The 3‐D Spatial Distribution of Shear Strain Energy Changes Associated With the 2016 Kumamoto Earthquake Sequence, Southwest Japan
The 3‐D Spatial Distribution of Shear Strain Energy Changes Associated With the 2016 Kumamoto Earthquake Sequence, Southwest Japan
复制标题
与 2016 年日本西南部熊本地震序列相关的剪切应变能变化的 3D 空间分布
DOI：
10.1029/2019gl086369
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发表时间：
2020
影响因子：
5.2
通讯作者：
Matsu'ura Mitsuhiro
中科院分区：
文献类型：
--
作者：
Noda Akemi;Saito Tatsuhiko;Fukuyama Eiichi;Terakawa Toshiko;Tanaka Sachiko;Matsu'ura Mitsuhiro
剪切应变能是控制地震发生的一个基本物理量。为了计算地震引起的剪切应变能变化，我们既需要同震应力变化，也需要背景地应力变化。背景应力的方向可以从震源机制中估计出来，但其绝对水平仍不确定。假设背景偏应力水平为地壳中的摩擦强度，我们评估了与2016年日本西南部熊本地震序列有关的剪切应变能变化的三维分布。其空间格局强烈依赖于背景应力水平。从剪切断裂的能量平衡出发，提出剪切应变能变化的体积积分可以约束背景偏应力水平。在10公里深的地方，压力至少应为14兆帕。我们发现，大约75%的余震发生在剪切应变能增加的地方。
Shear strain energy is an essential physical quantity governing earthquake generation. To calculate the shear strain energy changes due to an earthquake, we need both coseismic stress changes and background crustal stress. The orientation of the background stress can be estimated from earthquake focal mechanisms, but its absolute level is still uncertain. Assuming the level of the background deviatoric stress to be frictional strength in the crust, we evaluated the three‐dimensional distribution of shear strain energy changes associated with the 2016 Kumamoto earthquake sequence, southwest Japan. Its spatial patterns strongly depend on the background stress level. From the energy balance of shear faulting, we proposed that the volume integral of the shear strain energy changes could constrain the background deviatoric stress level. It should be >14 MPa at 10‐km depth at the very least. We showed that approximately 75% of aftershocks occurred where the shear strain energy increased.