purposes.
These cities may suffer tremendous
losses in terms of lives and
properties not only because of the
violent shaking of the structures
but
mainly
because
of
the
liquefaction of the foundation soils
due to the thick liquefiable sand
layer
predominantly
underlies
them. It is in this premise that this
study was initiated to be able to
make
effective
liquefaction
potential assessments for selected
areas vulnerable to liquefaction.
flooding due to typhoons, and
during high tides. Furthermore,
these cities became significant to
the Philippine government and the
general public as pertaining to the
rate of recurrence and severity of
flooding,
specifically
during
monsoon seasons and events of
high tide and due to the developing
global
warming,
and
the
substantiation of studies showing
evidences of ground subsidence in
the said areas.
Assessment of liquefaction potential
of the Malabon and Navotas was
conducted
by
collecting
SPT
borehole data and evaluating the
SPT “N” values using the semiempirical procedures of Idriss and
Boulanger (2004) for evaluating
liquefaction
potential
during
earthquakes. Thus, the factors for
safety against liquefaction that was
computed from the assessment
procedures were analyzed.
The city of Malabon and Navotas
are two places which are in the
outer ring of Metro Manila. These
are some of the cities which are
fronting Manila Bay. These cities
are known to experience frequent
Parallelisms between the BangongNujiang in Tibet and the Philippine suture
zones
D. Faustino-Eslava1*, J.A.
Aitchison2, R.A. Tamayo, Jr.1,
G.P. Yumul Jr.1,3 and C.B.
Dimalanta1
1
Philippines 1101
2
Department or Earth Sciences, The
University of Hong Kong, Pokfulam
Road, Hong Kong
3
Manila, Philippines
Abstract
within and against the island arc
system. Most of these terranes and
the general structural features of
the country are generally distributed
or oriented parallel to the length of
the archipelago and its bounding
subduction systems.
Reconstruction of the Cretaceous
Asian margin in Tibet suggests a
similar geographic setting to the
present Southeast and Eastern
Asian region, with several marginal
basins,
some
underlain
by
developed oceanic crusts, while
others
remain
floored
by
continental
lithosphere.
This
presentation
discusses
these
parallelisms
in
the
hope
of
understanding
the
geodynamic
histories of both the more ancient
BNS and the younger and presently
active Philippine suture zones.
The geology of the Tibetan plateau
documents
amalgamations
of
various terranes successively added
to the Eurasian plate during the
Paleozoic to Mesozoic eras. Major
structural features of the plateau
run east-west, parallel to the paleotrenches. One of these suture
zones is the Bangong-Nujiang
suture (BNS) which transects the
plateau’s
interior
and
is
characterized
by
numerous
exposures of Jurassic–Cretaceous
ophiolites and ophiolitic mélanges,
associated thick sequences of
Jurassic flysch and Middle to Late
Cretaceous
sedimentary
and
volcanic rocks. The Philippines is
similarly characterized by accretions
of various terranes juxtaposed
Gravity, seismic refraction and resistivity
signatures in Northwest Panay, Philippines:
Subsurface imaging of a terrane boundary
using geophysical methods
J.A.S. Gabo1*, C.B. Dimalanta1,
E.G.L. Ramos1, L.T. Armada1,
K.L. Queaño2,3, R.A. Tamayo Jr.1,
G.P. Yumul Jr.1,4, E.J. Marquez5
and D. Faustino-Eslava1
1
Philippines 1101
2
Mines and Geosciences Bureau –
Central Office, Department of
Environment and Natural Resources,
North Avenue, Diliman, Quezon City,
Philippines 1101
3
Earth and Materials Science and
Engineering Department, Mapua
Institute of Technology, Intramuros,
Manila
4
Manila, Philippines
5
University of the Philippines, Padre
Faura, Manila, Philippines
Abstract
Northwest Panay is composed of
two
terranes:
the
Buruanga
Peninsula and the northern portion
of the Antique Range (McCabe et
al., 1982; Tamayo et al., 2001).
These two terranes are believed to
be affected by the collision between
the Palawan Microcontinental Block
and the Philippine Mobile Belt
during the Miocene (Yumul et al.,
2005; Gabo et al., 2009). The
boundary
between
these
two
terranes is the Nabas Fault, located
at the neck of Buruanga Peninsula
(Zamoras et al., 2008). The
Northern portion of the Nabas Fault
is buried beneath Plio-Pleistocene
and Quaternary sediments.
To
investigate
this
terrane
boundary in Northwest Panay,
gravity, seismic refraction and
resistivity surveys were conducted.
The gravity method results show
that the Buruanga Peninsula exhibit
higher gravity anomaly values than
the rocks from the Antique Range.
This change in gravity anomaly
values can be observed to occur at
the neck of the peninsula, where
the Nabas Fault is located. There is
a sudden drop in the gravity
anomaly values at the location of
the Nabas Fault. The shallow
seismic refraction and resistivity
surveys conducted at the neck of
the Buruanga Peninsula agree with
the gravity data. Modeling of the
geophysical data shows that there
is a sudden decrease in density and
resistivity in the area between the
Buruanga
Peninsula
and
the
Antique Range terranes. Even
though it is covered with thick
alluvial deposits, the area at the
neck
of
Buruanga
Peninsula
consistently
shows
a
sudden
decrease in gravity, density and
resistivity values in the geophysical
survey results. These results are
evidence of the presence of the
Nabas Fault, the terrane boundary
between the Buruanga Peninsula
and the Antique Range. This
structure is believed to be an eastverging thrust fault that was
generated due to the collision
between
the
Palawan
Microcontinental Block and the
Philippine Mobile Belt (Zamoras et
al., 2008).
References
[1] McCabe, R., Almasco, J.N. and Diegor, W.
1982. Geologic and paleomagnetic evidence
for a possible Miocene collision in Western
Panay, central Philippines. Geology 10, 325329.
[2] Gabo, J.A.S., Dimalanta, C.B., Asio,
M.G.S., Queaño. K.L., Yumul, G.P.Jr. and
Imai, A. 2009. Geology and Geochemistry of
clastic sequences from Northwest Panay
(Philippines): Implications for provenance and
geotectonic
setting.
Tectonophysics,
http://dx.doi.org/10.1016/j.tecto.2009.02.00
4
[3] Tamayo, R.A. Jr., Yumul, G.P. Jr., Maury,
R.C., Polve, M., Cotten, J. and Bohn, M. 2001.
Petrochemical Investigation of the Antique
Ophiolite
(Philippines):
Implications
on
Volcanogenic massive sulfide and podiform
chromitite deposits. Resource Geology 51, 2,
145-164.
