山西临汾震区地壳上地幔构造的研究  

STUDY ON THE STRUCTURE OF THE CRUST AND UPPER MANTLE IN LINFEN EARTHQUAKE REGION IN SHANXI

作　　者：祝治平[1] 张建狮[1] 周雪松[1] 朱晚霞 

机构地区：[1]国家地震局地球物理勘探大队

出　　处：《华北地震科学》1994年第1期77-84,共8页North China Earthquake Sciences

摘　　要：利用郑州～临汾～靖边深地震测深剖面临汾、阳城炮点所获得的太行山至靖边段的观测资料，在以往解释的基础上重新进行了对比解释。研究结果表明：临汾与其东西两侧壳幔结构与构造的差异是极其明显的，其主要特征如下：（１）对仅在临汾以西出现的强震相Ｐ２进行了解释，并在ＰＭ波之前识别出一组来自下地壳的反射波Ｐ５；（２）根据临汾以西Ｐｇ与Ｐ２波的特征，我们确认在临汾盆地下方及其西侧，中地壳的上部８～１２ｋｍ深度内存在着一个长约５０ｋｍ的低速体；（３）在临汾盆地以东，利用Ｐ４波所求取的平均速度较Ｐ３波所求取的平均速度为低，据此判断它们之间存在着速度逆转，其深度范围在１５～２２ｋｍ之间。该低速层在临汾盆地下方及其西侧被—非常弱的速度逆转层所取代；（４）下部地壳在临汾盆地两侧速度差别不大，（５）莫霍面的埋藏深度在临汾盆地以东的浮山、沁水为４１．５ｋｍ；浮山向西２０ｋｍ变浅为３８ｋｍ。临汾盆地对应着上地幔的隆起，该隆起向西呈缓慢下倾趋势；（６）临汾断陷盆地的下方存在着超壳断裂。地幔物质沿断裂带上涌，可能是形成异常壳幔结构的原因。On the basis of the results obtained previously, we further interpret the observed D. S. S. data of Taihang As-Jingbian section of Zhengzhou Linfen-Jingbian profile. Our results show that the structures of the crustal and upper mantal in Linfen are very different from that of its east and west sides. The main characteristics of these structures are as follows: 1. The strong seismic phases P2 appeared at the west of Linfen were interpreted. P5 reflection wave from the lower crust was recognized before Pm wave; 2. Based on the Pg and P2 waves to the west of Linfen, we think that there is a low velocity body being about 50 km long in the depth of 8-12 km of upper part of middle crust under Lin fen basin and its west side; 3. Because the average velocity obtained from P4 wave in the east section of Lin fen basin is lower than that from P3 wave, we infer that there is a low velocity layer whose depth ranges from 15 -22 km. The low velovity layer was replaced by a very weak low velocity layer beneath Linfen basin and its west side; 4. The difference of the velocities of the lower crust at both sides of Linfen basin is small; 5. The Moho depth in Fushan and Qinshui to the east of Lin fen is 41. 5 km and changes to 38 km at the place of 20km from Fushan. Linfen basin corresponds to the uplift of upper mantal which decline down gradually towards the west; 6. There is a deep fracture under the fractured basin in Linfen region. The upwelling of the mantal substance along fractured zones may be the reason causing the abnormal crust and mantal structure.

关 键 词：山西 地震测深 地壳 上地幔构造 

分 类 号：P313.2[天文地球—固体地球物理学]