Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 2012 Aug 10;337(6095):724-6. doi: 10.1126/science.1224030. Epub 2012 Jul 19.
Seismological observations of the 2012 moment magnitude 8.6 Sumatra earthquake reveal unprecedented complexity of dynamic rupture. The surprisingly large magnitude results from the combination of deep extent, high stress drop, and rupture of multiple faults. Back-projection source imaging indicates that the rupture occurred on distinct planes in an orthogonal conjugate fault system, with relatively slow rupture speed. The east-southeast-west-northwest ruptures add a new dimension to the seismotectonics of the Wharton Basin, which was previously thought to be controlled by north-south strike-slip faulting. The rupture turned twice into the compressive quadrant, against the preferred branching direction predicted by dynamic Coulomb stress calculations. Orthogonal faulting and compressional branching indicate that rupture was controlled by a pressure-insensitive strength of the deep oceanic lithosphere.
对 2012 年苏门答腊 8.6 级地震的地震观测揭示了动态破裂前所未有的复杂性。令人惊讶的是，如此大的震级是由深度大、应力降高和多个断层破裂的综合作用导致的。回溯源成像表明，破裂发生在正交共轭断层系统的不同平面上，破裂速度相对较慢。东东南-西西北向的破裂为之前被认为受南北走向走滑断层控制的沃顿盆地的地震构造增加了一个新的维度。破裂两次转向压缩象限，与动态库仑应力计算预测的首选分支方向相反。正交断裂和压缩分支表明，破裂受到深海岩石圈压力不敏感强度的控制。
