In May 2015, we acquired high-resolution seismic profiles near six strong motion instruments located in Napa and Solano Counties, California. These strong motion instruments recorded horizontal peak accelerations (PGAs) from 0.329g to 0.611g, which were among the highest recorded in the Napa area during the 24 August 2014 Mw 6.0 South Napa Earthquake. Our goal is to measure the seismic velocities of the underlying geologic material at each strong motion site using P- and S-wave refraction tomography and analysis of surface waves, especially in the upper 30 m of the subsurface.

In August 2017, the U.S. Geological Survey acquired high-resolution P- and S-wave seismic data near six Southern California Seismic Network (SCSN) recording stations in southern California: CI.OLI Olinda; CI.SRN Serrano; CI.MUR Murrieta; CI.LCG La Cienega; CI.RUS Rush; and CI.STC Santa Clara (Figure 1). These strong-motion recording stations are located inside Southern California Edison electrical substations, critical infrastructures that provide essential services to millions of customers. The primary goals of the seismic survey were to understand the potential for amplified ground shaking and to evaluate lateral variability in shear-wave velocity at these sites. We deployed up to 88 geophones at 2-m or 4-m spacing along seven linear profiles surrounding the stations and collocated P- and S-wave sources at ~1-m offset from the geophones. We generated P waves using three types of active sources: a 226-kg vertical accelerated weight-drop (AWD), a 3.5-kg sledgehammer and steel plate combination, and a 2.7-kg hammer and steel plate combination. Active-source S-waves were generated by horizontally striking an aluminum block with a 3.5-kg sledgehammer and by striking a 45-angle aluminum block with a 45°-angle AWD. We first deployed vertical-component geophones (40-Hz, SercelTM L40A, sensitivity of 22.34 volts/meter/second) to record P-wave shots, after which the vertical-component geophones were replaced with horizontal-component geophones (4.5-Hz, SercelTM L28-LBH, sensitivity of 31.3 volts/meter/second) to record S-wave shots. All data were recorded using up to two 60-channel Geometrics Stratavisor NX-60TM seismographs with 24-bit analog-to-digital converters. The seismographs were connected to the geophones via refraction cables. Each shot was recorded at a 0.5-ms sampling rate for two seconds, with data recording starting 100 ms before the actual time of the shot. Ambient noise data were recorded with vertical-component geophones at a 2-ms sampling rate for 120 seconds. This report provides the metadata needed to utilize the seismic data. Acknowledgements: Keith Galvin, Koichi Hayashi, Dan Langermann, Tony Martin, Devin McPhillips, Ian Richardson, David Saucedo-Green, Luther Strayer, Nathan Suits, and Alan Yong Reference: Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, Pullan, S. E., Chairman, 1990, Recommended standard for seismic (/radar) data files in the personal computer environment: Geophysics, vol. 55, no. 9, p. 1260-1271.