[4] Yumul, G.P., Jr., Dimalanta, C.B.,
Tamayo, R.A., Jr. 2005. Indenter Tectonics in
the Philippines: Example from the Palawan
Microcontinental Block – Philippine Mobile Belt
Collision. Resource Geology 55, 3 189-198.
[5] Zamoras, L.R., Montes, M.G.A., Queaño,
K.L., Marquez, E.J., Dimalanta, C.B., Gabo,
J.A.S. and Yumul, G.P.Jr. 2008.
The
Buruanga Peninsula and the Antique Range:
Two contrasting terranes in Northwest Panay,
Philippines featuring an arc-continent collision
zone. Island Arc 17, 443-457.
Holocene coral reef development and sealevel rise of northwestern Luzon,
Philippines
S.-Y. Gong1, F.P. Siringan2, C.-C.
Shen3, K. Lin3 and C.-F. Dai4
(2) bioclastic facies, (3) clayey
facies and (4) tuffaceous facies.
1
The ages of fossil corals vary from
6,588 ± 27 ya at 1.4 m below the
PSL to 9,855 ± 42 ya at 22 m
below PSL. Results of this study
show that the minimum sea level,
relative to the western Luzon coast,
was about 25m below PSL when
reef started about 9.9 ka. During
9.2-8.2 ka, reef accretion rate was
as high as 13 m/ky. A reef
backstepping that likely resulted
from rapid sea-level rise took place
about 8-7 ka. Sea level then rose to
near PSL at about 6,862 ± 28 ya
before the reef was uplifted by
tectonics. The sea-level curve of
Currimao is generally similar to that
of the Western Australia coast but
about 10 m higher than that of
Tahiti at about 9.9 ka.
Department of Geology, National
Museum of Natural Science, Taichung,
Taiwan ROC
2
Philippines, Quezon City, Philippines
3
Department of Geosciences, National
Taiwan University, Taipei, Taiwan ROC
4
Institute of Oceanography, National
Taiwan University, Taipei, Taiwan ROC
Abstract
Holocene coral reefs occurred
extensively along the west coasts of
Luzon.
During
the
reef
development, the eustatic sea level
rose as a result of glacier retreat.
Meanwhile, Luzon was also uplifted
due to neo-tectonism. These reefs
thus offer an archive of eustatic
and neotectonic history of western
Luzon.
To study the Holocene coral-reef
growth and sea–level changes in
the Philippines, this study drilled
three boreholes on a raised
Holocene
reef
at
Currimao,
northwestern
Luzon,
and
establishes a new sea level record
during the early-mid Holocene with
230
Th-dated corals. The cores cover
a depth interval from 3.8 m above
present sea level (PSL) to 26.7 m
below PSL and consist of four
lithofacies including (1) reef facies,
Geohazard of submarine landslides in the
northern South China Sea
S.-K. Hsu, K.-T. Chen, C.-Y. Ku,
Y.-C. Yeh and C.-H. Tsai
Central University, Chung-Li 32001,
Taiwan
Abstract
Large and fast-moving turbidity
currents can incise and erode
continental margins and cause
damage to artificial structures such
as telecommunication cables on the
seafloor. In this study, we show
several
sites
of
submarine
landslides in the South China Sea.
The submarine landslides may be
triggered by earthquakes and then
produce turbidity currents. Strong
turbidity currents could jeopardize
artificial construction at sea. For
example,
the
2006
Pingtung
earthquake off SW Taiwan has
triggered
several
submarine
landslides and turbidity currents
along the Kaoping canyon. In
consequence, eleven submarine
cables across the Kaoping canyon
and Manila trench were broken in
sequence from 1500 m to 4000 m
deep. The full-scale calculation of
the turbidity current velocities are
calculated
along
the
Kaoping
canyon channel from the middle
continental slope to the adjacent
deep ocean. The results show that
turbidity current velocities vary
downstream at steps of 20 m/s, 3.7
m/s
and
5.7
m/s
which
demonstrate a positive relationship
between turbidity current velocities
and bathymetric slopes. In the
northern South China Sea, the
deposits of submarine landslides
(mass transported deposits, MTD)
are
distributed
at
foots
of
continental
margins,
canyon
channels or foots of seamounts.
The MTD is generally displayed in
terms of acoustic transparency in
seismic profiles. As evidenced by
the violent cable breaks happened
in the case of the 2006 Pingtung
earthquakes, the destructive power
of turbidity current to underwater
facilities is clearly underestimated.
East Luzon Trough: An inactive
subduction zone
A.M.F. Lagmay, R. Peña, M.A.
Aurelio and M.L.G. Tejada
National
Institute
of
Geological
Diliman, Quezon City, 1101 Philippines
Trough make it different
normal subduction zones.
•
Abstract
•
The East Luzon Trough is an intraplate depression separated from
the Philippine Trench by the E-W
sinistral Polillo Fault. It is flanked to
the east by the Benham Rise.
Unlike the Philippine Trench, the
East Luzon Trough is not a welldefined steep depression, which
broadens further into a domal-like
structure at about 16˚N latitude
and disappears northeastward. At
first glance, the East Luzon trough
appears to be a continuation of the
Philippine
Trench,
but
being
shallower and without a welldefined Wadati-Benioff Zone, it is
believed to be a nascent subduction
zone. The presence of an inactive
accretionary prism to the west of
the trough indicates the existence
of an ancient subduction zone that
has since become inactive. The
collision of Benham Rise with the
eastern side of northern Luzon led
to the cessation of west-verging
subduction of the West Philippine
Basin and the flipping of subduction
to the east along the Manila Trench.
The present East Luzon Trough may
be
considered
either
as
a
rejuvenation
of
its
ancient
counterpart or as a clogged
subduction
zone.
Nevertheless,
several features of the East Luzon
•
•
from
A review of the seismicity
along the East Luzon Trough
reveals that it lacks the deep
seismicity
exhibited
by
subduction
related
to
trenches.
Absence of Late Neogene
magmatism
along
the
northern Sierra Madre Range
related to subduction.
Undeformed
marine
sedimentary carapace over
crumpled sediments in the
accretionary prism
GPS measurements indicate
that the West Philippine
Basin in the region of
Benham
Rise
moves
in
lockstep
with
Northern
Luzon.
The accretion of Benham Rise to
the eastern seaboard of northern
Luzon has led to a reorganization of
the boundary of the Philippine Sea
Plate. In accordance with the
tectonic map of Bird (2003), the
tectonic
deformation
zone
constituting northern Luzon has
become a plate boundary zone with
respect to the Eurasian Plate.
