The Irpinia (Italy) 1980 earthquake: Waveform modelling of accelerometric data and macroseismic considerations

A detailed investigation, based on accelerometric and macroseismic data of the Irpinia 1980 event, is presented. The study is based on the use of synthetic seismograms, computed by the modal summation technique, and its purpose is to retrieve information concerning the rupturing process. Initially, for a first rough analysis, the 40 s sub-event has been neglected. The recorded accelerograms at the stations of Auletta, Bagnoli Irpino, Bisaccia, Brienza, Calitri and Sturno have been low-pass filtered with a cut-off frequency of 10 Hz, and the rupturing process has been modeled, by a trial-and- error technique, with twelve point sources properly distributed in space and time. An automatic inversion procedure has been successively applied to the whole observed waveforms, for frequencies not higher than 1 Hz. A very good fit has been achieved between observations and synthetics, and the obtained rupturing model is in gross accord with what retrieved by the first rough analysis. Finally, the information about the rupturing process has been used in order to compute synthetic isoseismals, which have been compared with the observed macroseismic field. Since the source radiation pattern has been also included in the computation, its influence on the shape of the isoseismals is discussed.