Horizontal-to-Vertical Seismic Ratio Passive-Seismic Data Collected at Edwards Air Force Research Laboratory, Antelope Valley, California, 2018

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.