深地震探测揭示的华北及东北地区莫霍面深度

The Moho Depth of North China and Northeast China Revealed by Seismic Detection

从20世纪70年代以来,在我国华北及东北地区进行了大量的深地震探测研究。本文通过对该地区的深地震探测研究的总结和梳理,探讨了该区的莫霍面深度与变化及其地球动力学意义。结果表明:华北地区最深的莫霍面出现在内蒙褶皱带内,最浅的莫霍面出现在渤海湾盆地。东北地区最深的莫霍面出现在大兴安岭地区,最浅的莫霍面出现在依兰-伊通断裂带内;大兴安岭-太行山重力梯度带为一重要的莫霍面陡变带,其西侧的莫霍面一般大于40km,东侧的莫霍面一般小于36km,郯庐断裂带及其北延的依兰-伊通断裂带内,莫霍面沿线均有隆起,但幅度不一。渤海湾盆地及方正断陷(位于依兰-伊通断裂带内)莫霍面上隆显著,敦密断裂带有莫霍错断现象;在出露古老结晶基底岩石的块体内,其莫霍面深度要深于相邻盆地;莫霍面在太行及燕山山前深度明显加大。这些特征说明华北及东北地区拼合到一起后共同经历了太平洋构造运动的影响,而大兴安岭-太行山梯度带限定了太平洋构造域的影响范围,太平洋板块的向西俯冲的前缘可能位于太行山以东,郯庐断裂带以西。

Since the 1970s,lots of research work on deep seismic detection has been conducted in North China and Northeast China.In this paper,the authors have summarized the results of the detection work,and discussed the Moho variation in this region.It is shown that in North China,the deepest Moho is beneath the Mongolia fold belt（48 km） and the shallowest Moho is in Bohai bay basin（28 km）,whereas in the Northeast China,the deepest Moho occurs under Da Hinggan Mountains region（42 km）,and the shallowest Moho is under the Yilan-Yitong（YY） fault zone（27 km）.The Da Hinggan Mountains-Taihang Mountain gradient zone is a remarkable Moho variation belt,with the Moho depth being ≥40 km to its west and ≤37 km to its east;the Moho depth is shallower than that of its both sides along the Tan-Lu fault belt and the YY fault belt,and the Moho offsets exist under the Dunhua-Mishan fault zone;under the regions with outcropped basement rocks,the Moho is deeper than that of the adjacent basins;the Moho obviously deepens at the mountain front.All these features suggest that North China and Northeast China must have experienced the peri-Pacific tectonism,and the Da Hinggan Mountains-Taihang Mountain gradient zone limited the influence range of this tectonism.