Berkeley Seismological Laboratory, University of California, Berkeley, CA 94720;
Department of Earth and Planetary Science, University of California, Berkeley, CA 94720.
Proc Natl Acad Sci U S A. 2021 May 18;118(20). doi: 10.1073/pnas.2102338118.
Industrial activity away from plate boundaries can induce earthquakes and has evolved into a global issue. Much of the induced seismicity in the United States' midcontinent is attributed to a direct pressure increase from deep wastewater disposal. This mechanism is not applicable where deep basement faults are hydraulically isolated from shallow injection aquifers, leading to a debate about the mechanisms for induced seismicity. Here, we compile industrial, seismic, geodetic, and geological data within the Delaware Basin, western Texas, and calculate stress and pressure changes at seismogenic depth using a coupled poroelastic model. We show that the widespread deep seismicity is mainly driven by shallow wastewater injection through the transmission of poroelastic stresses assuming that unfractured shales are hydraulic barriers over decadal time scales. A zone of seismic quiescence to the north, where injection-induced stress changes would promote seismicity, suggests a regional tectonic control on the occurrence of induced earthquakes. Comparing the poroelastic responses from injection and extraction operations, we find that the basement stress is most sensitive to shallow reservoir hydrogeological parameters, particularly hydraulic diffusivity. These results demonstrate that intraplate seismicity can be caused by shallow human activities that poroelastically perturb stresses at hydraulically isolated seismogenic depths, with impacts on seismicity that are preconditioned by regional tectonics.
远离板块边界的工业活动可能引发地震，这已成为一个全球性问题。美国中西部大部分诱发地震都归因于深部废水处理带来的直接压力增加。在深部基岩断层与浅层注入含水层水力隔离的情况下，这种机制并不适用，这导致了对诱发地震机制的争论。在这里，我们在德克萨斯州西部的特拉华盆地内编译了工业、地震、大地测量和地质数据，并使用耦合孔隙弹性模型计算了地震活动深度的应力和压力变化。我们表明，广泛的深部地震活动主要是由浅层废水注入引起的，假设未破裂的页岩在数十年的时间尺度上是水力屏障，通过孔隙弹性应力的传递。北部地震活动相对平静的区域表明，诱发地震的发生受到区域构造控制。比较注采作业的孔隙弹性响应，我们发现基底应力对浅层储层水文地质参数最敏感，特别是水力扩散系数。这些结果表明，板块内地震活动可能是由浅层人类活动引起的，这些活动通过水力隔离的地震活动深度引起的孔隙弹性应力干扰，其对地震活动的影响受到区域构造的制约。
