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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 ,在一定条件下可以获得与人工地震测深相似的效果
According to the data of 380 0 0 from the northeastern margin of China-DPRK (1 117 ° 0 0’-1 2 6 ° 0’E and 36 ° 0 0’-44 0 ° 0’N 1880-1997) P wave travel time data, using orthogonal projection method to reconstruct the three-dimensional velocity structure of the crust and upper mantle in this area.According to the detailed comparison with the deep analysis of artificial seismic sounding profile, the reliability of the imaging results is proved.The results show that: The crust and upper mantle medium in the northeastern margin of the platform has significant lateral inhomogeneities up to the depth of 120 km, and the velocity image of the upper crust clearly reflects the distribution of different rock units and the bedrock distribution of different nature In the velocity images of the upper and middle crust, several low-velocity anomalous zones (ie, velocity inversion zones) exist in the study area, including Haicheng, Chaoyang, Yixian, Dandongnan and Tangshan, among which Haicheng, Tangshan and Chaoyang The low velocity layer in the crust has been confirmed by deep seismic sounding data. Several strong earthquakes occurred on the land in the study area occurred in the high-speed brittle medium above the low velocity layer in the study area. However, the strong shocks in the Bohai Sea were not obvious , But all happen laterally And the mass velocity was significantly changed. The northwestern low-velocity anomalous zone from Pulandian to Shanhaiguan across the Bohai Sea was found at different depths of the crust. Comparisons of seismic tomographic 2D velocity images and deep seismic sounding data show that the use of the seismic layer Analytical imaging technology, under certain conditions, can be obtained with artificial seismic sounding similar results