Seismological Stress Drops for Confined Ruptures Are Invariant to Normal Stress
Seismological Stress Drops for Confined Ruptures Are Invariant to Normal Stress
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DOI：
10.1029/2022gl101366
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发表时间：
2023-05
影响因子：
5.2
通讯作者：
W. Steinhardt;Sam Dillavou;M. Agajanian;S. Rubinstein;E. Brodsky
中科院分区：
文献类型：
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作者：
W. Steinhardt;Sam Dillavou;M. Agajanian;S. Rubinstein;E. Brodsky
地震矩和破裂长度可以结合起来推断应力降，这是评估地震的关键参数。在自然地震中，应力降在很大程度上与深度无关，这是令人惊讶的，因为摩擦应力预期依赖于法向应力和覆盖层。我们已经开发出一种透明的实验断层，可以直接观察成千上万的滑动事件，断裂完全包含在断层内。令人惊讶的是，所观察到的应力下降在很大程度上独立于正常应力的大小及其异质性，捕获自然界中看到的独立性。然而，当断层面积减小时，我们观察到更大的正应力相关应力下降，这使得滑动事件频繁地到达界面的边缘。我们的结论是，封闭破裂具有与正应力无关的应力降，因此构造地震的与深度无关的应力降可能是其封闭性质的结果。
Seismic moment and rupture length can be combined to infer stress drop, a key parameter for assessing earthquakes. In natural earthquakes, stress drops are largely depth‐independent, which is surprising given the expected dependence of frictional stress on normal stresses and hence overburden. We have developed a transparent experimental fault that allows direct observation of thousands of slip events, with ruptures that are fully contained within the fault. Surprisingly, the observed stress drops are largely independent of both the magnitude of normal stress and its heterogeneity, capturing the independence seen in nature. However, we observe larger, normal stress‐dependent stress drops when the fault area is reduced, which allows slip events to frequently reach the edge of the interface. We conclude that confined ruptures have normal stress independent stress drops, and thus the depth‐independent stress drops of tectonic earthquakes may be a consequence of their confined nature.