南北地震带的构造特色

南北地震带是以青藏高原地壳为主体和兼并了扬子地块西部而成的新生构造实体,具弥漫性边界。构成其基本格架的巨型反S形或缓弧形构造带,分布在中部的弧顶朝南的弧形构造以及发育在东界附近的旋卷构造,成为南北地震带的三大构造特色,它们都是塑性伸展流动的产物。据弧形构造形态实际数据分析表明,地壳物质向南移动的规模,由北往南逐渐加大,从西到东渐逐减小;自北纬31.5°往南,青藏高原物质东移量逐渐加大。

TECTONIC FEATURES OF NORTH-SOUTH EARTHQUAKE ZONE

The North-South Earthquake Zone (NSEZ) in China and its adjacent area (the western part of Yangzi Block) is a newl-ycreated toctontc body with non-distinct boundaries to other adjacent tectonic units. There are three tectonic features in NSEZ, namely the large-scale reversed S-shaped or gentle arcuate tectonic zones showing the outline of NSEZ, the southward-convex arcuate tectonic belts appearing in the middle and the vortical structures located near the east side of NSEZ, which are all produced by plastic flow. An analysis of observational data of arcuate belts indicates that, the moving of plastic flow is increasing from north to south and decreasing from west to east, and the moving material of Qinghai-Xizhang Plateau speaded up toward east, south of 31. 5 N.