深地震探测揭示的华南地区莫霍面深度

The Moho Depth of South China Revealed by Seismic Probing

从20世纪70年代以来,在华南地区进行了大量的深地震探测研究。本文通过对华南地区的深地震探测研究的总结和梳理,探讨了华南大陆及其邻近海域的莫霍面变化情况,结果表明:华南大陆莫霍面形态变化较大,总体变化趋势是由西部向东部呈逐渐抬升;华南大陆最深的莫霍面出现在攀西地区北缘,最浅的莫霍面出现在衢州盆地,两者差35km;华南地区周缘断裂均存在莫霍面错断;华南加里东造山带莫霍面深度浅于台湾造山带;东海边缘海与南海北缘地壳厚度明显不同。这些特征可能指示了不同区域所经历的岩石圈及地壳演化过程不同,其中攀西地区的莫霍面较厚可能同青藏高原物质东流有关,华南造山带的地壳减薄缘于后期遭受的伸展作用,东海及南海的莫霍面深度反映了两者处于不同的陆缘位置,前者为活动大陆边缘,后者为被动大陆边缘。

Since the 1970s,lots of research work on seismic detection has been performed in South China.In this paper,the authors have summarized the results of deep seismic sounding,deep seismic profiling and broadband seismic observation and dealt with the variation features of the Moho depth.It is shown that the Moho depth has changed a lot in South China：the depth has on the whole become shallower from the west to the east;the deepest Moho appears in northern Panzhihua-Xichang area in South China continent,and the shallowest Moho lies in Quzhou basin,Zhejiang Province,with the Moho difference between them being 35 km;the Moho offset is existent beneath the marginal fault of South China;the South China Caledonian orogen is shallower than the newest Taiwan orogenic belt;the Moho depth of the East China Sea is quite different from that of the northern South China Sea.These features suggest that different regions have undergone different tectonic evolutions：the relatively great Moho depth in Panzhihua-Xichang area might be related to the eastward mass flow of Qinghai-Tibet plateau,whereas the crustal thinning in South China orogen was caused by the subsequent extension process.The Moho depth difference between the East China Sea and the northern margin of the South China Sea implies that they are located in different continental margins：the former is in an active continental margin,while the latter is in a passive continental margin.