Analysis of direct wave arrivals in a shallow multi-offset reverse VSP

Darryl G. Parry, Donald C. Lawton

A shallow, multi-offset, multi-azimuth reverse vertical seismic profile was recorded using three-component geophones. The borehole used was 30 m deep and penetrated four distinct velocity horizons. The upper layer is 3 m thick with Vp = 300 m/s, the second is 11 m thick with Vp = 650 m/s and Vs = 340 m/s, the third is 9 m thick with Vp = 2 660 m/s, and the lowest is at least 7 m thick with Vp = 1 500 m/s. The source used in the experiment was a 50 gm booster which provided substantial compressional wave energy. Converted shear wave energy was also recorded by the surface geophones.