Aftershocks near the updip end of the 2011 Tohoku-Oki earthquake
Aftershocks near the updip end of the 2011 Tohoku-Oki earthquake
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2011 年东北冲地震上倾末端附近的余震
DOI：
10.1016/j.epsl.2013.09.007
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发表时间：
2013
影响因子：
5.3
通讯作者：
N
中科院分区：
文献类型：
--
作者：
Obana K.;Kodaira;S.;Shinohara;M.;Hino;R.;Uehira;K.;H. Shiobara;H.;Nakahigashi;K.;Yamada;T.;Sugioka;H.;Ito;A.;Nakamura;Y.;Miura;S.;No;T.;Takahashi;N
摘要2011年3月日本东北冲地震在海沟轴附近激活了具有正断层震源机制的浅层余震。为了研究海沟轴附近浅俯冲带的应力状态，我们使用海底地震仪（OBS）记录了2011年8月至10月的地震。我们估计的震源位置和震源机制的记录地震，通过使用网格搜索方法在二维速度模型的基础上，一个积极的地震调查。结果表明，大部分地震都发生在俯冲板块和上覆板块内，很少发生在板块界面上，在上覆板块最靠海的45 km范围内没有发生地震。沿着板块界面的低地震活动性与M w 9.0级地震中巨型逆冲断层上几乎完全的应力下降相一致。震源机制研究表明，两个板块均以海沟法向张应力为主，其深度至少在30 km左右。另一方面，几个海沟正常的挤压地震位于向陆端的东亚楔。这些地震表明，可能是由于巨型逆冲断层最浅部分的加强而导致的覆盖棱柱体的水平压缩。
Abstract The March 2011 M w 9.0 Tohoku-Oki earthquake activated shallow aftershocks with normal faulting focal mechanisms near the trench axis. To investigate stress state in the shallow subduction zone near the trench axis, we used ocean bottom seismographs (OBSs) to record earthquakes from August to October 2011. We estimated hypocenter locations and focal mechanisms of the recorded earthquakes by using a grid-search method in a 2-D velocity model based on an active seismic survey. The results show that most of the earthquakes occurred within both the overriding and subducting plates, with very few on the plate interface and none in the most seaward 45 km of the overriding plate (aseismic wedge). The low seismicity along the plate interface is consistent with the nearly complete stress drop on the megathrust fault in the M w 9.0 earthquake. Focal mechanisms indicate that trench-normal tension is pre-dominant in both plates and extends to a depth of about 30 km at least. On the other hand, several trench-normal compressional earthquakes were located at the landward end of the aseismic wedge. These earthquakes suggest horizontal compression of the overriding prism that may be caused by a strengthening of the shallowest part of the megathrust.