In July 2016, July 2019, and March 2020, 318 seismic recordings were acquired at locations within Shenandoah National Park, Virginia, using MOHO Tromino Model TEP-3C three-component seismometers to assess depth to bedrock using the HVSR method. This method requires a measurement of estimate of shear wave velocity, which depends on the regolith sediment composition and density, for the conversion of measured resonance frequency to a depth to bedrock. Shear wave velocities were calculated for sediment in Shenandoah NP at locations where regolith thickness is known (e.g. at documented boreholes). The locations in this study were generally selected to characterize the depths to bedrock adjacent to streams monitored for coupled temperature and flow dynamics related to several ongoing USGS projects.

A combination of long-term daily temperature records and depth to bedrock measurements were used to parametrize one-dimensional models of shallow aquifer vertical heat transport in Shenandoah National Park, VA, USA. Depth to bedrock can directly influence shallow aquifer flow and thermal sensitivity, but is typically ill-defined along the stream corridor in steep mountain catchments. We employed rapid, cost-effective passive seismic measurements to evaluate the variable thickness of the shallow colluvial and alluvial aquifer sediments along a headwater stream supporting coldwater-dependent brook trout (Salvelinus fontinalis) in Shenandoah National Park. The methods are fully documented in the associated journal article, Briggs, M.A., J.W. Lane, C.D. Snyder, E.A. White, Z.C. Johnson, D.L. Nelms, and N.P. Hitt, 2017, Shallow mountain bedrock limits seepage-based headwater climate refugia, Limnologica, https://dx.doi.org/10.1016/j.limno.2017.02.005. This Data Release includes seismic data collected as part of the study.

A combination of long-term daily temperature records and depth to bedrock measurements were used to parametrize one-dimensional models of shallow aquifer vertical heat transport in Shenandoah National Park, VA, USA. Depth to bedrock can directly influence shallow aquifer flow and thermal sensitivity, but is typically ill-defined along the stream corridor in steep mountain catchments. We employed rapid, cost-effective passive seismic measurements to evaluate the variable thickness of the shallow colluvial and alluvial aquifer sediments along a headwater stream supporting coldwater-dependent brook trout (Salvelinus fontinalis) in Shenandoah National Park. The methods are fully documented in the associated journal article, Briggs, M.A., J.W. Lane, C.D. Snyder, E.A. White, Z.C. Johnson, D.L. Nelms, and N.P. Hitt, 2017, Shallow mountain bedrock limits seepage-based headwater climate refugia, Limnologica, https://dx.doi.org/10.1016/j.limno.2017.02.005. This Data Release includes seismic data collected as part of the study.

A total of 119 passive seismic soundings were collected with Tromino (MoHo s.r.l.) 3-axis seismometers in the Fountain Creek area to partially refine alluvial aquifer thickness (depth to bedrock) estimates, particularly over known or suspected paleochannels. Data were collected during June 21-24, 2021 with a team of 4-5 people, each equipped with a Tromino Blu or Tromino 3G passive seismometer. A subset of the data included measurements made for shear velocity calibration; this included data collected at 10 well sites where depth to bedrock was available from driller's logs, and 3 sites above cutbanks where bedrock outcropped and the thickness of alluvial sediments could be directly measured. Data were processed using a publicly available batch R processing script (Terry, 2022). In picking depths from the 119 measurements for alluvial aquifer thickness, roughly 30% were deemed unusable, 14% were picked with low confidence, 38% were picked with medium confidence, and 18% were picked with high confidence. Calibration data suggested a shear wave velocity of 195 meters per second. Using this value, estimated alluvial aquifer thicknesses ranged from 1.7 to 26.8 meters.

A total of 119 passive seismic soundings were collected with Tromino (MoHo s.r.l.) 3-axis seismometers in the Fountain Creek area to partially refine alluvial aquifer thickness (depth to bedrock) estimates, particularly over known or suspected paleochannels. Data were collected during June 21-24, 2021 with a team of 4-5 people, each equipped with a Tromino Blu or Tromino 3G passive seismometer. A subset of the data included measurements made for shear velocity calibration; this included data collected at 10 well sites where depth to bedrock was available from driller's logs, and 3 sites above cutbanks where bedrock outcropped and the thickness of alluvial sediments could be directly measured. Data were processed using a publicly available batch R processing script (Terry, 2022). In picking depths from the 119 measurements for alluvial aquifer thickness, roughly 30% were deemed unusable, 14% were picked with low confidence, 38% were picked with medium confidence, and 18% were picked with high confidence. Calibration data suggested a shear wave velocity of 195 meters per second. Using this value, estimated alluvial aquifer thicknesses ranged from 1.7 to 26.8 meters.

