| 河西走廊中部地区三维速度结构研究 |
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| 引用本文：董治平,张元生.2007.河西走廊中部地区三维速度结构研究[J].地球学报,28(3):270-276. |
| DOI：10.3975/cagsb.2007.03.05 |
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| 基金项目:地震科学联合基金项目(编号:504004,197025,106086) |
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| 中文摘要:利用天然地震记录资料,对河西走廊中部地区三维速度结构与震源参数进行了反演,获得了该区的三维速度图像.分层速度结果反映出研究区深部结构的一些重要信息.①浅部沉积层的速度为5.00～6.15 km/s,垂直速度梯度接近0.15 km/s;结晶基底埋深约7 km,速度为6.15 km/s.②上地壳深达18 km,速度约为6.33 km/s;民乐盆地速度略高于祁连山和龙首山,阿拉善地块存在明显的向河西走廊下插的现象.③中地壳底部深约30 km,速度为6.58 km/s;较显著的速度变化区正位于北祁连与河西走廊过渡带.④下地壳厚度显示祁连山偏厚,莫霍面埋深为54 km;河西走廊稍薄,莫霍面深约为52 km;阿拉善地块莫霍面深53.5～53.0 km,介于祁连山与河西走廊之间.在34～42 km深度存在明显的低速层,速度约为6.5 km/s.研究认为,龙首山断裂带可能是逆冲性质的上地壳断层,昌马-俄博断裂可能是一条近直立的中地壳断层. |
| 中文关键词:河西走廊中部地区 三维速度结构 反演 低速层 |
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| A study of the 3-D Velocity Structure in Central Hexi Corridor |
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| Abstract:The 3-D velocity tomography image of central Hexi Corridor was obtained by the joint inversion of 3-D velocity structure and focal parameters based on the S-P data of micro-earthquakes recorded by the digital seismic network. The inversed layering velocity structure does reflect some important features of the deep structure in the study area: ① The velocity of shallow deposition is about 5.006.15 km/s and the vertical velocity gradient is close to 0.15 km/s; the depth of the crystalline basement is about 7 km, with the velocity being 6.15 km/s. ② The depth of the upper crust is some 18 km, with the velocity being 6.33 km/s; the velocity of Minle basin is slightly higher than that of the North Qilian Mountain and the Longshou Mountain. The Alxa block is obviously thrusting under the Hexi Corridor. ③ The bottom of the middle crust is about 30 km in depth with the velocity being 6.58 km/s, and the low-velocity zone is located just between the Qilian Mountain and the Hexi Corridor. ④ The depths of the lower crust imply that the Moho depth is 54 km in the Qilian Mountain, 53.553.0 km in the Minle basin and 52 km in the Alxa block, and that there obviously exists a low-velocity layer of 6.5 km/s at the depth of 3442 km. The research results show that the Longshou Mountain fault may be a reverse one in the upper crust and the Changma-Ebo fault is probably a vertical one reaching the middle crust. |
| keywords:central Hexi Corridor 3-D velocity structure inversion low-velocity layer |
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