2020年阿拉斯加两次MW>7.5地震的应力触发关系研究

doi:10.12196/j.issn.1000-3274.2022.04.004

摘要/Abstract

摘要： 地震应力触发理论认为, 相邻的大地震之间存在应力触发关系。 2020年在阿拉斯加俯冲带发生了两次M_W>7.5地震, 分别为7月22日M_W7.8地震和10月19日M_W7.6地震, 为研究“双震型”大地震的触发作用提供了机会。利用近场的GPS同震位移和远场的地震波形资料, 采用不同的断层参数, 反演了M_W7.8地震的4个滑动破裂模型, 并结合初始破裂模型, 计算了在M_W7.6地震震中位置引起的库仑应力变化。研究结果显示, 在5个模型中有4个计算出的应力变化都远远超过了触发阈值0.01 MPa, 表明前一个地震对后一个地震有明显的触发作用。根据M_W7.6地震发震断层两侧的闭锁程度变化, 以及该区域板块俯冲速率, 估算M_W7.8地震使M_W7.6地震提前32年发生。

关键词: 2020年阿拉斯加地震, 地震触发, 库仑应力, 闭锁程度

Abstract: According to the theory of seismic stress triggering, triggering relationship exists between adjacent large earthquakes. In 2020, two earthquakes with M_W>7.5 occurred in the subduction zone of Alaska an M_W7.8 earthquake on July 22 and an M_W7.6 earthquake on October 19, which provides an opportunity for us to study the triggering effect of double-shock earthquakes. Using the near-field GPS coseismic displacement and far-field seismic waveform data, and with different fault parameters, four slip rupture models of M_W7.8 earthquake are obtained by inversion; combined with the initial rupture model, the Coulomb stress changes caused by the earthquake at the epicenter of the later M_W7.6 earthquake are estimated. The results show that the stress changes calculated by four of the five models far exceed the triggering threshold 0.01 MPa, indicating that the former earthquake has an obvious triggering effect on the latter one. Based on the variation of locking ratio on both sides of the seismogenic fault of the M_W7.6 earthquake and the plate subduction rate in the region, it is estimated that the former earthquake caused the latter earthquake to occur 32 years earlier.

Key words: Alaska earthquake, Earthquake triggering, Coulomb stress, Locking ratio

中图分类号:

P315.7

周云, 赵国强, 王洵, 王卫民. 2020年阿拉斯加两次M_W>7.5地震的应力触发关系研究[J]. 地震, 2022, 42(4): 47-59.

ZHOU Yun, ZHAO Guo-qiang, WANG Xun, WANG Wei-min. Study on Stress Triggering Relationship of Two M_W>7.5 Alaska Earthquakes in 2020[J]. EARTHQUAKE, 2022, 42(4): 47-59.

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