Relative vertical deformations in , revealed by Holocene coral microatolls

M.I. Abigania 1,2 , F.P. Siringan 2,3* , (HLS) of the annual growth rings G.M. Besana-Ostman 1,4* and Y. seen in x-radiograph of the sampled Yokoyama 5 living microatoll showed short periods of gradual submergence (2- 1Geology and Geophysics R&D Division, 4 mm/yr) in between abrupt Philippine Institute of Volcanology and relative sea-level falls. These are Seismology – Department of Science possibly periods of relaxation phase and Technology (PHIVOLCS-DOST), corresponding to interseismic Philippines adjustments. Two episodes in the coral’s band pattern are marked by 2National Institute of Geological a decrease in the extension rate of Sciences, University of the Philippines, Diliman, City, Philippines the growth bands. One took place in ca. 1938 and another in ca. 3Marine Science Institute, University of 1963. Incidentally, a Ms 7.0 the Philippines, Diliman, , earthquake occurred offshore of Philippines associated with Trench in 1938. The decrease in 4 Department of Geological Sciences, growth rate might be due to University of North Carolina at Chapel increased turbidity brought by Hill, NC, USA elevated sediment load from rivers due to landslides upstream 5Department of Earth and Planetary Sciences, University of Tokyo, Japan triggered by the earthquake. Rapid submergence of ~2cm ca.1938 is *present address possibly tectonic as a Ms 7.6 and 7.0 earthquake events in offshore northwest occurred in 1934 Abstract and 1938 respectively. Whereas, the growth rate pattern and rapid Coral microatolls have long been submergence noted in ca. 1963 used as good indicators of relative might be correlated with two sea level change especially in an earthquake events offshore of actively deforming region. Relative in 1963 and offshore of vertical deformations possibly northwest Ilocos in 1964. can be associated with paleoseismic events correlated with the growth pattern are reconstructed from the in ca.1964. Oceanographic effects morphology of living and emergent on sea level like the sea surface coral microatolls in Paraoir, temperature changes in the South , La Union facing Manila Sea was also recorded in the Trench in the Philippines. The living coral, marked by a 2-3 cm gradual microatolls exhibit emergence submergence and emergence in the throughout their life history by growth rings from 1989 to 2006. having a domal raised center and down-stepping terraces towards the rim. The highest level of survival

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Emerged microatolls 1km south of earlier events of relative sea level the sampled living coral changes. The final emergence of predominantly exhibit a “cup-like” the reef at about 1.4 kyBP lead to morphology having two exterior the demise of the microatolls . This raised rims with gentle outward sea level fall is also recorded in slopes and abrupt down-steps other places in the Philippines. The toward the center. One of the study can most probably identify sampled microatoll less than 1 m in other events older than the known diameter shows an initial historical record along Manila hemispherical growth for 23 years Trench. 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

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Electromagnetic, geochemical and thermal studies on Taal (Philippines) from 2005 to present

P.K.B. Alanis 1, J. Zlotnicki 2, J.P. Abstract Sabit 1, Y. Sasai 3, J. M. Cordon 1, M. Harada 4, J.P. Toutain 5, E.U. Taal Volcano is one of the most Villacorte 1, A. Bernard 6, H. active volcanoes in the Philippines. Hase 7, J.T. Punongbayan 1, T. Its first recorded eruption was in Nagao 8 and R.U. Solidum Jr1. 1573. It has since erupted 33 times resulting in hundreds of casualties 1Philippine Institute of Volcanology and and large damages to property. In Seismology, C. P. Garcia Avenue, U. P. 1995, it was declared one of the 15 Campus, Diliman, Quezon City, Decade Volcanoes. Beginning in the Philippines early 1990s it has experienced several phases of abnormal activity, 2 CNRS, UMR6524, UMS 833-UBP including seismic swarms, episodes Observatoire de Physique du Globe de of ground deformation, ground Clermont-Ferrand, 24 avenue des fissuring and hydrothermal landais, 63177 Aubiere Cedex, France activities. In January 2005, several 3Disaster Prevention Division, Tokyo felt earthquakes drove inhabitants Metropolitan Government, Nishi- living near the volcano to evacuate. Shinjuku, 2-8-1, Shinjuku-ku, Tokyo 163-8001, Japan Joint self-potential (SP), total magnetic field (TMF), ground 4Centre for Frontier Electronics and temperature, and carbon dioxide Photonics, Chiba University, 1-33 (CO 2) soil degassing surveys along Yayoi-cho, Inage-ku, Chiba 263-8522, with satellite thermal imaging were Japan begun in Taal Volcano in 2005,

which aims to study the geothermal 5Laboratoire des Mecanismes de Transfert en Geologie, UMR5563, activity occurring in the volcano. Observatoire Midi-Pyrenees, 14 avenue These surveys are repeated Edouard Belin, 31400 Toulouse, France regularly and several permanent and continuous TMF and SP stations 6Laboratoire de Geochimie et were also established on the Mineralogie Appliquee, Universite Libre northern part of the volcano, as de Bruxelles, CP160/02, avenue FD well as on the northeastern shore Roosevelt 50, 1050 Brussels, Belgium of the Main Crater Lake (MCL). The results from these combined 7Geological Survey of Japan, AIST, studies indicate strong thermal Tsukuba, Ibaraki 305-8567, Japan transfers and degassing in the area 8Earthquake Prediction Research of Daang Kastila on the northern Centre, Tokai University, 3-20-1, Orido, flank of the volcano along E-W Shimizu-ku, Shizuoka 424-8610, Japan 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

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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 CO 2 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.

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Harnessing ICT and high performance computing for environmental monitoring and hazard mitigation

The Philippine e-Science Grid Program, Among the focus areas include: Department of Science and Technology weather notification system; - Advanced Science and Technology remote data monitoring/ sensing/ Institute, Diliman, Quezon City, acquisition for research and Philippines 1101 disaster mitigation; and, real-time environmental data monitoring and Abstract acquisition. ASTI continues to build and The Advanced Science and strengthen its capabilities in the Technology Institute (ASTI), a areas of Sensor and Warning research and development institute Systems Development and under the Department of Science Deployment, and High-Performance and Technology (DOST), is Computing, among others. ASTI is mandated to conduct research and currently implementing the development in the advanced fields Philippine Real-time Environment of Information and Communications Data Acquisition and Interpretation Technology (ICT) and for Climate-related Tragedy Microelectronics. (PREDICT) Prevention and Mitigation. PREDICT aims to Over the years, ASTI's programs improve weather forecasting using and projects have focused on a system of automated weather providing more significant stations (AWS) that can remotely contributions to national send weather parameters to a development through ICT and central server using the nationwide Microelectronics. ASTI has been cellular network. The received data involved with a number of is then processed and analyzed to collaborations with government, come up with weather bulletins for academe, and industry to carry out general information. high-impact projects that contribute to agriculture, distance education, ASTI also initiated the Philippine e- weather forecasting, education, Science Grid (PSciGrid) Program, environmental monitoring, disaster which was conceptualized in mitigation, among others. response to the emerging need of the Filipino scientific community for Environment stands as one of the a national high-performance priority research areas of ASTI. The computing facility. PSciGrid aims to Institute’s activities on the area are establish a grid computing to conduct R&D and develop infrastructure in the Philippines that technologies and products that will will provide internet-accessible e- have useful and critical applications Science solutions to a diverse in disaster and hazard mitigation, community of researchers and as well as in monitoring scientists in the academe and environmental health and safety. government. Through the PSciGrid

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Program, ASTI has set up a high- performance 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.

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Caught off guard: the January 2009 flooding of , Philippines

L.T. Armada 1, D.V. Faustino- attributed to Tropical Depression Eslava 1, G.P. Yumul, Jr. 1,2 , R.C. Auring and the existence of a cold Viado 3 and C.B. Dimalanta 1 front in the region. The total amounts of precipitation exceed 160% of the thirty-year average for 1National Institute of Geological most areas in Mindanao. As a Sciences, University of the Philippines, consequence, catastrophic floods Diliman, Quezon City, Philippines and landslides devastated numerous communities in the 2Department of Science and region. This report presents an Technology, Bicutan, Taquig City, Metro account of the series of disasters Manila, Philippines that affected the cities of de Oro, Gingoog, Bislig and the 3Philippine Council for Industry and Energy Research and Development, township of Maco in Compostela Department of Science and Technology, Valley. Bicutan, Taquig City, , Philippines

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

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Deformational styles of sedimentary packages in offshore south Bondoc Peninsula, Luzon, Philippines

M. Aurelio 1, E. Cutiongco 2, J. gravity and magnetics gathered Foronda 3, K.J. Taguibao 1, Z. through air-borne techniques (e.g. Calucin 1 and M. Forbes 3 Pineda and Aurelio 1990, Bischke et al. 1990). In 1986, the then Bureau 1National Institute of Geological of Energy Development of the Sciences, University of the Philippines, Philippines published a Diliman, Quezon City, Philippines comprehensive summary of the sedimentary features of Philippine 2 Pearl Energy Limited, 80 Raffles Place, basins, based primarily from UOB Plaza 2, #12-20, Singapore regional data. Detailed studies have

been confined to areas surveyed by 3Philippine National Oil Company – Exploration Corporation, Energy Center, independent workers, mostly from Fort Bonifacio, Taguig, Philippines the petroleum industry. In 1989, studies more specific to the area were published in Porth Abstract and Von Daniels.

