Earthquake model experiments in a viscoelastic fluid : A scaling of decreasing magnitudes of earthquakes with depth
Earthquake model experiments in a viscoelastic fluid : A scaling of decreasing magnitudes of earthquakes with depth
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粘弹性流体中的地震模型实验：地震震级随深度减小的比例
DOI：
10.1002/2014jb011135
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
and S. Ide
中科院分区：
文献类型：
--
作者：
Namiki;A.;T. Yamaguchi;I. Sumita;T. Suzuki;and S. Ide
我们使用准麦克斯韦流体进行剪切变形实验。我们发现，取决于应变率，相同的材料产生与弹性回弹和粘性变形相关的地震。在临界值附近，弹性回弹释放了地震间位移的一部分，但另一部分由于粘性松弛而保留。我们将我们的实验结果应用到俯冲带，其中上盘的上部表现为弹性层并产生地震活动，而较深的部分表现为粘性流体并与板一起俯冲。我们的实验结果表明，在弹性层和粘性层的边界附近，可以发生地震活动，但只有一部分震间位移被释放。实验获得的地震活动阈值由俯冲速度vs、上盘粘度η、断层长度W和粘着应力σa的组合决定，vsη/（Wσa）>1。这个阈值表明，如果上盘的粘性随深度减小，地震的最大规模也随深度减小，最后，地震活动消失。这一假设与观测到的事实是一致的，即在孕震区的下倾极限观测到以震级小为特征的慢地震。
We performed shear deformation experiments using quasi‐Maxwell fluids. We found that, depending on the strain rates, the same material generates earthquakes associated with the elastic rebound and deforms viscously. Around the threshold, elastic rebound releases a certain fraction of the interseismic displacement, but the other fraction remains as a result of the viscous relaxation. We applied our experimental results to a subduction zone, in which the upper part of the hanging wall behaves as an elastic layer and generates seismicity, while the deeper part behaves as a viscous fluid and subducts with the slab. Our experimental results suggest that, around the boundary of the elastic and viscous layers, seismicity can occur, but only some part of the interseismic displacements is released. The experimentally obtained threshold of the seismic activity is determined by the combination of the subduction velocityvs, the viscosity of the hanging wallη, the fault lengthW, and the adhesive stressσa,vsη/(Wσa)>1. This threshold suggests that if the viscosity of the hanging wall decreases with depth, the maximum size of the earthquakes also decreases with depth, and, finally, seismicity disappears. This hypothesis is consistent with the observed fact that slow earthquakes, characterized by their small magnitudes, are observed at the downdip limit of the seismogenic zone.