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Subslab heterogeneity and giant megathrust earthquakes
Nature Geoscience ( IF 18.3 ) Pub Date : 2021-04-26 , DOI: 10.1038/s41561-021-00728-x
Jianke Fan , Dapeng Zhao

The nucleation and rupture processes of giant megathrust earthquakes (M ≥ 9.0) in subduction zones are still controversial. Most previous studies have focused on the subducting plate interface, and the structure beneath the subducting slab and its influence on earthquake generation remain unclear. Here, we present high-resolution seismic velocity tomography beneath six regions where giant earthquakes have occurred. Subslab low-velocity (slow) anomalies are revealed, which may reflect hot mantle upwelling. The giant earthquake hypocentres are generally located above the edges of the slow anomalies or above the gaps between them. Large coseismic slips of the giant earthquakes mainly occurred above gaps between the slow anomalies. We suggest that differential buoyancy force between the slow anomalies and their gaps may be an important factor for earthquake nucleation, and the rupture extent of a giant earthquake may be constrained by the slow anomalies. Hence, it is necessary to conduct seismic tomography to investigate the detailed subslab structure, which may help to pinpoint the potential location and damage zone of a future giant earthquake.



中文翻译:

次板岩非均质性和巨大的大逆冲地震

特大逆冲地震的成核破裂过程(M ≥ 9.0) 在俯冲带仍存在争议。以往的研究大多集中在俯冲板的界面上,俯冲板下方的结构及其对地震产生的影响尚不清楚。在这里,我们展示了在发生大地震的六个区域下方的高分辨率地震速度层析成像。揭示了亚板坯低速(慢)异常,这可能反映了热地幔上升流。大地震震源一般位于慢异常边缘之上或它们之间的间隙之上。大地震的大同震滑动主要发生在慢异常之间的间隙之上。我们认为慢异常及其间隙之间的不同浮力可能是地震成核的重要因素,大地震的破裂程度可能受到慢异常的限制。因此,有必要进行地震层析成像来研究详细的板结构,这可能有助于确定未来大地震的潜在位置和破坏区域。

更新日期:2021-04-26
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