Source studies of three earthquakes in eastern Taiwan

• Main Authors: Tzu-Wei Lin, 林祖慰
• Other Authors: Kuo-Fong Ma
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/45693466352127966561

碩士 === 國立中央大學 === 地球物理學系 === 84 === We investigated the source characteristics of the May 24, 1994 Hualien(ML=6.6)、June 5,1994 Nanao(ML=6.2) and June 25,1995 Ilan (ML=6.5)earthquakes using the long-period P-wave data recorded by the IRIS (Incorporated Research Institution for Seismology) and local strong motion data obtained from CWB (Central Weather Bureau). For teleseismic study，we applied complex body waveform inversion method to determine the source time function and focal mechanism. The results show that the 1994 May event was a thrust fault mechanism and resulted from a complex rupture process with source duration extending to 35 seconds. The earthquake took place on June 25,1995 shows a normal fault mechanism with source duration just as 3 seconds. According to the spectra analysis using teleseismic data, we obtained moment magnitude，Mw，of the three earthquakes of 6.7、 6.3 and 5.7，respectively. The stress drop calculated from the corner frequency measured from the spectra were also obtained. The stress drop differences of the June 25, 1995 event from the others implies that the tectonic structure of June 25, 1995 differs from the June 5, 1994 and May 24, 1994 earthquakes. The local strong motion data of June 25, 1995 earthquake shows the variation of pulse width of SH wave with azimuth. From the discussion of directivity，we believed this azimuthal variation was caused by rupture directivity。The actual fault plane of the earthquake is strike=133.5°、dip=61.2 °and rake=34.6°。The rupture direction of the fault plane is from southeastern to northwestern。The result is consistent with that from Joint Hypocenter Determination(JHD)。