The S to P convert wave from the bottom of sediment basin in the near-field seismic records  

作　　者：王培德 Stammler Klaus 

机构地区：[1]Institute of Geophysics, China Seismological Bureau, Beijing 100081, China [2]Seismological Central Observatory, Federal Institute for Geosciences and Natural Resources, Erlangen 91054, Germany

出　　处：《Acta Seismologica Sinica(English Edition)》2002年第5期493-502,共10页

基　　金：State Key Basic Research Development and Programming Project (95-13-05-02) ; the Federal Institute for Geosciences and Natural Resources, Germany.

摘　　要：From the near-field records of aftershock of Datong earthquakes in October 1989 and March 1991,an extra phase between P and S arrivals is found. High-precision epicenter location shows that some of these records are obtained with the incidental angle less than the critical angle. This excludes the possibility that the extra wave phase is a refractive wave from ground surface. Particle motion analysis shows that the characteristic of the extra wave is similar to that of wave, so it is possible that the extra phase is an S to P convert wave from the bottom of sediment basin. Suppose a low velocity layer covers a high velocity basement. Successful simulation by the synthetic seismogram confirms that the extra phase is an S-P convert wave from the interface of the basin bottom. Modifying the depth of interface at each ray path to match the waveform, we obtain an interface distribution in space. In this way, a brief bottom image could be shown, and the Datong basin has a 'V' shaped bottom.From the near-field records of aftershock of Datong earthquakes in October 1989 and March 1991,an extra phase between P and S arrivals is found. High-precision epicenter location shows that some of these records are obtained with the incidental angle less than the critical angle. This excludes the possibility that the extra wave phase is a refractive wave from ground surface. Particle motion analysis shows that the characteristic of the extra wave is similar to that of wave, so it is possible that the extra phase is an S to P convert wave from the bottom of sediment basin. Suppose a low velocity layer covers a high velocity basement. Successful simulation by the synthetic seismogram confirms that the extra phase is an S-P convert wave from the interface of the basin bottom. Modifying the depth of interface at each ray path to match the waveform, we obtain an interface distribution in space. In this way, a brief bottom image could be shown, and the Datong basin has a 'V' shaped bottom.

关 键 词：S to P convert wave Datong basin near-field observation 

分 类 号：P315[天文地球—地震学]