科氏力对中国大陆地区M_S≥7.0地震强余震的影响分析

Influence of the Coriolis Force on Strong Aftershock of M_S≥7.0 Earthquakes Occurred in China Mainland

利用1966—2017年中国大陆地区发生的28次M_S≥7.0地震资料,在仅考虑科氏力在断层面外法线方向的投影分量F_n的基础上分析了余震与受到的科氏力之间的关系。F_n>0表明科氏力使断层面松弛,将减小断层面上的摩擦力,有利于断层面错动并释放能量,余震的强度较小;反之,余震的强度较大。结果表明:15次F_n>0的地震中,有14次地震的主-余震震级差ΔM≥0.8,占93.3%;而13次F_n<0的地震中,只有5次地震的主-余震震级差ΔM<0.8,占38.46%。根据符号检验法可知,当F_n>0时,发生地震的主-余震震级差ΔM≥0.8具有显著性,在α=0.01显著性水平下通过显著性检验。因此,在实际地震趋势判定工作中,利用F_n>0对地震的余震进行判定将更为可靠。

The relationship between the occurrence of 28 M S≥7.0 earthquakes in the China Mainland during the period from 1966 to 2017 and the Coriolis force caused on their fault planes was analyzed.The normal component Fn of the Coriolis force on the fault plane was only considered in the analysis.When Fn>0,it shows that the Coriolis force will make the fault plane relax,and reduce the friction on the fault plane,beneficial to the dislocation and energy release of the fault plane.In this situation the magnitude of aftershock could be weaker.Otherwise,the magnitude of aftershock could be stronger.The results are as follows:Among the 28 M S≥7.0 earthquakes,there are 15 events for Fn>0 and 13 events for Fn<0.Further analysis shows that among the 15 earthquakes for Fn>0,there are 14 events for the magnitude difference between mainshock and aftershock Δ M ≥0.8 with a percent of 93.3%,and among 13 earthquakes for Fn<0,there are only 5 events for the magnitude difference between mainshock and aftershock Δ M <0.8 with a percent of 38.46%.According to sign test,for the earthquakes that occur when Fn>0,the possibility of Δ M ≥0.8 could be larger with a significant correlation(α=0.01).Therefore,it is more reliable in practice to predict the maximum magnitude of aftershock when Fn>0.