Collaborative Research: Earthquake swarms and aseismic slip in the Salton Trough: High-resolution imaging of the upper frictional stability transition.

为了了解沿活动断裂带的应力积累和释放，需要对各个断层进行详细研究，并将这些结果放置在与我们对岩石力学的知识相一致的物理框架中。近年来观察到的一种特别耐人寻味的断裂带行为涉及到地震滑动和震群活动之间的相互作用。在包括俯冲带、火山系统和大陆走滑断层在内的各种构造环境中，人们观察到缓慢的断层滑动会触发震群，例如南加州人口中心附近的大陆走滑断层。南加州的帝国谷/索尔顿海槽是研究地震群和无地震蠕变的最佳环境之一。震群、大地震(Mw7)和断层蠕变的瞬间幕都是沿索尔顿海槽内的板块边界断层频繁发生的。索尔顿海槽提供了一个很好的机会来研究这些不同类型的断层活动之间的相互作用，因为它们中的许多都是在相对较小的地理区域内观察到的，该区域也进行了非常详细的地质研究，并包含了世界上最密集的地震和大地测量台网之一-S。对地震和地震事件的详细研究提供了一个机会，将断裂带的物理属性(如岩石类型、深度和温度)与岩石力学属性(如摩擦稳定性)联系起来，并使我们能够更好地了解与单个断裂带相关的地震灾害的时间演化。我们建议结合2005年震群主要断裂带的活跃震源地震研究，以及对现有地震和大地测量数据的更详细分析。我们工作的核心是使用美国地质勘探局门洛帕克小组开发的高分辨率剖面技术进行为期一周的地震调查，该技术将对断裂带几何形状和刚性结构的细节提供约束。这些结果将被用来改进我们对2005年蜂群的研究。这些研究的结合将使我们能够研究岩石类型、硬度、热结构和摩擦稳定性之间的关系。由于浅层蠕变和震群是索尔顿海槽主要断裂的一般特征，我们的结果将为该地区基于物理的地震风险模型提供输入。

Efforts to understand the build-up and release of stress along active fault zones require detailed studies of individual faults and placement of those results in a physical framework consistent with our knowledge about rock mechanics. One particularly intriguing fault zone behavior that has been observed with increasing frequency in recent years involves the interplay between aseismic slip and seismic swarm activity. Slow fault slip has been observed to trigger earthquake swarms in a variety of tectonic environments including subduction zones, volcanic systems, and continental strike-slip faults such as those in close proximity to population centers in Southern California.One region that provides a prime environment to study seismic swarms and aseismic creep is the Imperial Valley/Salton Trough in Southern California. Seismic swarms, large (Mw7) earthquakes, and transient episodes of fault creep are all frequent occurrences along the plate boundary faults within the Salton Trough. The Salton Trough offers a prime opportunity to examine the interplay between these varied types of fault activity, since so many of them are observed within a relatively small geographic area, which also has had very detailed geologic studies and contains one of the world?s densest seismic and geodetic station networks. Detailed studies of aseismic and seismic events offer an opportunity to connect physical properties of the fault-zone such as rock type, depth, and temperature with rock-mechanical properties such as frictional stability, and will allow us to better understand the temporal evolution of seismic hazard associated with individual fault zones.We propose a combination of an active source seismic study of the 2005 swarm's primary fault zone, and a more detailed analysis of the existing seismic and geodetic data. The core of our effort is a one-week seismic survey using the high-res profiling techniques developed by the USGS-Menlo Park group that will provide constraints on the details of fault-zone geometry and rigidity structure. These results will be used to improve our studies of the 2005 swarm. The combination of these studies will allow us to study the relations between rock-type, rigidity, thermal structure and frictional stability. Because shallow creep and earthquake swarms are general properties of major faults in the Salton Trough, our results will provide inputs to physics based earthquake hazard models in the region.