RAPID: Collaborative Research: Response to the 2016 M5.8 Pawnee Earthquake: Using MT to map Fluids in Faults

RAPID：协作研究：响应 2016 年 M5.8 波尼地震：使用 MT 绘制断层中的流体图

• 批准号: 1664579
• 负责人: Kerry Key
• 金额: $ 1.42万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-11-01 至 2017-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1664579&HistoricalAwards=false
• 关键词: RAPID; Collaborative; Research; Response; 2016

Since 2008, there has been a dramatic increase in earthquake activity in the central United States in association with major oil and gas operations. Oklahoma is now considered one of the most seismically active states. Some of the earthquakes are occurring near populated cities and also in areas of high national security such as Cushing, Oklahoma, a major hub of the U.S. oil and gas pipeline transportation system. Unlike earthquakes in California and Alaska that can be clearly linked to deformation along plate boundaries, the cause of the earthquakes in Oklahoma remains a very contentious and highly debated topic. However, there is an increasing body of scientific evidence to suggest that the increased level of seismicity is linked to the injection of saline production wastewaters from drilling activity related to petroleum exploitation. Although seismic networks are able to detect activity and map its hypocenter, they are unable to image the distribution of fluids in the fault responsible for triggering seismicity. The magnetotelluric (MT) technique, uses naturally occurring electric and magnetic fields measured at Earth?s surface to measure conductivity structure. The 2016 M5.8 Pawnee, Oklahoma earthquake provides an unprecedented opportunity for scientists to provide a link between seismicity and imaging of fluids on or around faults. Thus we will carry out a series of two-dimensional (2D) profiles located through areas where the fault recently ruptured and seismic activity is concentrated and also across the faults in the vicinity that did not rupture. The integration of our results and ongoing seismic studies will lead to a better understanding of the links between fluid injection and seismicity. Results of this study can inform decisions by policy-makers. Electrical geophysical methods are ideally suited to image fluid bearing faults since the produced waters are highly saline and hence have a high electrical conductivity. To date, no study has imaged the fluids in the faults in Oklahoma and made a direct link to the seismicity. Several injection wells are located within a 20 km radius of the epicenter; and studies have suggested that injection of fluids in high-volume wells can trigger earthquakes as far away as 30 km. This proposal will collect MT geophysical data that will constrain the distribution of fluids in the fault zone that ruptured during the 2016 M5.8 Pawnee earthquake. Because most injection activities have been temporarily suspended following the September 3, 2016 earthquake, we have the unique opportunity to capture the state of the fluid induced seismicity process before the system is altered by additional wastewater injection. Given that seismicity in in Oklahoma has been met with public outcry, with demands for action by legislators. However, any decision by stakeholders and policy makers must be guided by sound science and unbiased data. Geologically informed approaches to characterizing induced seismicity for inclusion in seismic hazard evaluations is critical for evaluation of sensitive facilities. As a result, our proposed MT survey has multi-faceted broader impacts: (1) It will produce data-constrained results that will lead to a better understanding of migration of wastewater ? fault interactions. (2) We will produce relevant data that can be used to inform the decisions of policy-makers and stakeholders when assessing seismic hazards related to wastewater injection. (3) Our project will engage several students. Students will assist with the data acquisition and will gain hands-on experience from MT experts in how to deploy MT instrumentation. At least two of the students will come from under-represented groups, thereby building a diverse workforce in science and engineering

自 2008 年以来，美国中部与主要石油和天然气作业相关的地震活动急剧增加。俄克拉荷马州现在被认为是地震最活跃的州之一。一些地震发生在人口稠密的城市附近以及国家安全高度集中的地区，例如美国石油和天然气管道运输系统的主要枢纽俄克拉荷马州库欣。与加利福尼亚和阿拉斯加的地震明显与板块边界变形有关不同，俄克拉荷马州地震的原因仍然是一个非常有争议和备受争议的话题。然而，越来越多的科学证据表明，地震活动强度的增加与石油开采相关钻井活动注入盐水生产废水有关。尽管地震网络能够检测活动并绘制其震源图，但它们无法对触发地震活动的断层中的流体分布进行成像。 大地电磁 (MT) 技术利用在地球表面测量的自然产生的电场和磁场来测量电导率结构。 2016 年俄克拉荷马州 M5.8 波尼地震为科学家提供了前所未有的机会，可以将地震活动性与断层上或断层周围的流体成像之间的联系联系起来。因此，我们将在断层最近破裂且地震活动集中的区域以及附近未破裂的断层上进行一系列二维 (2D) 剖面分析。我们的结果与正在进行的地震研究相结合将有助于更好地理解流体注入和地震活动之间的联系。 这项研究的结果可以为政策制定者的决策提供信息。电地球物理方法非常适合对含流体断层进行成像，因为产出水含盐量高，因此具有高电导率。迄今为止，还没有研究对俄克拉荷马州断层中的流体进行成像并与地震活动建立直接联系。数个注入井位于震中20公里半径范围内；研究表明，在大容量井中注入流体可以引发远至 30 公里的地震。该提案将收集 MT 地球物理数据，这些数据将限制 2016 年 M5.8 波尼地震期间破裂的断层带中流体的分布。由于大多数注入活动在 2016 年 9 月 3 日地震后已暂时停止，因此我们有独特的机会在系统因额外的废水注入而改变之前捕获流体诱发的地震活动过程的状态。鉴于俄克拉荷马州的地震活动引起了公众的强烈抗议，要求立法者采取行动。然而，利益相关者和政策制定者的任何决定都必须以可靠的科学和公正的数据为指导。采用地质学方法来表征诱发地震活动以纳入地震危险性评估对于敏感设施的评估至关重要。因此，我们提出的 MT 调查具有多方面、更广泛的影响： (1) 它将产生数据受限的结果，从而更好地了解废水的迁移？故障相互作用。 (2) 我们将提供相关数据，为政策制定者和利益相关者在评估与废水注入相关的地震灾害时做出决策提供依据。 (3) 我们的项目将吸引多名学生。学生将协助数据采集，并从 MT 专家那里获得如何部署 MT 仪器的实践经验。至少两名学生将来自代表性不足的群体，从而在科学和工程领域建立一支多元化的劳动力队伍