Strong strain and pore pressure changes are observed after three Mw 4.5+ local and one Mw 7.2 regional earthquake during 2010–2017 in borehole strainmeters near Anza, California. The strain change emerges immediately after the earthquakes and lasts 40–100 days with amplitudes up to 10⁻⁷, larger than the coseismic strain offsets. The pore pressure exhibits change immediately after the earthquakes at some boreholes and with a delay of 4–10 days at the others. A joint analysis of the observed postseismic strain and pore pressure change suggests that the postseismic strains could be explained by combined effects of poroelastic deformation due to earthquake-induced pore pressure change and elastic deformation due to an earthquake-triggered aseismic slip on a local fault. Our study indicates that, in addition to possible aseismic fault slips triggered by an earthquake, pore pressure changes after the earthquake could be even more important in producing postseismic deformation.

中文翻译：

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由局部和区域地震引发的地震滑动和孔隙压力瞬变驱动的长达数月的地壳变形

在 2010 年至 2017 年期间，在加利福尼亚州安扎附近的钻孔应变计中，在 3 次 Mw 4.5+ 局部地震和一次 Mw 7.2 区域地震后观察到强烈的应变和孔隙压力变化。应变变化在地震后立即出现，持续 40-100 天，振幅可达 10 ^-7，大于同震应变偏移。一些钻孔的孔隙压力在地震后立即发生变化，而另一些则延迟 4-10 天。对观测到的震后应变和孔隙压力变化的联合分析表明，震后应变可以用地震引起的孔隙压力变化引起的多孔弹性变形和局部断层上地震引发的地震滑动引起的弹性变形的综合效应来解释。我们的研究表明，除了可能由地震引发的抗震断层滑动之外，震后孔隙压力变化对产生震后变形更为重要。