Fundamental Physical Mechanisms Leading to Initiation of Fault Rupture, With Application to Induced Seismicity at the Geysers Geothermal Field

该研究项目是一套实验室实验，使用所谓的纳米地震学，研究断层表面上接触结运动的动态演变，从而导致总破裂。 为了理解流体注入诱发地震活动的机制，必须确定导致破裂启动的机制。 该项目的新型传感器将允许在接近纳米结剪切的尺度上测量不断变化的摩擦行为。 波形反演和正演合成将模拟测量行为，将具有自相似摩擦机制的多个尺度联系在一起，导致实际的“滑动”。“实验活动的第一阶段是调查热弹性应变和胶结作用对断层强度的影响;第二阶段将调查接触熔化对断裂起始机制的影响。 第三组实验将在蒸汽驱动的真三轴地热储层模拟器中进行。 这组测试将研究热收缩的影响，以及注入水闪蒸成蒸汽，作为断层弱化的近因。通过和不断增长的水力裂缝将被模拟。增强型地热系统（EGS）是一个潜在的主要贡献者，为国家的清洁，可持续能源的供应。 EGS是一种工程地下热交换器，旨在改善传统的热液储层，或在热储层岩石具有低渗透性的情况下创建循环系统。 这通常通过注入加压流体来完成。 这种注入已被证明会诱发地震活动，因此了解为什么诱发地震活动发生的机制是利用这种资源的基础。 了解诱发地震活动的机制对于开发该国丰富的页岩气储量和碳封存也是必要的。 间歇泉热液场是世界上最大的此类发电厂，将作为现场试验台;通过与劳伦斯伯克利国家实验室的合作，将实验室结果与间歇泉的实际地震行为进行比较。

This research project is a suite of laboratory experiments examining the dynamic evolution of motion of a contact junction on a fault surface which results in gross rupture - using what is called nano-seismology. In order to understand the mechanisms leading to fluid-injection induced seismicity (IS), the mechanisms leading to rupture initiation must be defined. This project's novel sensors will allow measurement, at a scale approaching shear of nanojunctions, of evolving frictional behavior. Waveform inversion and forward synthetics will model measured behaviors, tying together the multiple scales across which there are self-similar frictional mechanisms, leading up to actual "slip." The first stage of the experimental campaign is the investigation of the effects of thermoelastic strain and cementation on fault strength; the second stage will investigate the effects of contact melting on rupture initiation mechanisms. The third set of experiments will take place in a steam driven true-triaxial geothermal reservoir simulator. This set of tests will investigate the effects of thermal contraction, and injected water flashing to steam, as proximate causes of fault weakening. Both through-going and growing hydraulic fractures will be modeled.Enhanced geothermal systems (EGS) are potentially a major contributor to the nation's supply of clean, sustainable energy. An EGS is an engineered subsurface heat exchanger designed to either improve a conventional hydrothermal reservoir, or to create a circulation system where hot reservoir rocks have low permeability. This is most often done by injection of pressurized fluids. This injection has been shown to induce seismicity, so understanding the mechanisms of why induced seismicity occurs is fundamental for utilizing this resource. Understanding the mechanisms of induced seismicity is also necessary for the exploitation of the country's rich deposits of shale gas, and for carbon sequestration. The Geysers hydrothermal field, which is the largest such electricity producer in the world, will serve as the field test bed; laboratory results being compared to actual seismic behavior from the Geysers through partnership with Lawrence Berkeley National Laboratory.