In April 2015, a total of 34 passive seismic surveys were conducted in the Cedar River Floodplain. The horizontal-to-vertical spectral ratio (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 approximately 0.1 to 1 Hertz (Hz) is caused by ocean waves, large regional storms, and tectonic sources. A resonance frequency (f0) is induced in the unconsolidated deposits when there is a substantial contrast (greater than 2:1) in shear-wave acoustic impedance between the 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.

In summer 2018, a total of 43 passive seismic surveys were conducted in the Des Moines River floodplain. The horizontal-to-vertical spectral ratio (HVSR) method is a passive seismic technique that uses a three-component seismometer to measure the vertical and horizontal components of ambient seismic noise. A resonance frequency (f0) is induced in the unconsolidated deposits when there is a substantial contrast (greater than 2:1) in shear-wave acoustic impedance between the 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. This data release contains a text file (Readme_HVSR.txt) that explains data files and processing references, 6 .zip folders 5 related to survey line(s) on a given date and one for individual measurements not related to survey lines with each zip folder containing measurement site folders and original data files and resultant measurement report (.trc, .saf or .dat, and .doc) , a notes file for archiving surface-geophysical data (HVSR_Archive_Notes_DesMoinesIA.csv), and another comma-separated values file (HVSR_Index_DesMoinesIA.csv) that can be used to help navigate the data files. Field notes taken at the time of data collection are not included in this data release but are available upon request.

In summer 2018, a total of 43 passive seismic surveys were conducted in the Des Moines River floodplain. The horizontal-to-vertical spectral ratio (HVSR) method is a passive seismic technique that uses a three-component seismometer to measure the vertical and horizontal components of ambient seismic noise. A resonance frequency (f0) is induced in the unconsolidated deposits when there is a substantial contrast (greater than 2:1) in shear-wave acoustic impedance between the 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. This data release contains a text file (Readme_HVSR.txt) that explains data files and processing references, 6 .zip folders 5 related to survey line(s) on a given date and one for individual measurements not related to survey lines with each zip folder containing measurement site folders and original data files and resultant measurement report (.trc, .saf or .dat, and .doc) , a notes file for archiving surface-geophysical data (HVSR_Archive_Notes_DesMoinesIA.csv), and another comma-separated values file (HVSR_Index_DesMoinesIA.csv) that can be used to help navigate the data files. Field notes taken at the time of data collection are not included in this data release but are available upon request.

In April 2015, approximately 22 miles of continuous seismic profiling (CSP) surveys were collected on the Cedar River in Iowa. The swept frequency (chirp) CSP subbottom profiler was used to characterize the unconsolidated materials above the bedrock. The CSP subbottom profiler is an acoustic sound source that travels through the water column and reflects off the bottom and sub-bottom layers and is received at the transducer. (see Collecting resistivity and seismic data Cedar River IA 2.JPG. Applying a water column velocity, the two-way travel time can be converted to distance. CSP methods provide the depth to water bottom, and when sufficient signal penetration is achieved, CSP can be used to delineate the depth of subbottom layers and topography of the bedrock surface.

In April 2015, approximately 22 miles of continuous seismic profiling (CSP) surveys were collected on the Cedar River in Iowa. The swept frequency (chirp) CSP subbottom profiler was used to characterize the unconsolidated materials above the bedrock. The CSP subbottom profiler is an acoustic sound source that travels through the water column and reflects off the bottom and sub-bottom layers and is received at the transducer. (see Collecting resistivity and seismic data Cedar River IA 2.JPG. Applying a water column velocity, the two-way travel time can be converted to distance. CSP methods provide the depth to water bottom, and when sufficient signal penetration is achieved, CSP can be used to delineate the depth of subbottom layers and topography of the bedrock surface.

A suite of geophysical methods was used along the Cedar River in Cedar Rapids, Iowa to support the hydrogeologic characterization of the alluvial aquifer associated with the river and to assess the area for suitability for larger-scale airborne geophysics. The aquifer is comprised of sand and gravel, interbedded with finer sediments, and underlain by carbonate-dominated bedrock. The aquifer is the principal source of municipal drinking water for the City of Cedar Rapids. The raw data files provided here include waterborne continuous resistivity profiling (CRP) and continuous seismic profiling (CSP) data, which were collected concurrently in April 2015, electrical resistivity tomography (ERT) profiles from April 2015, horizontal to vertical spectral ratio (HVSR) seismic from April 2015 and several borehole geophysical logs including nuclear magnetic resonance (NMR), gamma, and electromagnetic induction (EMI) from nine wells, collected in June, 2017. The CRP, ERT, and borehole logs measure the electrical properties of the subsurface, which can be related to stratigraphic layers. The HVSR, CSP, CRP and some of the borehole logs characterize the depth to bedrock. Collectively the suite of methods can help characterize the subsurface and map the extent of the sand and gravel aquifer. In addition, these geophysical measurements can be used to plan and to ground truth air-borne electromagnetic surveys.

