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首页> 外文期刊>Earth, planets and space: EPS >Nearly complete stress drop in the 2011 Mw 9.0 off the Pacific coast of Tohoku Earthquake
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Nearly complete stress drop in the 2011 Mw 9.0 off the Pacific coast of Tohoku Earthquake

机译：在东北太平洋太平洋沿岸的2011 Mw 9.0应力几乎完全下降

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摘要

Temporal change in the stress field after the 2011 Tohoku earthquake was observed by stress tensor inversions of focal mechanisms of earthquakes near the source region. The maximum compressive stress (σ1) axis before the earthquake has a direction toward the plate convergence, dipping oceanward at an angle of 25-30 degrees. Its dip angle significantly increased by 30-35 degrees after the earthquake, and σ1 axis came to intersect with the plate interface at a high angle of about 80 degrees. By using the observed rotation of σ1 axis, we estimated the ratio of mainshock stress drop to the background deviatoric stress Δτ/τ to be 0.9-0.95. This shows that the deviatoric stress causing the Mw 9.0 earthquake was mostly released by the earthquake, or the stress drop during the earthquake was nearly complete. Adopting the average stress drop obtained by GPS observation data, the deviatoric stress magnitude is estimated to be 21-22 MPa. This suggests the plate interface is weak. The nearly complete stress drop caused a high dip angle of σ1 axis, which is the reason why not a small number of normal fault type aftershocks have occurred.
机译：通过震源区附近地震震源机制的应力张量反演，可以观察到2011年东北地震后应力场的时间变化。地震前的最大压应力（σ 1 ）轴具有朝向板块收敛的方向，向海倾斜25-30度。地震后其倾角显着增加了30-35度，σ 1 轴以约80度的高角与板界面相交。通过使用观察到的σ 1 轴的旋转，我们估计主冲击应力下降与背景偏应力Δτ/τ之比为0.9-0.95。这表明引起 M w 9.0级地震的偏应力大部分是由地震释放的，或者地震过程中的应力下降已接近完成。采用GPS观测数据获得的平均应力降，偏应力大小估计为21-22 MPa。这表明板界面较弱。几乎完全的应力下降引起了σ 1 轴的高倾角，这就是为什么没有发生少量正常断层余震的原因。

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