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Numerical Approach to scattering and attenuation of high-frequency seismic waves

高频地震波散射和衰减的数值方法

基本信息

批准号：
10640409
负责人：
YOMOGIDA Kiyoshi
金额：
$ 1.28万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Using the boundary integral method, we investigated spatial distribution of small-scale heterogeneities in the crust. If heterogeneities are localized in a small region, observed amplitude of coda, after corrected by site effects, becomes systematically larger than in other regions. We first analyzed coda for aftershocks of the 1995 Hyogo-ken Nambu earthquake. Coda level becomes systematically large if an event is located in the Nojima fault region at depth of about 10 km in frequency of 1〜4Hz. This implies the concentration of small-scale heterogeneities there. When we used the K-net data provided by NIED, we also detected the concentration of heterogeneities in a small region of Southeastern Hokkaido. From the detected range of frequency (1〜2Hz) , their representative size is estimated to be around 1 km.From a theoretical point of view, we were successful in extending our boundary integral method from homogeneous media into media of vertically varying velocities. That is, we established a new scheme to compute waveforms for scattering in horizontally layered media. We tested our scheme for 2-D SH case, confirming that accurate waveforms can be obtained without significant increase of computational time. We simulated the interaction between scattered waves by heterogeneities and interfaces of layers, which produces waveforms quite different from those in homogeneous media.

利用边界积分方法研究了地壳小尺度非均匀性的空间分布。如果非均匀性局限在一个小区域内，观测到的尾波振幅，经场地效应校正后，变得系统地大于其他区域。我们首先分析了1995年兵库县南部地震余震的尾波。当地震发生在野岛断裂带10 km左右深度、频率为1 × 4 Hz时，尾波强度系统性变大。这意味着小规模异质性的集中。当我们使用NIED提供的K-net数据时，我们还检测到北海道东南部一个小区域的非均匀性浓度。从检测到的频率范围（1 ~ 2 Hz），它们的代表性的大小估计为1公里左右。从理论的角度来看，我们成功地将我们的边界积分方法从均匀介质扩展到介质的垂直变化的速度。也就是说，我们建立了一个新的计划来计算波形的散射水平分层介质。我们测试了我们的计划为2-D SH的情况下，确认可以获得准确的波形，而不会显着增加计算时间。本文模拟了非均匀介质与层间界面散射波的相互作用，产生了与均匀介质截然不同的波形。