Source analysis of the 2002 Molise, southern Italy, twin earthquakes (10/31 and 11/01)

On October 31, 2002, a moderate size earthquake
(Mw = 5.8) occurred in Molise region, southern Italy,
causing loss of young human lives in a school collapse and
destructions in several villages. The day after, a slightly
smaller earthquake happened a few kilometers westward
from the first one, without making strong damage. We use a
complete set of seismological data (global, regional and
local, including both body and surface waves) to better
understand the source process of these two events. We show
that the two earthquakes are similar, in terms of hypocentral
depth, focal mechanism, and source kinematics. Moreover,
the imaged slip zones are almost contiguous which makes
the time delay between the two shocks (29 hours) an open
question. The identified updip rupture propagation has
amplified the radiation usually created by such Mw = 5.8
earthquakes at 15–20 km depth. We model a maximum
acceleration zone in agreement with location of damaged
villages.