Microseismicity Simulated on Asperity‐Like Fault Patches: On Scaling of Seismic Moment With Duration and Seismological Estimates of Stress Drops
Microseismicity Simulated on Asperity‐Like Fault Patches: On Scaling of Seismic Moment With Duration and Seismological Estimates of Stress Drops
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DOI：
10.1029/2018gl078650
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发表时间：
2018-08
影响因子：
5.2
通讯作者：
Yen‐Yu Lin;N. Lapusta
中科院分区：
文献类型：
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作者：
Yen‐Yu Lin;N. Lapusta
观测表明，来自同一地点的微震事件可能具有相似的震源持续时间但不同的地震矩，这违反了通常假设的尺度。我们使用地震序列的数值模拟来证明，孕震斑块上的强度变化提供了对这种行为的解释，事件持续时间由斑块的大小控制，而事件的强度由斑块面积的多少来决定。结果表明，模拟震源的典型地震学分析估算的应力降随震级的增加而显著增大，范围在0.006~8兆帕之间。然而，由断层上的应力变化确定的实际应力降与震级无关，约为3兆帕。我们的研究结果表明，断层的非均质性导致了破裂区域的力矩-持续时间尺度的局部偏差和形状复杂的震源，其中一些应力降可能被典型地震学方法严重低估(~100-1000倍)。
Observations show that microseismic events from the same location can have similar source durations but different seismic moments, violating the commonly assumed scaling. We use numerical simulations of earthquake sequences to demonstrate that strength variations over seismogenic patches provide an explanation of such behavior, with the event duration controlled by the patch size and event magnitude determined by how much of the patch area is ruptured. We find that stress drops estimated by typical seismological analyses for the simulated sources significantly increase with the event magnitude, ranging from 0.006 to 8 MPa. However, the actual stress drops determined from the on‐fault stress changes are magnitude‐independent and ~3 MPa. Our findings suggest that fault heterogeneity results in local deviations in the moment‐duration scaling and earthquake sources with complex shapes of the ruptured area, for some of which stress drops may be significantly (~100–1,000 times) underestimated by the typical seismological methods.