This paper presents recent and Recently acquired 2-D seismic detailed data (primarily seismic profiles and gravity data in the profiles, magnetic and gravity data) offshore area between Bondoc gathered in the offshore area south Peninula and Burias Island, South of Bondoc Peninsula in Southern Luzon, Philippines, are interpreted Luzon, Philippines. The offshore in the context of known structural data is integrated with onshore styles observed onshore and in observations to gain a relation to paleo- and neo-tectonic comprehensive understanding of regimes in the region. the structural geology and tectonic character of the region. A preliminary effort to understand the Keywords implications of this structural and Seismic horizons, sedimentary tectonic nature to petroleum packages, basin formation, tectonic exploration is attempted. inversion

Methodology Introduction Offshore data (seismic profiles and Published materials in studies of bathymetry) gathered in 2007 offshore areas in inter-island seas (complimented with older profiles) of Luzon in the Philippines are were processed and interpreted. generally few and sporadic. If any, Among others, seismic processing these studies have been based on involved signal deconvolution, regional geophysical data such as stacking and velocity migration. Software-aided interpretation

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allowed 2D and 3D appreciation of similar stratigraphy, with indurated interpreted stratigraphy and Eocene volcanoclastics forming the structures. Seismic profiles were structural core and exposed in interpreted along with topographic Sombrero Island and on the NW contours and bathymetry, and coasts of the the main island compatible available map (Aurelio 1992). This core is topped information from other works. The by carbonates and clastic relationship between offshore sequences generally showing seismic data and stratigraphy was shallower depositional features established using onshore data as towards younger deposits and well as from few offshore wells. exposed widely over the island.

In Bondoc and Burias, three major Summary of Onshore Geology: unconformities since the Eocene are Southern Bondoc Penisula – observed to separate several Burias Island structurally-distinct sedimentary packages (Aurelio 1992). The

oldest unconformity (~NP21) The study area is located between separates Eocene limestones from Bondoc Peninsula and Burias Island Oligo-Miocene turbidites while the in Southern Luzon (Figure 1). middle unconformity (~NN5) marks Bondoc Peninsula is a large the contact between these strongly- anticlinorium with an anticlinorial deformed E. Miocene turbiditic axis oriented roughly N-S in the sequences with L. Miocene shallow south and bends NWesterly to the marine clastics and carbonates. The north (Aurelio et al. 1990, Aurelio youngest unconformity (~NN11) et al. 1991, Aurelio 1992). It is separates the L. Miocene clastics underlain by a pre-Tertiary volcano- from the youngest sedimentary ophiolitic basement topped by sequences. 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 Oligo- Miocene 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.

Burias Island, located to the SE of Bondoc Peninsula, presents a

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Figure 1 . Summarized geology of the Bondoc Peninsula – Burias Island area ( Island also shown) based from Aurelio (1992). Bathymetry is from GEBCO, topography is from SRTM. Offshore structures (red lines) in the area are from Sarewitz and Lewis (1991). Approximate location of seismic profile presented in Figure 2 is shown. See text for discussion. Above the H1 horizon is a package Summary of Observations from generally characterized by incoherent reflections on its lower Seismic Profiles half but by strong to moderately folded and truncated reflectors on Figure 2 shows a seismic profile in its upper half. This sequence, the study area and its structural together with the upper section of interpretation. A strong seismic the H1 horizon, is affected by reflector (Horizon 1 – H1) believed thrust-fold style deformation with to be the equivalent of Late the thrust plane – fold axis striking Oligocene – Early Miocene almost parallel to the longer fold limestone and carbonate sequences axis of H1. exposed in Bondoc peninsula, appears as a folded and faulted The truncation of the sequence horizon. The longer fold axis is overlying the H1 horizon is generally oriented NNW-SSE, represented by a faintly to expressed in an anticline-syncline moderately visible horizon (H2) sequence plunging to the NNW. The characteristic of an angular shorter fold axis orients sub- unconformity. Above H2 is a perpendicular to the longer fold generally coherent seismic package axis on an ENE-WSW direction. The occasionally affected by NNW plunge allows the reflector to moderately- to steeply-dipping emerge on the seabed normal faults forming half-grabens southeastwards in the direction of and horsts biased towards a Burias Island, where the same mid- westerly basinal dip. The block- Tertiary limestones are exposed. tilted unit is capped by a thin, Faulting is in the form of generally undeformed sequence. compressive faults but which show indications of initial normal faulting.

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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 Burias Island is the result of to the two most recent multiple tectonic events known to unconformities discussed in the have affected the region and summarized geology of the study nearby areas. These tectonic events area. involved basin deposition at different depths and time intervals, On the SW flank, a rugged seabed punctuated by compressional slope falls abruptly to the WSW periods in between. The alternance suggesting instability. Reflectors are of extensional (basin formation) highly disturbed, often truncated by and compressional (as in the case steeply dipping faults cutting of collision) tectonic regimes often through seabed. brings about tectonic inversion processes, which may generate Concluding Remarks geologic structures favourable for hydrocarbon accumulation. The complex deformational style observed in the sedimentary packages in the offshore area between Bondoc Peninsula and

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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), 403- 410. [2] Aurelio, M.A., Barrier, E., Rangin, C. and Müller, C. The Philippine Fault in the late Cenozoic evolution of the Bondoc--N. 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 as observed from aeromagnetic and seismic data. Tectonophysics, 183, 1-4 (1990), 243- 264. [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 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.

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Sibuyan Sea Fault, Marinduque Fault and Philippine Fault (Ragay segment): New insights from GPS data

T. Bacolcol 1,3 , S.-B. Yu 2 and R. also probable that the on-land Solidum Jr. 1 extension of the Sibuyan Sea Fault is the 30-km, northwest-trending 1Philippine Institute of Volcanology and Central Marinduque Fault in Seismology – Department of Science Marinduque Island. The gathered and Technology, PHIVOLCS Bldg., C.P. data also showed that Central Garcia Ave., University of the Marinduque Fault is probably Philippines Campus, Diliman, Quezon creeping at 15 mm/yr, which would City, Philippines 1101 explain for the sparse seismicity

2Institute of Earth Sciences, Academia recorded along its length. Another Sinica, Nankang, Taipei, major information gathered from these GPS data is the recognition of 3Département de Géotectonique, a significant NW movement (about Université Pierre et Marie Curie, 4 place 33 mm/yr) between and Jussieu, T26, E1, Paris, France the group of islands on the east (Marinduque, Banton and Sibuyan). This would imply that the suture Abstract zone between Palawan and the is located still further west of Marinduque and 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.

As expected, calculations with respect to Palawan showed NW- directed 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

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Mid-Holocene sea-level changes in , La Union using morphostratigraphic indicators

N.P. Baluda 1, F.P. Siringan 2 and A.M.F.A. Lagmay 1

1National Institute of Geological Sciences, University of the Philippines, Diliman, Quezon City, Philippines

2Marine Science Institute, University of the Philippines, Diliman, Quezon City, 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.

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Terrane characteristics and configuration in Northwestern Mindoro and their implications

the presence of distinct terranes: A.P.B. Canto 1, R. Tamayo Jr. 1, C. the Middle Oligocene Amnay Dimalanta 1, D. Faustino-Eslava 1, Ophiolite and the Mesozoic Halcon G. Yumul Jr. 1,2 , K.L. Queaño 3 and Metamorphics. A Late Pliocene to E. Marquez 4 Early Pleistocene dated sequence consisting of sandstone and limestone with minor mudstone and 1Rushurgent Working Group, National conglomerate (Balanga Formation) Institute of Geologic Sciences, unconformably overlies the two University of the Philippines, Diliman, terranes. Quezon City, Philippines

2 Aside from the age variance, the Department of Science and Amnay Ophiolite and Halcon Technology, Bicutan, Taguig Metro Metamorphics differ in petrological Manila, Philippines and geochemical characteristics and 3Mines and Geosciences Bureau- origin, as well. The former Department of Environment and corresponds to an exhumed piece Natural Resources, North Avenue, of the crust, Quezon City, Philippines whereas the latter correlates to a metamorphosed continent derive 4 2009 Centennial Faculty Grant fragment. Isolated ophiolitic blocks Awardee, Department of Physical previously identified to compose Sciences and Mathematics, University the Mangyan and Lubang – Puerto of the Philippines Manila, Padre Faura Galera Ophiolites are enclosed by St., Ermita, Manila, Philippines schists of the Halcon Metamorphics. Preliminary results suggest these Abstract peridotite and volcanic blocks have affinity with mid-oceanic ridge

materials, which contrast with the Mindoro represents a tectonically chemistry of the Amnay Ophiolite. complex island in central We propose the Mangyan and Philippines; the evolution of which Lubang – Puerto Galera Ophiolite and its importance to arc – represent megaclast materials, continent collision along the which were incorporated into the western Philippines remain unclear. Halcon Metamorphics protolith. As On northwestern Mindoro including such, the Halcon Metamorphics the offshore islands of Lubang and could well be the metamorphosed Ambil, remnants of multiple equivalent of the accretionary collision events appear as NW-SE complexes currently exposed in oriented tectonic slices that are northern Palawan and northwest separated by southwest verging Panay. Metamorphism must have thrust faults, essentially parallel to occurred prior to the Late Eocene the trend of the currently active as constrained by the Lasala . A profile from the Formation sedimentary package trench to Central Mindoro indicates that unconformably overlies the Halcon Metamorphics.

