Strain release at the trench during shallow slow slip: The example of Nicoya Peninsula, Costa Rica
Strain release at the trench during shallow slow slip: The example of Nicoya Peninsula, Costa Rica
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DOI：
10.1002/2017gl072803
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发表时间：
2017-05-28
影响因子：
5.2
通讯作者：
Protti, Marino
中科院分区：
文献类型：
--
作者：
Jiang, Yan;Liu, Zhen;Protti, Marino
俯冲巨型逆冲断层在海沟附近的行为对于理解地震灾害和海啸的产生至关重要。浅俯冲界面通常位于松散的沉积物中，这些沉积物被认为太弱而不能积累弹性应变。然而，浅层断层滑动行为的频谱仍然是难以捉摸的，这在很大程度上是由于缺乏近场观测。在这里，我们结合联合收割机测量的海底压力传感器附近的沟槽和陆上GPS网络的时间依赖性反演图像的启动和迁移的一个有据可查的慢滑事件（SSE）在2007年在尼科亚半岛，哥斯达黎加。我们的研究结果表明，浅SSE开始在浅俯冲界面上的深度类似于15公里，其中孔隙流体压力被推断为高，并传播到所有的方式沟槽。迁移事件可能触发了1个月后发生的第二子事件。我们的研究结果文件的弹性应变的释放在浅部的俯冲巨型逆冲断层，并建议事先积累的弹性应变。结合最近报道的Hikurangi俯冲带和沟槽破裂在一些大地震中发现的近沟槽浅慢滑，我们的研究结果表明，近沟槽应变积累和释放在俯冲界面的较浅部分比以前认为的更常见。
The near-trench behavior of subduction megathrust faults is critical for understanding earthquake hazard and tsunami generation. The shallow subduction interface is typically located in unconsolidated sediments that are considered too weak to accumulate elastic strain. However, the spectrum of shallow fault slip behavior is still elusive, due in large part to the lack of near-field observations. Here we combine measurements from seafloor pressure sensors near the trench and an onshore GPS network in a time-dependent inversion to image the initiation and migration of a well-documented slow slip event (SSE) in 2007 at the Nicoya Peninsula, Costa Rica. Our results show that the shallow SSE initiated on the shallow subduction interface at a depth of similar to 15km, where pore fluid pressure is inferred to be high, and propagated all the way to the trench. The migrating event may have triggered a second subevent that occurred 1 month later. Our results document the release of elastic strain at the shallow part of the subduction megathrust and suggest prior accumulation of elastic strain. In conjunction with near-trench shallow slow slip recently reported for the Hikurangi subduction zone and trench breaching ruptures revealed in some large earthquakes, our results suggest that near-trench strain accumulation and release at the shallower portions of the subduction interface is more common than previously thought.