Navas-Portella Víctor, Jiménez Abigail, Corral Álvaro
Centre de Recerca Matemàtica, Edifici C, Campus Bellaterra, E-08193, Barcelona, Spain.
Barcelona Graduate School of Mathematics, Edifici C, Campus Bellaterra, E-08193, Barcelona, Spain.
Sci Rep. 2020 Feb 19;10(1):2901. doi: 10.1038/s41598-020-59416-2.
Coulomb-stress theory has been used for years in seismology to understand how earthquakes trigger each other. Whenever an earthquake occurs, the stress field changes, and places with positive increases are brought closer to failure. Earthquake models that relate earthquake rates and Coulomb stress after a main event, such as the rate-and-state model, assume that the magnitude distribution of earthquakes is not affected by the change in the Coulomb stress. By using different slip models, we calculate the change in Coulomb stress in the fault plane for every aftershock after the Landers event (California, USA, 1992, moment magnitude 7.3). Applying several statistical analyses to test whether the distribution of magnitudes is sensitive to the sign of the Coulomb-stress increase, we are not able to find any significant effect. Further, whereas the events with a positive increase of the stress are characterized by a much larger proportion of strike-slip events in comparison with the seismicity previous to the mainshock, the events happening despite a decrease in Coulomb stress show no relevant differences in focal-mechanism distribution with respect to previous seismicity.
库仑应力理论在地震学中已应用多年，用于理解地震如何相互触发。每当发生地震时，应力场就会发生变化，库仑应力增加为正的区域就更接近破坏状态。一些将主震后地震发生率与库仑应力联系起来的地震模型，如速率-状态模型，假定地震的震级分布不受库仑应力变化的影响。通过使用不同的滑动模型，我们计算了1992年美国加利福尼亚州兰德斯地震（矩震级7.3）后每次余震在断层面上的库仑应力变化。应用多种统计分析来检验震级分布是否对库仑应力增加的符号敏感，我们未能发现任何显著影响。此外，尽管应力增加为正的事件与主震前的地震活动相比，走滑事件的比例要大得多，但库仑应力降低时发生的事件在震源机制分布方面与之前的地震活动没有显著差异。
