深地震探测揭示的西北地区莫霍面深度

从20世纪70年代以来, 在我国西北地区进行了大量的深地震探测研究。本文通过对西北地区的深地震探测研究的总结和梳理, 探讨了西北地区的莫霍面深度与变化及其地球动力学意义。结果表明: 比起我国其他地区, 西北地区莫霍面无论是埋深还是形态均变化最大, 反映出受印度板块与欧亚板块碰撞远程效应影响, 西北地区地壳整体变形强烈。莫霍面最深(约90 km)位于西昆仑与喀喇昆仑构造结合处, 最浅处位于准噶尔盆地西缘的克拉玛依(约35.5 km), 最深与最浅相差约55 km。在盆山结合部位及大型走滑断裂, 如阿尔金断裂、中天山北缘断裂带等均存在莫霍面错断。天山造山带东西段莫霍面深度变化明显, 西段深于东段。这些特征指示了中国西北部盆山之间的构造关系、天山造山带西段和东段不同的深部动力学机制以及古老断裂带的活化。

The Moho Depth of Northwest China Revealed by Seismic Detection

Since the 1970s, lots of research work on deep seismic detection has been conducted in Northwest China. In this paper, the authors have summarized the results of the detection work, and discussed the Moho variation in Northwest China. It is shown that the crustal deformation has changed remarkably in Northwest China: the deepest Moho is beneath the conjunction of west Kunlun and Karakorum, at the depth of about 90 km; the shallowest Moho is beneath the Jayir Mountain to the west of Karamay, about 35.5 km in depth; the Moho depth in the western segments of the Tienshan Mountains is deeper than that in the middle and eastern segments; there exist Moho offsets beneath Altyn fault, northern margin fault of Middle Tienshan and some other places. All these fea-tures suggest that the basin-range coupling in Northwest China, the different uplift mechanism in different seg-ments of Tienshan and the rejuvenation of the old deep faults in Cenozoic were probably caused by the distant consequences of the India-Eurasian collision.