Re-visit the West Philippine Basin after 1/4
century
C.-S. Lee
Institute of Applied Geosciences,
National Taiwan Ocean University,
Keelung, 202 Taiwan
Abstract
In mid-1980, the evolution of West
Philippine Basin was one of the
interesting, but also a controversial
tectonic problem. This is due to: (1)
the basin is one the largest
marginal basin in the world, (2) the
available data at that time showed
that this is either a normal ocean
basin or a back-arc basin, (3) the
basin is remote from the major land
area and is not so easy to conduct
the marine research, and (4) the
area is on the major track of the
typhoon and the planned survey
could be easily altered. For these
reasons, the existing dataset is like
a puzzle and the scientific debit is
continuing, even up to today. In the
last 1/4 century, particularly in the
last
10
years,
under
the
encouragement of United Nations
Law of the Sea Convention, every
neighboring
country
(including
China, Japan, Philippine, Palau, and
Taiwan) are entering the area for a
200 - 500 miles Continental Shelf
Survey. Because of this new data,
we are able to re-examine the
evolution of the West Philippine
Basin, particularly on the age,
spreading rate, spreading direction
and the reconstruction of the whole
basin. Through this exercise, we
found several interesting subjects,
such as an episode of very fast
spreading rate and the over-lapping
spreading centers in the north of
West Philippine Basin, resembling
to that of the East Pacific Rise
today. The estimated age is very
close to the 45 ma major change of
the Pacific Plate motion. How are
the plates evolved? What are the
responses of the deep crust? Is this
will impact our understanding of
the modern plate tectonics? In our
detail bathymetry survey, we also
begin to realize that the Eocene
West Philippine Basin is covered
with
a
lot
of
today-inactive
submarine volcanoes. Because of
being at the 5000 – 6000 m deep
sea environment, the sedimentation
rate
is
probably
very
low;
therefore, the volcanic summits are
clearly
exposed.
The
West
Philippine Basin is one of the wellknown big tuna fishing ground. Is
the volcano taken by the tuna as
their favorite dwelling? The deepsea ROV surveys also show the
thick manganese crust and a high
density of the manganese nodules.
Can the volcanic summits and
manganese crust become our
future
deep
resources?
Our
understanding of the deep sea is
believed just at begin.
A summary of geochemical study on Taal
Lake system: Searching proxies for
detecting of Taal volcano eruption
H.-C. Li1, X. Xu2, D.-R. Wen1, N.J. Wan1, T.-S. Kuo1, R.U. Solidum
Jr.3, J. Sincioco3, P.K.B. Alanis3
and Nora Campita3
1
Department of Earth Sciences,
National Cheng-Kung University,
Tainan, Taiwan 70101, ROC
2
Department of Earth System Science,
University of California, Irvine, CA
92697, USA
3
Seismology, Quezon, Philippines 1101
Abstract
Taal Lake is located in Batangas
Province of central Philippines
(14°0.01'N, 120°59.1'E), with a
surface area of 267 km2, a
maximum depth of 176 m and an
elevation of 3 m above sea level.
The lake occupies the famous Taal
Volcano system which consists of a
15×22-km prehistoric caldera. The
5-km-wide Taal Volcano Island
which has 47 craters and 4 maars,
lies in the north-central Taal Lake.
With 34 recorded eruptions, Taal
Volcano is one of the 16 monitored
volcanoes by the Global Volcanism
Network.
During the past 3 years, we have
conducted several trips to Taal and
measured water temperatures at
different stations and depths;
collected water samples from Taal
Lake, Main Crater Lake, springs,
streams, wells and rains in the
area; taken three gravity cores
from water depths of 15m and
~100m and one 64-m long drill
core from the western shore of Taal
Lake; and sampled a few outcrops
of volcanic and lake deposits in the
area.
The measured water
temperatures ranging from 26.5 to
29oC show that the thermal
gradient of Taal was very weak
during the late Novembers in 2006
and 2007, perhaps due to thermal
input from the Taal Volcano Island
and bottom of Taal Lake.
The
deepest part of Main Crater Lake is
61m
with
a
constant
water
o
temperature of 31 C throughout the
depth.
We have analyzed geochemical
properties including concentrations
of Na, K, Mg, Ca, Al, Fe, Mn, Sr, Ba,
Co, Ni, Cu, Zn, Pb, As, Ti, Cr, and
Cd, and isotopic values of δD, δ18O
and δ87Sr in the water samples.
From these results, we conclude:
(1) High concentrations of Na, K,
Mg, Ca, Al, Fe, Mn in geothermal
fluid at Taal are from input of
volcanic
water,
dissolution
of
volcanic rocks, and incursion of
seawater. However, the major ions
are introduced by both seawater
and geothermal inputs, so that they
could not be used as index of
volcanic activity. (2) Among trace
and heavy metal elements, Fe, Mn,
Cu and Zn may be used as
indicators of volcanic activity. (3)
Isotopic composition of Taal Lake
bias from MWL indicates mixing of
isotopically heavy geothermal fluid
and isotopically light surface input.
Therefore, heavier δ18O values of
the lake recorded in the lake
sediments may reflect increased
geothermal fluid caused by volcanic
activity.
(4) δ87Sr of Taal Lake
reveals mixing of three endmembers including surface runoff,
geothermal fluid and seawater. The
δ87Sr value of the geothermal fluid
is about 1000ppm lower than that
of the lake waters. Therefore, δ87Sr
may be a good indicator of volcanic
activity.
Our most significant study is on a
120-cm long gravity core, Core
TLS2, retrieved from 15-m water
depth of Taal Lake. Sixteen AMS
14
C dates were made on plant
remains at different layers of the
core, matching very well with the
bomb 14C curve determined in tree
rings. The distribution of the bomb
14
C profile allows us to establish the
chronology of the core which yields
a constant sedimentation rate of
2.04cm/year spanning the past 60
years. Based on this chronology,
living plants around Taal Lake may
have a lower initial ∆14C (-30‰)
compared to the Modern Standard.
For this core, we have measured
pore water content, weight loss by
0.5NHCl leaching, TOC, TON, δ18O
and δ13C of TIC, δ13C of TOC and
δ15N of TON, and concentrations of
Na, K, Mg, Ca, Fe, Mn, Sr, Ba, Cu,
Zn, Pb, Li in the acid-leachable
phase. The annual resolution δ18O
and δ13C records provide us detailed
variations of the lake’s hydrological,
biological and sedimentary history.
Carbonate was precipitated in
isotopic equilibrium with the lake
water at ~30oC which is close to
the measured water temperature.
The δ18O and δ13C of TIC co-vary in
the core, because of changes in
surface water input and geothermal
input. In general, when there is
more input surface water, both δ18O
and δ13C of the lake goes lighter
due to dilution effect.
