Seismic imaging of the middle and upper crust by double-difference tomography: the Haicheng earthquake (Ms 7.3) in Liaoning Province
Seismic imaging of the middle and upper crust by double-difference tomography: the Haicheng earthquake (Ms 7.3) in Liaoning Province
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双差层析成像中上地壳地震成像——辽宁省海城7.3级地震
DOI：
10.1007/s11770-018-0662-0
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发表时间：
2018
影响因子：
0.7
通讯作者：
Zhu Hong-Xiang
中科院分区：
文献类型：
--
作者：
Zheng Que;Liu Cai;Tian You;Zhu Hong-Xiang
1975年2月4日在辽宁省海城市（39°N-43°N，120°E-126°E）发生了7.3级地震。由于第一次及时准确的预测，死亡率仅为0.02%，尽管受地震影响的面积为9200平方公里，覆盖了人口密度为1000人/平方公里的城市。在这项研究中，双差（DD）层析成像方法被用来获得高分辨率的三维（3D）P波和S波速度（Vp和Vs）结构和Vp/Vs以及地震位置。层析成像结果表明，浅部速度结构与地形和沉积厚度吻合较好。地震位置与锦州断裂形成北西走向带，与海城河-大阳河断裂形成北东走向带，表明锦州断裂由三条断裂组成，海城7.3级地震发生在锦州断裂与三条断裂的交汇处。在海城地区15-20 km深度处存在低Vp/Vs的低速带。我们解释的LVZ在中地壳的流体区域，这表明在高温下的岩石脱水。上地壳的低电位带和低Vp/Vs是由于地下水充填的裂缝和孔隙。我们认为，该区的地壳大地震是由中地壳断裂和流体运动共同作用的结果。
The Haicheng earthquake (Ms 7.3) occurred in Liaoning Province (39°N–43°N, 120°E–126°E ), China on February 4, 1975. The mortality rate was only 0.02% owing to the first timely and accurate prediction, although the area affected by the earthquake was 9200 km2and covered cities with a population density of 1000 p/km2. In this study, the doubledifference (DD) tomography method was used to obtain high-resolution three-dimensional (3D) P- and S-wave velocity (Vp and Vs) structures and Vp/Vs as well as the earthquake locations. Tomography results suggest that velocity structure at shallow depth coincides well with topography and sediment thickness. The earthquake locations form a northwest-striking zone associated with the Jinzhou(JZ) Fault and a northeast-striking zone associated with the Haichenghe-Dayanghe (HD) Fault, and suggest that the JZ Fault consists of three faults and the Ms 7.3 Haicheng earthquake originated at the intersection of the JZ and the Faults. Lowvelocity zones (LVZs) with low Vp/Vs are observed at 15–20 km depth beneath the Haicheng (HC) region. We interpret the LVZs in the middle crust as regions of fluids, suggesting rock dehydration at high temperatures. The LVZs and low Vp/Vs in the upper crust are attributed to groundwater-filled cracks and pores. We believe that large crustal earthquakes in this area are caused by the combination of faulting and fluid movement in the middle crust.