The locations of magma chambers at Mt. Etna, Italy, mapped by <i>b</i>‐values

Abstract

We mapped b ‐values in three dimensions in a cube of the crust with approximately 20 km dimensions under Mt. Etna. The earthquake catalog used contains 450 events with M≥2.5 for 1990‐1997.9. Comparison of b ‐values derived from samples of N =50 events, extracted from volumes with radii ranging from 2.5 to 6 km, showed statistically highly significant differences between b =1.5±0.3 in most of the crust and b =3.0±0.5 in two volumes with r ≤5 km, one located 2 km E of the summit of Etna and at 10±3 km depth and the other one WSW of Etna at a depth of about 3±2 km below sea level. We interpret these high b ‐value anomalies as an expression of two active magma chambers at those locations.