The lake
productivity at this time will be
lower, and carbonate precipitation
is less. When the lake experiences
less surface water input and/or
more evaporation, δ18O and δ13C of
the lake goes heavier due to the
hydrological balance and increased
lake productivity. However, when
the volcanic activity increases,
significant amount of hydrothermal
input and deep CO2 input will lead
to increase of lake’s δ18O and δ13C.
Both carbonate and organic carbon
will decrease due to the influence of
volcanic input. This situation was
occurred around 1991. However, if
a
volcanic
eruption
causes
significant amount of dead carbon
from vegetation and organism in
and around the lake, the lake’s δ13C
will be depleted. At the time, the
δ18O and δ13C of the lake goes the
opposite way. The 1965 eruption
may be an example of such a case.
With the detailed geochemical
profiles of Core TLS2, we have
found
anomalies
of
high
concentrations of Fe, Mn, Cu, K and
heavy δ18O and δ13C values of TIC
around 1991-1994 when the Taal
volcano was active. These proxies
may be considered as indicators of
geochemically monitoring volcanic
activity for long-term prediction.
Seismic monitoring at Taal Volcano in the
Philippines
C,-H. Lin1, R.U. Solidum, Jr.2, T.M. Chang3 and B.C. Bautista2
1
Sinica, Taipei, Taiwan
2
Seismology, Quezon, Philippines
has been low recently, except some
seismic swarms in Aug. and Sept.
2008.
In
addition
to
the
continuation of seismic monitoring
at Taal volcano, we will carefully
examine the seismic data for
finding any volcanic earthquakes or
tremors.
3
National Center of Research on
Earthquake Engineering, Taipei, Taiwan
Abstract
Since the Philippines is located in
the “Ring of Fire”, there are more
than 20 active volcanoes in the
Philippines, such as Pinatubo,
Mayon, Bulusan, Kanlaon and Taal.
Among them, Taal volcano is only
60 km south to Manila, the capital
of the Philippines. Thus, volcanic
monitoring in Taal volcano becomes
one of the major hazard works in
the Philippines. In order to improve
the
understanding
of
general
seismic characteristics at Taal
volcano, we have deployed a
seismic network to record volcanic
earthquakes in the Taal volcanic
area since Feb. 2008. This seismic
network consists of seven shortperiod seismic stations with a
sampling rate of 100 Hz. Among
them, three stations on the volcanic
island within the main Crater Lake
have also added with long-period
sensors for detecting any longperiod
tremors.
Some
microearthquakes have been detected
from the continuous seismic data at
the
seismic
network.
The
preliminary
results
show
the
seismicity at the Taal volcanic area
Extreme climate events: Implications of El
Niño Southern Oscillation (ENSO) and
coping with its impacts in the Philippines
D.F. Ortega, F.D. Hilario and N.T.
Servando
Philippine Atmospheric, Geophysical
and Astronomical Services
Administration, Department of Science
and Technology, Quezon City,
Philippines
Abstract
The highest rainfall variability in the
Philippines was well documented
and is greatly associated with the
ENSO events which exhibited two
phases, the El Niño (warm) and La
Niña (cold). The El Niño conditions
typically
result
in
warm
temperature
anomalies
and
increased chance of below normal
(drier) rainfall across the country.
While the La Niña (cold) exhibits
the reverse manifestations, usually
increased rainfall and below normal
temperature
anomalies.
The
climate-related hazards brought by
the extreme climate event in the
country are in the form of flooding,
landslides,
drought
and
high
temperatures.
Changes in the
usual climate pattern in the country
as effected by the ENSO event are
typically manifested in the monsoon
activity,
frequency
of
tropical
cyclone and onset and termination
of rain.
impacts
of
extreme
events,
mitigating
factors
are
being
initiated and continuously being
improved
by
the
Philippine
Atmospheric,
Geophysical
and
Astronomical
Services
Administration (PAGASA), which
include
the
seasonal
climate
forecast (SCF).
This paper will illustrate the
different impacts of ENSO events in
the
country,
its
monitoring,
prediction and the ways of coping
with
the
negative
effects,
identifying the challenge of bringing
the understanding of the climate
science that can be used in risk
management.
Adverse impacts of ENSO events
have been experienced in the
country although beneficial ones
were also assessed but to a lesser
degree. To address these harmful
Utilizing calcareous nannofossils as
paleoproductivity proxies in Sulu Sea core
sediments
A.M. Peleo-Alampay1, D.N.
Tangunan1, F.P. Siringan2, R.
Maneja2, J.L. Soria2 and Z. Liu3
1
Sciences, College of Science, University
of the Philippines, Diliman, Quezon
City, Philippines
2
Philippines
Abstract
Calcareous
nannoplanktons
(coccolithophores)
are
marine
haptophyte algae which thrive in
the photic zone. These organisms
are sensitive to changes in the
temperature,
water
movement,
salinity and chemistry of the
surface waters of the ocean. Their
calcareous skeletons are important
contributors to the deep sea
sediments, making them valuable
recorders of variations in climate
and sedimentation. This research
aims to use calcareous nannofossils
from core sediments to determine
productivity changes in Sulu Sea
through time.
This study investigates calcareous
nannofossils from two sediment
cores collected from the Sulu Sea in
southwestern Philippines during
Philex cruise Leg 2 onboard R/V
Melville in December 2007. These
two
core
sites
from
the
southeastern Sulu Sea subbasin
were chosen for their difference in
productivity based on present-day
chlorophyll
data.
The
high
productivity site, Core MC10 is
located closer to the coast of
Zamboanga Peninsula at 8°23.10’N,
122°09.15’E and 4022m water
depth while Core MC8 is located in
the central portion of the sub-basin
at 8°38.97’N, 121°31.83’E and
4492m water depth.
A
distinct
difference
in
the
distribution of total nannofossils is
apparent from the two cores
studied. Nannofossil abundance
was very low (1-16 x 106 liths/
gram sediment) to zero in most of
the sample intervals in the top ~38
cm of Core MC 8-8. Abundances
start to increase at 38-39 cm depth
(1920±30 years). In the other core
(MC 10-3), nannofossils are present
throughout, ranging from 207-626
x 106 liths/ gram sediment, except
for a sharp excursion at 25 cm
depth yielding only 75 x 106 liths/
gram sediment. This may reflect
differences
in
nannofossil
productivity,
consistent
with
chlorophyll data today. Sandy silt
horizons in Core MC10-3 generally
yielded more nannofossils.
The nannofossil assemblages from
both cores are of relatively lower
diversity
typical
of
restricted
marginal sea assemblages and
dominated by three (3) species.
This
type
of
assemblage
is
prevalent on the eastern and
western coasts of the South China
Sea. In both cores, Gephyrocapsa
oceanica,
G.
ericsonii
and
Florisphaera profunda have the
highest
abundances
downcore.
