A Geophysical Investigation of a Fault as a Hydrologic Barrier in Reno, Nevada
CLARK, M., LOUIE, J. N., PANCHA, A., SCOTT, J. B., and HEATH, K., Nevada Seismological Laboratory, University of Nevada, Reno, NV 89557, firstname.lastname@example.org; and BENEDICT, C., Washoe County Dept. of Water Resources, Reno, NV 89502, email@example.com
The Truckee Meadows area is an alluvium-filled basin situated in the transition zone between the Sierra Nevada and the more moderate elevation of the Basin and Range Province. The Genoa Fault system (GFS) makes up the eastern boundary of a broad structural corridor between these two zones. The northern extension of the main fault in the GFS has been mapped into the Reno, Nevada metropolitan area of the Truckee Meadows. Groundwater elevation differences across the projection of this fault suggest that it is a locally significant groundwater flow barrier in the basin. The Central Truckee Meadows Remediation District is currently updating a groundwater flow and transport model used as a management tool for addressing a PCE contamination problem. Better characterization of the location, orientation, and hydrologic properties of the fault are needed to reduce the uncertainty in modeling groundwater flow in this part of the basin. High-resolution seismic-reflection surveys allow for the evaluation of the possible extension of the fault trace in an area approx. 750 m to the north and 500 m to the east of the north end of the mapped trace. These surveys also further constrain the geometry of the fault. Microtremor seismic surveys allow for a comparison of shallow shear velocities on opposite sides of the fault, suggesting the possible location of the fault for evaluation by reflection imaging. Aquifer test and geotechnical data may provide insights into the hydraulic characteristics of the fault as well.