A suite of geophysical methods was used along the Cedar River in Cedar Rapids, Iowa to support the hydrogeologic characterization of the alluvial aquifer associated with the river and to assess the area for suitability for larger-scale airborne geophysics. The aquifer is comprised of sand and gravel, interbedded with finer sediments, and underlain by carbonate-dominated bedrock. The aquifer is the principal source of municipal drinking water for the City of Cedar Rapids. The raw data files provided here include waterborne continuous resistivity profiling (CRP) and continuous seismic profiling (CSP) data, which were collected concurrently in April 2015, electrical resistivity tomography (ERT) profiles from April 2015, horizontal to vertical spectral ratio (HVSR) seismic from April 2015 and several borehole geophysical logs including nuclear magnetic resonance (NMR), gamma, and electromagnetic induction (EMI) from nine wells, collected in June, 2017. The CRP, ERT, and borehole logs measure the electrical properties of the subsurface, which can be related to stratigraphic layers. The HVSR, CSP, CRP and some of the borehole logs characterize the depth to bedrock. Collectively the suite of methods can help characterize the subsurface and map the extent of the sand and gravel aquifer. In addition, these geophysical measurements can be used to plan and to ground truth air-borne electromagnetic surveys.

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 2018, U.S. Geological Survey (USGS) in cooperation with the U.S. Environmental Protection Agency (EPA) collected geophysical measurements to help evaluate the suitability of a proposed landfill site for disposing mine-waste materials in Fredericktown, MO. A total of 35 horizontal-to-vertical spectral ratio (HVSR) passive seismic measurements were collected at the site. The HVSR technique uses a three-component seismometer to measure the vertical and horizontal components of ambient seismic noise. Seismic noise in the range of approximately 0.1 to 1 Hertz (Hz) is caused by ocean waves, large regional storms, and tectonic sources. A resonance frequency (f0) is induced in the unconsolidated sediments when there is a substantial contrast (greater than 2 to 1 ratio) in shear-wave acoustic impedance between the overburden and the bedrock. The HVSR data were interpreted to determine the f0 from analysis of the spectral ratio of the horizontal and vertical components of the seismic data. The thickness of the overburden can be related to f0. In general, lower f0 relates to thicker sediments, and higher f0 relates to relatively thinner overburden. At the Fredericktown, MO, site the resonance frequency was related to the depth of the overburden using an average shear-wave velocity that was measured at the site using active seismic source measurements. About two thirds of the HVSR surveys exhibited low to zero amplitude peaks, which is consistent with either a low amplitude acoustic impedance, an overburden layer, or a combination of both that is too thin to measure. The median value of the depth to bedrock for the 10 reliable measurements was 1.6 meters.

In June 2018, U.S. Geological Survey (USGS) in cooperation with the U.S. Environmental Protection Agency (EPA) collected geophysical measurements to help evaluate the suitability of a proposed landfill site for disposing mine-waste materials in Fredericktown, MO. A total of 35 horizontal-to-vertical spectral ratio (HVSR) passive seismic measurements were collected at the site. The HVSR technique uses a three-component seismometer to measure the vertical and horizontal components of ambient seismic noise. Seismic noise in the range of approximately 0.1 to 1 Hertz (Hz) is caused by ocean waves, large regional storms, and tectonic sources. A resonance frequency (f0) is induced in the unconsolidated sediments when there is a substantial contrast (greater than 2 to 1 ratio) in shear-wave acoustic impedance between the overburden and the bedrock. The HVSR data were interpreted to determine the f0 from analysis of the spectral ratio of the horizontal and vertical components of the seismic data. The thickness of the overburden can be related to f0. In general, lower f0 relates to thicker sediments, and higher f0 relates to relatively thinner overburden. At the Fredericktown, MO, site the resonance frequency was related to the depth of the overburden using an average shear-wave velocity that was measured at the site using active seismic source measurements. About two thirds of the HVSR surveys exhibited low to zero amplitude peaks, which is consistent with either a low amplitude acoustic impedance, an overburden layer, or a combination of both that is too thin to measure. The median value of the depth to bedrock for the 10 reliable measurements was 1.6 meters.