Short term precursors of Strombolian explosions at Yasur volcano (Vanuatu)

Abstract

AbstractThe seismic wavefield associated with Strombolian activity is usually dominated by explosion quakes (EQs), tremor, and various signals generated by surface phenomena. Looking at the seismicity recorded at Yasur volcano in 2008, we found that beside the transient events which occur simultaneously with surface explosions, the seismicity includes events related to a deeper process. These long period (LP) events form a family of similar events located below the southeastern part of the crater rim at a depth of about 700–1200 m below the summit. They are commonly followed by EQs with a variable delay. The examination of about 20,000 LP‐EQ sequences at several stations near the summit shows that interevent delays follow distributions peaked around 11–12 s. This short delay compared to the relatively great source depth of the LPs favors a causal relationship linked to pressure transfer rather than gas slug propagation after nucleation at the LP source.