地震预测方法Ⅲ:固体潮与地震

Earthquake prediction methods Ⅲ:correlation between tidal and earthquake

本文从分析研究固体潮与地震发生的相关性的物理机制出发,探讨了用观测固体潮的方法来预测地震发生的可能性.首先,根据地震发生的物理力学过程,给出了地震产生所需要的应力应变条件.实验室岩石力学实验结果和地震应力的观测以及计算结果给出,完整地壳岩石的强度界于10~103 MPa之间,断层介质的强度界于1~10~2 MPa之间.其次,将固体潮所引起的全球地壳变形在某个活动断裂带附近产生的形变值与地震触发的应变值进行对比,讨论了固体潮触发地震的可能性.计算分析表明:固体潮在地表对应的应变在10^(-8)的量级,对岩石介质所引起的应力最高可以达到1.6×10^(-2)MPa量级,这样的载荷水平不足以引发地震.最后,本文结合固体潮观测资料表明,地震活动性与固体潮的周期性变化无明显相关性,固体潮对于临震前的含有活动断裂的岩体在某个方向发生地震可能有触发作用,但是由于这种触发作用与地震发震的时间、地点和震级关系的不确定性,从而无法用来作为地震预测的方法.

This paper discussed the possibility of earthquake prediction by tidal observation method by analysis of the correlation between the physical mechanisms of tidal and earthquake.First,the stress-strain conditions for earthquake to occur were introduced according to mechanical process of earthquake.From the observation and result of rock mechanics experiments as well as seismic stress calculation,the strength of crustal rock is between 10-10^-3 MPa,and the strength of fault medium is between 1-10^-2 MPa.Then,the possibility for tidal to trigger the earthquake was analyzed by comparing the global crustal deformation value along the active fault induced by tidal to the critical deformation value for earthquake to happen.Analysis shows that the order of the surface strain corresponding to tidal is around 10^-8,induced elastic stress in rock media is around 1.6×10^-2 MPa.This load level is not enough to trigger earthquake.Finally,combined with the tidal observation,we demonstrated that there is no significant correlation between seismic activity and cyclical change of tidal.Tidal may play a role in triggering earthquake in rock which has fault in certain direction before breaking occurs.However,there is no obvious correlation among this effect and time,place,magnitude of seismic earthquake.Therefore,tidal can＇t be used as an earthquake prediction method.