Using the horizontal-to-vertical spectral-ratio (HVSR) method, we inferred the depth to bedrock at the Slate River Floodplain, CO, USA. The point-scale passive seismic data were collected using Model TEP-3C Tromino seismometers over 20 min or less intervals with the instruments coupled directly to the floodplain ground surface at 42 non-flooded locations during June 2021. The ratio of horizontal-to-vertical Fourier spectra (HVSR), determined using Grilla software (MOHO, S.R.L.), along with the estimated sediment shear-wave velocity, was used to calculate the depth to the bedrock contact. This passive seismic dataset indicates that the deepest bedrock is 16 m below the surface, while the bedrock reaches the surface at the hillslope. This release contains the inferred bedrock depths based on likely shear wave velocities (Vs) intrinsic to the underlying sediment, ranging from 300 m/s to 400 m/s, listed in the processed_data subdirectory in the file 'SLAC_HVSR_June2021.csv.' The range of possible depth to bedrock interpretations is included for demonstration purposes only.

Using the horizontal-to-vertical spectral-ratio (HVSR) method, we inferred the depth to bedrock at the Slate River Floodplain, CO, USA. The point-scale passive seismic data were collected using Model TEP-3C Tromino seismometers over 20 min or less intervals with the instruments coupled directly to the floodplain ground surface at 42 non-flooded locations during June 2021. The ratio of horizontal-to-vertical Fourier spectra (HVSR), determined using Grilla software (MOHO, S.R.L.), along with the estimated sediment shear-wave velocity, was used to calculate the depth to the bedrock contact. This passive seismic dataset indicates that the deepest bedrock is 16 m below the surface, while the bedrock reaches the surface at the hillslope. This release contains the inferred bedrock depths based on likely shear wave velocities (Vs) intrinsic to the underlying sediment, ranging from 300 m/s to 400 m/s, listed in the processed_data subdirectory in the file 'SLAC_HVSR_June2021.csv.' The range of possible depth to bedrock interpretations is included for demonstration purposes only.

Using the horizontal-to-vertical spectral-ratio (HVSR) method, we infer regolith thickness (i.e., depth to bedrock) throughout the Farmington River Watershed, CT, USA. Between Nov. 2019 and Nov. 2020, MOHO Tromino Model TEP-3C (MOHO, S.R.L.) three-component seismometers collected passive seismic recordings along the Farmington River and the upstream West Branch of Salmon Brook. From these recordings, we derived resonance frequencies using the GRILLA software (MOHO, S.R.L.), and then inferred potential regolith thicknesses based on likely shear wave velocities, Vs, intrinsic to the underlying sediment. Three potential shear wave velocities (Vs = 300m/s, 337m/s, 362 m/s) were considered for Farmington River watershed sediments, providing a range of potential depth estimates along the Farmington. This release contains raw passive seismic recording data, processed resonance frequency data, and the resulting inferred depth estimates displayed in both tabular and vector form. This dataset currently contains 3 zipped files: 1) ‘Processed.zip’ is a zipped directory containing .asc text files of processed passive seismic data, individual processed reports, tabulated results, and an associated summary text file, 'readme_Processed.txt'; 2) 'Raw.zip' contains .saf text files of passive seismic recordings and an associated 'readme_Raw.txt;' and 3) ‘XYLegacyN_HVSR.zip'’ contains ESRI shapefile of HVSR point locations with attribute data & a map image offering a visualization of the depth results (where, Vs = 300m/s). Additionally, the main folder contains LegacyN_HVSR_readme.txt which describes these sub-directories in further detail

Using the horizontal-to-vertical spectral-ratio (HVSR) method, we infer regolith thickness (i.e., depth to bedrock) throughout the Farmington River Watershed, CT, USA. Between Nov. 2019 and Nov. 2020, MOHO Tromino Model TEP-3C (MOHO, S.R.L.) three-component seismometers collected passive seismic recordings along the Farmington River and the upstream West Branch of Salmon Brook. From these recordings, we derived resonance frequencies using the GRILLA software (MOHO, S.R.L.), and then inferred potential regolith thicknesses based on likely shear wave velocities, Vs, intrinsic to the underlying sediment. Three potential shear wave velocities (Vs = 300m/s, 337m/s, 362 m/s) were considered for Farmington River watershed sediments, providing a range of potential depth estimates along the Farmington. This release contains raw passive seismic recording data, processed resonance frequency data, and the resulting inferred depth estimates displayed in both tabular and vector form. This dataset currently contains 3 zipped files: 1) ‘Processed.zip’ is a zipped directory containing .asc text files of processed passive seismic data, individual processed reports, tabulated results, and an associated summary text file, 'readme_Processed.txt'; 2) 'Raw.zip' contains .saf text files of passive seismic recordings and an associated 'readme_Raw.txt;' and 3) ‘XYLegacyN_HVSR.zip'’ contains ESRI shapefile of HVSR point locations with attribute data & a map image offering a visualization of the depth results (where, Vs = 300m/s). Additionally, the main folder contains LegacyN_HVSR_readme.txt which describes these sub-directories in further detail

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.