RII Track-4: NSF: Gouge Mineral Strain Mapping under Shearing and Implications for EGS-Induced Seismicity

在过去几年中，由于增强型地热系统（EGS）中的大量流体注入，引发地震的频率在全球范围内急剧增加，其中小的扰动可能会过早引发地震。最近的观测与EGS和故意重新激活故障在现场试验中表现出显着大于预测的幅度。诱发大地震事件的可能性增加，危及了几个地热项目。然而，人们对这些事件的认识并不清楚，如何预防和减轻EGS诱发的地震事件仍然是一个令人关注的问题。随着阿拉斯加EGS从浅温泉向深井钻井的传输，迫切需要更好地了解热交换和流体侵入影响下触发地震活动的机制。 本研究计画将以实验方式研究断层泥在热处理后的性质演化，从微观角度揭示ESG相关地震活动的触发机制。该项目将通过与美国48个州的机构的广泛合作，建立在阿拉斯加地质灾害评估和与地球环境系统相关的地质风险评估能力的基础上。通过奖学金项目获得的这些研究资源将被用来开发新的课程和研讨会材料，为妇女，少数民族和阿拉斯加偏远社区的学生提供研究经验和培训。这个研究基础设施改善轨道4 EPSCoR研究员（RII轨道4：NSF）项目将提供奖学金，以助理教授和培训的研究生在阿拉斯加大学费尔班克斯（UAF）。PI建议与宾夕法尼亚州立大学地质力学、地质流体和地质灾害中心的专家合作开发一种新的断层滑动测试系统。实践证明，断层泥层中矿物晶格应变是预测表面残余应力及其破坏状态的关键。断层泥层中矿物应变随热处理和流体侵入的变化对于预测地震事件的局部稳定性至关重要。然而，在实验室中没有直接证据来识别和量化矿物应变，这是由于在原位条件下用动态滑动过程直接测量矿物应变的障碍和困难。建议的测试系统，使独特的能力，使用中子衍射进行矿物应变映射的断层泥层剪切滑动。粘滑断层试验将使用建议的热处理和流体侵入试验系统进行。结合中子衍射和纳米压痕技术，从微观角度研究断层泥层中矿物的性质，以揭示ESG相关地震活动的触发机制。建议的测试系统，使调查的矿物性质的演化剪切及其对地震事件与热处理和流体入侵的影响。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。

The frequency of induced earthquakes has increased dramatically over the past few years globally due to massive fluid injection in enhanced geothermal systems (EGS), where small perturbations may prematurely trigger earthquakes. Recent observations associated with EGS and a purposely reactivated fault in a field pilot experiment exhibit significantly larger magnitudes than predicted. The increased likelihood of inducing large seismic events has jeopardized several geothermal projects. However, there is not a clear understanding of these events and the prevention and mitigation of EGS-induced seismic events are still a concern. With the transmission of Alaska EGS from shallow hot springs to deep borehole drilling, there is a pressing need to develop a better understanding of the mechanism of triggering the seismicity with the influence of heat exchange and fluids intrusion. This fellowship project will experimentally investigate the property evolution of the fault gouge with thermal treatment to reveal the triggering mechanism of ESG-related seismicity from a microscale perspective. The project will build on the capacity of geohazards evaluation and EGS-related geo-risk evaluation in Alaska through extended collaborations with institutions in the lower forty-eight (48) states. These research resources acquired through the fellowship project will be leveraged to develop new course and workshop materials to provide women, minorities, and Alaska remote community students with research experience and training.This Research Infrastructure Improvement Track-4 EPSCoR Research Fellows (RII Track-4:NSF) project would provide a fellowship to an Assistant Professor and training for a graduate student at the University of Alaska Fairbanks (UAF). The PI proposes to develop a novel fault sliding test system in collaboration with experts from the Center for Geomechanics, Geofluids, and Geohazards at the Pennsylvania State University. It has been proved that the mineral lattice strain in the gouge layer is critical for predicting the residual stress on the surface and its failure status. Mineral strain variation with thermal treatment and fluid intrusion within the fault gouge layer is critical for predicting localized stability that initializes seismic events. However, direct evidence has not been reported in the lab to identify and quantify the mineral strains due to the hurdle and difficulties of direct measurement of mineral strains under in situ conditions with a dynamic sliding process. The proposed test system enables the unique capacity of using neutron diffraction to conduct mineral strain mapping of the gouge layer with shear sliding. The stick-slip faulting test will be conducted using the proposed test system with thermal treatment and fluid intrusion. Combining neutron diffraction and nanoindentation techniques, the properties of minerals in the gouge layer will be investigated from a microscale perspective to reveal the triggering mechanism of ESG-related seismicity. The proposed test system enables the investigation of the evolution of mineral properties under shearing and its implications on seismic events with thermal treatment and fluids intrusion. The outcome will provide a unique perspective for evaluating the EGS-related geohazards and their prediction and prevention.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.