An instrument for recording the ground vibrations caused by heavy quarry blasts. The relationship between the amount of vibration, the distance from the blast, and the weight of explosive fired may be expressed thus: A = (KE)/D, where A = maximum amplitude in thousandths of an inch; K = constant depending on the quarry site; E = weight of explosive in pounds; and D = distance in feet. The constant K can be determined by firing a specimen blast of a given size at a given distance and measuring the amplitude of the record obtained. Amplitudes in excess of 0.04 in (1 mm) may give rise to damage. A movement of 0.008 in (0.2 mm) can be felt, and if used an excessive number of times may give rise to complaints of nuisance and damage. Short-delay blasting methods with small diameter holes reduce vibration hazards.