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

自2008年以来，美国中部与主要石油和天然气作业有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密集的城市附近，也发生在国家安全级别较高的地区，如俄克拉荷马州的库欣，这是美国石油和天然气管道运输系统的主要枢纽。与加州和阿拉斯加的地震可以明确地与沿着板块边界的变形联系在一起不同，俄克拉荷马州地震的原因仍然是一个非常有争议和高度争论的话题。然而，越来越多的科学证据表明，地震活动水平的增加与石油开采相关的钻探活动中注入的含盐生产废水有关。虽然地震网络能够检测活动并绘制其震源，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，使用自然发生的电场和磁场测量地球？S表面测量电导率结构。2016年俄克拉荷马州波尼5.8级地震为科学家提供了前所未有的机会，可以将地震活动与断层上或周围流体成像联系起来。因此，我们将进行一系列的二维（2D）配置文件位于通过最近破裂的断层和地震活动集中的地区，也横跨附近的断层，没有破裂。我们的结果和正在进行的地震研究的整合将导致更好地了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决策者的决策提供信息。电地球物理方法理想地适合于对含流体断层成像，因为产出的沃茨是高盐度的，因此具有高电导率。到目前为止，还没有研究对俄克拉荷马州断层中的流体进行成像，并与地震活动直接相关。几口注入威尔斯的井位于震中半径20公里范围内;研究表明，向大容量威尔斯井注入流体可引发远至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年波尼5.8级地震期间破裂的断层带中的流体分布。由于大多数注入活动在2016年9月3日地震后暂时停止，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地震活动过程的状态。考虑到俄克拉荷马州的地震活动已经引起了公众的强烈抗议，立法者要求采取行动。然而，利益攸关方和决策者的任何决定都必须以可靠的科学和公正的数据为指导。以地质学为依据的方法来描述诱发地震活动的特征，以便纳入地震危险性评估，这对敏感设施的评估至关重要。因此，我们提出的MT调查具有多方面的更广泛的影响：（1）它将产生数据约束的结果，这将导致更好地了解迁移的废水？断层相互作用(2)我们将提供相关数据，在评估与废水注入有关的地震危害时，这些数据可用于为决策者和利益相关者的决策提供信息。(3)我们的项目将吸引几个学生。学生将协助数据采集，并将获得MT专家在如何部署MT仪器方面的实践经验。至少有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多元化的劳动力队伍

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