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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 micro- continental 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.

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A plate tectonic mechanism fluid migration in the convergent margin, southwestern Taiwan

W.-B. Cheng 1, S.-K. Hsu 2 and C.- available OBS data set consists of H. Chang 3 ~700 detected earthquakes, from which around 500 could be well 1Department of Environment and located where about 450 events Property Management, Jinwen have been used in simultaneous University of Science and Technology, inversion for hypocenters, three- Taiwan dimensional Vp and Vp/Vs models for the study area. Gravity data are 2Institute of Geophysics, National used to improve the model for the Central University, Taiwan offshore area, where it is poorly 3Central Weather Bureau, Taiwan sampled by local earthquakes. This study found three crustal anomalies: (1) two prominent high Abstract velocity/high Poisson's ratio anomalies in the mid to lower crust beneath the eastern coastal and In a zone, the most offshore area; (2) several volumes likely source of the fluid would be of relatively high-velocity/high water contained in the hydrous Poisson's ratio rocks in the upper- minerals of the subducting oceanic to mid-crust beneath the Central crust, because dehydration of clay Range; (3) a thin low-velocity zone minerals in sediments is completed is detected above the subducting at depths shallower than 10 km. Eurasian slab in the mantle wedge Therefore, the sources and and earthquakes are distributed pathways of upward expelled fluid along the transition zone between flow on the accretionary prism of this thin low-velocity zone and the southern Taiwan have been the high-velocity Eurasian slab. Based subjects of intense debate. This on gravity modeling and our paper investigates velocity resulting velocity and Poisson's structure of the active plate ratio models suggest that the boundary in southwestern Taiwan subduction decollement, which is by joint analysis of gravity anomaly characterized beneath the and seismic arrival time data. P and can be traced S-P arrival time data from 3,238 landward into a duplex structure in earthquakes. In addition to CWBSN the lower crust near southern permanent networks, seismic data Taiwan. This study also suggested include the Central Weather Bureau that the geochemical and geologic permanent networks and a setting in a convergent plate temporary network consisting of 11 boundary exerts specific controls on ocean bottom seismometers (OBSs) the formation of a bottom that was deployed to detect the simulating reflections and the aftershocks of the 2006 (ML7.1) inferred distribution of gas Henchun earthquake occurred hydrates. This crustal thickening beneath southern Taiwan. The total occurred above the locked plate

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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.

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Rapid seismic tsunami warning for the South China Sea Region

P.-F. Chen which make the W phase source inversion method effectively for Institute of Geophysics, National rapid and robust tsunami warning Central University purposes (Kanamori and Rivera, 2008). The purpose of this study is to build a seismic tsunami warning Abstract system for the South China Sea region by combining the W phase source inversion method and the The widespread tsunami hazards of unit tsunami method. the 2004 Sumatra-Andaman Is. Earthquake prompted us to build a tsunami warning system for the References South China Sea Region. We adopt [1] Lee, H.-J., Y.-S. Cho and S.-B. Woo, the principle that tsunami waves Quick tsunami forecasting based on database, can be expressed as a linear Tsunamis: Case Studies and Recent Developments, K. Satake (ed.) , 231-240, combination of unit tsunamis and 2005. then divide the potential source region (the Taiwan-Luzon trench) [2] Liu, P. L.-F., S.-B. Woo and Y.-S. Cho, into sub-regions of squares, called Computer programs for tsunami propagation and inundation, Cornell University, 1998. unit tsunami event (Lee et al., 2005). The propagation of each unit [3] Kanamori, H., and Rivera. L, Source tsunami event is simulated using inversion of W phase: speeding up seismic the COMCOT package (Liu et al., tsunami warning, Geophys. J. Int. , 175 , 222- 238 doi:10.1111/j.1365-246X.2008.03887.x 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,

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Applications of 2-D resistivity surveys in characterizations of active faults in Luzon: Implications for fault occurrence beneath the Nuclear Power Plant

M. Collado 1 and C.A. Arcilla 2 Comparing results of the BNPP resistivity survey with our 1Department of Agriculture numerous surveys on active faults, we conclude that there are no 2 National Institute of Geological anomalies that indicate faults or Sciences fractures underneath and along the vicinity of the nuclear building. This study, however, DOES NOT preclude Abstract the existence of fault/s close to the vicinity of the nuclear building that may be outside the range of the Resistivity surveys have found wide resistivity profile lines. The data applications in determining presented, however, arguably rules groundwater levels and, when used out the existence of a fault beneath with other geophysicial and the nuclear plant. It must be noted geological parameters, provide that the “existence” of such a fault imaging of the subsurface. Given was one of the main reasons why the presence of active segments of the BNPP was never operated. 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.

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Petrographic and geochemical data from the Klondyke and Zigzag Formations: Implications on the oceanic to island arc evolution of the Mineral District, Philippines

C.B. Dimalanta 1, G.P. Yumul Jr. 1,2 Cataguintingan Formation samples and R.A. Concepcion 1 were derived from a mafic source whereas samples from the Zigzag 1Rushurgent Working Group - Tectonics Formation indicate derivation from and Geodynamics Group, National intermediate to felsic igneous Institute of Geological Sciences, rocks. These results suggest that College of Science, University of the the Zigzag Formation was derived Philippines, Diliman, Quezon City, from an active continental margin Philippines 1101 setting whereas the Klondyke,

2Department of Science and Amlang and Cataguintingan Technology, Bicutan, Taguig, Metro Formations are associated with an Manila, Philippines oceanic island arc environment.

Abstract Introduction

This study presents a petrographic The amount of literature and geochemical examination of documenting the application of the clastic rock units that underlie petrography and geochemistry to the Baguio Mineral District and the the study of sedimentary rocks has nearby areas. The results obtained increased over the last years. from this investigation will offer These techniques are now being clues on the evolution, not only of applied to investigations of the northern Luzon, but of the sedimentary units capping the Philippine island arc system as well. basement rocks in the Philippines. The Cretaceous to Eocene Petrographic examination of sandstone sequence in Palawan was samples collected from the investigated by Suzuki et al. sedimentary units in the Baguio (2000). A significant amount of Mineral District show that the quartz grains and lithic acidic Zigzag Formation samples have fragments was noted during the more quartz but less plagioclase petrographic examination of the compared to the Klondyke, Amlang sandstone samples. In terms of and Cataguintingan Formation the geochemical characteristics, samples. Lithic fragments are more high SiO and low FeO plus MgO abundant in the Klondyke 2 values were obtained for the Formation sandstone samples. samples. This suggests derivation The major and immobile trace from a continental source region element data suggest that the which is consistent with existing Klondyke, Amlang and

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models that Palawan is a fragment siltstones characterize this derived from the southern margin formation (Leith, 1938). This is of mainland Asia. best observed along Marcos Highway, , Asin Road This work presents the petrographic and the lower portion of Kennon and geochemical compositions of Road. Previous studies revealed clastic units from the Baguio that the Klondyke Formation has Mineral District and nearby areas well-defined proximal, midfan and (Figure 1). The results are used to distal slope portions. A Middle to constrain the composition and Late Miocene age was assigned to tectonic setting of the source rocks. this unit based on calcareous This, in turn, will give insights into nannofossil assemblage (De Leon et the geologic evolution not only of al., 1991). Northern Luzon but also of the whole Philippine island arc system. Other clastic units The results contained herein will also help build up the database on Aside from the Zigzag and Klondyke the petrographic and geochemical Formations, samples were also compositions of sedimentary units collected from sedimentary units in in the Philippine island arc system, the nearby La Union area. These which, at the moment, is almost include the Amlang and lacking. Cataguintingan Formations. The Amlang Formation is a “flysch-type” sequence of thin, rhythmically Clastic units in the Baguio interbedded sandstones, shales and Mineral District minor conglomerates (Lorentz, Zigzag Formation 1984). A gradational contact separates the basal portion of the The Zigzag Formation, best Amlang Formation from the exposed along , is Klondyke Formation. A Middle to subdivided into the Early to Middle Late Miocene age is assigned to this Miocene Upper Zigzag and unit based on the calcareous Oligocene Lower Zigzag members nannofossil assemblage (Catinaster which are separated by an sp., Discoaster pentaradiatus and unconformity (Peña and Reyes, Sphenolithus abies ) (De Leon, pers. 1970). The alternating layers of comm.). red and green sandstones and siltstones comprise the Lower A sequence of tuffaceous Zigzag member. Upper Zigzag, on sandstones interbedded with the other hand, is made up of siltstones, shales and massive, well indurated and conglomerates with some limestone oligomictic conglomerates lenses makes up the consisting dominantly of to Cataguintingan Formation (Lorentz, basaltic andesite clasts. 1984). An unconformity serves as the boundary between the Klondyke Formation Cataguintingan Formation and the Amlang Formation. This formation A thick sequence of coarse clastic has been given a Late Pliocene age rocks, polymictic conglomerate, based on the molluscan shell conglomeratic sandstones, fragments, echinoid spines, sandstones, flow breccias, vitric ostracods and red algae (Maleterre, tuffs, with minor shales and 1989).

