Intensity field of the 19 June 1975 Gargano (Southern Italy) earthquake

Abstract

Many moderate events reported by Italian earthquake catalogues (either historical or recent) are listed with an epicentral intensity derived from intensity-magnitude relationships or evaluated based on preliminary sources. Contradictions may arise among different catalogues when the effects of a given earthquake are not assessed through a specific macroseismic study as each catalogue uses its own criteria for evaluating the intensity. In this paper we present the case of the 19 June 1975 earthquake, a ML=5.1 (ING seismological bulletin) event that occurred in the Gargano area (southern Italy). The intensity reported by the ING catalogue is VIII MCS (estimated from magnitude), that reported by the NT4.1 catalogue is VI MCS, while the PFG catalogue does not report any intensity. The case of this event is well representative of a period during which macroseismic studies were not undertaken systematically in Italy. In this paper we reasses the macroseismic intensity of this event using procedures implemented and routinely used at ING.