Department of Geological and Environmental Sciences, Chonnam National University, Yongbong-ro 77, Buk-gu, Gwangju, 61186, Republic of Korea.
Department of Geology and Environmental Geosciences, Northern Illinois University, 1425 W. Lincoln Hwy., DeKalb, IL, 60115, USA.
Nat Commun. 2020 May 26;11(1):2614. doi: 10.1038/s41467-020-16408-0.
Causal mechanisms for fluid injection-induced earthquakes remain a challenge to identify. Past studies largely established spatiotemporal correlations. Here, we propose a multi-process causal mechanism for injection-induced earthquakes through a case study of the 2017 M 5.5 induced earthquake near Pohang Enhanced Geothermal System, Korea, where detailed hydraulic stimulation and on-site seismicity monitoring data provide an unprecedented opportunity. Pore pressure modeling reveals that pore pressure changes initiate seismicity on critically stressed faults and Coulomb static stress transfer modeling reveals that earthquake interactions promote continued seismicity, leading to larger events. On the basis of these results, we propose the following causal mechanism for induced seismicity: pore pressure increase and earthquake interactions lead to fault weakening and ultimately triggering larger earthquakes later in the process. We suggest that it is prudent that pore pressure change, initial seismicity locations, and Coulomb static stress transfer from seismicity earlier in the sequence are assessed in real-time.
注水诱发地震的因果机制仍然难以确定。过去的研究主要建立了时空相关性。在这里，我们通过对韩国浦项增强地热系统 2017 年 M5.5 诱发地震的案例研究，提出了一个多过程诱发地震的因果机制，该地区提供了详细的水力刺激和现场地震活动监测数据，这是前所未有的机会。孔隙压力建模表明，孔隙压力变化引发临界受力断层的地震活动，库仑静态应力传递建模表明，地震相互作用促进了持续的地震活动，导致更大的地震。基于这些结果，我们提出了诱发地震的以下因果机制：孔隙压力增加和地震相互作用导致断层弱化，最终在过程后期引发更大的地震。我们建议在实时评估孔隙压力变化、初始地震位置以及序列早期地震产生的库仑静态应力传递。
