Depth to Bedrock Using Gravimetry in the Reno and Carson City, Nevada, Area Basins

Abstract: Sedimentary basins can trap earthquake surface waves and amplify the magnitude and lengthen the duration of seismic shaking at the surface. Poor existing gravity and well-data coverage of the basins below the rapidly growing Reno and Carson City urban areas of western Nevada prompted us to collect 200 new gravity measurements. By classifying all new and existing gravity locations as on seismic bedrock or in a basin, we separate the basins gravity signature from variable background bedrock gravity fields. We find an unexpected 1.2 km maximum depth trough below the western side of Reno; basin enhancement of the seismic shaking hazard would be greatest in this area. Depths throughout most of the rest of the Truckee Meadows basin below Reno are less than 0.5 km. The Eagle Valley basin below Carson City has a 0.53 km maximum depth. Basin depth estimates in Reno are consistent with depths to bedrock in the few available records of geothermal wells and in one wildcat oil well. Depths in Carson City are consistent with depths from existing seismic reflection soundings. The well and seismic correlations allow us to refine our assumed density contrasts. The basin to bedrock density contrast in Reno and Carson City may be as low as -0.33 g/cm3. The log of the oil well, on the deepest Reno subbasin, indicates that Quaternary deposits are not unusually thick there and suggests that the subbasin formed entirely before the middle Pliocene. Thickness of Quaternary fill, also of importance for determining seismic hazard below Reno and Carson City may only rarely exceed 200 m. To download this resource, please see the link provided.

Data and Resources

Metadata Source

Additional Info

Field Value
Citation Date 2000-03-01T12:00:00

Harvest Information

Original ID 50ec3aefb656b70647f32e38bccbeb9b
Index Date 2015-07-01T21:47:45Z
Original Format ISO-USGIN
Original Version 1.2

Authors

Name Abbott, R.E.
Position missing
Organization University of Nevada, Reno Seismological Lab
Email rabbott@seismo.unr.edu
Name Louie, J.N.
Position missing
Organization University of Nevada, Reno Seismological Lab
Email louie@seismo.unr.edu.

Geographic Extent

North Bound 39.5797
South Bound 39.0143
East Bound -119.561
West Bound -120.001