Collaborative research: The generation of triggered tremor

调查人员计划解决非火山地震背后的一些基本问题。在加利福尼亚州和世界其他地方，触发的地震发生在转换板块边界的什么地方？地震是否优先在有限的构造范围内触发？为什么地热区有许多触发地震，但没有明显的触发地震？是否存在触发震颤的压力阈值？他们的初步调查显示，只有少数远震地震在SAF的Parkfield段周围引发了震动，但触发阈值仍不清楚。需要对许多不同幅度和频率含量的地震的面波进行系统的检查。目前还不清楚瑞利波的体积变化引起的流体流动，还是乐夫波的瞬时剪应力是触发震颤的最有效机制。对许多远震事件引发的震动进行系统调查，将有助于区分不同的触发机制。触发的地震是否与环境(非触发)地震的现象相同，它们是否遵循慢震的新尺度关系？慢滑和触发地震是否伴随触发地震？是否有持续的震颤背景？这项工作将提供对断层滑动的更好理解，并将对地震学、大地测量学、地质学、摩擦学和岩石力学等产生革命性的影响，甚至更多。更好地了解加州和其他地方SAF系统发生的地震及其与慢滑事件和大地震发生的关系，与减轻地震灾害直接相关。这项研究将涉及两个参与机构的研究生教育，也将涉及本科生。

The investigators plan to address some fundamental issues behind non-volcanic tremor. Where does triggered tremors occur along the transform plate boundary in California, and elsewhere in the world? Are tremors preferentially triggered in a limited range of tectonic regimes? Why do the geothermal regions have many triggered earthquakes, but no apparent triggered tremors? Is there a stressing threshold for triggered tremors? Their initial survey has shown that only a few teleseismic earthquakes triggered tremors around the Parkfield section of the SAF, but the triggering threshold is still not clear. A systematic examination of surface waves of many earthquakes with different amplitudes and frequency content is needed. It is still not clear whether fluid flow induced by volumetric changes of Rayleigh waves, or transient shear stresses from Love waves is the most effective mechanism for tremor triggering. A systematic survey of tremors triggered by many teleseismic events will help to distinguish different triggering mechanisms. Are the triggered tremors the same phenomenon as the ambient (non-triggered) tremors and do they follow the new scaling relationship of slow earthquakes? Does slow slip and triggered earthquake accompany triggered tremors? Is there a constant background of tremor? The work will provide better understanding of fault slip, and would have a transformative impact for seismology, geodesy, geology, friction and rock mechanics, and perhaps more. A better understanding of tremor occurrence along the SAF system in California and elsewhere and its relation to slow slip events and occurrence of large earthquakes is directly relevant to seismic hazard mitigation. The research will involve the education of graduate students in both participating institutions, and will also involve undergraduate students.