Umbilicosphaera
sibogae
and
Calcidiscus leptoporus, the next
most abundant taxa in Core MC103 comprise less than 10% of the
total nannofossils.
In Core MC 8-8, F. profunda
abundance increases from the
bottom of the core, reaching its
peak at 44cm. Thereafter the
counts start to decline until it
reaches a steady low at 38 cm
(1920 ± 30 years) continuing up to
present time. The high F. profunda
at the lower portion of the core is
joined by equally high amounts of
G. oceanica.
interrupted by the sudden low at 25
cm (~1000-1100 years ago). This
abrupt decrease which seemed to
affect most of the coccolithophorid
record in the basin (F. profunda
included) can be interpreted as a
dissolution signal owing to the
shallowing of the CCD or an
increase in the terrigenous input
into the basin from erosional
processes
onland.
This
latter
phenomenon can be seen to some
extent in slightly higher Al2O3 and
TiO2 and Y values together with
total organic carbon.
The overall calcareous nannofossil
distribution in Core MC 10-3 shows
a higher productivity environment.
This is evidenced by the very good
anticorrelation between F. profunda
and G. oceanica counts downcore.
G. oceanica represents the upper
photic zone dwellers which are
advantaged
during
upwelling
events. The inverse relationship
shown by these two species in this
core is therefore validation of the
use of F. profunda as a productivity
signal indicator for this Sulu Sea
core.
Two lobes of F. profunda increases
can be seen from the MC 10-3
record: the first starting from the
bottom ending at 25 cm and the
next starting immediately after and
tapering down to core top. These
are interpreted as strong nonupwelling
(low
primary
productivity) signals in Sulu Sea
basin history. The older low
productivity
event
is
more
significant
since
the
other
coccolithophorid indicators such as
Umbilicosphaera
sibogae
and
Helicosphaera carteri, high nutrient
species, show significant decreases
during this time. In both records,
the non-productivity lobes are
Geochemical heterogeneity of volcanic
rocks from the Fragante Formation,
Northwest Panay, Central Philippines
A.dC. Perez1, D.V. FaustinoEslava1, J.A.S. Gabo1, G.P. Yumul
Jr.1,2, R.A. Tamayo Jr.1, K.L.
Queaño1,3, C.B. Dimalanta1 and
L.T. Armada1
1
Rushurgent Working Group-Tectonics
Philippines
2
Technology, Bicutan, Taguig City,
Philippines
3
Lands Geological Survey Division,
Mines and Geosciences Bureau-DENR,
North Avenue, Quezon City
Abstract
Following a major landslide incident
in Guinsaugon, Southern Leyte in
Central Philippines, the Mines and
Geosciences Bureau-Department of
Environment and Natural Resources
(MGB-DENR) immediately set out
to rationalize and speed up the
implementation of the National
Geohazards
Mapping
and
Assessment Program. This program
intends
to
adequately
and
comprehensively
address
and
mitigate the possible effects or
impacts of geological hazards,
particularly landslide, flood and
coastal erosion. The program has
five
components
namely:
(1)
capacity
building,
2)
data
acquisition,
generation
and
integration, (3) conduct of field
survey, (4) generation of geohazard
maps,
and
(5)
conduct
of
information
and
education
campaign
(IEC),
including
installation of warning signages. To
date, a total of 1348 municipalities
have been assessed and 311,
1:50,000
landslide
and
flood
susceptibility maps have been
produced.
The MGB has also
assessed 2,383 line kilometers of
coastal areas in the country.
Although the efforts of the MGBDENR
and
other
government
agencies have helped significantly
in strengthening the country’s
capacity
in
minimizing
and
mitigating the impacts of natural
hazards, recent events still indicate
some lapses particularly in the
implementation
by
the
local
government
of
the
recommendations set forth by the
said agencies. These events include
the landslides in Itogon, Benguet in
northern Luzon and in Maco,
Compostela
Valley
in
eastern
Mindanao, both events occurring in
September 2008. More recently, a
flashflood occurred in August 2009
in Botolan, Zambales that wiped
out several communities.
These
examples clearly demonstrate the
consequences when information
and recommendations pertaining to
disaster
preparedness
and
mitigation are not taken seriously.
Geohazard mapping in the Philippines: The
Mines and Geosciences Bureau
experience
K.L. Queaño
Lands Geological Survey Division,
Mines and Geosciences Bureau-DENR,
North Avenue, Quezon City
Abstract
Following a major landslide incident
in Guinsaugon, Southern Leyte in
Central Philippines, the Mines and
Geosciences Bureau-Department of
Environment and Natural Resources
(MGB-DENR) immediately set out
to rationalize and speed up the
implementation of the National
Geohazards
Mapping
and
Assessment Program. This program
intends
to
adequately
and
comprehensively
address
and
mitigate the possible effects or
impacts of geological hazards,
particularly landslide, flood and
coastal erosion. The program has
five
components
namely:
(1)
capacity
building,
2)
data
acquisition,
generation
and
integration, (3) conduct of field
survey, (4) generation of geohazard
maps,
and
(5)
conduct
of
information
and
education
campaign
(IEC),
including
installation of warning signages. To
date, a total of 1348 municipalities
have been assessed and 311,
1:50,000
landslide
and
flood
susceptibility maps have been
produced.
The MGB has also
assessed 2,383 line kilometers of
coastal areas in the country.
Although the efforts of the MGBDENR
and
other
government
agencies have helped significantly
in strengthening the country’s
capacity
in
minimizing
and
mitigating the impacts of natural
hazards, recent events still indicate
some lapses particularly in the
implementation
by
the
local
government
of
the
recommendations set forth by the
said agencies. These events include
the landslides in Itogon, Benguet in
northern Luzon and in Maco,
Compostela
Valley
in
eastern
Mindanao, both events occurring in
September 2008. More recently, a
flashflood occurred in August 2009
in Botolan, Zambales that wiped
out several communities.
These
examples clearly demonstrate the
consequences when information
and recommendations pertaining to
disaster
preparedness
and
mitigation are not taken seriously.
Continuous monitoring along the Valley
Fault, the Philippines
R.-J. Rau1, Y.-P. Wen1, H.-K.
Hung1, T.C. Bacolcol2, P.K.B.
Alanis2 and R.M. Lumbang2
1
Department of Earth Sciences,
National Cheng Kung University,
Tainan, Taiwan
2008. With the ~one year GPS
continuous monitoring, we shall
present the GPS results and the
inferred
mode
of
crustal
deformation of the Valley Fault
system in the meeting.
2
Seismology, PHIVOLCS Building, C.P.
