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.