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Petrographic results Provenance and tectonic setting Twenty-two fine- to medium- grained sandstone samples were An examination of the geochemical petrographically examined and compositions of sedimentary rocks point counted. Angular to sub- can offer useful information on the angular grains comprise the composition of its source area or sandstone samples and these are source rocks. When plotted on the embedded in <15% clay matrix. discrimination diagram for The cement, on the other hand, is provenance using the major usually in the form of calcite and elements, most of the Klondyke, quartz overgrowth. Amlang and Cataguintingan samples plot in the mafic igneous The samples from the Zigzag provenance field. The Zigzag Formation are mainly composed of samples show derivation from both quartz (60-80%). The quartz intermediate igneous rock sources crystals are mostly monocrystalline, and mafic igneous provenance (e.g. non-undulatory and devoid of Yan et al., 2007). inclusions. These characteristics commonly imply that the quartz Some workers are not too eager to might have been derived from the use the Rb versus K 2O diagram surrounding volcanic rocks as a arguing that these elements are result of weathering and erosion quite mobile during diagenesis or (Tucker, 2001). metamorphism. But when the diagram is used along with other A considerable amount of plots, some useful information may plagioclase minerals (17-30%) are still be derived. The samples from also present in the Zigzag samples the Baguio Mineral District can be but this is much less than the divided into two groups based on number of plagioclase grains the K and Rb contents. Low K, Rb observed in the Amlang (45-58%) and K/Rb ratios exhibited by the and Klondyke (25-50%) Klondyke, Amlang and Formations. Abundant plagioclase Cataguintingan samples suggest crystals are indicative of a derivation from basic igneous rocks compositionally immature (Figure 2). The Zigzag samples, in sandstone since plagioclase is a contrast, are characterized by high labile mineral. Compositional K, Rb and K/Rb ratios typical of maturity reflects the weathering rocks derived from intermediate to process in the source area and the felsic igneous rocks. degree and extent of reworking and transportation (Tucker, 2001). It is To determine the tectonic setting of also evident that some of the the provenance region, Roser and plagioclase grains of the Klondyke Korsch (1986) proposed plotting samples exhibit zoning while some the SiO 2 versus K 2O/Na 2O values are almost completely altered into (Figure 3). This diagram calcite. differentiates oceanic island arc environments from more evolved Lithic fragments, which are mostly arcs (i.e. active continental margins in the form of volcanic clasts, are or continental island arcs). The common in the Klondyke (15-30%) K2O/Na 2O ratios of the Zigzag samples. Formation samples are generally higher compared to the ratios of

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the Klondyke, Amlang and signatures of the Klondyke and Zigzag Cataguintingan Formation samples. Formations and its implication on the oceanic to island-arc setting evolution of the Baguio This suggests that the sediments Mineral District, Philippines. Terminal Report, that make up the Zigzag Formation National Research Council of the Philippines, samples were derived from an 36pp. evolved arc. Conversely, the [4] Leith, A. 1938. Geology of the Baguio Klondyke, Amlang and gold district. Philippine Department of Agriculture and Communication Technology Cataguintingan Formation samples Bulletin 9, 38. have lower K O/Na O and indicates 2 2 [5] Lorentz, R.A.Jr. 1984. Stratigraphy and that their sediments were derived sedimentation of the Late Neogene sediments from oceanic island arcs. on the southwest flank of Luzon, Central Cordillera, Philippines. Journal of the Conclusions 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 The clastic units from the Baguio transpresion: La Cordillere Centrale de Luzon, Mineral District and the nearby a l'extremite de la faille Philippine, sur les areas were analyzed in terms of transects de Baguio et de Cervantes-Bontoc, Contexte structural et geodynamique des their petrography and mineralisations epithermales auriferes. geochemistry. The results show Universite de Bretagne Occidentale, Brest, that the sediments of the Zigzag France. Doctoral thesis. 304pp. Formation were sourced from [7] Peña, R.E. and Reyes, M.V. 1970. intermediate to felsic igneous rocks Sedimentological study of a section of the “Upper Zigzag” Formation along , within an active continental margin Tuba, . Journal of the Geological setting. Mafic source rocks from an Society of the Philippines 24, 1-19. oceanic island arc setting comprise [8] Roser, B.P. and Korsch, R.J. 1986. the sediments of the Klondyke, Determination of tectonic setting of Amlang and Cataguintingan sandstone-mudstone suites using SiO 2 content Formations. and K 2O/Na 2O ratio. Journal of Geology 94, 635-650.

[9] Suzuki, S., Asiedu, D.K., Takemura, S., Acknowledgements Yumul, G.P.Jr., David, S.D.Jr. and Asiedu D.K. This work was supported by the National 2000. Composition and provenance of the Research Council of the Philippines, Upper Cretaceous to Eocene sandstones in Department of Science and Technology, Central Palawan, Philippines: Constraints on the tectonic development of Palawan. Island Commission on Higher Education and National Arc 9, 611-26. Institute of Geological Sciences. Our thanks also go to T.A. Tam III, E.G.L. Ramos, A. Imai [10] Tucker, M.E. 2001. Sedimentary Petrology: An Introduction to the Origin of for help in the fieldwork and in the processing Sedimentary Rocks . 3rd edition. Blackwell of samples. Science Ltd, USA, 262 pp. [11] Yan, Y., Xia, B., Lin, G., Cui, X., Hu, X., Yan, P. and Zhang, F. 2007. Geochemistry of References the sedimentary rocks from the Nanxiong [1] De Leon, M.M., Tamesis, E.V. and Basin, South China and implications for Militante-Matias, P.J. 1991. Calcareous provenance, paleoenvironment and nannofossil study of the Klondyke Formation paleoclimate at the K/T boundary. section along km posts 278-251, Marcos Sedimentary Geology 197, 127-140. Highway, Baguio City – Pugo, La Union Province, Philippines. Journal of the Geological Society of the Philippines 47, 35- 92.

[2] Dimalanta, C.B. and Yumul, G.P.Jr. 2009. A geochemical approach on the provenance

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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 3. Discrimination diagram from Roser and Korsch (1986) shows the Zigzag Formation samples mostly Figure 2. Binary diagram using K occupying the active continental and Rb to characterize the source margin (ACM) field whereas the other rocks of the Baguio Mineral District samples plot within the oceanic island sedimentary units (Dimalanta and arc (ARC) field. PM is passive margin Yumul, 2009). (Dimalanta and Yumul, 2009).

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Liquefaction potential assessment of Malabon & Navotas cities, Philippines

J.R. Dungca flooding due to typhoons, and during high tides. Furthermore, De La Salle University-Manila these cities became significant to 2401 Taft Ave., Malate, the Philippine government and the Manila, Philippines general public as pertaining to the rate of recurrence and severity of flooding, specifically during Abstract monsoon seasons and events of high tide and due to the developing global warming, and the The geotectonic setting of the substantiation of studies showing Philippines makes it prone to evidences of ground subsidence in various types of seismic related the said areas. hazards. The devastating Luzon earthquake of 1990 is one of the Assessment of liquefaction potential most recent manifestations of this of the Malabon and Navotas was phenomenon and it has also conducted by collecting SPT opened opportunities to better borehole data and evaluating the understand the liquefaction SPT “N” values using the semi- phenomenon. Many areas in the empirical procedures of Idriss and Philippine archipelago including Boulanger (2004) for evaluating Malabon and Navotas are believed liquefaction potential during to have deposits of potentially earthquakes. Thus, the factors for liquefiable sand exist and are safety against liquefaction that was presently used for residential, computed from the assessment commercial or industrial purposes. procedures were analyzed. 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.