In August 2017, the U.S. Geological Survey acquired high-resolution P- and S-wave seismic data near six Southern California Seismic Network (SCSN) recording stations in southern California: CI.OLI Olinda; CI.SRN Serrano; CI.MUR Murrieta; CI.LCG La Cienega; CI.RUS Rush; and CI.STC Santa Clara (Figure 1). These strong-motion recording stations are located inside Southern California Edison electrical substations, critical infrastructures that provide essential services to millions of customers. The primary goals of the seismic survey were to understand the potential for amplified ground shaking and to evaluate lateral variability in shear-wave velocity at these sites. We deployed up to 88 geophones at 2-m or 4-m spacing along seven linear profiles surrounding the stations and collocated P- and S-wave sources at ~1-m offset from the geophones. We generated P waves using three types of active sources: a 226-kg vertical accelerated weight-drop (AWD), a 3.5-kg sledgehammer and steel plate combination, and a 2.7-kg hammer and steel plate combination. Active-source S-waves were generated by horizontally striking an aluminum block with a 3.5-kg sledgehammer and by striking a 45-angle aluminum block with a 45°-angle AWD. We first deployed vertical-component geophones (40-Hz, SercelTM L40A, sensitivity of 22.34 volts/meter/second) to record P-wave shots, after which the vertical-component geophones were replaced with horizontal-component geophones (4.5-Hz, SercelTM L28-LBH, sensitivity of 31.3 volts/meter/second) to record S-wave shots. All data were recorded using up to two 60-channel Geometrics Stratavisor NX-60TM seismographs with 24-bit analog-to-digital converters. The seismographs were connected to the geophones via refraction cables. Each shot was recorded at a 0.5-ms sampling rate for two seconds, with data recording starting 100 ms before the actual time of the shot. Ambient noise data were recorded with vertical-component geophones at a 2-ms sampling rate for 120 seconds. This report provides the metadata needed to utilize the seismic data. Acknowledgements: Keith Galvin, Koichi Hayashi, Dan Langermann, Tony Martin, Devin McPhillips, Ian Richardson, David Saucedo-Green, Luther Strayer, Nathan Suits, and Alan Yong Reference: Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, Pullan, S. E., Chairman, 1990, Recommended standard for seismic (/radar) data files in the personal computer environment: Geophysics, vol. 55, no. 9, p. 1260-1271.

In September 2017, the U.S. Geological Survey acquired high resolution P- and S-wave seismic data across the suspected trace of the West Napa Fault zone in St. Helena, California, approximately 70 m north of the previous seismic survey conducted in April 2017 (Chan et al., 2018). We acquired seismic reflection, refraction, and guided-wave data along a 75-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 1 and 2 m along the profile. We used 77 SercelTM L40A P-wave (40-Hz vertical-component) geophones with a sensitivity of 22.34 volts/meter/second to record 60 P-wave shots, and 77 SercelTM L28-LBH S-wave (4.5-Hz horizontal-component) geophones with a sensitivity of 31.3 volts/meter/second to record 60 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-wave (226-kg accelerated weight-drop, AWD) and S-wave (angle AWD) energies approximately 160 m north of the recording arrays. All data were recorded using one 60-channel Geometrics Stratavisor NX-60TM seismograph with a 24-bit analog-to-digital converter (Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, 1990); the seismograph was 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. Reference: Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, Pullan, S. E., Chairman, 1990, Recommended standard for seismic (/radar) data files in the personal computer environment: Geophysics, vol. 55, no. 9, p. 1260-1271.

In September 2017, the U.S. Geological Survey acquired high resolution P- and S-wave seismic data across the suspected trace of the West Napa Fault zone in St. Helena, California, approximately 70 m north of the previous seismic survey conducted in April 2017 (Chan et al., 2018). We acquired seismic reflection, refraction, and guided-wave data along a 75-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 1 and 2 m along the profile. We used 77 SercelTM L40A P-wave (40-Hz vertical-component) geophones with a sensitivity of 22.34 volts/meter/second to record 60 P-wave shots, and 77 SercelTM L28-LBH S-wave (4.5-Hz horizontal-component) geophones with a sensitivity of 31.3 volts/meter/second to record 60 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-wave (226-kg accelerated weight-drop, AWD) and S-wave (angle AWD) energies approximately 160 m north of the recording arrays. All data were recorded using one 60-channel Geometrics Stratavisor NX-60TM seismograph with a 24-bit analog-to-digital converter (Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, 1990); the seismograph was 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. Reference: Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, Pullan, S. E., Chairman, 1990, Recommended standard for seismic (/radar) data files in the personal computer environment: Geophysics, vol. 55, no. 9, p. 1260-1271.