Garcia Avenue, University of the
Philippines Campus, Diliman, Quezon
City, Philippines
Abstract
Manila in the central segment of the
Luzon arc, with a population of
about 10 million, is subject to
threatening
from
strong
earthquakes on nearby faults and
on more distant plate boundary
faults. For the past 400 years
Manila may have experienced more
than six damaging earthquakes, but
with
no
specific
seismogenic
sources identified. Paleo-seismic
and neotectonic studies indicate
that the 135-km long Valley Fault
system on the northeastern edge of
the Metro Manila is a right-lateral
fault; however, the modern mode of
deformation
as
well
as
its
earthquake
potential
remains
unclear. The purpose of this study
is to estimate the earthquake
potential of the Valley Fault system
and its impact on the Manila
metropolitan
area
by
using
continuous GPS observations along
the fault. We have installed six
dual-frequency GPS and six singlefrequency GPS stations along the
Valley Fault system since April,
Late Holocene sediment facies and relative
sea-level changes along the PampangaAngat delta, Northern Manila Bay
J.L.A. Soria1, F.P. Siringan2, Y.
Yokoyama3 and K.S. Rodolfo4
1
Philippines 1101
2
Philippines 1101
3
Ocean Research Institute, University
of Tokyo, 1-15-1 Minami-dai,
Tokyo 164-8639 , Japan
4
Department of Earth and
Environmental Sciences, University of
Illinois at Chicago, IL, USA
Abstract
Paleo-environmental changes along
the delta complex on the bayhead
of Manila Bay during the late
Holocene were established using
near-surface
core
stratigraphy.
Mollusks and diatoms were used as
proxies for salinity. Radiocarbon
dates from peats and mollusks
provided age control. Knowledge of
previous changes may help in
understanding
present-day
processes on the delta plain. The
delta plain, occupied by wetlands
on the bayhead of Manila Bay was
formed mainly during a period
when sea level was higher than
present from about 5,500 to 1,400
yBP. Four parasequences were
identified
within
an
overall
shallowing upward sequence. The
ages
of
the
parasequences
correspond to the timing of relative
stillstands in the reconstructed
regional fluctuations of sea level
from rocky coastlines in the
Philippines. Faulting also plays a
role in delta evolution. Relative
vertical motions across the Lubao
Lineament, which could be as much
as 3.5 meters over the past 1,500
yBP, helped maintain the position of
the wetland and dryland boundary
along the western margin of the
delta plain. Aside from faulting,
natural sediment compaction also
contributes to subsidence. In recent
years,
however,
anthropogenic
activities
such
as
excessive
groundwater
extraction
have
enhanced subsidence contributing
greatly to delta-wide worsening
floods.
79
Figure 1. 2001 Landsat image (band 4) of the Pampanga-Angat delta plain. The wetlands
corresponding to the dark-colored areas in the lower delta plain are easily distinguished from
the light-colored dry lands. The stratigraphy of selected cores taken across the delta plain is
shown in Figure 2 (transect A) and Figure 3 (transect B).
Figure 2. Near-surface stratigraphy of selected cores along the Hagonoy-Bocaue coastal plain
in Bulacan.
Figure 3. Near-surface stratigraphy of selected cores along the Lubao-Masantol coastal plain in
Pampanga.
Acknowledgements
This study is an offshoot of a DA BAR-funded project of F.P. Siringan and K.S. Rodolfo entitled “Net
sea level change in the Pampanga Delta Region: Causes and Consequences”. Supplemental funding
came from a thesis research grant 040415 TNSE of the University of the Philippines (UP)-Office of the
Vice Chancellor for Research and Development to J.L.A. Soria. Field assistance and logistics were
provided by the National Institute of Geological Sciences and Marine Science Institute of the
University of the Philippines-Diliman.
Disaster risk management using sensors:
Early warning systems for landslides,
slope failures and debris flow
M.C. Talampas1, J.J. Marciano
Jr.2, S.G. Catane3 and M.A.H.
Zarco4
1
Instrumentation Robotics and Control
Laboratory, Institute of Electrical and
Electronics Engineering, University of
the Philippines Diliman, Quezon City
1101
2
Instrumentation Robotics and Control
Laboratory, Institute of Electrical and
Electronics Engineering, University of
the Philippines Diliman, Quezon City
1101
3
Sciences, University of the Philippines
Diliman, Quezon City 1101
4
Geotechnical Engineering Group,
Institute of Civil Engineering,
University of the Philippines Diliman,
Quezon City 1101
Abstract
A system consisting of alternation
instrumentation
for
monitoring
slope deformation and piezometric
water level was designed and
developed as an early warning
system for landslides, slope failures
and debris flows. The landslide
monitoring system is composed of a
sensor column array that is buried
vertically underground. The sensor
column consists of pipe segments
each
containing
triaxial
accelerometers for measuring tilt,
and capacity type sensors for water
content measurements. A modified
version of the Casagrande type
piezometer is also integrated into
the sensor column for purposes of
measuring excess
pore
water
pressure. Measurements taken in
each segment are accessed via the
Controller Area Network (CAN)
communications
protocol.
The
sensor column and piezometer are
capable
of
communicating
wirelessly with a central based
station via a Wireless Fidelity
(WIFI) link. Data is collected
stored, process and displayed via
the Python based GUI on the base
station.
The sensor column and piezometer
is tested on laboratory bench-scale
landslide box. Tests are performed
on slopes built from cohesionless
material
under
steady
state
seepage conditions. A mathematical
model assuming a Mohr-Coulomb
elasto-plastic
type
material
is
developed. The resulting coupled
unconfined fluid flow and limit
equilibrium problem is solved using
the finite element method. Results
of the experiments show close
agreement
with
deformation
patterns and failure mechanism
predicted by the model.
Crustal growth and mantle source
evolution in the Philippines
M.L.G. Tejada
Diliman, Quezon City, Philippines 1101
Abstract
The
present
location
of
the
Philippine archipelago along a
complex boundary among three
plates, Eurasian, Philippine, and
Indo-Australian, makes it a natural
laboratory
for
studying
and
understanding the early stages of
continental growth. Prior to this
present stage, the archipelago may
have undergone previous histories
of multiple arc and back-arc basin
generation, crustal accretion, as
well as tectonic displacements from
a more southerly location. The arc’s
tectonic evolution from its birth to
its present stage of development is
reflected in the available data from
combined studies of igneous rocks
of Cretaceous to recent ages, which
also reveal a record of the changing
or evolving mantle source regions
that
accompanies
the
arc’s
evolution.
eastern side of the island. The
western margin of the island is
currently being modified by active
subduction and collision with the
Eurasian margin. As a result, the
geochemical signatures of igneous
rocks suggest that local processes
tend to modify the nature of this
pre-existing mantle as a result of
changing tectonic setting and
subduction recycling of materials
from previously rifted fragment of
the Eurasian margin.
