Dynamic triggering of creep events in the Salton Trough, Southern California by regional M ≥ 5.4 earthquakes constrained by geodetic observations and numerical simulations
Dynamic triggering of creep events in the Salton Trough, Southern California by regional M ≥ 5.4 earthquakes constrained by geodetic observations and numerical simulations
复制标题
受大地测量观测和数值模拟约束的区域 M ≥ 5.4 地震对南加州索尔顿海槽蠕变事件的动态触发
DOI：
10.1016/j.epsl.2015.06.044
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发表时间：
2015
影响因子：
5.3
通讯作者：
R. Bilham
中科院分区：
文献类型：
--
作者：
M. Wei;Yajing Liu;Y. Kaneko;J. McGuire;R. Bilham
自1951年区域性地震以来，南加州索尔顿海槽走滑断层上的浅层蠕变事件在200公里范围内至少10次由5.4级以上地震引发。索尔顿海槽地区的高地震和蠕变活动以及悠久的数字记录历史为研究附近地震触发蠕变事件的机制提供了独特的机会。在这里，我们记录了自1988年以来迷信山断层断层蠕变事件的历史，这是基于蠕变仪、InSAR和实地调查的数据。我们专注于这些蠕变事件的一个子集，这些蠕变事件是由附近的重大地震引发的。我们通过将实际的静态和动态扰动添加到基于速率和状态依赖摩擦的理论故障模型中来模拟这些事件。研究发现，因震引起的静应力变化小于0.1 MPa，不足以瞬间触发蠕变事件。相比之下，我们可以再现触发滑动的特征与动态扰动单独。蠕变事件的瞬时触发取决于动态库仑应力变化的峰值和时间积分幅值。根据观测和模拟，触发0.01 mm表面滑移的蠕变事件所需的应力变化幅度约为0.6 MPa。该阈值至少比报道的非火山地震（2-60 kPa）、地热田地震（5 kPa）和页岩气生产地点附近地震（0.2-0.4 kPa）的触发阈值大一个数量级，这可能是由于这些系统中有效正应力、断层摩擦、成核点密度或触发机制的差异造成的。我们认为，浅层摩擦非均质性可以解释迷信山断层的自发和动态触发蠕变事件。
Since a regional earthquake in 1951, shallow creep events on strike-slip faults within the Salton Trough, Southern California have been triggered at least 10 times by M≥ 5.4 earthquakes within 200 km. The high earthquake and creep activity and the long history of digital recording within the Salton Trough region provide a unique opportunity to study the mechanism of creep event triggering by nearby earthquakes. Here, we document the history of fault creep events on the Superstition Hills Fault based on data from creepmeters, InSAR, and field surveys since 1988. We focus on a subset of these creep events that were triggered by significant nearby earthquakes. We model these events by adding realistic static and dynamic perturbations to a theoretical fault model based on rate-and state-dependent friction. We find that the static stress changes from the causal earthquakes are less than 0.1 MPa and too small to instantaneously trigger creep events. In contrast, we can reproduce the characteristics of triggered slip with dynamic perturbations alone. The instantaneous triggering of creep events depends on the peak and the time-integrated amplitudes of the dynamic Coulomb stress change. Based on observations and simulations, the stress change amplitude required to trigger a creep event of a 0.01-mm surface slip is about 0.6 MPa. This threshold is at least an order of magnitude larger than the reported triggering threshold of non-volcanic tremors (2–60 kPa) and earthquakes in geothermal fields (5 kPa) and near shale gas production sites (0.2–0.4 kPa), which may result from differences in effective normal stress, fault friction, the density of nucleation sites in these systems, or triggering mechanisms. We conclude that shallow frictional heterogeneity can explain both the spontaneous and dynamically triggered creep events on the Superstition Hills Fault.