Frictional and structural controls of seismic super-cycles at the Japan trench
Frictional and structural controls of seismic super-cycles at the Japan trench
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DOI：
10.1186/s40623-020-01185-3
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发表时间：
2020-05-11
影响因子：
3
通讯作者：
Barbot, Sylvain
中科院分区：
文献类型：
--
作者：
Barbot, Sylvain
俯冲带在地震周期中的各种力学行为是脆性变形和韧性变形相互作用的复杂力学系统的非线性动力学的结果。2011年东北大地震代表了板块界面部分和完全破裂的超级周期的高潮，但对大逆冲断层下倾分段的物理控制仍不清楚。在这里，我们提出了一个二维流变模型的日本海沟解释地震规模的变化在宫城部分，在北方本州，在过去的世纪。我们模拟地震活动在一个连续的物理为基础的速率和状态相关的本构关系断层滑动，产生非周期性地震序列的幂律分布的破裂大小。虽然一些巨型逆冲断层的局部破裂是自发行为的结果，但其他的则是结构控制的。1978年和2005年Mj级的7次板间地震发生在地幔楔角的变质带中，弧莫霍面构成了永久的构造边界。我们解释了1981年Mw = 7.1和2003年Mw = 6.9的大地震在弧前和2011年的大地震作为一个大的连续速度减弱断层的自然响应与一个小的成核尺寸的继承。额柱下方的浅段只会在巨大的贯穿裂缝中滑动，从而拉开整个速度减弱界面。该模型一致地解释了宫城段历史地震的规模、复发时间和震源位置，2011年东北地震的缓慢滑动和前震准备阶段，巨大破裂期间海沟附近的大滑动，以及震后变形的重要特征。通过在一个解释性的物理框架内吸收地震周期各个时期的地质和地球物理观测，可以更好地理解日本海沟地震活动的复杂模式。
The diverse mechanical behaviors of subduction zones during the seismic cycle emerge from the nonlinear dynamics of a complex mechanical system with interacting brittle and ductile deformation. The 2011 Tohoku mega-quake represents the culmination of a super-cycle of partial and full ruptures of the plate interface, but the physical controls on the down-dip segmentation of the megathrust remain unclear. Here, we propose a two-dimensional rheological model of the Japan trench to explain the variability of earthquake size at the Miyagi section, in northern Honshu, during the last century. We simulate seismicity in a continuum with a physics-based rate- and state-dependent constitutive law for fault slip, producing aperiodic earthquake sequences with a power-law distribution of rupture sizes. Although some partial ruptures of the megathrust are the result of self-emergent behavior, others are structurally controlled. The 1978 and 2005 Mj similar to 7 interplate earthquakes took place in a metamorphic belt in the mantle wedge corner bounded up-dip by the arc Moho that constitutes a permanent structural boundary. We explain the succession of the great 1981 Mw = 7.1 and 2003 Mw = 6.9 earthquakes within the forearc and the 2011 giant earthquake as the natural response of a large continuously velocity-weakening fault with a small nucleation size. The shallow segment below the frontal prism only slips in giant through-going ruptures that unzip the whole velocity-weakening interface. The model consistently explains the size, recurrence time, and hypocenter location of historical earthquakes in the Miyagi segment, the slow-slip and foreshock preparatory phase of the 2011 Tohoku earthquake, the large slip near the trench during the giant rupture, and important features of its postseismic deformation. The complex patterns of seismicity at the Japan trench can be better understood by assimilating geological and geophysical observations at various periods of the seismic cycle within an explicative physical framework.