汶川小断裂带地震机理与监测建议

龙门山断裂带全长约560 km,宽30~50 km,面积约20 000 km2,深度在40 km左右,本文将其定义为小断裂带,它是由3条主干断裂和若干个狭小断裂块体组成的小规模断裂带群。单个块体具有刚体特征,其内部缝隙、孔隙可以忽略,在挤压剪切破碎时将其假设为剪切面,块体剪切破碎或者块体间错位滑动,从而引发地震。当应力释放时,整体表现为下沉稳定,同时,与其邻近大块体接触面因卸荷而出现上、下、左、右相对滑动,从而引发余震。本文针对龙门山小断裂带卸荷前后各块体运动特征,提出监测建议。

Earthquake Mechanism of Wen Chuan Small Fault Belt and Suggestions for Monitoring Its Behavior

The Longmen mountain fault belt is about 560km long,30～50 km wide and 40km deep,covering an area of approximate 20,000 km2.It is defined as a small fault zone in this paper,which is a small-scale fault group,composed of three main faults and some small fault blocks.Each single block is of rigid-body characteristics,in which the internal gaps and porosities can be ignored.They are supposed to be shear planes when extruded,and shear fractures of the block or sliding dislocation between blocks will result in an earthquake.The whole block will be sinking steadily while the stress releasing.At the same time,there will be a relative sliding between the contacted faces of these blocks by unloading,which will result in aftershocks.Based on the movement characteristics of the small-scale fault belts of Longmen Mountain before and after unloading,some suggestions for monitoring its behavior are proposed.