穿过张家口—渤海地震带西缘的折射剖面所揭示的地壳上地幔构造与速度结构

THE CRUSTAL-MANTLE TECTONICS AND ITS VELOCITY STRUCTURE REVEALED BY THE REFRACTION PROFILE PASSING THROUGH THE WEST EDGE OF THE ZHANGJIAKOU-BOHAI SEISMIC BELT

近期完成的北北东向的繁峙～太仆寺旗宽角反射／折射剖面，由山西断隆进入内蒙地轴，它穿过了山西地震带的大同～阳高震区和北西西向张家口～渤海地震带的西北缘。其主要目的是探测研究张～渤地震带及其两侧壳幔构造与速度结构的差异及其与地震活动的相关性。结果表明：张～渤地震带壳内界面及莫霍面较其两侧有１．０～２．０ｋｍ的不同程度的上隆；在阳原～张家口之间地壳结构纵向与横向非均匀性明显，上地壳和下地壳上部有局部的速度逆转，下地壳下部的低速层由山西断隆一直延伸至内蒙地轴，上地幔顶部的速度梯度明显增大；在阳原、怀安和张北附近分别存在着延伸至莫霍面的地壳深断裂带；在内蒙地轴一系列壳内界面不明显。

The Fanshi-Taipusi wide angle reflectiona/refraction profile in NNE finished recently, which enters into Inner Mongolia earth axis from Shanxi block dome and passes through the Datong-Yanggao earthquake area of the Shanxi seismic belt and the northwest edge of the Zhangjiakon-Bohai seismic belt NEE, mainly is used to explore and study the crustal-mantle tectonics and velocity structure in the Zhangjiakou-Bohai Seimicity. The results show that in the Zhangjiakou-Bohai seismic belt, the 1 0-2 0 Km uplift of interface in crustal and Moho surface appers against the two sides; from Yangyuan to Zhangjiakou, there are clear longitudinal and transverse nonhomogeneity of crustal tectonics and local velocity reverse of upper and lower crustals, and the low velocity layer of lower part in lower crustal extends from Shanxi block dome to Inner-Mongolia earth axis; velocity gradient in top part of upper mantle obviously raises; deep crustal fault belts extending to Moho surface exist in Yangyuan, Huaian and Zhangbei respectively and no obvious interfaces in crustal exist in Inner-Mongolia earth axis.