Large-scale dynamic triggering of shallow slow slip enhanced by overlying sedimentary wedge
Large-scale dynamic triggering of shallow slow slip enhanced by overlying sedimentary wedge
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DOI：
10.1038/ngeo3021
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发表时间：
2017-10-01
影响因子：
18.3
通讯作者：
Fry, Bill
中科院分区：
文献类型：
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作者：
Wallace, Laura M.;Kaneko, Yoshihiro;Fry, Bill
在过去的十年中，慢滑事件已被公认为是断层滑动的一种重要方式，并且在俯冲带中被最广泛地观察到。许多构造震颤（与缓慢滑动有关）都是由远距离地震触发的，这是由于通过地震波的动态应力变化。然而，很少有明确的例子，大，大地测量检测到的慢滑事件引发的遥远的地震。在这里，我们使用地震和大地测量数据的分析表明，2016年新西兰凯库拉7.8级地震引发了250至600公里远的大型缓慢滑动事件。缓慢滑动是浅的，深度不到15公里，跨越超过15，000公里（2）的中央和北方希库兰吉俯冲边缘。缓慢滑动在地震后立即开始，持续一到两周，并伴随着一系列地震活动。我们发现，在慢滑源区域的动态应力的变化范围从100至600千帕，约1,000倍以上的静态应力的变化0.2至0.7千帕。因此，我们认为慢滑动事件是由通过的地震波引起的动应力变化触发的。此外，动态应力的变化是最大的浅俯冲界面，在不到10公里的深度，在一个区域覆盖的沉积楔，作为波导，捕获地震能量，并可能促进触发滑动。这表明，浅慢滑事件更容易触发的动态应力变化相比，深部事件。
Slow slip events have become recognized in the last decade as an important mode of fault slip, and are most widely observed at subduction zones. Many episodes of tectonic tremor (related to slow slip) have been triggered by distant earthquakes due to dynamic-stress changes from passing seismic waves. However, there are few clear examples of large, geodetically detected slow slip events triggered by distant earthquakes. Here we use analyses of seismic and geodetic data to show that the magnitude 7.8 Kaikoura earthquake in New Zealand in 2016 triggered a large slow slip event between 250 and 600 km away. The slow slip was shallow, at less than 15 km deep, and spanned more than 15,000 km(2) of the central and northern Hikurangi subduction margin. The slow slip initiated immediately after the earthquake, lasted one to two weeks and was accompanied by a swarm of seismicity. We show that changes in dynamic stress in the slow slip source area ranged from 100 to 600 kPa-approximately 1,000 times greater than the static-stress changes of 0.2 to 0.7 kPa. We therefore propose that the slow slip event was triggered by dynamic-stress changes caused by passing seismic waves. Furthermore, the dynamic-stress changes were greatest on the shallow subduction interface, at less than 10 km depth, in a region overlain by a sedimentary wedge that acts as a waveguide, trapping seismic energy and probably promoting triggering of slip. This suggests that shallow slow slip events are more easily triggered by dynamic-stress changes compared with deep events.