Seismic and hydroacoustic effects of the May 29, 2010 submarine South Sarigan volcanic explosion: Energy release and interpretation

Abstract The May 2010 submarine volcanic crisis of the shallow South Sarigan Seamount (Marianas arc) ended on May 29 by a violent explosion that emitted a 12 km high atmospheric plume and created a crater 350 m in diameter. The application of the multiphase localization method to the Pg, P, T phases of this explosion allows us to refine considerably (mainly based on the intense and impulsive T phases) the location of their source, that fits the position of the newly-formed South Sarigan crater. We highlight the numerous similarities of this final explosion with artificial underwater explosions (conventional or nuclear tests of known energy). Especially, the explosive nature of the source in the volcanic basement is confirmed by the similarity of the P phases with those of underground nuclear tests and the application of discriminating criteria Ms. – mb. The explosive nature of the source in the water is also confirmedby the application of the identification criteria for hydroacoustic sources and the T phases exceptionally impulsive and of short durations. These similarities allow us to provide a rough evaluation of the energy released by the South Sarigan final explosion using the methods commonly applied to man-generated explosions. We estimate a minimal released energy of 1 kt (4.2 × 1012 J) for the seismic effects of the shock and ca 1 t of equivalent TNT (i.e. 4.2 × 109 J) for the hydroacoustic effects of the explosive source in the water. The processes leading to this final explosion are discussed on the basis of the sequence of the earlier seismic and eruptive events. Within the Comprehensive Nuclear-Test Ban Treaty framework, this explosion that affected concomitantly the solid, liquid and subaerial media is the first well documented one having generated intense waves: (P), hydroacoustic (T), acoustic (infrasounds) and tsunamis.