Goebel Thomas H W, Walter Jacob I, Murray Kyle, Brodsky Emily E
University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
Oklahoma Geological Survey, University of Oklahoma, Norman, OK 73019, USA.
Sci Adv. 2017 Aug 9;3(8):e1700441. doi: 10.1126/sciadv.1700441. eCollection 2017 Aug.
The state of Oklahoma has experienced an unprecedented increase in earthquake activity since 2009, likely driven by large-scale wastewater injection operations. Statewide injection rates peaked in early 2015 and steadily decreased thereafter, approximately coinciding with collapsing oil prices and regulatory action. If seismic activity is primarily driven by fluid injection, a noticeable seismogenic response to the decrease in injection rates is expected. Langenbruch and Zoback suggest that "the probability of potentially damaging larger events, should significantly decrease by the end of 2016 and approach historic levels within a few years." We agree that the rate of small earthquakes has decreased toward the second half of 2016. However, their specific predictions about seismic hazard require reexamination. We test the influence of the model parameters of Langenbruch and Zoback based on fits to observed seismicity distributions. The results suggest that a range of realistic aftershock decay rates and values can lead to an increase in moderate earthquake probabilities from 37 to 80% in 2017 without any further alteration to the model. In addition, the observation that all four ≥ 5 earthquakes to date occurred when injection rates were below the triggering threshold of Langenbruch and Zoback challenges the applicability of the model for the most societally significant events.
自2009年以来，俄克拉荷马州经历了前所未有的地震活动增加，这可能是由大规模废水注入作业导致的。全州的注入率在2015年初达到峰值，此后稳步下降，这大致与油价暴跌和监管行动同时发生。如果地震活动主要由流体注入驱动，那么预计会对注入率的下降产生明显的地震成因响应。兰根布鲁赫和佐巴克指出，“到2016年底，潜在破坏性更大事件的发生概率应会显著降低，并在几年内接近历史水平。”我们认同在2016年下半年小地震的发生率已经下降。然而，他们关于地震危险性的具体预测需要重新审视。我们基于对观测到的地震活动性分布的拟合来测试兰根布鲁赫和佐巴克模型参数的影响。结果表明，一系列现实的余震衰减率和 值可能会导致2017年中等地震概率从37%增加到80%，而无需对模型进行任何进一步修改。此外，迄今为止所有4次震级≥5级的地震均发生在注入率低于兰根布鲁赫和佐巴克触发阈值的情况下，这一观测结果对该模型在对社会影响最大的事件中的适用性提出了挑战。
