Gravitational body forces focus North American intraplate earthquakes.
Gravitational body forces focus North American intraplate earthquakes.
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DOI：
10.1038/ncomms14314
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发表时间：
2017-02-17
影响因子：
16.6
通讯作者：
Briggs R
中科院分区：
文献类型：
--
作者：
Levandowski W;Zellman M;Briggs R
远离板块边界的地震通常利用古老的断层，但并非所有的板内断层都同样活跃。北美大平原就存在这样的板内地震局部化现象，自然地震和诱发地震通常聚集在离散的区域。在这里，我们使用地震速度，重力和地形生成一个三维岩石圈密度模型的区域，随后的有限元建模表明，地震活动集中在高重力派生的偏应力区域。此外，预测的主应力方向通常与地震矩张量和钻孔崩落中独立观察到的主应力方向一致。因此，体力似乎控制了应力状态，从而控制了美国中部板内地震的位置和类型，而不需要地幔对流或地壳薄弱的影响。这些结果表明，绘制重力体力激发地震活动的地图对于理解和评估板内地震危险性至关重要。板内地震发生在远离构造板块边界的地方，因此了解它们如何以及在哪里发生是至关重要的。在这里，Levandowski等人创建了北美大平原的3D密度图，显示重力在板内地震位置中起着控制作用。
Earthquakes far from tectonic plate boundaries generally exploit ancient faults, but not all intraplate faults are equally active. The North American Great Plains exemplify such intraplate earthquake localization, with both natural and induced seismicity generally clustered in discrete zones. Here we use seismic velocity, gravity and topography to generate a 3D lithospheric density model of the region; subsequent finite-element modelling shows that seismicity focuses in regions of high-gravity-derived deviatoric stress. Furthermore, predicted principal stress directions generally align with those observed independently in earthquake moment tensors and borehole breakouts. Body forces therefore appear to control the state of stress and thus the location and style of intraplate earthquakes in the central United States with no influence from mantle convection or crustal weakness necessary. These results show that mapping where gravitational body forces encourage seismicity is crucial to understanding and appraising intraplate seismic hazard. Intraplate earthquakes occur far from tectonic plate boundaries and so it is vital to understand how and where they may happen. Here, Levandowski et al. create a 3D density map of the North America Great Plains showing that gravitational forces play a controlling role in intraplate earthquake locations.