In September 2021, the U.S. Geological Survey acquired high-resolution P- and S-wave data near seismic station CE.57213 in Fremont, California, approximately 100 m east of the mapped trace of the Hayward Fault. We acquired the seismic data to evaluate the time-averaged shear-wave velocity in the upper 30 m (VS30) and to better understand ground-shaking near the station CE.57213. The seismic data were acquired using a linear array of SmartSolo 3-component nodal seismometers (nodes), which continuously recorded at 2000 samples per second (0.5-ms sampling rate). We deployed 60 nodes, spaced at 2-m increments, along a 180-m-long, northeast-southwest-trending linear array. We generated P-wave seismic sources (shots) adjacent to each node at a 1-m offset using a 3.5-kg sledgehammer to vertically strike a steel plate on the ground surface. S-wave sources (shots) were generated adjacent to each node by horizontally striking an aluminum block with a 3.5-kg sledgehammer. For each shot point, we extracted approximately 2 seconds of data from each node following the shot times, combined the seismic traces into a single shot gather, and stored the data in SEG-Y format (Barry et al, 1975). This report provides the metadata needed to analyze the seismic data.

In November of 2021, the U.S. Geological Survey acquired high-resolution P- and S-wave seismic data at two seismic recording stations in Tulare and Fresno counties, California: Berkeley Digital Seismic Network BK.LIND and BK.KARE. We deployed 60 DTCC SmartSolo 3-component nodal seismometers (“nodes”) at 2-m intervals along a linear array at each seismic recording station. The nodes recorded seismic data continuously at a 0.5-ms sampling interval, and shot timing was recorded by GPS event capture hardware to precisely determine the shot times. We generated active-source P-waves by vertically striking a steel plate with a 3.5-kg sledgehammer, and active-source S-waves by horizontally striking an aluminum block with a 3.5-kg sledgehammer. The active-sources were generated at about 1-m offset from the nodes along the arrays.

The U.S. Geological Survey acquired high-resolution P- and S-wave seismic data across the Frijoles Fault strand of the San Gregorio Fault Zone (SGFZ) at northern Año Nuevo, California in 2012. SGFZ is a right-lateral fault system that is mainly offshore, and prior studies provide highly variable slip estimates, which indicates uncertainty about the seismic hazard it poses. Therefore, the primary goal of the seismic survey was to better understand the structure and geometry of the onshore section of the Frijoles Fault strand of the SGFZ. We deployed 118 geophones (channels) at 5-m spacing along a linear profile centered on the mapped surface trace of the Frijoles Fault and co-located active P- and S-wave sources at ~1-m offset from the geophones. Channel numbers increase from west to east along the profile. We generated P-waves using either a seisgun (www.utep.edu/science/ssf/Manuals/betsy_seisgun.pdf, accessed August 2022) or an accelerated weight-drop and S-waves by horizontally striking an aluminum block on both sides with a sledgehammer. We first deployed vertical-component geophones (40-Hz, SercelTM L40A, sensitivity of 22.34 volts/meter/second) to record P-wave sources, after which we replaced the vertical-component geophones with horizontal-component geophones (4.5-Hz, SercelTM L28-LBH, sensitivity of 31.3 volts/meter/second) to record S-wave sources. Refraction cables connected all geophones to two 60-channel Geometrics Stratavisor NX-60TM seismographs with 24-bit analog-to-digital converters. Each shot was recorded at a 0.5-ms sampling rate for two seconds, with data recording at 100 ms before the actual time of the shot. This data release provides the metadata needed to utilize the seismic data. Data Format and Files We combined each seismic trace for a given shot time into a shot gather, and the traces in each shot gather are ordered by channel numbers (1-118) based on the position of the geophones along the profile. Furthermore, we assigned a unique field number (FFID) to each shot gather, and we combined the shot gathers recorded from both seismographs into two SEG-Y files (Barry et al., 1975), 78023.segy (channels 1 to 60) and marine.segy (channels 61 to 118), which are stored in big-Endian, 4-byte IBM-floating-point format (format code 1). Data samples are in millivolts and can be converted to velocity using the geophone sensitivity values. Metadata for all profiles are contained in two text files and one xml file: PIE12.setup.csv, PIE12.location.csv, and PIE12Metadata.xml. The setup file describes the identification of shots recorded by the two seismographs, channel number, recording stations (geophones), and the source type for both SEG-Y files. The location file describes the channel number, latitude, and longitude of all geophone locations. Reference Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics, vol. 40, no. 2, p. 344-352, doi: 10.1190/1.1440530.

