Lecturer: HU, Jyr-Ching (National Taiwan University, Taiwan)

Date: September 26, 15:00-16:30

Place: DPRI Main Building E232D, Kyoto University Uji Campus

Title: Reassessment of Seismic Hazards in SW Taiwan: Insight from Multiple Fault Slip Triggered by 2016 Mw 6.4 Meinong Earthquake

Jyr-Ching HU1, Mong-Han HUANG2, Hsin TUNG1, Chung HUANG1, Ying-Ping KUO1, Eh TAN3

1. Department of Geosciences, National Taiwan University, Taiwan
2. Jet Propulsion Laboratory, California Institute of Technology, USA
3. Institute of Earth Sciences, Academia Sinica, Taiwan

Abstract:
Rapid strain accommodation across the fold-and-thrust belt in SW Taiwan are revealed by the Continuous GPS, precise leveling and SAR interferometry. The previous block model based on GPS measurement suggested a high seismic risk in SW Taiwan. However, a clear vidence of multiple fault slip along a fold-and-thrust belt at 5-10 km depth was triggered by the 2016 Mw Meinong earthquake at 15-20 km depth. The primary coseismic fault slip was deduced with kinematic model based on seismic and geodetic measurements and riggered fault slip along the shallow fold-and-thrust belt was constrained by SAR interferometry. We hypothesize that the  surface coseismic deformation is mainly controlled by a structure related to the shallow detachment at around 5-10 km depth, which a proposed duplex in a region of high pressure and high interseismic uplift rate might be sensitive to stress perturbations induced by moderate lower crustal earthquake.
It is surprising to notice that the footwall of Longchuan reverse fault demonstrates a high uplift rate of ~20-30 mm/yr in interseismic period. This anomalous deformation rate might part be related with a ramp duplex located in the footwall and the triggered slip of moderate earthquake in nearby area. In addition, the mechanical heterogeneity of mudstone in the Gutingkang formation might play a crucial role of anomalous deformation. Consequently, we use an Efficient Unstructured Finite Element method (DynearthSol2D) to simulate and discuss the contrast of viscosity in mudstone and sandstone contributed in deformation pattern and upward mobility. We also want to check the previous hypothesis of mud diapirism of recent study and incorporate a new mud cored anticline model for mechanic explanation of anomalous interseismic deformation occurred in SW Taiwan.