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Journal Articles - UP - MSI

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    Geomorphological and sedimentological records of recent storms on a volcaniclastic coast in Bicol, Philippines
    Soria, Janneli Lea A.; Switzer, Adam D.; Pile, Jeremy; Siringan, Fernando P.; Brill, Dominik; Daag, Arturo (Elsevier, 2021-08-01)
    Typhoon Durian in November 2006 was most notable for a series of devastating lahars that buried communities at the base of Mayon volcano in Bicol, Philippines. Typhoon Durian delivered extreme rainfall that remobilized volcanic debris that caused more than ~1200 deaths and extensive property damage. Although not as deadly as the lahar, Typhoon Durian also generated a storm surge that caused localized dune breaching on Malinao barrier sand spit in Lagonoy Gulf. In the absence of instrumental data of the storm surge, we used the geomorphical and sedimentary imprints including erosion scarps, washover fans and terraces to infer the inundation heights on the barrier spit. The surface elevations of washover fans, terraces and relic dunes indicate inundation heights above 1.5 m but not exceeding 3 m. Typhoon Durian's overwash deposit is characterized by typical washover fan stratigraphy, and exhibits horizontal to sub-horizontal lamination on the front to mid-fan and foreset stratification near the fan terminus. Subsurface stratigraphy using shore-normal ground penetrating radar (GPR) imaging reveals at least two buried erosional surfaces farther inland from the erosional surface of Typhoon Durian. Similar to Durian, the older erosional surfaces were probably sustained from previous typhoons. We infer that episodic erosional events most likely have repeatedly disrupted the prograding development of the Malinao barrier spit. Typhoon Durian highlights the exposure of volcanic landscapes to multiple hazards from cyclone landfall.
    This work comprises Earth Observatory of Singapore contribution no. 169. This research is supported by the Singapore National Research Foundation fellowship scheme (Grant No: NRF-RF2010-04) and the Singapore Ministry of Education under the Research Centres of Excellence initiative. This paper is a contribution to IGCP Project 639 Sea-Level Changes from Minutes to Millennia. We thank German Gonzaga of the Malinao Local Government Unit who facilitated our access to the study site. We also appreciate Cabria family for being our hospitable host during the series of field campaigns. We thank Mr. Raul Capistrano on behalf of NAMRIA for providing tide gauge data, and the Mines and Geosciences Bureau for granting us permit to transport sediments. We are grateful to Joan Reotita, Ronald Lloren, Yo Muan, Lester Valle, Arlene Tengonciang, Mabelline Cahulogan, Ariel Malonda, Antonio Ceres and Elmer Cas for their generous help in collecting field data.
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    Seafloor structures and static stress changes associated with two recent earthquakes in offshore southern Batangas, Philippines
    Sarmiento, Keanu Jershon S.; Aurelio, Mario A.; Flores, Paul Caesar M.; Carrillo, Anne Drew V.; Marfito, Bryan J.; Abigania, Maria Isabel T.; Daag, Arturo S.; Siringan, Fernando P. (Frontiers Media SA, 2022-02-02)
    The 1994 Mw 7.1 Mindoro Earthquake and the 2017 Mw 5.9 Batangas Earthquake Sequence both occurred in offshore southern Batangas and devastated southern Luzon and Mindoro. These earthquakes exhibited NW-striking right-lateral slip in an area presumably defined by a WNW-striking left-lateral fault, therefore implying the existence of previously unmapped offshore faults. High resolution multibeam bathymetry grid and subbottom profiles revealed a conjugate strike-slip fault system under an approximately EW-directed extension. NW-striking right-lateral faults (F1 Faults: Central Mindoro Fault, Aglubang River Fault, and Batangas Bay Fault System) bound the western part of the study area. On the other hand, a series of almost parallel NE-trending left-lateral and normal faults (F2 Faults: Macolod Corridor, North Verde Fault System, Central Verde Fault System, South Verde Fault, and Northeast Mindoro Fault System) approach the F1 faults from the northeast. The distribution of the 1994 and 2017 earthquakes suggests that the possible rupture areas for these events are the Aglubang River Fault and the southwest Batangas Bay Fault System, respectively. These two traces appear to be connected and a restraining bend is suggested to have acted as a rupture barrier between the two events. Coulomb stress transfer modeling showed that the 1994 earthquake promoted the failure of the 2017 earthquake. Furthermore, results from the stress transfer models showed stress increase on the F1 faults (Batangas Bay Fault System and Central Mindoro Fault) and the northern F2 faults (North Verde Fault System and Central Verde Fault System). The newly recognized faults redefine the knowledge of the neotectonic structure of the area but are still consistent with the ongoing east-west extension in southern Luzon and the overall extension in northern Central Philippines. These faults pose seismic hazards, and more studies are needed to determine their seismogenic potential.
