Remote Triggering Inside Versus Outside Geothermal Fields

自1992年加州兰德斯7.3级地震以来，全球范围内对大地震的远程触发进行了广泛的观测和研究。然而，大多数以前的研究是在数百公里的空间尺度上进行的，并没有区分实际运作的地热田与人为设置和其邻近的断层带与自然设置。提出了一个为期两年的项目，详细分析远程触发的地震活动，以检查假设，即由于应力状态的变化，与地热田内的人类活动有关的地热田从其附近的远程地震不同的反应。预期的结果将提高知识的影响孔隙流体压力对地震的启动和相互作用，并有助于远程触发和诱发地震活动的模型，这将是重要的评估潜在的未来地震危险的地热田由于远程地震和人类活动。在这项拟议的工作中，在加州的活动构造环境下的三个业务地热田对应于三个大的远程地震被选中。本研究的重点是比较每个地热田（~ 10 x10平方公里）与其相邻的断裂带（~ 100 x100平方公里）之间的不同行为，断裂带分为几个子区域。结果将解决以下问题：（1）如何改变地震活动率内部和外部的地热田响应于每一个远程地震？(2)地热田内外的应力场有何不同？(3)浅源地震和深源地震如何对远程触发作出反应？(4)地热田内部的净生产率与地震活动率之间是否存在相关性？(5)地热田内外的地震速度结构和现场Vp/Vs有何不同？

Remote triggering by large earthquakes at regional distances has been globally observed and intensely studied since the 1992 Mw 7.3 Landers earthquake in California. However, most of the previous studies were conducted at spatial scales of hundreds of kilometers and did not differentiate the actual operational geothermal fields with anthropogenic setting and their adjacent fault zones with natural setting. A two-year project is proposed for detailed analyses of the remotely triggered seismicity to examine hypothesis that geothermal fields respond differently from their vicinity to remote earthquakes due to the stress-state changes that are associated with the anthropogenic activity inside the geothermal field. The expected results will improve knowledge of the effect of pore fluid pressure on earthquake initiation and interaction and contribute to models of remotely triggered and induced seismicity, which will be important for evaluating the potential of future seismic hazards in geothermal fields due to remote earthquakes and human activity. In this proposed work, three operational geothermal fields under active tectonic settings in California corresponding to three large distant earthquakes are selected. The focus of this research is to compare different behaviors between each geothermal field (~10x10 km^2) and their adjacent fault zones (~100x100 km^2) that are split into several subareas. The results will address the following questions: (1) How does seismicity rate change inside and outside the geothermal fields responding to each remote earthquake? (2) How different are the stress fields inside and outside the geothermal fields? (3) How do shallow and deep earthquakes respond to remote triggering? (4) Is there any correlation between the net production rate and the seismicity rate inside the geothermal field? (5) What is the difference in the seismic velocity structure and in situ Vp/Vs inside and outside the geothermal fields?