The Relationship Between Seismic and Aseismic Slip on the Creeping Segment of the Philippine Fault: Insight to Earthquake Recurrence and Fault Mechanics
Session: Effects and Uses of Aseismic Deformation and Fault Creep in Seismic Hazard and Warning
Type: Oral
Date: 4/20/2021
Presentation Time: 05:30 PM Pacific
Description:
Shallow creep on the Leyte island section of the Philippine Fault was first estimated with campaign GPS data in the early 1990s. With the occurrence of a significant moment magnitude (Mw) 6.5 earthquake in July 2017 in northern Leyte, exploring the variability of the slip mode and the seismogenic potential of the “creeping segment” is important for furthering our understanding of fault mechanics and seismic hazard.
We present the first distributed interseismic slip model of the Philippine Fault, along ~100 km of the mappable trace on Leyte island. We make a direct comparison of the interseismic slip distribution (from ALOS InSAR time-series) to the coseismic slip (from Sentinel-1 and ALOS-2 interferograms), with models derived in a Bayesian framework.
Assuming a linear velocity between 2007-2011, we find fast aseismic slip rates throughout most of the fault across the seismogenic zone, around the 3.3 ± 0.2 cm/yr secular slip rate. The only exception is an area of significant slip deficit on a 20-km long, 7-km deep segment in the middle of the fault (the ‘Tongonan Segment’). Our coseismic models of the July 2017 Mw 6.5 mainshock and a Mw 5.8 aftershock suggest that the extent of seismic slip was largely complementary to the interseismic distribution, hence suggesting that the Tongonan segment is a seismogenic asperity. The time between a similar earthquake in 1947 falls within the 95% probability range of the earthquake return period based on a moment budget analysis from the slip models. Geological factors, such as the abundance of fluids from the active hydrothermal systems along the fault, as well as the presence of rate-weakening minerals, may provide conditions suitable for the aseismic slip on the fault.
Presenting Author: John Dale B. Dianala
Student Presenter: Yes
Authors
John Dale Dianala Presenting Author Corresponding Author jddianala@nigs.upd.edu.ph COMET, Department of Earth Sciences, University of Oxford, U.K.; National Institute of Geological Sciences, University of the Philippines - Diliman |
Romain Jolivet romain.jolivet@ens.fr Laboratoire de Géologie, Département de Géosciences, Ecole Normale Supérieure, PSL Université, UMR98538 |
Marion Thomas marion.caltech@gmail.com Sorbonne Université, CNRS-INSU, Institut des Sciences de la Terre Paris, ISTeP UMR 7193, F-750 |
Yo Fukushima fukushima@irides.tohoku.ac.jp International Research Institute of Disaster Science, Tohoku University |
Barry Parsons barry.parsons@earth.ox.ac.uk COMET, Department of Earth Sciences, University of Oxford |
Richard Walker richard.walker@earth.ox.ac.uk COMET, Department of Earth Sciences, University of Oxford |
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The Relationship Between Seismic and Aseismic Slip on the Creeping Segment of the Philippine Fault: Insight to Earthquake Recurrence and Fault Mechanics
Category
Effects and Uses of Aseismic Deformation and Fault Creep in Seismic Hazard and Warning