Global large deep-focus earthquakes: Source process and cascading failure of shear instability as a unified physical mechanism
Global large deep-focus earthquakes: Source process and cascading failure of shear instability as a unified physical mechanism
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DOI：
10.1016/j.epsl.2015.04.031
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发表时间：
2015-08-01
影响因子：
5.3
通讯作者：
Wen, Lianxing
中科院分区：
文献类型：
--
作者：
Chen, Yu;Wen, Lianxing
基于P波、pP波、SH波和sSH波数据的波形建模，应用多震源反演方法，系统研究了1994年至2012年25次Mw>7.0的深源（深度>400 km）大地震的震源过程。根据推断子事件的空间分布和震源机制，将地震分为三类：1）一类，子事件非平面分布，震源机制可变，以1994年玻利维亚Mw 8.2地震和2013年Mw 8.3鄂霍次克地震为代表； 2）第二类，平面分布但震源机制与平面不一致，共18次地震； 3）三类，平面分布和震源机制与平面一致，包括6次地震。我们在平面破裂、转换断层和剪切热不稳定的背景下讨论了每一类地震的可能物理机制。我们认为，推断的大深源地震的震源过程可以通过预先存在的薄弱区域中剪切热不稳定的级联破坏来最好地解释，剪切不稳定产生的应力扰动触发了由预先存在的薄弱区域的方向控制的另一个子事件的震源机制。该机制还可以解释先前研究中观察到的震源机制的巨大变化、CLVD（补偿线性矢量偶极子）大值的存在以及深源地震的超剪切破裂。此外，我们的研究表明，在大深源地震中，存在类似于（震源持续时间）（3）的地震矩和类似于（震源尺寸）（3）的矩的关系。 (C) 2015 Elsevier B.V. 保留所有权利。
We apply a multiple source inversion method to systematically study the source processes of 25 large deep-focus (depth >400 km) earthquakes with Mw > 7.0 from 1994 to 2012, based on waveform modeling of P, pP, SH and sSH wave data. The earthquakes are classified into three categories based on spatial distributions and focal mechanisms of the inferred sub-events: 1) category one, with non-planar distribution and variable focal mechanisms of sub-events, represented by the 1994 Mw 8.2 Bolivia earthquake and the 2013 Mw 8.3 Okhotsk earthquake; 2) category two, with planar distribution but focal mechanisms inconsistent with the plane, including eighteen earthquakes; and 3) category three, with planar distribution and focal mechanisms consistent with the plane, including six earthquakes. We discuss possible physical mechanisms for earthquakes in each category in the context of plane rupture, transformational faulting and shear thermal instability. We suggest that the inferred source processes of large deep-focus earthquakes can be best interpreted by cascading failure of shear thermal instabilities in pre-existing weak zones, with the perturbation of stress generated by a shear instability triggering another and focal mechanisms of the sub-events controlled by orientations of the pre-existing weak zones. The proposed mechanism can also explain the observed great variability of focal mechanisms, the presence of large values of CLVD (Compensated Linear Vector Dipole) and the super-shear rupture of deep-focus earthquakes in the previous studies. In addition, our studies suggest existence of relationships of seismic moment similar to (source duration)(3) and moment similar to (source dimension)(3) in large deep-focus earthquakes. (C) 2015 Elsevier B.V. All rights reserved.