UC Berkeley

Groundwater affects volcanic and fault processes at a wide range of spatiotemporal scales. This dissertation focuses on two questions. First, what role does groundwater play in volcanoes and fault zones? Evenly spaced columns of alteration within the Bishop Tuff and numerical models show that boiling controls the cooling rate and pressure within shallow volcanic systems (Chapter 2). Geodetic data and seismic catalogs show that regional hydrologic loads trigger seismic and aseismic slip on faults in and around the Tibetan Plateau (Chapter 6) and on the Longitudinal Valley Fault in Taiwan (Chapter 5) by changing pore pressure within the fault zone. Observations of water level changes in groundwater wells are coincident with dynamically triggered seismicity. I propose that changing permeability during the passage of surface waves drives flow into fractures and faults potentially triggering earthquakes. The second question addressed is how do distant earthquakes change groundwater systems? I document changes in groundwater wells (Chapter 3 and 4), fault zones (Chapter 5), and seismic velocity (Chapter 4 and 5) after the passage of surface waves. These interactions can extend thousands of kilometers from earthquake epicenters and require mechanisms for small stresses to resonate and amplify. This thesis shows that resonances form between tectonic forces and hydrologic systems by changing pore pressure in dilating fractures (Chapter 3), boiling fronts (Chapter 2), and fault zones (Chapter 5 and 6). Together, this dissertation contributes to our understanding of how hydrology and the solid earth interact.