【摘要】 该文首先将汶川余震序列分成西南、东北两段,用加卸载响应比方法分别进行分析,结果表明震后两段的响应比值都比较低,明显小于1,这可判断汶川地震属于主余震型地震;且地震序列中的强余震(M≥5.0)发生前加卸载响应比值出现明显异常,大都是加卸载响应比出现峰值,之后发生强余震。考虑到主震后余震的时空丛集现象,结合ETAS模型对原有的加卸载响应比计算式进行改造,并分析了主震之后15天的改造后响应比值,发现改造后的响应比在一定程度上消除了丛集的影响,并展示了对紧随主震发生的强余震的预测能力。更多还原

【Abstract】 On 12 May 2008,Wenchuan earthquake with magnitude MS8.0 occurred in Sichuan,China.Because of the different focal mechanisms,we divide the distribution region of Wenchuan aftershocks into two parts,namely the southwest part and the northeast part,which are analysed using the Load/Unload Response Ratio(LURR) method separately.The results showed that LURR-values in both the two parts are obviously smaller than 1.0 after the main shock,so the Wenchuan earthquake can be determined to be the usual mainshock-aftershock type.On the other hand,before the occurrence of strong aftershocks(M≥5.0) in the sequence,the LURR-values show anomalies of high values and most strong aftershocks occurred after LURR experienced a peak value.Considering the temporal clustering and spatial concentration of aftershock sequences after the occurrence of most major earthquakes,an improved version of LURR combining the epidemic-type aftershock sequence(ETAS) model is applied to the analyses of the sequence in the first 15 days after the main shock.The results showed that the new LURR can eliminate the fluctuations caused by aftershock clusters to some extent and is better for forecasting strong aftershocks.更多还原