Chilean megathrust earthquake recurrence linked to frictional contrast at depth
Chilean megathrust earthquake recurrence linked to frictional contrast at depth
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DOI：
10.1038/s41561-018-0089-5
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发表时间：
2018-04-01
影响因子：
18.3
通讯作者：
Oncken, O.
中科院分区：
文献类型：
--
作者：
Moreno, M.;Li, S.;Oncken, O.
俯冲带地震周期的基本过程，包括那些控制大地震复发和规模的过程，仍然知之甚少。在这里，通过研究2016年智利南部的地震--这是1960年地震破裂带内的第一次大型事件（矩震级（M-w）= 9.5）-我们表明，板块界面断层在深度上的摩擦分带性机械地控制了更频繁、中等规模的深部事件（M-w < 8）和不太频繁的事件，引发海啸的浅源大地震（M-w > 8.5）。我们模拟了具有非均匀摩擦的孕震区的应力积累演化，以研究2016年和1960年地震之间的联系。我们的研究结果表明，更深的孕震巨型逆冲断层段较弱，地震间加载的更强的耦合，浅的凹凸。较深的地震段较早发生地震（~ 60年复发），在较浅的地震段发生地震（复发>110年）之前发生中等规模的地震。我们解释的摩擦强度和滞后时间的对比深，浅地震孔隙流体压力的变化控制。我们的综合分析加强了对巨大逆冲断层地震的力学和时间的理解，因此可以帮助其他俯冲带的地震危险性评估。
Fundamental processes of the seismic cycle in subduction zones, including those controlling the recurrence and size of great earthquakes, are still poorly understood. Here, by studying the 2016 earthquake in southern Chile-the first large event within the rupture zone of the 1960 earthquake (moment magnitude (M-w) = 9.5)-we show that the frictional zonation of the plate interface fault at depth mechanically controls the timing of more frequent, moderate-size deep events (M-w < 8) and less frequent, tsunamigenic great shallow earthquakes (M-w > 8.5). We model the evolution of stress build-up for a seismogenic zone with heterogeneous friction to examine the link between the 2016 and 1960 earthquakes. Our results suggest that the deeper segments of the seismogenic megathrust are weaker and interseismically loaded by a more strongly coupled, shallower asperity. Deeper segments fail earlier (-60 yr recurrence), producing moderate-size events that precede the failure of the shallower region, which fails in a great earthquake (recurrence >110 yr). We interpret the contrasting frictional strength and lag time between deeper and shallower earthquakes to be controlled by variations in pore fluid pressure. Our integrated analysis strengthens understanding of the mechanics and timing of great megathrust earthquakes, and therefore could aid in the seismic hazard assessment of other subduction zones.