Radon mapping, automatic measurements and extremely high 222Rn emissions during the 2002-2007 eruptive scenarios at Stromboli volcano

Extremely high radon emissions (up to ~ 1.7 × 106 Bq/m3) were recorded along the fractures of the SW crater during the first two months of the 2002-2003 effusive eruption. Very high radon emissions (up to ~ 470,000 Bq/m3 for 222Rn, and ~ 780,000 Bq/m3 for 220Rn, respectively) were also detected by the automatic measurements at the summit station during June 20-early July 2007: i.e., just prior to the resuming of the Strombolian activity at summit craters. These data give us the opportunity to estimate the relative depths of the summit fractures during fracturing (being constrained between 200 and 310 m). This is in good agreement with the hypocentral depths of the so called “hybrid events” and the source of the very long period seismic signals (VLP) localized at a depth of about 500 m a.s.l. below the upper-central part of the Sciara del Fuoco.