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

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Parallelisms between the Bangong- Nujiang in Tibet and the Philippine suture zones

D. Faustino-Eslava 1*, J.A. within and against the island arc Aitchison 2, R.A. Tamayo, Jr. 1, system. Most of these terranes and G.P. Yumul Jr. 1,3 and C.B. the general structural features of Dimalanta 1 the country are generally distributed or oriented parallel to the length of the archipelago and its bounding 1Rushurgent Working Group - Tectonics subduction systems. and Geodynamics Group, National Institute of Geological Sciences, Reconstruction of the Cretaceous College of Science, University of the Asian margin in Tibet suggests a Philippines, Diliman, Quezon City, similar geographic setting to the Philippines 1101 present Southeast and Eastern

Asian region, with several marginal 2Department or Earth Sciences, The University of Hong Kong, Pokfulam basins, some underlain by Road, Hong Kong developed oceanic crusts, while others remain floored by 3Department of Science and continental lithosphere. This Technology, Bicutan, Taguig, Metro presentation discusses these Manila, Philippines parallelisms in the hope of understanding the geodynamic histories of both the more ancient Abstract 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 during the Paleozoic to Mesozoic eras. Major structural features of the plateau run east-west, parallel to the paleo- trenches. 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

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Gravity, seismic refraction and resistivity signatures in Northwest Panay, Philippines: Subsurface imaging of a terrane boundary using geophysical methods

J.A.S. Gabo 1* , C.B. Dimalanta 1, and the Philippine Mobile Belt E.G.L. Ramos 1, L.T. Armada 1, during the Miocene (Yumul et al., K.L. Queaño 2,3 , R.A. Tamayo Jr. 1, 2005; Gabo et al., 2009). The G.P. Yumul Jr. 1,4 , E.J. Marquez 5 boundary between these two and D. Faustino-Eslava 1 terranes is the Nabas Fault, located at the neck of Buruanga Peninsula

(Zamoras et al., 2008). The 1Rushurgent Working Group - Tectonics Northern portion of the Nabas Fault and Geodynamics Group, National is buried beneath Plio-Pleistocene Institute of Geological Sciences, and Quaternary sediments. College of Science, University of the Philippines, Diliman, Quezon City, To investigate this terrane Philippines 1101 boundary in Northwest Panay,

2 gravity, seismic refraction and Mines and Geosciences Bureau – resistivity surveys were conducted. Central Office, Department of The gravity method results show Environment and Natural Resources, North Avenue, Diliman, Quezon City, that the Buruanga Peninsula exhibit Philippines 1101 higher gravity anomaly values than the rocks from the Range. 3Earth and Materials Science and This change in gravity anomaly Engineering Department, Mapua values can be observed to occur at Institute of Technology, Intramuros, the neck of the peninsula, where Manila the Nabas Fault is located. There is a sudden drop in the gravity 4 Department of Science and anomaly values at the location of Technology, Bicutan, Taguig, Metro the Nabas Fault. The shallow Manila, Philippines seismic refraction and resistivity 5University of the Philippines, Padre surveys conducted at the neck of Faura, Manila, Philippines the Buruanga Peninsula agree with the gravity data. Modeling of the geophysical data shows that there Abstract is a sudden decrease in density and resistivity in the area between the Buruanga Peninsula and the Northwest Panay is composed of Antique Range terranes. Even two terranes: the Buruanga though it is covered with thick Peninsula and the northern portion alluvial deposits, the area at the of the Antique Range (McCabe et neck of Buruanga Peninsula al., 1982; Tamayo et al., 2001). consistently shows a sudden These two terranes are believed to decrease in gravity, density and be affected by the collision between resistivity values in the geophysical the Palawan Microcontinental Block survey results. These results are

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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 east- verging 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, 325- 329. [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.

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Holocene coral reef development and sea- level rise of northwestern Luzon, Philippines

S.-Y. Gong 1, F.P. Siringan 2, C.-C. (2) bioclastic facies, (3) clayey Shen 3, K. Lin 3 and C.-F. Dai 4 facies and (4) tuffaceous facies.

1Department of Geology, National The ages of fossil corals vary from Museum of Natural Science, Taichung, 6,588 ± 27 ya at 1.4 m below the Taiwan ROC PSL to 9,855 ± 42 ya at 22 m

2 below PSL. Results of this study Marine Science Institute, University of show that the minimum sea level, Philippines, Quezon City, Philippines relative to the western Luzon coast, 3Department of Geosciences, National was about 25m below PSL when Taiwan University, Taipei, Taiwan ROC reef started about 9.9 ka. During 9.2-8.2 ka, reef accretion rate was 4Institute of Oceanography, National as high as 13 m/ky. A reef Taiwan University, Taipei, Taiwan ROC backstepping that likely resulted from rapid sea-level rise took place about 8-7 ka. Sea level then rose to Abstract near PSL at about 6,862 ± 28 ya before the reef was uplifted by tectonics. The sea-level curve of Holocene coral reefs occurred is generally similar to that extensively along the west coasts of of the Western Australia coast but Luzon. During the reef about 10 m higher than that of development, the eustatic sea level Tahiti at about 9.9 ka. 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,

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Geohazard of submarine landslides in the northern South China Sea

S.-K. Hsu, K.-T. Chen, C.-Y. Ku, and bathymetric slopes. In the Y.-C. Yeh and C.-H. Tsai northern South China Sea, the deposits of submarine landslides Institute of Geophysics, National (mass transported deposits, MTD) Central University, Chung-Li 32001, are distributed at foots of Taiwan continental margins, canyon channels or foots of seamounts. The MTD is generally displayed in Abstract terms of acoustic transparency in seismic profiles. As evidenced by the violent cable breaks happened Large and fast-moving turbidity in the case of the 2006 Pingtung currents can incise and erode earthquakes, the destructive power continental margins and cause of turbidity current to underwater damage to artificial structures such facilities is clearly underestimated. 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

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East Luzon Trough: An inactive subduction zone

A.M.F. Lagmay, R. Peña, M.A. Trough make it different from Aurelio and M.L.G. Tejada normal subduction zones.

National Institute of Geological • A review of the seismicity Sciences, University of the Philippines, along the East Luzon Trough Diliman, Quezon City, 1101 Philippines reveals that it lacks the deep seismicity exhibited by subduction related to Abstract trenches. • Absence of Late Neogene magmatism along the The East Luzon Trough is an intra- northern Sierra Madre Range plate depression separated from related to subduction. the by the E-W • Undeformed marine sinistral Polillo Fault. It is flanked to sedimentary carapace over the east by the . crumpled sediments in the Unlike the Philippine Trench, the accretionary prism East Luzon Trough is not a well- • GPS measurements indicate defined steep depression, which that the West Philippine broadens further into a domal-like Basin in the region of structure at about 16˚N latitude Benham Rise moves in and disappears northeastward. At lockstep with Northern first glance, the East Luzon trough Luzon. appears to be a continuation of the Philippine Trench, but being The accretion of Benham Rise to shallower and without a well- the eastern seaboard of northern defined Wadati-Benioff Zone, it is Luzon has led to a reorganization of believed to be a nascent subduction the boundary of the zone. The presence of an inactive Plate. In accordance with the accretionary prism to the west of tectonic map of Bird (2003), the the trough indicates the existence tectonic deformation zone of an ancient subduction zone that constituting northern Luzon has has since become inactive. The become a plate boundary zone with collision of Benham Rise with the respect to the Eurasian Plate. 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

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Re-visit the West Philippine Basin after 1/4 century

C.-S. Lee spreading rate and the over-lapping spreading centers in the north of Institute of Applied Geosciences, West Philippine Basin, resembling National Taiwan Ocean University, to that of the East Pacific Rise Keelung, 202 Taiwan today. The estimated age is very close to the 45 ma major change of the motion. How are Abstract the plates evolved? What are the responses of the deep crust? Is this In mid-1980, the evolution of West will impact our understanding of Philippine Basin was one of the the modern ? In our interesting, but also a controversial detail bathymetry survey, we also tectonic problem. This is due to: (1) begin to realize that the Eocene the basin is one the largest West Philippine Basin is covered marginal basin in the world, (2) the with a lot of today-inactive available data at that time showed submarine volcanoes. Because of that this is either a normal ocean being at the 5000 – 6000 m deep basin or a back-arc basin, (3) the sea environment, the sedimentation basin is remote from the major land rate is probably very low; area and is not so easy to conduct therefore, the volcanic summits are the marine research, and (4) the clearly exposed. The West area is on the major track of the Philippine Basin is one of the well- typhoon and the planned survey known big tuna fishing ground. Is could be easily altered. For these the volcano taken by the tuna as reasons, the existing dataset is like their favorite dwelling? The deep- a puzzle and the scientific debit is sea ROV surveys also show the continuing, even up to today. In the thick manganese crust and a high last 1/4 century, particularly in the density of the manganese nodules. last 10 years, under the Can the volcanic summits and encouragement of United Nations manganese crust become our Law of the Sea Convention, every future deep resources? Our neighboring country (including understanding of the deep sea is China, Japan, Philippine, Palau, and believed just at begin. 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

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A summary of geochemical study on Taal Lake system: Searching proxies for detecting of Taal volcano eruption

H.-C. Li 1, X. Xu 2, D.-R. Wen 1, N.- from water depths of 15m and J. Wan 1, T.-S. Kuo 1, R.U. Solidum ~100m and one 64-m long drill Jr. 3, J. Sincioco 3, P.K.B. Alanis 3 core from the western shore of Taal and Nora Campita 3 Lake; and sampled a few outcrops of volcanic and lake deposits in the 1Department of Earth Sciences, area. The measured water National Cheng-Kung University, temperatures ranging from 26.5 to Tainan, Taiwan 70101, ROC 29 oC show that the thermal gradient of Taal was very weak 2 Department of Earth System Science, during the late Novembers in 2006 University of California, Irvine, CA and 2007, perhaps due to thermal 92697, USA input from the Taal Volcano Island and bottom of Taal Lake. The 3Philippine Institute of Volcanology and Seismology, Quezon, Philippines 1101 deepest part of Main Crater Lake is 61m with a constant water temperature of 31 oC throughout the Abstract depth.

