中朝地台东北缘地区的地震层析成像  

SEISMIC TOMOGRAPHY IN THE NORTHEAST MARGIN AREA OF SINO-KOREAN PLATFORM

作　　者：卢造勋[1] 蒋秀琴[1] 潘科[1] 白云[1] 姜德录[1] 肖立萍[1] 刘建华[2] 刘福田[2] 陈辉[2] 何建坤[2] 

机构地区：[1]辽宁省地震局,沈阳110031 [2]中国科学院地质与地球物理研究所,北京100101

出　　处：《地球物理学报》2002年第3期338-351,T004,共15页Chinese Journal of Geophysics

基　　金：国家自然科学基金 (4 96742 2 0 );地震科学联合基金项目 (95 1 5 2 )

摘　　要：根据中朝地台东北缘地区 (东经 1 1 7°0 0′— 1 2 6°0 0′ ,北纬 36°0 0′— 44°0 0′) 1 980— 1 997年的 380 0 0余条P波走时数据 ,利用正交投影法重建了该区地壳和上地幔的三维速度结构 .通过分析及同人工地震测深剖面的详细对比 ,证明了成像结果的可靠性 .结果表明 :中朝地台东北缘地区地壳上地幔介质存在显著的横向不均匀性 ,直至 1 2 0km深度处依然明显 ;地壳上部的速度图像清楚地反映了不同岩石单元的分布与该区不同性质的基岩分布基本吻合 ;从上、中地壳的速度图像中发现了研究区存在海城、朝阳、义县、丹东南、唐山等几个低速异常区(即速度逆反层区 ) ,其中海城、唐山、朝阳等地区的壳内低速层已由深地震测深资料所证实 ;研究区陆地发生的几次强震均发生于壳内低速层上方的高速脆性介质内 ,而渤海发生的强震 ,此现象不明显 ,但都发生于横向介质速度显著突变的位置 ;在地壳不同深度上发现了普兰店至山海关横跨渤海的北西向低速异常带 ;地震层析二维速度图像与深地震测深资料的对比表明 ,研究区利用地震层析成像技术 。Based on 38?000 P wave arrival times recorded during the period of 1980 to 1997 in the northeast margin area of Sino Korean platform (117°00′\_126°00′E, 36°00′\_44°00′N) the 3D velocity structures of the crust and upper mantle have been reconstructed by using orthogonal projection. The tomography results have been proved to be reliable by analyzing and comparing in detail the results with the deep seismic prospecting profiles. It is shown that there exists obvious lateral inhomogeneity in the medium of the crust and upper mantle which is still distinct even at the 120km depth in the northeast margin area of Sino Korean platform. It is reflected clearly in the velocity image of the upper crust that the distribution of all kinds of rock elements corresponds to that of rocks with different nature in this area. Several lower velocity anomaly regions (i.e. regions with velocity reversed layer) have been discovered in the studied area from the velocity images of upper and middle crust, such as Haicheng, Chaoyang?Yixian, south of Dandong, Tangshan etc., among which the lower velocity layers in Haicheng, Tangshan, Chaoyang have also been proved by the deep seismic sounding data. In the area several strong continental earthquakes all happened in crispy medium with higher velocity above lower velocity layers in the crust, whereas in Bohai sea all strong earthquakes happened in positions where the medium velocity changes abruptly and clearly in horizontal. At different depth, Pulandian Shanhaiguan lower velocity anomaly zone across Bohai sea with strike NW has been found. Comparison of the velocity images obtained from 2D seismic tomography with that from deep seismic sounding data, we can consider to gain similar effect with deep seismic sounding by taking advantage of seismic tomography under certain condition in this area.

关 键 词：地壳 地幔 中朝地台 横向不均匀性 壳内低速层 地震层析成像 

分 类 号：P544.1[天文地球—构造地质学] P631.44[天文地球—地质学]