Earthquake potential of SW Taiwan inferred from GPS and seismic data

• Main Authors: Su-Miao Kuo, 郭素妙
• Other Authors: Ruey-Juin Rau
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/48820318352613477497

碩士 === 國立成功大學 === 地球科學系碩博士班 === 96 === In order to recognize the present-day crustal deformation and the earthquake potential of southwestern Taiwan, this study analyzed the GPS measurements from 325 campaign-mode GPS stations between 1996 and 2006. Horizontal velocities relative to the Chinese continental margin station, S01R, reveal dramatically decrease from ~55 mm/yr with the direction of 272° in SE of the study area to nearly no deformation in NW of the study area. The subsidence areas mainly distributed over the Coastal Plain with 40-60 mm/yr. The uplift areas of 10-30 mm/yr mainly concentrates on the region east of the Muchiliao fault (MCLF) and the Liuchia fault (LCAF) boundaries of the Western Foothills. Along the Chukou fault (CKUF), the Tsochen fault (TCNF) and the Lungchuan Fault (LCNF) with ~50×10 km^2 in area undergoes a maximum shortening rate of 2 μstrain/yr. Strains accumulated adjacent to major faults are largely elastic. The minimum geodetic moment rate represents the conservative average energy of all contributing sources of deformation in the crust while the seismic moment rate counts only the seismic component of deformation. The minimum geodetic moment rate exceeds the seismic moment rate by more than two orders of magnitude in southwestern Taiwan. The minimum geodetic moment rate minus the seismic moment rate leaves the deficit of moment rate, as the missing energy which could be accumulated then release seismically later on or released aseismically. The maximum deficit of moment rate mainly concentrates along CKUF, TCNF, LCNF and the Chishan fault (CHNF) with 5×10^16 - 7×10^17 Nm/yr. The minimum geodetic moment rate divided by the seismic moment rate equals to the ratio of moment rate. The ratio of moment rate of 1 means the magnitude of two moment rates are similar. The Western Foothills and western Central Range include MCLF, LCAF, CKUF and CHNF with the larger deficit of moment rate (5×10^16 - 7×10^17 Nm/yr), the smaller ratio of moment rate (4×10^1 - 1×10^4) and the smaller b-value (0.3 - 0.6) suggest that the accommodated energy in the crust tends to release seismically. The Coastal Plain and the area surrounded by the Houchiali fault (HCLF), the Hsinhua fault (HHAF), TCNF and CHNF with the smaller deficit of moment rate (5×10^16 - 6×10^17 Nm/yr), the larger ratio of moment rate (10^3 - 10^5) and the larger b-value (0.45 - 0.9) suggest that the energy of these areas may release by the occurrences of small earthquakes or release aseismically. The orientation of geodetic strain rate field is similar to that of the seismic strain rate field.