Southern-Tyrrhenian seismicity in space-time-magnitude domain

Abstract

An analysis is conducted on a catalogue containing more than 2000 seismic events which occurred in the Southern-Tyrrhenian Sea between January 1988 and October 2002, of minimum observed local magnitude 1.5, as an attempt to characterise the main seismogenetic processes active in the area in space, time and magnitude domain by means of the parameters of phenomenological laws. We chose to adopt simple phenomenological models, since the narrow space-time area did not allow us to use more complex laws. The two main seismogenetic volumes present in the area were considered for the purpose of this work. The first includes a nearly homogeneous distribution of hypocentres in a NW steeply dipping layer as far as about 400 km depth. This is probably the seismological expression of the Ionian lithospheric slab subducting beneath the Calabrian Arc. The second contains hypocentres concentrated about a sub-horizontal plane lying at an average depth of about 10 km. It is characterised by a background seismicity spread all over the area and by clusters of events that generally show a direction of maximum elongation. The estimated parameters of the statistical models describing seismogenetically homogeneous subsets of the earthquake catalogue in the three analysis domains, along with their confidence intervals, are reported and analysed to establish whether they can be regarded as representative of a particular subset