A., F. Courboulex, S. Gaffet, A.Lomax, J.
Virieux, A. Amato, A. Azzara, B. Castello, C. Chiarabba, G.B. Cimini,
M. Cocco, M. Di Bona, L. Marghereti, F. Mele, G. Selvaggi, L.
Chiaraluce, D. Piccinini, and M. Ripepe (2000), Spatio-Temporal distribution of seismic
activity during the Umbria-Marche crisis, 1997 - J. of Seism., 4, 377-386.
We present the
distribution of more than 2000 earthquakesthat occurred during the
Umbria-Marche seismic crisis, between September 26and November 3, 1997.
This distribution was obtained from recordings of atemporary network
that was installed after the occurrence of the first two largest shocks
(Mw =, 5.7, Mw = 6.0) of September 26. This network wascomposed of 27
digital 3-components stations densely distributed in theepicentral
area. The aftershock distribution covers a region of about 40 km long
and about2 km wide along the NW-SE central Apennines chain. The
activity is shallow,mostly located at less than 9 km depth. We
distinguished three main zonesof different seismic activity from NW to
SE. The central zone, that containsthe hypocenter of four earthquakes
of magnitude larger than 5, was the moreactive and the more complex
one. Sections at depth identify 40–50°dipping structures
that agree well with the moment tensor focalmechanisms results. The
clustering and the migration of seismicity from NW to SE and the
generalfeatures are imaged by aftershock distribution both horizontally
and at depth.
words: Seismicity - Central Italy - Umbria-Marche - Aftershock
sequence - seismic crisis