We have analyzed geochemical Taal Lake is located in properties including concentrations Province of central Philippines of Na, K, Mg, Ca, Al, Fe, Mn, Sr, Ba, (14°0.01'N, 120°59.1'E), with a Co, Ni, Cu, Zn, Pb, As, Ti, Cr, and 18 surface area of 267 km 2, a Cd, and isotopic values of δD, δ O 87 maximum depth of 176 m and an and δ Sr in the water samples. elevation of 3 m above sea level. From these results, we conclude: The lake occupies the famous Taal (1) High concentrations of Na, K, Volcano system which consists of a Mg, Ca, Al, Fe, Mn in geothermal 15 ×22-km prehistoric . The fluid at Taal are from input of 5-km-wide Taal Volcano Island volcanic water, dissolution of which has 47 craters and 4 maars, volcanic rocks, and incursion of lies in the north-central Taal Lake. seawater. However, the major ions With 34 recorded eruptions, Taal are introduced by both seawater Volcano is one of the 16 monitored and geothermal inputs, so that they volcanoes by the Global Volcanism could not be used as index of Network. volcanic activity. (2) Among trace and heavy metal elements, Fe, Mn, During the past 3 years, we have Cu and Zn may be used as conducted several trips to Taal and indicators of volcanic activity. (3) measured water temperatures at Isotopic composition of Taal Lake different stations and depths; bias from MWL indicates mixing of collected water samples from Taal isotopically heavy geothermal fluid Lake, Main Crater Lake, springs, and isotopically light surface input. 18 streams, wells and rains in the Therefore, heavier δ O values of area; taken three gravity cores the lake recorded in the lake

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sediments may reflect increased and δ13 C of the lake goes lighter geothermal fluid caused by volcanic due to dilution effect. The lake activity. (4) δ87 Sr of Taal Lake productivity at this time will be reveals mixing of three end- lower, and carbonate precipitation members including surface runoff, is less. When the lake experiences geothermal fluid and seawater. The less surface water input and/or δ87 Sr value of the geothermal fluid more evaporation, δ18 O and δ13 C of is about 1000ppm lower than that the lake goes heavier due to the of the lake waters. Therefore, δ87 Sr hydrological balance and increased may be a good indicator of volcanic lake productivity. However, when activity. the volcanic activity increases, significant amount of hydrothermal Our most significant study is on a input and deep CO2 input will lead 120-cm long gravity core, Core to increase of lake’s δ18 O and δ13 C. TLS2, retrieved from 15-m water Both carbonate and organic carbon depth of Taal Lake. Sixteen AMS will decrease due to the influence of 14 C dates were made on plant volcanic input. This situation was remains at different layers of the occurred around 1991. However, if core, matching very well with the a volcanic eruption causes bomb 14 C curve determined in tree significant amount of dead carbon rings. The distribution of the bomb from vegetation and organism in 14 C profile allows us to establish the and around the lake, the lake’s δ13 C chronology of the core which yields will be depleted. At the time, the a constant sedimentation rate of δ18 O and δ13 C of the lake goes the 2.04cm/year spanning the past 60 opposite way. The 1965 eruption years. Based on this chronology, may be an example of such a case. living plants around Taal Lake may With the detailed geochemical have a lower initial ∆ 14 C (-30‰) profiles of Core TLS2, we have compared to the Modern Standard. found anomalies of high concentrations of Fe, Mn, Cu, K and For this core, we have measured heavy δ18 O and δ13 C values of TIC pore water content, weight loss by around 1991-1994 when the Taal 0.5NHCl leaching, TOC, TON, δ18 O volcano was active. These proxies and δ13 C of TIC, δ13 C of TOC and may be considered as indicators of δ15 N of TON, and concentrations of geochemically monitoring volcanic Na, K, Mg, Ca, Fe, Mn, Sr, Ba, Cu, activity for long-term prediction. Zn, Pb, Li in the acid-leachable phase. The annual resolution δ18 O and δ13 C 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 δ18 O and δ13 C 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 δ18 O

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Seismic monitoring at Taal Volcano in the Philippines

C,-H. Lin1, R.U. Solidum, Jr. 2, T.- has been low recently, except some M. Chang 3 and B.C. Bautista 2 seismic swarms in Aug. and Sept. 2008. In addition to the 1Institute of Earth Sciences, Academia continuation of seismic monitoring Sinica, Taipei, Taiwan at Taal volcano, we will carefully examine the seismic data for 2 Philippine Institute of Volcanology and finding any volcanic earthquakes or Seismology, Quezon, Philippines 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 short- period 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 long- period tremors. Some micro- earthquakes have been detected from the continuous seismic data at the seismic network. The preliminary results show the seismicity at the Taal volcanic area

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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. impacts of extreme events, Servando mitigating factors are being initiated and continuously being Philippine Atmospheric, Geophysical improved by the Philippine and Astronomical Services Atmospheric, Geophysical and Administration, Department of Science Astronomical Services and Technology, Quezon City, Administration (PAGASA), which Philippines include the seasonal climate forecast (SCF).

Abstract This paper will illustrate the different impacts of ENSO events in the country, its monitoring, The highest rainfall variability in the prediction and the ways of coping Philippines was well documented with the negative effects, and is greatly associated with the identifying the challenge of bringing ENSO events which exhibited two the understanding of the climate phases, the El Niño (warm) and La science that can be used in risk Niña (cold). The El Niño conditions management. 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.

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

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Utilizing calcareous nannofossils as paleoproductivity proxies in Sea core sediments

A.M. Peleo-Alampay 1, D.N. productivity site, Core MC10 is Tangunan 1, F.P. Siringan 2, R. located closer to the coast of Maneja 2, J.L. Soria 2 and Z. Liu 3 Zamboanga Peninsula at 8°23.10’N, 122°09.15’E and 4022m water 1National Institute of Geological depth while Core MC8 is located in Sciences, College of Science, University the central portion of the sub-basin of the Philippines, Diliman, Quezon at 8°38.97’N, 121°31.83’E and City, Philippines 4492m water depth.

2 Marine Science Institute, University of A distinct difference in the the Philippines, Diliman, Quezon City, distribution of total nannofossils is Philippines apparent from the two cores studied. Nannofossil abundance 6 Abstract was very low (1-16 x 10 liths/ gram sediment) to zero in most of

the sample intervals in the top ~38 Calcareous nannoplanktons cm of Core MC 8-8. Abundances (coccolithophores) are marine start to increase at 38-39 cm depth haptophyte algae which thrive in (1920±30 years). In the other core the photic zone. These organisms (MC 10-3), nannofossils are present are sensitive to changes in the throughout, ranging from 207-626 temperature, water movement, 6 x 10 liths/ gram sediment, except salinity and chemistry of the for a sharp excursion at 25 cm surface waters of the ocean. Their 6 depth yielding only 75 x 10 liths/ calcareous skeletons are important gram sediment. This may reflect contributors to the deep sea differences in nannofossil sediments, making them valuable productivity, consistent with recorders of variations in climate chlorophyll data today. Sandy silt and sedimentation. This research horizons in Core MC10-3 generally aims to use calcareous nannofossils yielded more nannofossils. from core sediments to determine productivity changes in The nannofossil assemblages from through time. both cores are of relatively lower diversity typical of restricted This study investigates calcareous marginal sea assemblages and nannofossils from two sediment dominated by three (3) species. cores collected from the Sulu Sea in This type of assemblage is southwestern Philippines during prevalent on the eastern and Philex cruise Leg 2 onboard R/V western coasts of the South China Melville in December 2007. These Sea. In both cores, Gephyrocapsa two core sites from the oceanica, G. ericsonii and southeastern Sulu Sea subbasin Florisphaera profunda have the were chosen for their difference in highest abundances downcore. productivity based on present-day Umbilicosphaera sibogae and chlorophyll data. The high

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Calcidiscus leptoporus , the next interrupted by the sudden low at 25 most abundant taxa in Core MC10- cm (~1000-1100 years ago). This 3 comprise less than 10% of the abrupt decrease which seemed to total nannofossils. affect most of the coccolithophorid record in the basin ( F. profunda In Core MC 8-8, F. profunda included) can be interpreted as a abundance increases from the dissolution signal owing to the bottom of the core, reaching its shallowing of the CCD or an peak at 44cm. Thereafter the increase in the terrigenous input counts start to decline until it into the basin from erosional reaches a steady low at 38 cm processes onland. This latter (1920 ± 30 years) continuing up to phenomenon can be seen to some present time. The high F. profunda extent in slightly higher Al 2O3 and at the lower portion of the core is TiO 2 and Y values together with joined by equally high amounts of total organic carbon. G. oceanica .

