阿拉善地块深部壳幔速度结构研究及其构造启示

阿拉善地块紧邻祁连造山带和鄂尔多斯块体，在青藏高原的东北向扩展隆升及其与华北克拉通之间的相互运动中，阿拉善地块在其中起到了什么样的作用？搞清这个问题有助于理解青藏东北缘的隆升演化过程。但是由于该区地震台站和数据的缺乏，阿拉善地块尚缺乏较高分辨率的壳幔速度结构。申请人在前期研究中发现阿拉善地块的壳幔速度结构存在东西分区差异性。为进一步探究阿拉善地区的速度结构差异性及其构造意义，本项目拟以密集的喜马拉雅二期台阵和中国地震台网数据为基础，拾取高精度P波和S波到时数据，采用近、远震联合反演获得阿拉善地区高精度的地壳上地幔P波、S波速度结构和波速比分布特征，重点研究阿拉善地块的结构差异性，探讨阿拉善地块在青藏高原向北的扩展隆升过程中的与祁连和鄂尔多斯之间的相互作用及其构造意义，为构建阿拉善地块深部动力学模型提供直接的地震学证据。

Alashan Block, located between Qilian Fold belt and Ordos block, is a key region in terms of understanding the tectonic evolution of NE Tibet and the North China Craton（NCC）. But the deep seismic structure of Alashan block stills be unclear due to the lack of high resolution seismic images of this region because of poor seismic stations and data coverage. We found the difference of seismic structure between the western and eastern part of Alashan block in previous study. In order to further explore the seismic structure features of Alashan block and its tectonic significance, this project intends to perform joint inversions of a large number of high-quality arrival-time data of local earthquakes and teleseismic events, based on the dense seismic data of the ChinArray–Himalaya II and the China Seismic Network, to get detailed 3-D P and S wave velocity images of high resolution, which might provide direct evidence for constructing deep dynamic model under Alashan block and its adjacent area to understand the tectonic dynamics of convergence between NE Tibet and the NCC.