华北地区构造应力场年动态变化特征的数值模拟

摘要

On the basis of a 3-D visco-elastic finite element model of lithosphere in North China, we simulated numerically the recent annual changing characteristics of tectonic stress field in the region as follows. 1) The maximum principal extensional stress is 3 - 9 kPa a-1 and its azimuth lie in NNW-SSE, the maximum principal com-pressive stress is about 1-6 kPa a-1 and its azimuth lie in NEE-SWW. The whole North China is under the extensional stress field. 2 ) The maximum principal extensional stress presents high in the west and low in the east, in general , and the stress of whole NE area is high, and the maximum compressive is high in the NE and SN area. This kind of change is benefical for the enhancement of the fault action in Shanxi and Liaoning areas and many speed up the potencial seismogenic process. 3 ) Annual cumulative rates of coulomb fracture stress in Tanlu fault belt is of a segmentation pattern that the rate of Jiashan-Guangji segment is highest(6 kPa a-1) ,in Anshan-Liaodong Bay segment it is higher(5 kPa a-1) and others are lower (3-4 kPa a-1).%利用华北地区岩石圈三维黏弹性有限元数值模型,模拟得出华北地区构造应力场现今年变化特征:1)构造应力年变化场的主张应力方向为NNW-SSE,平均量级为3～9 kPa a-1；构造应力年变化场的主压应力方向为NEE-SWW,平均量级为1～6 kPa a-1；华北地区现今主要处于张性构造应力场作用下；2)构造应力年变化场的最大主张应力(NNW向)总体呈现西高东低,且东北部地区较高的空间分布特征,构造应力年变化场的最大主压应力(NEE向)的高值区位于东北部和西南部,上述变化特征有利于山西地区和辽宁地区断裂活动的增强,进而有可能加速这些地区潜在地震的孕震过程；3)郯庐带断裂面库仑破裂应力年累积速率具有分段特征:嘉山-广济段的年累积速率最高,平均达6 kPa a-1；鞍山-辽东湾段的年累积速率次之,平均达5 kPa a-1；渤海段和莱州湾-嘉山段的年累积速率相对较低,平均为3 ～4 kPa a-1.