中国西北地区东部地震序列参数与预测余震发生的关系分析

Relation between Earthquake Sequence Parameters and the Prediction of Aftershocks in the Eastern Part of Northwest China

对1970—2012年西北地区东部的51次5级以上地震序列进行E_2/E_0、（M_0-M_3）lgN_3、h值、K值和b值等参数的计算,结果表明：在震后地震类型初期判别上可优先考虑E_2/E_0计算和K值计算。E_2/E_0对主余型地震和孤立型地震均有较好的预测效果,且不受早期阶段余震数量的限制,当E_2/E_0参数判断结果为主余型地震或孤立型地震时,基本上可以确定该结果是准确的;K值计算对样本量的限制也较为宽松,通过震例计算发现,一般中强震后2~3天内,余震数量基本都可满足K值计算,且K值具有较高的判别能力,其计算结果也有很好的一致性和稳定性。参数（M_0-M_3）lgN_3对主余型地震类型判断具有较好的判别能力,但计算条件较为严格,在实际工作中可作为依据参考。h值对多震型地震有较高的判断能力,能很好地为震后震情趋势的判断提供参考依据,但该计算参数对样本量要求较高,且其计算结果的稳定性和一致性较弱,因而建议该参数在实际工作中仅可作为参考。

In this study,we calculated the parameters E_2/E_0,（M_0-M_3）lgN_3,h value,K value,and b value of 51 earthquake sequences of M ≥5.0in the eastern part of Northwest China from 1970 to 2012.The results show that priority should be given to the E_2/E_0 and K value calculations in making the initial judgment of the earthquake type after the main earthquake.There is a good prediction result regarding the mainshock aftershock earthquake type and isolated earthquake sequence using E_2/E_0.Moreover,E_2/E_0 is unrestricted with respect to the aftershock number in the early stage.Historically,when the judgment result was based on E_2/E_0 to determine the mainshock-aftershock earthquake type and isolated earthquake sequence,it has generally been correct.The restrictions on the K value calculation are also relatively light.Through earthquake sample calculation,we found that the number of aftershocks within 2~3days after most moderate-strong earthquakes could satisfy the K value calculation,and the discriminating power of the K value is relatively high.The parameter（M_0-M_3）lgN_3has a high discriminatory power when judging the mainshock-aftershock earthquake type,but there are associated strict requirements and could be used as reference in practical work.The h value has a high discriminatory power when judging the multiple mainshock type and can provide a reference for earthquake trend judgment after the mainshock,but calculations by the h value require a sufficient sample number and the consistency and stability of the calculation results are weak.As such,it is suggested for use only as a reference in practical work.