Extended researches of shallow subsurface structure with using the seismic waveform correlation methods

本项目主要做了以下几个方面的研究。首先，比较了利用地震记录相关函数的各种方法。二是将该方法应用于火山区地震勘探。第三，在震源变化的地震剖面间进行了再现性试验。第四，讨论了探测地下结构动态变化的可行性。我们在这些任务上取得了成功。用地震相关方法对富士火山和草津shirane火山的地震记录进行了处理，并在第一年和第二年成功地获得了地震剖面。每项研究结果已分别于2007年和2008年发表。并尝试将地震相关方法应用于火山地震处理，成功实现了浅层火山构造的横波成像。由所有相关图叠加而成的等效震源地震记录，对于讨论剖面的再现性或入射小波的影响是有用的。当量源小波的变化已被发现，这表明在重复性火山震颤中可能存在某些变化。结果表明，火山地震事件的地震相关方法是探测火山导管周围动态变化的有效而灵敏的工具。

These following researches have been made in this project. The first, comparison among various methods with using correlation functions of seismograms have been made. The second, the methods have been applied to seismic exploration in volcanic area. The third, reproductivity tests have been made among seismic sections with source variation. The fourth, the feasibility has been discussed for detection of dynamic changes of subsurface structure. Our results on these tasks were successful.Seismograms in Fuji and Kusatsu-Shirane volcanoes have been processed with the seismic correlation methods and seismic sections have been obtained successfully in the first and the second years. Each result has been published as papers on 2007 and 2008. An application to volcanic tremor was also tried to process with the seismic correlation method and S-wave imaging of shallow volcanic structure have been successfully achieved. The equivalent source seismogram which is derived as a stack of all correlerograms has been found as useful to discussing reproductivity of the sections or effect of incident wavelet. Variations in the equivalent source wavelets have been detected and this suggests there may be certain changes among repetitive volcanic tremor.It is concluded that applications of the seismic correlation methods on volcanic seismic events are useful and sensitive tools to detect dynamic changes around volcanic conduits.