青藏高原东北部天然地震探测与岩石圈深部特征

为了研究青藏高源东北部块体构造变形的深部驱动机制，笔者对青藏高原东北部的天然地震观测数据进行地震层析反演，并结合同一剖面的接收函数及各向异性结果进行讨论。介绍了ACH方法的基本原理，论述了由于印度板块向北俯冲的强大的持续作用力，造就了NE向俯冲到柴达木盆地之下的昆仑造山带，并发现在巴颜喀拉地体下方壳幔内的仰冲活动。壳幔内的低速体十分显著地出现在阿尼玛卿缝合线以北，深度可达300km。推断该低速体可能与昆仑断裂的深层的剪切作用有关。深部资料显示该区莫霍界面由北向南逐渐加深，这与青藏高原东北部的岩石圈减薄现象一致，而且与印度板块向北运动的远程效应有关。另外，地震层析结果及各向异性分析也支持青藏高原东北部主应力方向转为NE向的观点。

Studies on the Velocity Structure of Crust-Upper Mantle beneath Northeast Qinghai-Tibet Plateau, China

To better understand the driving mechanism in depth controlling deformation across the blocks in the northeast part of the Qinghai-Tibetan Plateau, the authors gave some tomographic analysis on the teleseismic data recorded in the area, and the results on receiver function and anisotropy of the same area are discussed in combination. The ACH basics is introduced. It is suggested that the Kunlun orogeny, driven by the continuing northward movement of the Indian plate,is induced underthrust northeastward beneath the Qaidam basin, and a south-dipping ramp is observed in the upper mantle under the Bayan Har block. Low velocity zones (LVZ) in the upper mantle appear well defined to the north of Animaqin Suture, reaching as deep as 300 km. The LVZs are presumably associated with the shearing at a deeper level of Kunlun fault. The velocity image reveals that Moho deepens southward in the study area, which is in consistency with the lithospheric thinning trend in the northeastern Tibetan Plateau. This is believed to be the so-called Remote Effect of the northward motion of India. In addition, the tomographic and anisotropic analysis seems to support the arguement that the main strain turns from northward to northeastward in the northeastern Tibetan Plateau.