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 non- upwelling (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

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Geochemical heterogeneity of volcanic rocks from the Fragante Formation, Northwest Panay, Central Philippines

A.dC. Perez 1, D.V. Faustino- integration, (3) conduct of field Eslava 1, J.A.S. Gabo 1, G.P. Yumul survey, (4) generation of geohazard Jr. 1,2 , R.A. Tamayo Jr. 1, K.L. maps, and (5) conduct of Queaño 1,3 , C.B. Dimalanta 1 and information and education L.T. Armada 1 campaign (IEC), including installation of warning signages. To

date, a total of 1348 municipalities 1Rushurgent Working Group-Tectonics and Geodynamics Group, National have been assessed and 311, Institute of Geological Sciences, 1:50,000 landslide and flood College of Science, University of the susceptibility maps have been Philippines, Diliman, Quezon City, produced. The MGB has also Philippines assessed 2,383 line kilometers of coastal areas in the country. 2 Department of Science and Technology, Bicutan, Taguig City, Although the efforts of the MGB- Philippines DENR and other government

agencies have helped significantly 3Lands Geological Survey Division, Mines and Geosciences Bureau-DENR, in strengthening the country’s North Avenue, Quezon City capacity in minimizing and mitigating the impacts of natural hazards, recent events still indicate Abstract some lapses particularly in the implementation by the local government of the Following a major landslide incident recommendations set forth by the in Guinsaugon, in said agencies. These events include Central Philippines, the Mines and the landslides in , Benguet in Geosciences Bureau-Department of northern Luzon and in Maco, Environment and Natural Resources Compostela Valley in eastern (MGB-DENR) immediately set out Mindanao, both events occurring in to rationalize and speed up the September 2008. More recently, a implementation of the National flashflood occurred in August 2009 Geohazards Mapping and in Botolan, that wiped Assessment Program. This program out several communities. These intends to adequately and examples clearly demonstrate the comprehensively address and consequences when information mitigate the possible effects or and recommendations pertaining to impacts of geological hazards, disaster preparedness and particularly landslide, flood and mitigation are not taken seriously. coastal erosion. The program has five components namely: (1) capacity building, 2) data acquisition, generation and

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Geohazard mapping in the Philippines: The Mines and Geosciences Bureau experience

K.L. Queaño Although the efforts of the MGB- DENR and other government Lands Geological Survey Division, agencies have helped significantly Mines and Geosciences Bureau-DENR, in strengthening the country’s North Avenue, Quezon City capacity in minimizing and mitigating the impacts of natural hazards, recent events still indicate Abstract some lapses particularly in the implementation by the local government of the Following a major landslide incident recommendations set forth by the in Guinsaugon, Southern Leyte in said agencies. These events include Central Philippines, the Mines and the landslides in Itogon, Benguet in Geosciences Bureau-Department of northern Luzon and in Maco, Environment and Natural Resources Compostela Valley in eastern (MGB-DENR) immediately set out Mindanao, both events occurring in to rationalize and speed up the September 2008. More recently, a implementation of the National flashflood occurred in August 2009 Geohazards Mapping and in Botolan, Zambales that wiped Assessment Program. This program out several communities. These intends to adequately and examples clearly demonstrate the comprehensively address and consequences when information mitigate the possible effects or and recommendations pertaining to impacts of geological hazards, disaster preparedness and particularly landslide, flood and mitigation are not taken seriously. 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.

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Continuous monitoring along the Valley Fault, the Philippines

R.-J. Rau 1, Y.-P. Wen 1, H.-K. 2008. With the ~one year GPS Hung 1, T.C. Bacolcol 2, P.K.B. continuous monitoring, we shall Alanis 2 and R.M. Lumbang 2 present the GPS results and the inferred mode of crustal 1Department of Earth Sciences, deformation of the Valley Fault National Cheng Kung University, system in the meeting. Tainan, Taiwan

2Philippine Institute of Volcanology and 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 single- frequency GPS stations along the Valley Fault system since April,

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Late Holocene sediment facies and relative sea-level changes along the - Angat delta, Northern Manila Bay

J.L.A. Soria 1, F.P. Siringan 2, Y. shallowing upward sequence. The Yokoyama 3 and K.S. Rodolfo 4 ages of the parasequences correspond to the timing of relative 1Marine Science Institute, University of stillstands in the reconstructed the Philippines, Diliman, Quezon City, regional fluctuations of sea level Philippines 1101 from rocky coastlines in the Philippines. Faulting also plays a 2Marine Science Institute, University of role in delta evolution. Relative the Philippines, Diliman, Quezon City, vertical motions across the Lubao Philippines 1101 Lineament, which could be as much as 3.5 meters over the past 1,500 3 Ocean Research Institute, University of Tokyo, 1-15-1 Minami-dai, yBP, helped maintain the position of Tokyo 164-8639 , Japan the wetland and dryland boundary along the western margin of the 4Department of Earth and delta plain. Aside from faulting, Environmental Sciences, University of natural sediment compaction also Illinois at Chicago, IL, USA contributes to subsidence. In recent years, however, anthropogenic activities such as excessive Abstract groundwater extraction have enhanced subsidence contributing greatly to delta-wide worsening Paleo-environmental changes along floods. 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

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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 .

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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.

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Disaster risk management using sensors: Early warning systems for landslides, slope failures and debris flow

M.C. Talampas 1, J.J. Marciano version of the Casagrande type Jr. 2, S.G. Catane 3 and M.A.H. piezometer is also integrated into Zarco 4 the sensor column for purposes of measuring excess pore water 1Instrumentation Robotics and Control pressure. Measurements taken in Laboratory, Institute of Electrical and each segment are accessed via the Electronics Engineering, University of Controller Area Network (CAN) the Philippines Diliman, Quezon City communications protocol. The 1101 sensor column and piezometer are capable of communicating 2 Instrumentation Robotics and Control wirelessly with a central based Laboratory, Institute of Electrical and station via a Wireless Fidelity Electronics Engineering, University of (WIFI) link. Data is collected the Philippines Diliman, Quezon City 1101 stored, process and displayed via the Python based GUI on the base 3National Institute of Geological station. Sciences, University of the Philippines Diliman, Quezon City 1101 The sensor column and piezometer is tested on laboratory bench -scale 4Geotechnical Engineering Group, landslide box. Tests are performed Institute of Civil Engineering, on slopes built from cohesionless University of the Philippines Diliman, material under steady state Quezon City 1101 seepage conditions. A mathematical model assuming a Mohr -Coulomb Abstract elasto -plastic type material is developed. The resulting coupled

unconfined fluid flow and limit A system consisting of alternation equilibrium problem is solved using instrumentation for monitoring the finite element method. Results slope deformation and piezometric of the experiments show close water level was designed and agreement with deformation developed as an early warning patterns and failure mechanism system for landslides, slope failures predicted by the model. 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

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Crustal growth and mantle source evolution in the Philippines

M.L.G. Tejada eastern side of the island. The western margin of the island is National Institute of Geological currently being modified by active Sciences, University of the Philippines, subduction and collision with the Diliman, Quezon City, Philippines 1101 Eurasian margin. As a result, the geochemical signatures of igneous rocks suggest that local processes Abstract tend to modify the nature of this pre-existing mantle as a result of changing tectonic setting and The present location of the subduction recycling of materials Philippine archipelago along a from previously rifted fragment of complex boundary among three the Eurasian margin. 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.

