Tomographic Imaging outside a Seismic Network: Application to the Northeast Japan Arc
Tomographic Imaging outside a Seismic Network: Application to the Northeast Japan Arc
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DOI：
10.1785/0120050256
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发表时间：
2007-08
影响因子：
3
通讯作者：
Dapeng Zhao;Zhi Wang;N. Umino;A. Hasegawa
中科院分区：
文献类型：
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作者：
Dapeng Zhao;Zhi Wang;N. Umino;A. Hasegawa
传统的局部层析成像可以确定地震台网正下方的3D地震速度结构，但无法确定地震台网之外的3D地震速度结构。在这项研究中，我们表明，如果地震网络之外发生许多地震，则可以克服层析成像的这种限制。在日本东北部，从日本海沟到太平洋沿岸，弧形地震活跃。我们检测并使用 sP 深度相位来准确地重新定位海底地震，然后利用重新定位的海底事件和日本东北陆地区域下方的地震的纵波和横波到达时间，确定从日本海沟到日本海沿岸的整个日本东北弧的 3D 纵波和横波速度以及泊松比结构。我们的结果显示出弧前区域下强烈的横向异质性。板间大地震（7.0～8.2级）的主震震源主要集中在俯冲太平洋板片上方的高低速边界和泊松比边界附近。一些大地震发生在速度高、泊松比低的地区。这些结果表明板片边界的横向非均质性会影响大逆冲地震的破裂成核和板间地震耦合程度。
The conventional local tomography can determine the 3D seismic velocity structure right beneath a seismic network, but it cannot determine the 3D structure outside a seismic network. In this study we show that such a limitation of tomography can be overcome if many earthquakes occur outside a seismic network. In the northeast Japan arc earthquakes occur actively from the Japan Trench to the Pacific coast. We detected and used sP -depth phase to relocate the suboceanic earthquakes accurately, and then used P - and S -wave arrival times from the relocated suboceanic events and the earthquakes under the northeast Japan land area to determine the 3D P - and S -wave velocity and Poisson’s ratio structures of the entire northeast Japan arc from the Japan Trench to the Japan Sea coast. Our results exhibit strong lateral heterogeneities under the forearc region. The mainshock hypocenters of large interplate earthquakes ( M 7.0–8.2) mainly cluster near the boundaries of high and low velocity and Poisson’s ratio above the subducting Pacific slab. A few large earthquakes are located in areas with high velocity and low Poisson’s ratio. These results suggest that lateral heterogeneities on the slab boundary can affect the rupture nucleation of large thrust earthquakes and the degree of interplate seismic coupling.