Detecting Aseismic Stressing Transients using Stochastic Seismicity Models

试图了解控制地震发生时间的物理机制，往往集中在地震生产力的变化与改变地壳内应力状态的事件相联系的观察。 常见的例子包括由大型地壳地震引发的余震序列和由火山下岩浆运动引发的地震群。 这些研究所依据的是这样一种观点，即在我们容易观察到的小地震的发生和我们通常不能观察到的地壳应力状态的时空变化以及导致应力随时间迅速变化的基本物理现象之间存在直接联系。我们正在开发一种新的技术，可以反转地震活动目录（即地震时间，地点和震级的列表）的应力率在目录区域的时空历史。 这项技术将有三个主要应用。 首先，它有望成为一个非常灵敏的地壳瞬变探测器，包括地表大地测量数据无法探测到的流体流动。 其次，它将使我们能够测试地震发生的本构律，已从实验室岩石力学数据。 以前的研究表明，这一定律似乎在数量级水平上起作用，但我们的方法将允许更广泛和更敏感的测试。 第三，有许多关于控制地震发生时间和触发的物理过程的基本问题，这些问题需要关于断层上应力和应力率的时空变化的详细信息。 如果这项技术获得成功，它将为我们理解地震成核和地壳内部导致大地震群的力量提供新的限制。该项目将促进与日本科学家的合作，并为一名女研究生提供培训，她也将前往日本参加国外合作。

Attempts to understand the physical mechanisms controlling the timing of earthquake occurrence often focus on linking observations of changes in earthquake productivity to events that alter the stress state within the crust. Common examples include the aftershock sequences triggered by large crustal earthquakes and seismic swarms triggered by the movement of magma beneath volcanoes. These studies rely on the idea that there is a direct link between what we can easily observe, namely the occurrence of small earthquakes, and what we typically cannot, namely the space-time variations in the stress-state of the crust and the underlying physical phenomena that cause stress to vary rapidly in time. We are developing a new technique that can invert seismicity catalogs (i.e. lists of earthquake times, locations and magnitudes) for the space-time history of the stressing-rate in the catalog region. This technique will have three primary applications. First, it will hopefully be a very sensitive detector of crustal transients, including fluid flow, that cannot be detected with surface geodetic data. Second, it will allow us to test a constitutive law for earthquake generation that has been derived from laboratory rock mechanics data. Previous studies have demonstrated that this law appears to work at the order of magnitude level, but our approach will allow for much more widespread and sensitive tests. Thirdly, there are numerous fundamental questions about the physical processes controlling the timing and triggering of earthquakes that require detailed information about the space-time variations in stress and stressing-rate on faults. If the technique is successful, it will provide new constraints on our understanding of earthquake nucleation and the forces within the crust that cause large earthquake swarms.The project will foster a collaboration with Japanese scientists and provide training for a female graduate student, who will also travel to Japan and participate in the foreign collaboration.