用微震记录监测冲击地压前的应力变化

Monitoring the Stress Change before the Rock Burst by Using Microseismogram

1988年10—11月间门头沟矿井下的慢速磁带记录系统共记到100多个事件,其中M_L=2.9的冲击地压为最大。通过地震记录图分析,我们发现这个冲击地压发生时和发生前十几小时,波通过震源区传播,波形发生畸变,S波波速增加、S波到时偏离正常情况。据非线性波动理论,我们认为这些现象是波通过非线性固体介质的直接效应。这些观测事实将为用微震记录监测冲击地压前的应力变化提供有力的理论依据。 矿山冲击地压和地震都是地壳内部岩体的不稳定性问题。它们有着以连续介质力学规律为基础的共同物理学本质。因此本文的结果不仅对矿山冲击地压的预报甚至对地震预报都是有意义的。

From October to November of 1988,more than 100 events were recorded by three underground stations in Mentougou,Bejing,the bigest one is the rock burst ( ML =2. 9),It was found that seismic wave shape is distorted as a wave travel throungh the source region when the rock burst occuring or more than the hours before it occurs. In comparison with usual microseismogram, the distorted seismic waves, which likes saw, shows a important characters that S-wave arrival time deviated from normal value or even S-wave disappeared. It forms a striking contrast to no distored seismic waves which didn' t travel through the source region at same time. We infered that the distorted seismic wave is a some non-linear effect in a non-linear solid medium according to a general characters of a solution of non-linear partial differential equation. This observed facts provide strong evidences to monitoring stress change of the source region before the rock burst. A measured results of the stress of the coal bodies in mines is consistent with our observed results. Because the earthquakes and the rock burst are both about stable problems of a rock body in the crust medium having complex physical properties, so that is not only significant for the rock burst prediction in mine but also is significant for earthquake prediction.In addition the striking single frequency signals were observed four-five days before the rock burst occurring.