High-resolution seismic imaging of the West Napa Fault Zone at Buhman Avenue, Napa, California

In November 2016, the U.S. Geological Survey acquired high resolution P- and S-wave seismic data across the trace of the West Napa Fault zone near Buhman Avenue in Napa, California. The primary goal of the seismic survey was to image the subsurface damage from the 2014 MW 6.0 South Napa earthquake to assist in a near-surface fault slip and deformation investigation. We acquired seismic reflection, refraction, and guided-wave data along a 117-m-long profile across the expected trend of the West Napa Fault zone. To acquire the reflection and refraction data, we co-located shots and geophones, spaced every meter along the profile. We used 118 SercelTM L40A P-wave (40-Hz vertical-component) geophones with a sensitivity of 22.34 volts/meter/second to record 118 P-wave shots, and 118 SercelTM L28-LBH S-wave (4.5-Hz horizontal-component) geophones with a sensitivity of 31.3 volts/meter/second to record 118 S-wave shots. We generated P-wave data using a 3.5-kg sledgehammer and steel plate combination. S-wave sources were generated by horizontally striking an aluminum block with a 3.5-kg sledgehammer. We acquired fault-zone guided-wave data by generating P- and S-wave energy (3.5-kg sledgehammer and steel plate or aluminum block) approximately 44 and 45 m northwest of the P- and S-wave recording arrays. All data were recorded using two 60-channel Geometrics Stratavisor NX-60TM seismographs with a 24-bit analog-to-digital converter (Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, 1990); the seismographs were connected to the P- and S-wave geophones via refraction cables. Each shot was recorded for two seconds, with data recording starting 100 ms before the actual time of the shot. Data were recorded at a sampling rate of 0.5 ms, or 2000 samples per second. This report provides the metadata needed to utilize the seismic data.