Toward systematic retrieval of earthquake source parameters from regional seismic waveforms

地震是地球断层活动的结果，断层的几何形状、大小和位移的时空分布特征并不简单。为了了解控制复杂震源特性的物理机制，积累大量用相同技术确定的震源参数是很重要的。为了实现这样的系统分析，需要任何人都可以简单操作的软件。在本项目中，我们开发了一个可以方便地从区域地震波形中反演震源参数的软件。区域地震台网越来越多地部署在世界各地，其波形包括从地震台网数据中很难检测到的震源特征信息。该软件在土耳其、巴基斯坦和智利进行了地震测试，并取得了成功。最后对2005年智利北方中深地震进行了仔细的软件测试。智利大学在震中300公里范围内使用五个强震加速度计记录了波形数据，这是我们测试国外地震软件的好机会。总的来说，分析是好的。虽然我们遇到了一个问题，从该地区的速度模型的不确定性，我们克服了这个问题，重新定位地震与使用的数据和添加到我们的软件的过程。由于软件的这种改进，我们相信我们的软件适用于许多地区的地震速度模型没有很好地确定。在土耳其和巴基斯坦，我们成功地估计了小地震的震源机制解，并将其用于获得区域应力场。该软件随其英文手册沿着分发。该软件在未来世界地震中的进一步应用将建立一个重要的震源参数数据库。

Earthquakes are results of faulting in the Earth, and the characteristics of faulting are not simple in terms of fault geometry, size, and spatiotemporal distribution of displacement. In order to understand the physics controlling the complex source characteristics, it is important to accumulate a number of earthquake source parameters determined with the same technique. To attain such systematic analysis, software, which can be simple handling for anybody, is desired. In the present project, we have developed the software that can easily retrieve earthquake source parameters from regional seismic waveforms. Regional seismic networks are increasingly deployed over the world, and the waveforms include information on earthquake source characteristics that are hardly detected from teleseismic data. The software was tested for earthquakes in Turkey, Pakistan, and Chile, and provided successful results. A careful test of the software was finally done for the 2005 northern Chile, intermediate-depth earthquake. Waveform data were recorded by University of Chile using their five strong-motion accelerometers within 300 km of the epicenter, and it was a good chance for us to test our software for foreign earthquakes. The analysis generally came well. Although we met a problem from uncertainty of a velocity model in the region, we overcome the problem by relocating the earthquake with used data and adding the process to our software. Due to this improvement of the software, we believe that our software is applicable to earthquakes in many regions where velocity models are not well determined. In Turkey and Pakistan, we succeeded to estimate focal mechanisms of small earthquakes using the software, and the solutions were used to obtain the regional stress fields. The software is distributed along with its English manual. Further applications of the software to future earthquakes in the world will build up a significant database of earthquake source parameters.