Role of fluids in the initiation of the 2008 Iwate earthquake (M7.2) in northeast Japan
Role of fluids in the initiation of the 2008 Iwate earthquake (M7.2) in northeast Japan
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DOI：
10.1029/2008gl035869
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发表时间：
2008-12
影响因子：
5.2
通讯作者：
Zhi Wang;Y. Fukao;S. Kodaira;Run-qiu Huang
中科院分区：
文献类型：
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作者：
Zhi Wang;Y. Fukao;S. Kodaira;Run-qiu Huang
地震速度（Vp, Vs）和泊松比（σ）图像显示，2008年岩手-宫城（M7.2）地震震源位于10 km以上深度的低Vp、略低v和低σ的特殊带，其机械强度可能弱于正下方的高速度和低泊松比的正常发震层。岩手主震震源下地壳和上地幔显示出明显的低Vp、低Vs和高σ带，这可能反映了日本东北部俯冲太平洋板块脱水形成的流体。侵入震源区的流体含水成分可能降低了岩石基质的机械强度，从而引发了岩手地震。研究结果表明，发震层下的地壳流体在大地震的发生中起着重要作用。
Seismic velocity (Vp, Vs) and Poisson's ratio (σ) images show that the hypocenter of the 2008 Iwate‐Miyagi earthquake (M7.2) is located in a distinctive zone with low‐Vp, slightly low‐Vs and low‐σ within the upper 10 km depths, where the mechanical strength might be weaker than the normal seismogenic layer with high velocity and low Poisson's ratio immediate below. A prominent low‐Vp, low‐Vs and high‐σ zone is revealed in the lower crust and uppermost mantle under the Iwate mainshock hypocenter, which may reflect fluids resulting from the dehydration of the subducting Pacific slab under northeast Japan. The aqueous component of fluids intruded into the source region may have reduced the mechanical strength of the rock matrix and so triggered the Iwate earthquake. Our results indicate that crustal fluids beneath the seismogenic layer can play an important role in the initiation of large crustal earthquakes.