Figure 2 – Vertical wave test data acquired with the geometry exhibited on figure 1. (a) Downhole wavelets generated by small 10-ounce (280 grams) directional charges detonated in shallow 10-foot (three-meter) shot holes and recorded at depth intervals of 500 feet (150 meters). (b) Downgoing wavelets produced by a 40,000-pound vibrator and recorded at depth intervals of 50 feet (15 meters).