Near-surface geophysical data collected in the Sunflower Drain study area near Delta, Colorado, March 2018

Near-surface geophysical surveys were conducted during March 2018 in an irrigated agricultural drainage near Delta, Colorado, locally know as Sunflower Drain. This data release presents results of two surveys, one using fiber-optic distributed temperature sensing (FO-DTS) and the second using a horizontal-to-vertical spectral ratio (HVSR) passive seismic method. For the FO-DTS, a temperature sensitive armored cable with a spatial resolution of 3.31 feet (1.01 meter) was deployed along a 0.3 mile reach of Sunflower Drain. Data were collected and processed using an Oryx model SR Remote Logging DTS unit (Sensornet, 2020) run over a 48-hour period and integrated at 10-minute intervals. The DTS data are provided in two comma separated values (csv) files, one with raw values extracted from the instrument files (DTS_raw.csv) and a second with georeferenced minimum and average temperature data along the cable (DTS_summary.csv). Thirteen HVSR measurements were acquired at 8 sites within the study area using a MoHo Tromino Model TEP-3C three-component seismometer (MoHo, 2020). The HVSR method requires a measurement or estimate of shear-wave velocity, which depends on sediment composition and density, for the conversion of measured resonance frequency to a depth to bedrock (Lane and others, 2008). The shear-wave velocity was estimated from a HVSR measurement made adjacent to an observation well (Poly 7, U.S. Geological Survey (USGS) station 384428107573901) with a well log (Thomas and others, 2019). Data provided in the 'HVSR_saf_files.zip' folder includes the raw HVSR data in SESAME ASCII format version 1 (SAF), showing the three-component time-series trace data for 1 vertical and 2 horizontal (north [N] and east [E]) components. The processed HVSR data for 6 sites shown in figure 12 of Mast (2020) are also included in pdf format in the 'Proccessed_HVSR.zip' folder.