西藏高原北缘色林错—雅安多地带的二维速度结构及断裂分布特征

本文首先论述了测区及断裂地带的地质和地球物理特征；通过对藏北高原地带纵剖面处理分析和计算，指出了各组波场特征并建立了二维横向和纵向不均匀的初始数学模型，最后对地壳表层的沉积特征、上—中—下地壳结构特征进行了论述。

CHARACTERISTICS OF THE 2-D CRUSTAL STRUCTURE AND FAULT DISTRIBUTION BENEATH THE SEILING CO YANGAMDO IN THE NORTHERN XIZANG PLATEAU

In order to study the crust structure and the characteristics of the velocity distribution along the east-west profile from Seili Co to Yangamdo, we used the seis 81 program that consists of two point tracing to compute the velocity/depth distribution along the profile. Based on the work that has been done before in this region, we emphasized the shallow crustal structure, the existence of faults and low velocity zones. It is seen from the study that the crust in this region is inhomogeneous both laterally and longitudinally. The crust has a thickness of 68-70 km and an average velocity of 6.25-6.35 km/s. The crust is divided approximately into two parts, the upper and the lower layers, and the thickness of the upper crust is 20-27 km. The velocity/depth distribution in each of them varies continuously from top to bottom. The velocity ranges are 3.4-6.25 and 6.35-6.85 km/s in the upper and lower crust respectively. A low velocity zone exists in either upper or lower layer. In the upper crust, it exists from Yangamdo to Baingion, and has a thickness of 4-5 km. This low velocity zone is discontinuous laterally with a velocity range of 5.60-5.80 km/s. In the lower crust, it exists along the whole profile from east to west, and the velocity is 6.10 km/s. The existence of the low velocity zone in the lower crust is thought to be distinctive from other regions. The paper also discusses the characteristics and genesis of the crustal structure and the tectonic features of the study area based on geophysical data.