Fault Creep and Kinematics of the Chihshang Fault in Eastern Taiwan Derived from the PSInSAR and Geodetic Techniques

Abstract:

The Chihshang fault, one segment of the plate suture between the Eurasian and the Philippine Sea plates in eastern Taiwan, is a rapid creeping reverse fault, which has been considered to show interseismic creep near the surface while contemporaneously being capable of producing large earthquakes at depth. In order to understand its seismic hazard, we integrate the near-fault total station measurements and the data from 10 campaign GPS stations for analyzing the nature of creep with 25 continuous GPS observations and the data from PsInSAR method for recognizing the kinematics of deep seismogenic zone. The GPS coordinate daily solution is calculated using the software Bernese v.5.0 under the ITRF2008. Horizontal velocity field is relative to the station S01R located in Penghu island. The average velocity of six campaign-mode GPS stations is about 47.9 mm/yr with the azimuth of 296° at southern segment of the Chihshang fault. The average velocity of the other four campaign-mode GPS stations is about 67.5 mm/yr with the azimuth of 307° at the central segment of the fault. Continuous GPS stations show a great horizontal velocity decreases from hanging wall (eastern side) to footwall (western side). Velocities for stations on the eastern side of the Chihshang fault are 62.5–84.4 mm/yr in directions 291°–314°, whereas those on the western side of the Chihshang fault hanging wall are 24.8–45.3 mm/yr in directions 294°–304°. A major discontinuity about 30 mm/yr on the rate of crustal motion across the Chihshang fault is believed to be the aseismic slip along the fault. Next step, the PSInSAR methods and total station data will be used and integrated with other geodetic data to monitor a wide range of surface activities in the Eastern Taiwan. Finally we hope to reveal the spatiotemporal nature of the creep on the Chihshang fault for helping us associating the creep with potential lithological controls, and providing a new perspective to better understand the underlying causes and mechanisms.