The Accumulation of Slip Deficit in Subduction Zones in the Absence of Mechanical Coupling: Implications for the Behavior of Megathrust Earthquakes
The Accumulation of Slip Deficit in Subduction Zones in the Absence of Mechanical Coupling: Implications for the Behavior of Megathrust Earthquakes
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DOI：
10.1029/2018jb016336
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发表时间：
2018-09-01
影响因子：
3.9
通讯作者：
Govers, Rob
中科院分区：
文献类型：
--
作者：
Herman, Matthew W.;Furlong, Kevin P.;Govers, Rob
俯冲巨型逆冲地震期间滑移的分布取决于事件发生前板块界面上积累的滑移不足。我们开发了俯冲带的 3D 有限元模型，以研究锁定带如何限制板块边界周围区域的滑动。新鲜的是，我们量化了巨型逆冲断层上粗糙体周围的滑移。模型显示板块界面滑移从锁定区边缘的零开始增加到沿着巨型逆冲断层约 200 公里的距离内相对板块运动。该滑动减少的区域累积的地震力矩不足比单独的粗糙体中的力矩不足大 10 倍。锁定区域的上倾、沟槽处的滑移可减少50%以上的板块运动。尽管沟槽附近的上板位移很大，但该区域作为半刚性块移动。 2011年东北地震的破裂模型、海啸特征以及海沟附近的地球物理观测可以解释为反映了在地震发生带的低摩擦界面上倾处积累的滑移赤字的后果。邻近的粗糙体以非线性方式影响板界面滑移。多个粗糙体具有重叠的伪耦合区域，这可能限制单粗糙体破裂中同震滑移的幅度。一旦地震的破裂长度大于250公里，就可能恢复全部累积的滑移赤字。这与最近几次大逆冲地震中同震滑移的震级是一致的。
The distribution of slip during subduction megathrust earthquakes depends on the slip deficit that accumulates on the plate interface prior to the event. We develop 3-D finite element models of subduction zones to investigate how locked zones restrict surrounding regions on the plate boundary from sliding. What is new is that we quantify the slip around asperities on the megathrust. The models show plate interface slip increasing from zero at the edge of a locked zone to the relative plate motion over a distance of similar to 200km along the megathrust. This area of reduced slip accumulates a seismic moment deficit up to 10 times larger than the moment deficit in the asperity alone. Updip of locked areas, slip at the trench can be reduced by more than 50% of the plate motion. Despite large displacements of the upper plate near the trench, this region moves as a semirigid block. Rupture models of the 2011 Tohoku earthquake, its tsunami characteristics, and geophysical observations near the trench can be interpreted to reflect the consequences of slip deficit accumulated on a low friction interface updip of the seismogenic zone. Neighboring asperities affect plate interface slip in a nonlinear way. Multiple asperities have overlapping pseudo-coupled regions that may restrict the magnitude of coseismic slip in single-asperity ruptures. Once an earthquake has a rupture length greater than similar to 250km, it may recover the entire accumulated slip deficit. This is consistent with the magnitude of coseismic slip in several recent great megathrust earthquakes.