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

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Low temperature thermochronology of Buruanga Peninsula, Panay Island, Central Philippines

M. Walia 1, T.F. Yang 1, T.K. Liu 1, hornblende to obtain ages over a L.S. Teng 1, W.M. Yuan 2, G.P. range of closure temperatures of 3,4 4 about 110°C to 510±50°C. The age Yumul Jr. and C.B. Dimalanta data suggest two consecutive

1 tectonic events at 9-12 Ma and 16- Department of Geosciences, National 17 Ma that resulted in the Taiwan University, Taipei, Taiwan exhumation of rocks. This

2 exhumation may be related to the China University of Geosciences, collision events. Due to different Beijing, 100083, China closure temperatures of the FT and 40 Ar/ 39 Ar systems it is possible to 3 Department of Science and recognize both Cenozoic and Technology, Bicutan, Taguig, Metro Mesozoic tectonic events in the Manila area. Furthermore, these ages can be used to define the intrusion time 4 National Institute of Geological of the diorite besides giving an Sciences, University of the Philippines, estimate of the timing of arc- Diliman, Quezon City, Philippines continent 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 40 Ar/ 39 Ar 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 40 Ar/ 39 Ar dates of biotite and

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Middle Pliocene El Niño events recorded in fossil corals of the Tartaro Formation, Province of Bulacan, , Philippines

T. Watanabe 1, A. Suzuki 2, T. controversial in previous records of Kase 3, S. Minobe 1, Y. Maac- the PWP is the role of El Niño- Aguilar 4, K. Kameo 5, K. Southern Oscillation (ENSO) in the Minoshima 2, R. Wani 3 and H. greenhouse warming due to lack of Kawahata 6 information about seasonal to inter- annual variability of sea surface 1Hokkaido University, Japan water in low latitude regions.

2Agency of Industrial Science and In the Philippines, well-preserved Technology, Japan Middle Pliocene (3.5-3.8 Ma) coral fossils discovered from Madlum 3National Science Museum, Japan River, central Luzon provided 35- years coral oxygen isotopic 4 Mines and Geosciences Bureau, evidences with monthly resolutions. Department of Environment and These fossils were collected from Natural Resources, Philippines muddy sand layers of the Tartaro 5Chiba University, Japan Formation exposed along the Madlum River in the vicinity of 6University of Tokyo, Japan barrios Tartaro and Sibul, San Miguel, province of Bulacan. Based from associated fossil contents and Abstract sedimentary features, the corals are inferred to be part of a coral mound deposited in an intertidal to In the study of future climates, the subtidal setting. The Porites coral Middle Pliocene Warm Period (PWP) blocks from Tartaro were sliced into can be an analog for the impending slabs and X-rayed to observe the global warming. This period is density of growth banding. characterized by significantly warm Powdered microsamples from each climate with high global surface band were processed for isotope temperature ranging from 3 ° to 5 °C analysis. Results of these analyses higher than today. Attested by showed several significant many paleoclimate archives and attenuations of seasonal amplitude several climate model studies, this in the 18 O/ 16 O ratios of PWP coral time slice is rather preferred in record which were also detected in simulating future climate because recent corals during modern El Niño many conditions that prevailed events. These findings suggest during that time matches well with that east-western movements of modern values. Also, continents the Western Pacific Warm Pool then were virtually in the same (WPWP) were active that caused geographic positions and the living ENSO events during the warm flora and fauna are still extant. period. The average sea surface One thing that remains temperatures in Luzon during that

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time records to about 2-4°C higher than today. Results of analysis also indicate that the corals are not calcified during ENSO periods.

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Plate boundary geometry of the northern Manila Trench: Inference from seismic and bathymetric data

Y.-C. Yeh and S.-K. Hsu could be one of the key role that cause the change of the Manila Institute of Geophysics, National Trench orientation from NE-SW to Central University, Chung-Li, Taiwan NW-SE.

Abstract

The Manila Trench marks as the plate boundary that western 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

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A dislocation model for crustal deformation along the fault system in Luzon

S.-B. Yu 1, Y.-J. Hsu 1, C.-C. Yang 2, the interseismic velocity field in the T. Bacolcol 3 and R.U. Solidum 3 Luzon region is derived by utilizing QOCA software. The velocity field in 1Institute of Earth Sciences, Academia the Luzon region gradually Sinica, Taipei, Taiwan increases from south to north with respect to the Eurasia plate. The 2Institute of Geophysics, National velocity vectors to the west of the Central University, Taoyuan, Taiwan Philippine Fault range from 44 to 59 mm/yr, while that to the east of the 3 Philippine Institute of Volcanology and fault are from 59 to 79 mm/yr. The Seismology, Quezon City, Philippines azimuths of velocity vectors range from 285° to 314°. This indicates Abstract that there is significant internal deformation in the Luzon Arc.

Based on the GPS observed 1996- The Philippine Fault system is a 2008 velocity field in the Luzon result of the oblique convergence region and using the interseismic between the Philippine Sea plate crustal deformation model of and the Sundaland Block/Eurasia Matsu’ura et al. (1986), we invert plate. It is a left-lateral strike slip for the fault geometry parameters fault that trends in N 30°- 40°W and fault slip rates of the Philippine and transects the Philippine Fault. The fault dip and width are archipelago from the northwest fixed to be 89° and 30 km, corner of Luzon to the southeast respectively. The inverted results end of Mindanao for about 1200 indicate that the average left-lateral km. For studying crustal strike-slip rate of southern segment deformation along the Philippine is 20.6 mm/yr, and northern Fault system, eight GPS surveys segment is 32 mm/yr. The block were conducted from 1996 to 2008 motion is 31 (95% confidence interval, 23~35) mm/yr with in the Luzon region through a joint effort by the Institute of Earth azimuth of 332° (323°~341°). Sciences, Academia Sinica and the Because the density and aperture Philippine Institute of Volcanology of the current GPS array are and Seismology. Summing up the insufficient, it is not able to 12-year survey-mode GPS data in successfully detect crustal the Luzon region and continuous deformation of the entire fault GPS data in Taiwan, along with system and strain partition between other 14 IGS sites in the Asia- the branch faults. Pacific region, we use the

GAMIT/GLOBK software to calculate the coordinates of each site and obtain the GPS time series. Then

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Climate change adaptation in the Philippine context

G.P. Yumul Jr. 1, 2 , C.B. nature of the Philippines and being Dimalanta 1, N.T. Servando 3 and a very minor emitter of greenhouse N.A. Cruz 3 gases, adaptation is the Government’s national policy. 1National Institute of Geological Measures involving both disaster Sciences, University of the Philippines, risk management and climate Diliman, Quezon City, Philippines change adaptation are being implemented especially in the 2 Department of Science and community level. This is with the Technology, Bicutan, Taguig City, end in view of mainstreaming both Philippines disaster risk management and 4Philippine Atmospheric, Geophysical climate change adaptation in a and Astronomical Services changing climate regime. Administration, Department of Science and Technology, PAGASA Science The progress that are being Garden, BIR Road, Quezon City, achieved, the issues and challenges Philippines 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 .

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Paleoclimatic implications of Late Cretaceous planktonic foraminifera from the mid-latitude ODP holes 758A, 761B and 762C, Indian Ocean

M.A. Zepeda 1,2 (late Santonian to early Campanian) suggests a relatively 1Department of Earth and Materials warm paleoclimate as evidenced Science and Engineering, Mapua by: an abundance of Tethyan and Institute of Technology, Intramuros, warm indices; high species diversity Manila, Philippines and equitability; and high positive

values in the paleoclimatic curves. 2Paleontolgy Unit/PETROLAB, Lands Geological Survey Division, Mines and Interval 2 (late Campanian to Geosciences Bureau, North Avenue, middle Maastrichtian) indicates Diliman, Quezon City, Philippines warm and cool fluctuations as depicted by: the mixture of Tethyan and Austral species within the Abstract Transitional realm; varying abundances of warm and cool water species; fluctuations in the species A detailed biostratigraphic and diversity, equitability and climatic statistical analysis of faunal curve values, with a pronounced assemblage of Ocean Drilling negative peak during the latest Program (ODP) sites from the mid- Campanian. This peak represents latitude showed great variability the coolest interval of the late and instability in the paleoclimatic Santonian to Maastrichtian as conditions in the Indian Ocean reflected by the preponderance of during the late Cretaceous (late cool indices; low species diversity Santonian to Maastrichtian). and equitability and high negative values in the paleoclimatic curve. Faunal composition, species Interval 3 (late Maastrichtian) diversity and equitability, species marked another warm interval due distribution, ratios of climatic index to: a shift in the dominance of cool species and paleoclimatic curves indices to warm indices; high were used to deduce paleoclimatic diversity and equitability; and high conditions. The paleoclimatic positive values in the paleoclimatic curves constructed showed curve. Such results imply that particularly striking and similar paleoclimatic conditions in the trends for most of the sites studied. Indian Ocean during the late Santonian to Maastrichtian are very Three paleoclimatic intervals unstable. This instability could be namely, Interval 1 (late Santonian attributed to an interplay of several to early Campanian), Interval 2 geologic and tectonic events (i.e. (late Campanian to middle break of the southern Maastrichtian), and Interval 3 (late Gondwanaland continents, seafloor Maastrichtian) can be identified in spreading and subsidence between the paleoclimatic curves. Interval 1 Antarctica, Australia and New

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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.

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