Earthquakes as multiscale dynamic ruptures with heterogeneous fracture surface energy
Earthquakes as multiscale dynamic ruptures with heterogeneous fracture surface energy
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DOI：
10.1029/2004jb003591
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发表时间：
2005-11-05
影响因子：
3.9
通讯作者：
Aochi, H
中科院分区：
文献类型：
--
作者：
Ide, S;Aochi, H
基于对三维均匀弹性空间中平面裂纹的多尺度模拟，我们提出了一个地震过程中动态破裂的大尺度扩展模型。一个简单的滑移弱化规律支配断裂/摩擦过程，其特征参数，滑移弱化距离和断裂表面能，具有多尺度非均匀分布。我们考虑一组随机分布的圆形补丁，其直径是成比例的断裂表面能。每个斑块代表不规则断层面之间的一个粗糙面，斑块的大小-数量关系服从幂律统计。我们评估破裂传播从一个小的不稳定性使用边界积分方程方法与重整化技术。虽然大多数事件在开始后不久就停止了，但有些事件会发展，引发类似大小的相邻斑块。小事件和大事件显示破裂增长的统计自相似特性，并且自发地停止，而不需要特殊的停止机制。破裂速度局部超过剪切波速度，但由于平均破裂能随着破裂的增长而增加，因此总体上保持亚剪切速度。事件的大小与频率之间的关系是一个幂律，这是由补丁之间的触发概率解释。作为统计自相似随机触发增长的结果，我们观察到一个明显的“主相”类似的地震波的自然地震，但我们不能估计的地震波的初始部分的事件的最终大小。如果这对真实的地震是正确的，预测未来地震的规模将是相当困难的。
We propose a model of the wide-scale growth of dynamic rupture during an earthquake, based on our multiscale simulation of a planar crack in a three-dimensional homogeneous elastic space. A simple slip-weakening law governs the fracture/friction processes, and its characteristic parameters, slip-weakening distance and fracture surface energy, have multiscale heterogeneous distributions. We consider a set of randomly distributed circular patches, whose diameter is proportional to the fracture surface energy. Each patch represents an asperity between irregular fault surfaces, and the size-number relation of the patches obeys power law statistics. We assess rupture propagation from a small instability using a boundary integral equation method with a renormalization technique. Although most events stop shortly after their initiation, some grow, triggering neighboring patches of similar size. Small and large events show statistically self-similar properties of rupture growth and stop spontaneously without requiring a special stopping mechanism. The rupture velocity locally exceeds the shear wave speed but globally remains subshear speed due to the increase of the average fracture energy as the rupture grows. The relation between size and frequency of events is a power law, which is explained by the triggering probability between patches. As a consequence of statistically self-similar random triggering growth, we observe a distinct "main phase'' in seismic waves similar to those of natural earthquakes, but we cannot estimate the final size of the event from the initial part of the seismic waves. If this is true for the real earthquakes, predicting the size of a future earthquake would be quite difficult.