Experimental laboratory study on the formation of multiple shock waves observed during volcanic eruptions

Abstract

Sequences of multiple pressure waves have recently been observed in different explosive volcanic eruptions, but their origin is not clearly understood. Although a pulsating type of eruption with many individual discharges can produce this effect, the formation of multiple shock waves could also result from a single discharge through (1) the dynamics of the shock wave itself, (2) the coupled shock wave-supersonic jet dynamics, or (3) a combination of these factors. Shock tube experiments were performed to evaluate these potential mechanisms under controlled laboratory conditions. The amount of energy released was varied to achieve different weak shock wave conditions and to promote formation of single or multiple shock waves through both shock wave dynamics and coupled shock wave-supersonic jet interactions. Our analysis indicates that both mechanisms may play a role in the formation of multiple pressure waves in low-intensity eruptions.