Bimodal seismicity in the Himalaya controlled by fault friction and geometry
Bimodal seismicity in the Himalaya controlled by fault friction and geometry
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DOI：
10.1038/s41467-018-07874-8
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发表时间：
2019-01-03
影响因子：
16.6
通讯作者：
Avouac, Jean-Philippe
中科院分区：
文献类型：
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作者：
Dal Zilio, Luca;van Dinther, Ylona;Avouac, Jean-Philippe
越来越多的证据表明，喜马拉雅的地震活动可以是双峰式的：盲地震（高达Mw类似于7.8）往往集群在下倾部分的孕震区，而罕见的大地震（Mw 8+）传播到喜马拉雅前锋冲断。为了探索这种双峰地震活动的原因，我们开发了一个二维的尼泊尔喜马拉雅山地震周期模型。我们的粘弹塑性模拟再现了地震周期的重要特征，包括震间应变和双峰地震活动模式。双峰地震活动出现的结果，相对较高的摩擦和非平面的几何形状的主喜马拉雅逆冲断层。这就引入了一个巨大的强度过剩区域，只有当足够的应力通过盲地震向上转移时，这个区域才能被激活。这支持了这样的观点，即喜马拉雅山的大多数部分可能会产生比2015年Mw7.8 Gorkha地震大得多的完全破裂，这应该在未来的地震危险性评估中得到考虑。
There is increasing evidence that the Himalayan seismicity can be bimodal: blind earthquakes (up to Mw similar to 7.8) tend to cluster in the downdip part of the seismogenic zone, whereas infrequent great earthquakes (Mw 8+) propagate up to the Himalayan frontal thrust. To explore the causes of this bimodal seismicity, we developed a two-dimensional, seismic cycle model of the Nepal Himalaya. Our visco-elasto-plastic simulations reproduce important features of the earthquake cycle, including interseismic strain and a bimodal seismicity pattern. Bimodal seismicity emerges as a result of relatively higher friction and a non-planar geometry of the Main Himalayan Thrust fault. This introduces a region of large strength excess that can only be activated once enough stress is transferred upwards by blind earthquakes. This supports the view that most segments of the Himalaya might produce complete ruptures significantly larger than the 2015 Mw 7.8 Gorkha earthquake, which should be accounted for in future seismic hazard assessments.