Investigation on static stress interaction among the 1930 Irpinia Earthquake and other large events in Southern Apennines (Italy)

Abstract

On July 23rd 1930, a strong earthquake (Ms=6.6) occurred in the Irpinia region, the most seismically active area of the Southern Apennines (Italy). Destructive effects were reported in a wide area of about 6300 km2, causing more than 1400 victims. The same region had already been struck by several large earthquakes in 1456 (Me=6.9), 1694 (Me=6.0), 1702 (Me=6.0), 1732 (Me=6.6), and 1910 (Me=5.9). Other major events have hit Irpinia since the 1930 earthquake, including that of 1962 (Mw = 6.2) and the catastrophic one of 23 Nov 1980 (Mw = 6.9).

Formerly published studies concerning the 1930 Irpinia event include analysis of macroseismic data, first motion polarities and a single station waveforms. By using the available bulletins and the historical seismograms, in our previous study we estimated the source parameters in terms of focal mechanism, magnitude, hypocentral location and seismic moment. Fault length, rupture velocity and other characteristics are also obtained by performing body waveform inversion for moment rate retrieval.

These results are here used to study the static stress transfer between the 1930 Irpinia earthquake and subsequent large events like the 1962, and 1980 ones in order to investigate the possible fault interaction and earthquake triggering. To improve our knowledge on the region of the1930 event, we also study the Coulomb stress field related to E-W trending seismogenic sources, responsible for the main sub-events of the multiple 1456 historical earthquake. Modelling of such effects is useful both to obtain more information on seismogenic sources and to gain an improved evaluation of seismic hazard in this region.