Passive seismic (HVSR) data from Fountain Creek, CO

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.