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地震引起邻近断层的静应力变化可能推迟、加速、甚至触发以后的地震(Das and Scholz, 1981; Stein and Lisowski, 1983; Hudnut et al., 1989; Reasenberg et al., 1992; Du and Aydin, 1993; Harris et al., 1992; Joumé et al., 1992; Stein et al., 1992; Simpson et al., 1994; Harris and Simpson, 1993)。这种作用的持续时间长度对地震灾害估计中应力分析的可能作用具有很大影响,但现在还不知道。这里我们采用弹性半空间模型(Okada,1992)来估计过去26a来南加州破坏性地震(M≥5)所产生的静应力变化,并且观察这些变化对以后的地震活动的影响。我们发现在M≥5地震之后的1.5a内,任何一个后来附近的M≥5地震几乎总是使受第一次地震加载而趋于破坏的断层破裂。在这个时期以后,破坏性地震使加载和卸载的断层破裂的可能性几乎是相同的。我们的结果显示,在南加州破坏性地震之后的短时期内,简单的库伦应力破坏模型可以用来识别地震危险性增大的地区。
Changes in the static stress caused by the earthquakes near the fault may be postponed, accelerated, and even triggered subsequent earthquakes (Das and Scholz 1981; Stein and Lisowski 1983; Hudnut et al. 1989; Reasenberg et al 1992; Du and Aydin 1993 ; Harris et al., 1992; Joumé et al., 1992; Stein et al., 1992; Simpson et al., 1994; Harris and Simpson, 1993). The duration of this effect has a great influence on the possible role of stress analysis in earthquake disaster estimation, but it is not yet known. Here, we use the elastic half-space model (Okada, 1992) to estimate the static stress changes caused by the devastating Southern California earthquake (M ≥ 5) over the past 26 years and observe the effect of these changes on future seismic activity. We find that within 1.5 years after the M ≥ 5 earthquakes, the M ≥ 5 earthquakes near any one of the later earthquakes almost always rupture faults ruptured by the first earthquake loading. After this period, the destructive earthquakes make the probability of fault loading and unloading broken almost the same. Our results show that in the short time after the devastating earthquake in Southern California, a simple Coulomb stress failure model can be used to identify areas of increased seismic risk.