The U.S. Geological Survey acquired high-resolution P- and S-wave seismic data across the Frijoles Fault strand of the San Gregorio Fault Zone (SGFZ) at northern Año Nuevo, California in 2012. SGFZ is a right-lateral fault system that is mainly offshore, and prior studies provide highly variable slip estimates, which indicates uncertainty about the seismic hazard it poses. Therefore, the primary goal of the seismic survey was to better understand the structure and geometry of the onshore section of the Frijoles Fault strand of the SGFZ. We deployed 118 geophones (channels) at 5-m spacing along a linear profile centered on the mapped surface trace of the Frijoles Fault and co-located active P- and S-wave sources at ~1-m offset from the geophones. Channel numbers increase from west to east along the profile. We generated P-waves using either a seisgun (www.utep.edu/science/ssf/Manuals/betsy_seisgun.pdf, accessed August 2022) or an accelerated weight-drop and S-waves by horizontally striking an aluminum block on both sides with a sledgehammer. We first deployed vertical-component geophones (40-Hz, SercelTM L40A, sensitivity of 22.34 volts/meter/second) to record P-wave sources, after which we replaced the vertical-component geophones with horizontal-component geophones (4.5-Hz, SercelTM L28-LBH, sensitivity of 31.3 volts/meter/second) to record S-wave sources. Refraction cables connected all geophones to two 60-channel Geometrics Stratavisor NX-60TM seismographs with 24-bit analog-to-digital converters. Each shot was recorded at a 0.5-ms sampling rate for two seconds, with data recording at 100 ms before the actual time of the shot. This data release provides the metadata needed to utilize the seismic data. Data Format and Files We combined each seismic trace for a given shot time into a shot gather, and the traces in each shot gather are ordered by channel numbers (1-118) based on the position of the geophones along the profile. Furthermore, we assigned a unique field number (FFID) to each shot gather, and we combined the shot gathers recorded from both seismographs into two SEG-Y files (Barry et al., 1975), 78023.segy (channels 1 to 60) and marine.segy (channels 61 to 118), which are stored in big-Endian, 4-byte IBM-floating-point format (format code 1). Data samples are in millivolts and can be converted to velocity using the geophone sensitivity values. Metadata for all profiles are contained in two text files and one xml file: PIE12.setup.csv, PIE12.location.csv, and PIE12Metadata.xml. The setup file describes the identification of shots recorded by the two seismographs, channel number, recording stations (geophones), and the source type for both SEG-Y files. The location file describes the channel number, latitude, and longitude of all geophone locations. Reference Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics, vol. 40, no. 2, p. 344-352, doi: 10.1190/1.1440530.

In April 2017, the U.S. Geological Survey acquired high resolution P- and S-wave seismic data across the suspected trace of the West Napa Fault zone in St. Helena, California. We acquired seismic reflection, refraction, and guided-wave data along a 215-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 2 m along the profile. We used 109 SercelTM L40A P-wave (40-Hz vertical-component) geophones with a sensitivity of 22.34 volts/meter/second to record 108 P-wave shots, and 109 SercelTM L28-LBH S-wave (4.5-Hz horizontal-component) geophones with a sensitivity of 31.3 volts/meter/second to record 108 S-wave shots. We generated P-wave data using one of two active sources depending on site accessibility: a 226-kg accelerated weight drop (AWD) and 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- (AWD) and S-wave (angle AWD) energy approximately 225 m north 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 with a roll-along descaling factor (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. Reference: Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, Pullan, S. E., Chairman, 1990, Recommended standard for seismic (/radar) data files in the personal computer environment: Geophysics, vol. 55, no. 9, p. 1260-1271.