Passive seismic data collection was done northwest of the Air Force Research Laboratory (AFRL) at Edwards Air Force Base using the horizontal-to-vertical spectral ratio (HVSR) technique. HVSR surveys were done at 43 locations between May and September 2018 to refine the understanding of the bedrock-alluvial aquifer transition zone downgradient from the AFRL. Specifically, the data were collected to help determine the depth to bedrock. The HVSR method is a passive seismic technique that uses a three-component seismometer to measure the vertical and horizontal components of ambient seismic noise. Seismic noise in the range of ~0.1 to 1 Hertz (Hz) is caused by ocean waves, large regional storms, and tectonic sources. A resonance frequency (f0) is induced in unconsolidated alluvium when there is a substantial contrast (greater than 2:1) in shear-wave acoustic impedance between the alluvial overburden and the bedrock. The f0 is determined from the analysis of the spectral ratio of the horizontal and vertical components of the seismic data. The thickness of the overburden can be related to the f0. In general, lower f0 relates to thicker sediments, and higher f0 relates to relatively thinner overburden. Other geophysical techniques–including time-domain electromagnetics and electrical resistivity tomography–co-located with the HVSR data are made available in other child pages within this data release: https://doi.org/10.5066/P9ZGZTA4HVSR. This page contains the raw HVSR data.

The Air Force Research Laboratory (AFRL) is about 7 kilometers southwest of Boron, California, and covers 320 square kilometers of Edwards Air Force Base. The AFRL consists of 12 facilities for testing full-size rocket engines, engine components, and liquid and solid propellants. The historical release of contaminants from rocket test stands, evaporation ponds, burn pits, catch basins, and leaking waste-collection tanks has contaminated groundwater in the AFRL. Groundwater aquifers near the AFRL are mostly restricted to fractured granitic bedrock, but previous studies indicate that groundwater and associated contaminants have moved into alluvium to the north and northwest. The U.S. Geological Survey (USGS) and the U.S. Air Force entered into a cooperative agreement to refine the understanding of the bedrock-alluvial aquifer transition zone downgradient from the AFRL. As part of that effort, surface geophysical data were collected to: (1) assess changes in the depth to bedrock with increasing distance from the AFRL; (2) to provide information on shallow geologic structures near the AFRL; and (3) to assess the presence of any faults that could present partial barriers to groundwater flow. The surface geophysical methods collected northwest of the AFRL in 2018 were electrical resistivity tomography (ERT), horizontal-to-vertical spectral ratio (HVSR) passive seismic, and time-domain electromagnetic (TEM).

The Air Force Research Laboratory (AFRL) is about 7 kilometers southwest of Boron, California, and covers 320 square kilometers of Edwards Air Force Base. The AFRL consists of 12 facilities for testing full-size rocket engines, engine components, and liquid and solid propellants. The historical release of contaminants from rocket test stands, evaporation ponds, burn pits, catch basins, and leaking waste-collection tanks has contaminated groundwater in the AFRL. Groundwater aquifers near the AFRL are mostly restricted to fractured granitic bedrock, but previous studies indicate that groundwater and associated contaminants have moved into alluvium to the north and northwest. The U.S. Geological Survey (USGS) and the U.S. Air Force entered into a cooperative agreement to refine the understanding of the bedrock-alluvial aquifer transition zone downgradient from the AFRL. As part of that effort, surface geophysical data were collected to: (1) assess changes in the depth to bedrock with increasing distance from the AFRL; (2) to provide information on shallow geologic structures near the AFRL; and (3) to assess the presence of any faults that could present partial barriers to groundwater flow. The surface geophysical methods collected northwest of the AFRL in 2018 were electrical resistivity tomography (ERT), horizontal-to-vertical spectral ratio (HVSR) passive seismic, and time-domain electromagnetic (TEM).

This dataset contains passive seismic data collected using a three-component seismometer during 2018-2020 at Pinnacles National Park, California. The data were acquired for the purpose of estimating depth to the bedrock surface underlying alluvial deposits, using the horizontal-to-vertical spectral ratio (HVSR) technique. Data were collected along ten transects, with 3 to 14 points collected along each transect, and at the locations of 6 existing or abandoned wells. A total of 81 passive seismic measurements were collected and the raw data are included in this dataset. The passive seismic data record ambient seismic noise in the range of approximately 0.1 to 1 Hertz (Hz), which is caused by ocean waves, large regional storms, and tectonic sources. The HVSR method analyzes the spectral ratio of the vertical and horizontal components of the passive seismic data to determine the fundamental seismic resonance frequency (f0), which is induced in unconsolidated sediments when there is a substantial contrast (greater than 2 to 1 ratio) in shear-wave acoustic impedance between these sediments and the bedrock. The thickness of the sediments is a function of f0.

In June of 2020, the U.S. Geological Survey conducted a high-resolution seismic survey at Edwards Air Force Base in Kern County, California. Seismic data were acquired using 601 DTCC SmartSolo 3-component nodal seismometer systems (“nodes”), which continuously recorded at 2000 samples per second. Nodes were deployed 5 meters apart along a southwest-northeast trend to create an approximately 3-km-long linear profile. P-wave seismic sources were generated primarily using a 500-lb (227-kg) accelerated weight drop at each recording station. P-wave sources were also generated at every 40 stations using downhole explosions. Fault-zone-guided waves were generated using explosive sources that were placed within a mapped trace of a nearby fault (Kramer Hills Fault zone), located approximately 1 km southeast of the seismic profile. Shot gathers were created in SEG-Y format (Barry et al, 1975) by extracting several seconds of data from each node for each recorded shot time. This report provides the metadata needed to analyze the seismic data.

In June of 2020, the U.S. Geological Survey conducted a high-resolution seismic survey at Edwards Air Force Base in Kern County, California. Seismic data were acquired using 601 DTCC SmartSolo 3-component nodal seismometer systems (“nodes”), which continuously recorded at 2000 samples per second. Nodes were deployed 5 meters apart along a southwest-northeast trend to create an approximately 3-km-long linear profile. P-wave seismic sources were generated primarily using a 500-lb (227-kg) accelerated weight drop at each recording station. P-wave sources were also generated at every 40 stations using downhole explosions. Fault-zone-guided waves were generated using explosive sources that were placed within a mapped trace of a nearby fault (Kramer Hills Fault zone), located approximately 1 km southeast of the seismic profile. Shot gathers were created in SEG-Y format (Barry et al, 1975) by extracting several seconds of data from each node for each recorded shot time. 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 utility of passive seismic emission tomography for mapping geothermal permeability has been tested at San Emidio in Nevada. The San Emidio study area overlaps a geothermal field in production since 1987 and another resource to the south of the production field. Passive seismic data collections were completed at San Emidio in late 2016 by Microseismic Inc as part of a DOE project. The PSET results are being analyzed as part of the WHOLESCALE project. This submission includes P-wave velocity model data, and the passive seismic data with more information on each bellow.

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.