Acoustic‐to‐seismic coupling under winter conditions

Abstract

A field program to investigate acoustic‐to‐seismic coupling under winter conditions took place in Maine during December 1985‐January 1986. The test area was packed sand with a top layer (30 cm) of loose sand. Site conditions were: 20‐cm frost with no snow cover, 6‐cm snow or 18‐cm snow; and 45‐cm frost, 28‐cm snow. Microphones were at heights of 1/2–2 m or at the sand (snow) surface. Geophones were placed at the snow surface, the sand surface, and several depths in the sand layer. Acoustic‐to‐seismic coupling through frozen sand was investigated under controlled conditions using geophones in a sandbed at the USACRREL Frost Effects Research Facility. Test conditions were: dry sand, frozen or unfrozen; saturated sand, frozen or unfrozen; and thawing sand. The acoustic source for both investigations was blank pistol fire. Results on acoustic‐to‐seismic coupling through a snow layer and/or frozen sand are presented and contrasted with summer conditions for the frequency band 5–500 Hz. [Work supported by Direc...