[J05-4] Crustal dynamics: Multidisciplinary approach to seismogenesis IV

[J05-4-04] Rapid crustal deformation in SW Taiwan caused by the interaction between active faults and reactivated mud diapirs

^○Kuo-En Ching¹, Yuan-Hsi Lee², Ruey-Juin Rau¹, Ming Yang¹, Yi-Jhen Hung¹, Song-Chuen Chen³, Lingho Chung², Jei-Ching Hung⁴, Chien-Liang Chen³ (1.National Cheng Kung University, Taiwan, 2.National Chung Cheng University, Taiwan, 3.Central Geological Survey, Taiwan, 4.Taiwan High Speed Rail Corporation, Taiwan)

The geodetic data from 2002 to 2016 and 17 ALOS SAR images between 2007 and 2011 were collected in this study to understand the rapid surface deformation in SW Taiwan. The geodetic data comprise 35 dual-frequency and 9 single-frequency continuous GPS stations, 65 campaign-mode GPS stations between 2002 and 2015 and 10 precise leveling routes between 2010 and 2016. All surface velocities are relative to the Chinese continental margin. From north to south, three regions (HLVRs) with extremely high line-of-sight velocity of larger than 40 mm/yr were identified in SW Taiwan. Two of them (middle and southern HLVRs) are located within the central gap between two NE-SW-striking faults, which are the Lungchun fault (LCNF) to the west and the Chishan fault (CSNF) to the east. An uplift rate of ~80 mm/yr is detected at the middle HLVR. At the middle HLVR, a shortening rate of ~47 mm/yr and a left-lateral rate of ~6 mm/yr are shown across the LCNF, while an extension rate of ~32 mm/yr, and a right-lateral rate of ~11 mm/yr are represented across the CHNF. For the region south of the southern HLVR, a shortening rate of ~2 mm/yr and a right-lateral rate of ~10 mm/yr are shown across the LCNF, while a shortening rate of ~3 mm/yr, and a left-lateral rate of ~1 mm/yr are presented across the CHNF. Therefore, the middle HLVR is moving toward NE while the southern HLVR is moving toward SW. After comparing with the locations of mud diapirs and the seismic reflection profiles in SW Taiwan, we proposed that these three isolated HLVRs are the ongoing active inland mud diapirs. The overpressured sediments and fluid are squeezed and pushed upward due to the tectonic compression. Because these inland mud diapirs are bounded by the active faults, the materials are also extruded toward the free boundaries along the channel constructed by these faults.