Felzer K R, Brodsky E E
US Geological Survey, 525 S. Wilson, Pasadena, California 91106, USA.
Nature. 2006 Jun 8;441(7094):735-8. doi: 10.1038/nature04799.
The majority of earthquakes are aftershocks, yet aftershock physics is not well understood. Many studies suggest that static stress changes trigger aftershocks, but recent work suggests that shaking (dynamic stresses) may also play a role. Here we measure the decay of aftershocks as a function of distance from magnitude 2-6 mainshocks in order to clarify the aftershock triggering process. We find that for short times after the mainshock, when low background seismicity rates allow for good aftershock detection, the decay is well fitted by a single inverse power law over distances of 0.2-50 km. The consistency of the trend indicates that the same triggering mechanism is working over the entire range. As static stress changes at the more distant aftershocks are negligible, this suggests that dynamic stresses may be triggering all of these aftershocks. We infer that the observed aftershock density is consistent with the probability of triggering aftershocks being nearly proportional to seismic wave amplitude. The data are not fitted well by models that combine static stress change with the evolution of frictionally locked faults.
大多数地震都是余震，但余震的物理机制尚未得到很好的理解。许多研究表明，静态应力变化会引发余震，但最近的研究表明，震动（动态应力）也可能起作用。在这里，我们测量了余震随距离2 - 6级主震的衰减情况，以阐明余震触发过程。我们发现，在主震后的短时间内，当低背景地震活动率有利于良好的余震检测时，在0.2 - 50千米的距离范围内，衰减情况可以用单一的反幂律很好地拟合。这种趋势的一致性表明，在整个范围内相同的触发机制在起作用。由于距离较远的余震处的静态应力变化可以忽略不计，这表明动态应力可能正在触发所有这些余震。我们推断，观测到的余震密度与触发余震的概率几乎与地震波振幅成正比这一情况是一致的。将静态应力变化与摩擦锁定断层的演化相结合的模型并不能很好地拟合这些数据。
