Subduction Zone Coupling and Strain Partitioning in the Philippine Plate Boundary Zone

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This pilot research project seeks to examine active tectonic processes in a complex, subduction-dominated plate boundary zone in the Philippines island arc through analysis of the surface deformation field using high-precision GPS measurements. The project takes advantage of a newly available suite of data from a 240-station network of continuous and campaign GPS sites in the Philippine plate boundary zone, collected by the Philippine Institute of Volcanology and Seismology (PHIVOLCS), together with international collaborators. The project builds on a successful research collaboration between Indiana University, PHIVOLCS, and two research institutes in Taiwan. The work will focus on (1) improvement of regional plate motion and intraplate deformation models for the Philippine island arc; (2) evaluation of strain partitioning between subduction-related compression and intra-arc shear deformation in Luzon, including assessment of post-seismic transient effects associated with the large (Mw 7.7) 1990 Luzon earthquake; and (3) assessment of spatially variable subduction zone coupling along the Manila and Philippine trenches and its impact on earthquake potential. This proposal seeks to extend and expand the ongoing studies in Luzon through analysis of existing crustal deformation data, in collaboration with Philippine and Taiwanese counterparts. Tasks include (1) extending kinematic modeling of elastic block interaction to include the entire Philippine archipelago; (2) developing 3-D deforming block models of fault-related deformation at the Philippine Fault and interaction with subduction boundaries; and (3) examining spatially variable coupling along the Manila and Philippine subduction zones through dynamic modeling of subduction-zone creeping and locked segments. The expected models of plate boundary earthquake potential can be used as input for ground-motion and tsunami-generation models.This project has significant societal impacts in the form of improved methods for detecting fault-related deformation and subduction-zone activity in active plate boundary zones. In particular, these observations will provide critical information for assessment of long-term seismic hazards for the Philippines.PHIVOLCS and other Philippine collaborators provides an avenue for technology transfer to colleagues in the developing world. Because of the large population at risk from future earthquakes and related secondary effects, the research conducted as part of this project could have significant impacts in hazard mitigation for the Philippines. The project would provide support for students at Indiana University and ongoing science outreach activities.