Collaborative Research: The Generation of Triggered Tremor

研究人员计划解决非火山震动背后的一些基本问题。沿着加利福尼亚和世界其他地方的变形板块边界，触发性地震发生在哪里？地震是否优先发生在有限范围的构造体系中？为什么地热区有很多触发地震，但没有明显的触发震动？触发性震颤有压力阈值吗？他们的初步调查显示，只有少数远震地震在新加坡空军的帕克菲尔德地区附近引发了震动，但触发阈值仍然不清楚。需要对许多地震的不同振幅和频率含量的表面波进行系统的检查。究竟是瑞利波体积变化引起的流体流动，还是洛夫波的瞬态剪应力引起的流体流动才是触发地震的最有效机制，目前还不清楚。对许多远震事件引发的地震进行系统的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（非触发的）地震相同？它们是否遵循慢震的新标度关系？缓慢滑动和诱发地震是否伴随诱发震颤？是否有持续的震颤背景？这项工作将有助于更好地理解断层滑动，并将对地震学、大地测量学、地质学、摩擦和岩石力学等领域产生革命性的影响。更好地了解加利福尼亚和其他地方沿SAF系统发生的震颤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。这笔资金将支持一位年轻助理教授的职业发展。

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. The funding would support the career development of a young assistant professor.