The results of the geochemical
study of ~100 Ma basement rocks
of the eastern margins of Luzon,
the largest island, suggest that an
Indian MORB-type mantle may
have underlain the archipelago
since the Cretaceous. This mantle
signature continues to be tapped by
the younger volcanic products and
plutonic rocks emplaced along the
Low temperature thermochronology of
Buruanga Peninsula, Panay Island, Central
Philippines
M. Walia1, T.F. Yang1, T.K. Liu1,
L.S. Teng1, W.M. Yuan2, G.P.
Yumul Jr. 3,4 and C.B. Dimalanta4
1
Department of Geosciences, National
Taiwan University, Taipei, Taiwan
2
China University of Geosciences,
Beijing, 100083, China
3
Manila
4
hornblende to obtain ages over a
range of closure temperatures of
about 110°C to 510±50°C. The age
data suggest two consecutive
tectonic events at 9-12 Ma and 1617 Ma that resulted in the
exhumation
of
rocks.
This
exhumation may be related to the
collision events. Due to different
closure temperatures of the FT and
40
Ar/39Ar systems it is possible to
recognize
both
Cenozoic
and
Mesozoic tectonic events in the
area. Furthermore, these ages can
be used to define the intrusion time
of the diorite besides giving an
estimate of the timing of arccontinent collision in Panay Island.
Abstract
Buruanga Peninsula forms the
westernmost part of Panay Island,
Central Philippines and is part of
the Palawan continental fragment,
which was formerly attached to the
south-eastern China. It acted as
the leading edge of the moving
continental fragment and collided
with Philippine Belt followed by
convergence beneath the latter.
Getting information about the
timing of the collision event is
crucial
in
understanding
the
evolution
of
the
archipelago.
Samples collected from Buruanga
Peninsula were dated using fission
track (FT) and 40Ar/39Ar techniques
to constrain the timing of the
collision of Philippines arc with
Palawan continental block. First
time reported fission track dates of
zircon and apatite are combined
with 40Ar/39Ar dates of biotite and
Middle Pliocene El Niño events recorded in
fossil corals of the Tartaro Formation,
Province of Bulacan, Central Luzon,
Philippines
T. Watanabe1, A. Suzuki2, T.
Kase3, S. Minobe1, Y. MaacAguilar4, K. Kameo5, K.
Minoshima2, R. Wani3 and H.
Kawahata6
1
Hokkaido University, Japan
2
Agency of Industrial Science and
Technology, Japan
3
National Science Museum, Japan
4
Mines and Geosciences Bureau,
Department of Environment and
Natural Resources, Philippines
5
Chiba University, Japan
6
University of Tokyo, Japan
Abstract
In the study of future climates, the
Middle Pliocene Warm Period (PWP)
can be an analog for the impending
global warming.
This period is
characterized by significantly warm
climate with high global surface
temperature ranging from 3° to 5°C
higher than today.
Attested by
many paleoclimate archives and
several climate model studies, this
time slice is rather preferred in
simulating future climate because
many conditions that prevailed
during that time matches well with
modern values.
Also, continents
then were virtually in the same
geographic positions and the living
flora and fauna are still extant.
One
thing
that
remains
controversial in previous records of
the PWP is the role of El NiñoSouthern Oscillation (ENSO) in the
greenhouse warming due to lack of
information about seasonal to interannual variability of sea surface
water in low latitude regions.
In the Philippines, well-preserved
Middle Pliocene (3.5-3.8 Ma) coral
fossils discovered from Madlum
River, central Luzon provided 35years
coral
oxygen
isotopic
evidences with monthly resolutions.
These fossils were collected from
muddy sand layers of the Tartaro
Formation
exposed
along
the
Madlum River in the vicinity of
barrios Tartaro and Sibul, San
Miguel, province of Bulacan. Based
from associated fossil contents and
sedimentary features, the corals
are inferred to be part of a coral
mound deposited in an intertidal to
subtidal setting. The Porites coral
blocks from Tartaro were sliced into
slabs and X-rayed to observe the
density
of
growth
banding.
Powdered microsamples from each
band were processed for isotope
analysis. Results of these analyses
showed
several
significant
attenuations of seasonal amplitude
in the 18O/16O ratios of PWP coral
record which were also detected in
recent corals during modern El Niño
events.
These findings suggest
that east-western movements of
the Western Pacific Warm Pool
(WPWP) were active that caused
ENSO events during the warm
period. The average sea surface
temperatures in Luzon during that
time records to about 2-4°C higher
than today. Results of analysis also
indicate that the corals are not
calcified during ENSO periods.
Plate boundary geometry of the northern
Manila Trench: Inference from seismic and
bathymetric data
Y.-C. Yeh and S.-K. Hsu
Central University, Chung-Li, Taiwan
could be one of the key role that
cause the change of the Manila
Trench orientation from NE-SW to
NW-SE.
Abstract
The Manila Trench marks as the
plate
boundary
that
western
Philippine Sea plate has overrided
the oceanic lithosphere of the
South China Sea (SCS). The
northern part of the SCS crust was
created between magnetic isochron
C17 (i.e. 37 Ma) and isochron C10
(i.e. 28 Ma) and is terminated in
the north by a fossil transform
boundary,
the
Luzon-Ryuku
transform plate boundary (LRTPB).
Due
to
a
deeper
basement
topography, the crust north of
LRTPB could be an older oceanic
crust or a rifted continental crust.
In short, the age of the northern
SCS is gradually older from south
to north. The new collected
multichannel
seismic
data
demonstrate more intense normal
faulting north of LRTPB than south
of LRTPB. In addition, outer rise
normal
faulting
mechanism
earthquakes
extraordinary
clustered northeastern of the LRTPB
around 120。10’ E, 20。 30’ N which
are evidenced by the new seismic
profiles and detailed bathymetry
data. Moreover, the intersection of
the LRTPB and the accretionary
prism
shows
indentation
bathymetry which implies the
southeastern end of the LRTPB
A dislocation model for crustal
deformation along the fault system in
Luzon
S.-B. Yu1, Y.-J. Hsu1, C.-C. Yang2,
T. Bacolcol3 and R.U. Solidum3
1
Sinica, Taipei, Taiwan
2
Central University, Taoyuan, Taiwan
3
Seismology, Quezon City, Philippines
Abstract
The Philippine Fault system is a
result of the oblique convergence
between the Philippine Sea plate
and the Sundaland Block/Eurasia
plate. It is a left-lateral strike slip
fault that trends in N 30°- 40°W
and
transects
the
Philippine
archipelago from the northwest
corner of Luzon to the southeast
end of Mindanao for about 1200
km.
