Mode of slip and crust-mantle interaction at oceanic transform faults
Mode of slip and crust-mantle interaction at oceanic transform faults
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DOI：
10.1038/s41561-018-0287-1
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发表时间：
2019-02-01
影响因子：
18.3
通讯作者：
Braunmiller, Jochen
中科院分区：
文献类型：
--
作者：
Kuna, Vaclav M.;Nabelek, John L.;Braunmiller, Jochen
海洋转换断层，连接偏置的海洋中部扩张中心，在地震中准周期性地破裂，最高震级约为7.0级，通常在前震之前。除了地震滑动外，大部分的滑动以地震蠕变的形式发生，这可能影响大地震的发生。虽然海洋转换断层是板块边界的主要类型之一，但其滑动的确切方式以及地震运动与地壳运动之间的相互作用尚不清楚。在这里，我们提出了一个详细的模式，在海洋转换断层的基础上获得的数据从最近的临时部署的海底地震仪在布兰科转换断层和现有的区域和海洋地震观测的滑动。在该模型中，断层的地壳部分是脆性的，完全地震耦合，而在地幔中的断层，浅于600摄氏度等温线的深度，部分和间歇性蠕变。蠕变激活了地幔中的小凸起，产生了地震群。地幔和地壳带在大规模地震期间释放了大部分板块运动应变。大地震之前似乎有一个简短的情节浅地幔蠕变，伴随着地震群，这解释了前震的观察，并表明地幔蠕变可能影响大地震事件的启动。
Oceanic transform faults, connecting offset mid-ocean spreading centres, rupture quasi-periodically in earthquakes up to about magnitude M 7.0 that are often preceded by foreshocks. In addition to seismic slip, a large portion of slip takes place as aseismic creep, which likely influences initiation of large earthquakes. Although oceanic transform faults are one of the major types of plate boundaries, the exact mode of slip and interaction between the seismic and aseismic motion remains unclear. Here we present a detailed model of the mode of slip at oceanic transform faults based on data acquired from a recent temporary deployment of ocean-bottom seismometers at the Blanco Transform Fault and existing regional and teleseismic observations. In the model, the crustal part of the fault is brittle and fully seismically coupled, while the fault in the mantle, shallower than the depth of the 600 degrees C isotherm, creeps partially and episodically. The creep activates small asperities in the mantle that produce seismic swarms. Both mantle and the crustal zones release most of the plate-motion strain during large-magnitude earthquakes. Large earthquakes appear to be preceded by a brief episode of shallow mantle creep, accompanied by seismic swarms, which explains the observation of foreshocks and shows that mantle creep likely influences initiation of large seismic events.