Origin of hydrologic responses to earthquakes: constraints from the response of the Alum Rock Springs to the 2007 Alum Rock earthquake

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)资助的。液化就是一个例子，它是地震后造成破坏的主要原因。其他例子包括水流增加、水井水位变化以及泥火山喷发。这种水文反应很重要，因为它们提供了在空间和时间尺度上对水文和构造过程耦合的独特洞察，否则很难研究这些过程。这一认识对改进地震危险性评估是有价值的。地震的水文响应的起源一直是有争议的主题，很大程度上是因为有许多模型来解释观测结果，而几乎没有适合区分假说的测量方法。我们将使用加利福尼亚州铝石城的一组泉水对2007年10月30日发生的5.6级地震的反应来检验这些假设。在过去的5年里，我们一直在监测这些泉水，以便为地震后流量和水成分的变化提供基准。我们将把以前的测量和持续监测与地下水流和泉水流量的数值模拟相结合，以测试所提出的流量增加的来源模型。由于每个泉水在地球化学上是不同的，各个泉水的变化将使我们能够记录断裂带管道的变化。通过将测量和建模相结合，我们还应该能够确定观测到的过剩弹簧流量的来源是深部还是浅层，以及是静态应变还是动态应变导致了这些变化。广泛的影响：这个项目提供了一个跨学科的机会来了解断裂带的结构和演化。特别是，它将对流体在断裂带过程中的作用提供新的限制。研究人员将把对泉水的监测与加州大学伯克利分校教授的课程结合起来，包括新生研讨会、本科生水平的地球动力学和研究生水平的课程。他们还将与泉水所在的明石山公园的经理们交流结果。该公园是当地居民和K-12学生实地考察的热门目的地。位于该公园的青年科学学院每年招收3.3万名学生。温泉是公园的主要吸引力，我们的工作可以用来更新教育活动和解说展示。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)Hydrologic responses to earthquakes are common. One example, liquefaction, is the major source of damage following earthquakes. Other examples include increases in stream flow, changes in the water level in wells, and the eruption of mud volcanoes. Such hydrologic responses are important because they provide unique insight into the coupling of hydrologic and tectonic processes at spatial and temporal scales that are otherwise difficult to study. This understanding is valuable to improve earthquake hazard assessment.The origin of hydrologic responses to earthquakes has been the subject of controversy, in large part because there are many models to explain observations and almost no measurements suitable for distinguishing between hypotheses. We will test these hypotheses using the response of a set of springs in Alum Rock, California to magnitude 5.6 earthquake that occurred on the October 30, 2007. We had been monitoring these springs for the previous 5 years in order to provide a benchmark for post-seismic changes in discharge and water composition. We will combine previous measurements and continued monitoring with numerical modeling of the subsurface flow and spring discharge to test proposed models for the origin of the increased discharge. Because the water at each spring is geochemically distinct, changes at individual springs will enable us to document changes in fault zone plumbing. By integrating measurements and modeling we should also be able to determine whether the source of the observed excess spring discharge originates either at depth or in the shallow subsurface, and whether static strain or dynamic strain is responsible for the changes.Broader impacts:This project offers an interdisciplinary opportunity to understand fault zone structure and evolution. In particular it will provide new constraints on the role of fluids in fault zone processes. The investigators will integrate the monitoring of the springs with courses taught at UC Berkeley, including freshman seminars, undergraduate-level geodynamics, and graduate level classes. They will also communicate results with the managers of Alum Rock Park where the springs are located. The park is a popular destination for local residents and K-12 student field trips. The Youth Science Institute, housed at the park, reaches 33,000 students/year. The springs are the main draw of the park and our work can be used to update educational activities and interpretive displays.