    The authors would like to thank the National Mapping and Resource Information Authority (NAMRIA) for generously providing the multibeam bathymetry data and the Department of Science and Technology - Philippine Institute of Volcanology and Seismology for providing the earthquake catalog. The research party and the ship crew of M/Y Panata of the University of the Philippines Marine Science Institute is also thanked for their assistance in data collection during the research cruise in Verde Island Passage last July 2019. The authors are very much grateful to editor GR and reviewers YL and WF for providing valuable comments that greatly improved this manuscript. Topography data is from JAXA ALOS World 3D–30 m (AW3D30) DEM (https://www.eorc.jaxa.jp/ALOS/en/aw3d30/index.htm) while global bathymetry is from the GEBCO_2020 grid (https://www.gebco.net/data_and_products/gridded_bathymetry_data/). Focal mechanism solutions were obtained from Harvard GCMT (https://www.globalcmt.org/).
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    Shallow structures, interactions, and recurrent vertical motions of active faults in Lingayen Gulf, Philippines
    Flores, Paul Caesar M.; Siringan, Fernando P.; Mateo, Zenon Richard P.; Marfito, Bryan J.; Sarmiento, Keanu Jershon S.; Abigania, Maria Isabel T.; Daag, Arturo S.; Maac-Aguilar, Yolanda (Elsevier, 2023-06-01)
    The surface trace of the East Zambales Fault (EZF) and its associated faults in the Lingayen Gulf have been previously mapped but no other characteristics were reported. This study utilized seismic reflection, multi-beam bathymetry, and side scan sonar to characterize the offshore EZF in terms of magnitudes of vertical displacement. Sequence stratigraphy and radiocarbon dates provided age constraints on the recurrence interval within the Holocene. The EZF extends for ∼ 57 km into the gulf, follows a north-northwest trend, and bounds the karstic terrane (west) and fluvio-deltaic deposits (east). Sinistral motion is indicated by: 1) normal and reverse drag geometries, 2) reversal in the sense of throw with depth, 3) flower structure, and 4) right-stepping and the uplift of a pressure ridge named Pudoc Bathymetric High. The Central Lingayen Gulf Fault (CLGF), to the east of EZF, follows the same trend. The Lingayen Gulf Transverse Fault (LGTF), oriented east–west, forms a flower structure with the CLGF. The EZF, CLGF, and LGTF combined form the Lingayen Gulf Fault System, which divides the gulf into five fault blocks where uplift and subsidence locally occurred. A paleo-delta at −60 m yielded an age of 6.8 kyBP, indicating it was formed during the first Holocene highstand. With natural compaction considered, fault-associated subsidence of 46–53 m may have occurred. The average Holocene vertical displacement is 2.1–2.2 m, which translates to a recurrence interval of 320–270 years for the fault system. The faults can likely generate earthquakes with magnitudes 7.5 (EZF), 6.7 (CLGF), and 6.6 (LGTF).
    This work was supported by grants to F. P. Siringan by the Department of Science and Technology – Philippine Council for Industry, Energy and Emerging Technology Research and Development through the Mapping of Active Offshore Faults for Resilient Coasts Project; and the Department of Environment and Natural Resources – Biodiversity Management Bureau through the Coral Reef Visualization and Assessment - Deep Coral Mapping Project. We are thankful to Deo Carlo Llamas for the meaningful discussions about the current knowledge of the East Zambales Fault. We also thank the anonymous reviewers who provided significant insights for the improvement of this manuscript.