For
studying
crustal
deformation along the Philippine
Fault system, eight GPS surveys
were conducted from 1996 to 2008
in the Luzon region through a joint
effort by the Institute of Earth
Sciences, Academia Sinica and the
Philippine Institute of Volcanology
and Seismology. Summing up the
12-year survey-mode GPS data in
the Luzon region and continuous
GPS data in Taiwan, along with
other 14 IGS sites in the AsiaPacific
region,
we
use
the
GAMIT/GLOBK software to calculate
the coordinates of each site and
obtain the GPS time series. Then
the interseismic velocity field in the
Luzon region is derived by utilizing
QOCA software. The velocity field in
the
Luzon
region
gradually
increases from south to north with
respect to the Eurasia plate. The
velocity vectors to the west of the
Philippine Fault range from 44 to 59
mm/yr, while that to the east of the
fault are from 59 to 79 mm/yr. The
azimuths of velocity vectors range
from 285° to 314°. This indicates
that there is significant internal
deformation in the Luzon Arc.
Based on the GPS observed 19962008 velocity field in the Luzon
region and using the interseismic
crustal
deformation
model
of
Matsu’ura et al. (1986), we invert
for the fault geometry parameters
and fault slip rates of the Philippine
Fault. The fault dip and width are
fixed to be 89° and 30 km,
respectively. The inverted results
indicate that the average left-lateral
strike-slip rate of southern segment
is 20.6 mm/yr, and northern
segment is 32 mm/yr. The block
motion is 31 (95% confidence
interval,
23~35)
mm/yr
with
azimuth of 332° (323°~341°).
Because the density and aperture
of the current GPS array are
insufficient, it is not able to
successfully
detect
crustal
deformation of the entire fault
system and strain partition between
the branch faults.
Climate change adaptation in the
Philippine context
G.P. Yumul Jr.1, 2, C.B.
Dimalanta1, N.T. Servando3 and
N.A. Cruz3
1
2
Technology, Bicutan, Taguig City,
Philippines
4
Philippine Atmospheric, Geophysical
and Astronomical Services
Administration, Department of Science
and Technology, PAGASA Science
Garden, BIR Road, Quezon City,
Philippines
nature of the Philippines and being
a very minor emitter of greenhouse
gases,
adaptation
is
the
Government’s
national
policy.
Measures involving both disaster
risk management and climate
change
adaptation
are
being
implemented especially in the
community level. This is with the
end in view of mainstreaming both
disaster risk management and
climate change adaptation in a
changing climate regime.
The progress that are being
achieved, the issues and challenges
recognized and possible solutions to
gaps encountered will be presented
Abstract
Climate change, involving both
natural climate variability and
anthropogenic global warming, has
been a major concern of the world
today. Negotiations within the
United
Nations
Framework
Convention on Climate Change is
ongoing. It is hoped that by
December
2009,
substantial
agreements would be reached in
the
Copenhagen
UNFCCC
negotiations. Within the context of
the Bali Action Plan involving the
four pillars of: a) Mitigation; b)
Adaptation; c) Technology Transfer
and d) Financing, it is hoped that
the world will be better prepared by
2012 when the Kyoto Protocol ends.
It is in this light that the different
climate change-related initiatives in
the Philippines would be looked
into. Considering the archipelagic
.
Paleoclimatic implications of Late
Cretaceous planktonic foraminifera from
the mid-latitude ODP holes 758A, 761B and
762C, Indian Ocean
M.A. Zepeda1,2
1
Department of Earth and Materials
Science
and
Engineering,
Mapua
Institute of Technology, Intramuros,
Manila, Philippines
2
Paleontolgy Unit/PETROLAB, Lands
Geological Survey Division, Mines and
Geosciences Bureau, North Avenue,
Abstract
A detailed biostratigraphic and
statistical
analysis
of
faunal
assemblage
of
Ocean
Drilling
Program (ODP) sites from the midlatitude showed great variability
and instability in the paleoclimatic
conditions in the Indian Ocean
during the late Cretaceous (late
Santonian to Maastrichtian).
Faunal
composition,
species
diversity and equitability, species
distribution, ratios of climatic index
species and paleoclimatic curves
were used to deduce paleoclimatic
conditions.
The paleoclimatic
curves
constructed
showed
particularly striking and similar
trends for most of the sites studied.
Three
paleoclimatic
intervals
namely, Interval 1 (late Santonian
to early Campanian), Interval 2
(late
Campanian
to
middle
Maastrichtian), and Interval 3 (late
Maastrichtian) can be identified in
the paleoclimatic curves. Interval 1
(late
Santonian
to
early
Campanian) suggests a relatively
warm paleoclimate as evidenced
by: an abundance of Tethyan and
warm indices; high species diversity
and equitability; and high positive
values in the paleoclimatic curves.
Interval 2 (late Campanian to
middle
Maastrichtian)
indicates
warm and cool fluctuations as
depicted by: the mixture of Tethyan
and Austral species within the
Transitional
realm;
varying
abundances of warm and cool water
species; fluctuations in the species
diversity, equitability and climatic
curve values, with a pronounced
negative peak during the latest
Campanian. This peak represents
the coolest interval of the late
Santonian to Maastrichtian as
reflected by the preponderance of
cool indices; low species diversity
and equitability and high negative
values in the paleoclimatic curve.
Interval 3 (late Maastrichtian)
marked another warm interval due
to: a shift in the dominance of cool
indices to warm indices; high
diversity and equitability; and high
positive values in the paleoclimatic
curve. Such results imply that
paleoclimatic conditions in the
Indian Ocean during the late
Santonian to Maastrichtian are very
unstable. This instability could be
attributed to an interplay of several
geologic and tectonic events (i.e.
break
of
the
southern
Gondwanaland continents, seafloor
spreading and subsidence between
Antarctica, Australia and New
Zealand; northward drift of South
America
from
the
Antarctic
Peninsula; global rise in sea level
during the middle Campanian; and
opening, re-emergence and closure
of gateways) which occurred in the
Indian Ocean before, during and
after the identified paleoclimatic
intervals.
To summarize, the paleoclimatic
conditions from the late Santonian
to early Campanian period of the
sites under study, fluctuated from
warm-Tethyan (Holes 761B and
762C) during the late Santonian;
warm-Transitional
(Holes
758A,
761B and 762C) during early
Campanian;
Transitional
with
varying
Tethyan
and
Austral
influences (Holes 758A, 761B and
762C) during the late Campanian to
middle Maastrichtian; Tethys with
Transitional influence (Holes 758A
and 761B) and Transitional with
pronounced Tethyan influence (Hole
762C)
during
the
late
Maastrichtian.

RP-Taiwan - Rushurgent Working Group

Transcription

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