Crustal heterogeneity around active faults and volcanoes in southwestern part of Japan-Inversion analysis of coda envelopes-

尾波包络的反演分析方法被应用于几个活动断层区，也包括活动火山区，包括福井地震断层，野岛断层，六港断层系统，山崎断层系统，山。通过估算尾波散射体的三维分布，获得了地壳非均匀性的以下特征：（1）活火山下方10-20 km深度处存在强散射体，这些散射体被解释为S波反射体。（2）得到了比通常反射分析更详细的反射面分布。(3)A散射体的垂直分布也估计在0-7公里深度以下的Mt. Ontake。（4）沿活动断裂沿着存在强散射体，深度在0-20 km之间。(5)A福井地震断层附近的低震区与弱散射区有很好的对应关系。（6）在1995年兵库县南部地震（M7.2）断层面下20-30 km处估计有强散射带。该带可能对应于本区的下地壳。（7）1995年兵库县南部地震的震源附近是上述散射带中非均匀性最强的区域。如上述（6）和（7）所示，地壳的不均匀性与大地震的发生密切相关，因此有必要通过这种反演分析进一步研究地壳的不均匀性。

The inversion analysis method of coda envelopes was applied to several active fault regions and also active volcano regions that include Fukui-earthquake fault, Nojima fault, Rokko fault system, Yamasaki fault system, Mt.Ontake, Mt.Hakusan, and Mt.Nikko-Shirane. Through estimating the 3-D distribution of coda scatterers, the following characteristics of crustal heterogeneities are obtained : (1)Strong scatterers exist at 10-20 km depth below active volcanoes and the scatters are interpreted as S wave reflectors. (2)The distribution of reflectors is obtained in more detail than usual reflection analyzes. (3)A vertical distribution of scatterers is also estimated at 0-7 km depth below Mt.Ontake. (4)Strong scatterers exist along active faults at depths of 0-20 km. (5)A low seismicity area near the Fukui-earthquake fault well correlates to a weak scattering region. (6)Strong scattering zone are estimated at depths of 20-30 km just below the fault plane of the 1995 Hyogo-ken Nanbu earthquake (M7.2). This zone may correspond to the lower crust in this area. (7)The strongest heterogeneity in the above stated scattering zone is located close to the hypocenter of the 1995 Hyogo-ken Nanbu earthquake.This study has revealed several meaningful heterogeneous structures around active faults and volcanoes. Crustal heterogeneity is supposed to be strongly related to the occurrence of major earthquakes as shown in (6) and (7) above, and further investigation of crustal heterogeneities through this kind of inversion analysis will be necessary.