Highlights from a seismic broadband array on Stromboli Volcano

Abstract

An array of nine three‐component broadband seismometers was deployed in two different configurations on Stromboli volcano. The analysis of the seismic wavefield related to volcanic explosions revealed some observations which offer a completely new insight into the internal dynamics of a volcano. These new observations are restricted to the low‐frequency range below 1 Hz and underline, therefore, the superiority of broadband recordings over conventional short‐period observations. Surprisingly simple wavelets indicate an initially contracting source mechanism. Gas‐jets, that could not be seen in a short‐period seismic record at all, generate a clear dilatational wavelet in a broadband recording suggesting the same contracting source mechanism. The analysis of particle motion and seismic array techniques permits a location of the seismic source. We find low‐frequency signals of 3s and 6s period that are not related to eruptions and do not share a common source with the eruption‐related events. A video recording of visible volcanic activity at the crater region allows one to correlate precisely eruptive features with seismic signals.