CAREER: Fluid-driven Deformation in Underground Salt Caverns and Wastewater Injection Sites

由人类活动引起的地震--如废水注入、地热开采和地下碳储存--往往很小。除了2016年波尼俄克拉荷马州地震等明显的例外，这些地震往往隐藏在文化地震噪音之下。这对监测和检测它们都提出了挑战。这妨碍了研究其原因和评估相应的危害。在美国，没有地震的地区现在被迫寻找可靠的方法来应对地震风险。在过去的十年中，对诱发地震活动的研究有所扩大;但研究主要集中在阿肯色州、科罗拉多、堪萨斯、俄亥俄州、俄克拉荷马州、德克萨斯州和怀俄明州的已知热点。然而，预计诱发地震将发生在以前没有面临这种威胁的地区。因此，在诱发地震发生之前，对这些地区的自然基线地震活动进行监测和编目至关重要;这可以检测地震活动何时超过背景水平并评估风险。其中一个地方是路易斯安那州。它目前正处于实施二氧化碳储存和增加石油和天然气勘探的门槛。然而，路易斯安那州缺乏全州范围的地震网络和监测计划来评估地震灾害。在这里，研究人员整合了研究和教育，旨在了解路易斯安那州人为驱动的变化。他们部署了地球物理和地震仪器，研究与人类活动和资源有关的三个关键地点。这些地点是：1）在路易斯安那州西北部，一个废水注入率很高的地区; 2）一个地下储存洞穴，据报道，在那里发生了地面运动，附近的天坑形成（伴随着地震前兆活动）; 3）横跨巴吞鲁日断层，该断层也是盐水的片状屏障。通过整合多种数据类型，该团队逐渐揭示了路易斯安那州面临的新威胁。该项目还向一名职业生涯初期的女科学家、一名博士后研究员以及研究生和本科生提供支助。它包括建立以学生为中心的区域讲习班，特别是关于地球物理学中的机器学习应用。该项目还促进扩大对科学的参与，例如，通过让巴吞鲁日南方大学的学生参与进来，这是一所历史上的黑人大学。该项目由地球物理计划和激励竞争性研究的既定计划（EPSCoR）共同资助。该项目是多种数据类型的综合地球物理研究。它产生了流体参与地壳变形的详细特征。这些结果对正在经历人类快速变化的能源走廊具有重要的社会意义。他们描述了一个供应美国石油和天然气主要部分的地区下方的地下变形。该地区面临着持续的沉降、地下水盐碱化以及与油气勘探废水处理相关的地震活动增加的挑战。安装在三个关键地点的地震台阵不仅测量地震活动水平，而且还限制了人们知之甚少的地震变形。事实上，创新技术的应用，如裂缝地震成像，图像充满流体的网络，通过使用谐波共振裂缝。将地震学方法与全球定位系统数据分析相结合，以了解地壳的变形预算。这种方法提供了深入了解由人类活动驱动的地壳变形模式。 一个预期的成果是第一次高分辨率绘制该地区的裂缝几何形状和连通性、地下物质特性以及地震和抗震变形。因此，这项研究对我们理解流体驱动过程及其对地壳形变的影响具有深远的影响。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Earthquakes caused by human activities - such as wastewater injection, geothermal extraction, and underground carbon storage - tend to be small. With notable exceptions, such as the 2016 Pawnee Oklahoma earthquake, these earthquakes often hide below cultural seismic noise. This presents a challenge for both monitoring and detecting them. It impedes studying their causes and assessing corresponding hazards. In the U.S., regions that have been free of earthquakes are now pressed to find reliable ways to address earthquake risks. Research on induced seismicity has expanded in the last decade; but studies have mostly focused on known hotspots in Arkansas, Colorado, Kansas, Ohio, Oklahoma, Texas, and Wyoming. Yet, it is expected that induced earthquakes will occur in regions which did not face this threat before. It is, thus, critical to monitor and catalog the natural baseline seismicity in these regions before induced earthquakes happen; this allows detecting when seismicity rises above background levels and assessing the risks. One such location is the State of Louisiana. It is currently at the threshold of implementing CO2 storage and increased oil and gas exploration. However, Louisiana lacks a statewide seismic network and monitoring program to assess seismic hazards. Here, the researchers integrate research and education in the aim to understand human-driven changes in Louisiana. Deploying geophysical and seismic instruments, they study three key locations related to human activities and resources. These locations are: 1) in northwest Louisiana, a region with high wastewater injection rates; 2) an underground storage cavern, where ground motions have been reported and nearby sinkhole formation has occurred (with precursor earthquake activity); 3) across the Baton Rouge fault that also acts as a patchy barrier for salt water. Integrating multiple data types, the team gradually unveils the new threats Louisiana is facing. The project also provides support to an early-career female scientist, one postdoctoral researcher, and graduate and undergraduate students. It includes the establishment of student-focused regional workshops, notably on Machine Learning applications in Geophysics. The project also fosters broadening participation in science, e.g., by involving students from the Southern University at Baton Rouge, a Historically Black University. This project is jointly funded by the Geophysics Program and the Established Program to Stimulate Competitive Research (EPSCoR).The project is an integrated geophysical study of multiple data types. It produces a detailed characterization of fluid-involved crustal deformation. The results have important societal implications for energy corridors undergoing rapid human change. They characterize the largely unknown deformation of the subsurface beneath a region that supplies a major part of the U.S. oil and gas. This region is challenged by ongoing subsidence, groundwater salinization, and increasing seismicity associated with wastewater disposal from hydrocarbon exploration. The seismic arrays installed at three key locations not only measure the levels of seismicity, but also constrain the poorly understood aseismic deformation. Indeed, innovative techniques are applied, such as Fracture Seismic imaging, that image fluid-filled networks by using harmonic resonances within fractures. Seismological methods are integrated with GPS data analysis to understand the deformation budget of the crust. This approach provides insight into the pattern of crustal deformation driven by human activities. One expected outcome is the first high-resolution mapping of fracture geometry and connectivity, subsurface material properties, and seismic and aseismic deformation in the region. The study, thus, has far-reaching impacts on our general understanding of fluid-driven processes and their effects on crustal deformation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.