地球内部应变与应力固体潮

本文详细介绍了地球内部应变和应力固体潮的计算理论,基于PREM地球模型计算了地球内部的Love数,并计算了地球内部的应力和应变的6个独立分量在不同深度和纬度处的时间变化序列.结果表明:应力潮汐的振幅达到103Pa,应变潮汐振幅达到10-8;不管应力或是应变潮汐,其振幅随深度的不同都有较大的变化;6个应力和应变分量对纬度依赖较大,但没有表现出南北纬度上的严格的对称性,与纬度的对应关系由引潮位展开的大地系数确定.本文结果可有效应用于地球内部应变或应力潮汐观测的固体潮改正;另外,将本文结果应用于研究潮汐触发地震问题,给出了中国中部地区的一个算例,结果表明地震断层正应力潮汐和应力张量第一不变量潮汐与发震时刻具有明显的相关性,而这种相关性并未在其他如剪切应力以及库伦破坏应力潮汐中表现出来.

Tidal strain and tidal stress in the Earth’s interior

The computation theory of tidal strain and tidal stress in the Earth's interior was introduced in detail. Based on the PREM Earth model, the Love numbers in the Earth's interior were computed. Consequently, the time series of the six independent components of tidal strain and tidal stress at different depths and different latitudes were constructed, respectively. The numerical results show that the magnitude of the tidal stress is of the order of 10³ Pa while the magnitude of the tidal strain is of the order of 10^-8. The magnitudes of both tidal stress and tidal strain vary heavily with respect to the depth. Similarly, the six independent components of the tidal stress or the tidal strain are highly dependent on the latitude. But there is no strict north-south symmetric change of magnitude with respect to latitude. However the relation between magnitude and latitude can be derived from the geodetic coefficients of spherical harmonic expansion of tide generating potential. The results in this study are effectively applicable in tidal correction on tidal strain or tidal stress observations in the Earth's interior. On the other hand, the results were applied in the problem of tidal triggering of earthquake in central China area. The statistic results imply high correlations between occurrence times of earthquakes and the tidal normal stresses on fault planes as well as the first invariant of tidal stress tensor. On the contrary, the correlations do not appear in other stress components such as tidal shear stress and tidal Coulumb failure stress.