Seismic and ground deformation monitoring in the seismogenetic region of the southern Apennines, Italy

Abstract

The 23 November, 1980, magnitude ( M s ) 6.9 southern Italy earthquake has been associated by Crosson et al. (1986) with a faulting system consisting predominantly of two high-angle sub-perpendicular normal faults forming the corner of down-dropped crustal block. This model was inferred from a detailed analysis of the space-time distribution of aftershocks and their focal mechanisms, some features of the acceleration field, the focal mechanism of the main shock and the observed displacements along two leveling profiles. Quantitative modelling of ground displacements (which amounted to up to 70 cm) was performed through a forward analysis, with a dislocation source consisting of several fault segments, and by inverse methods with a priori information, allowing the parameters of a multiple rectangular fault system to be retrieved. Quantitative modeling of vertical displacements observed in a nearby seismic region showed a similar mechanism, with coseismic movements of up to 12 cm, which are consistent with uniform dislocation on two rectangular faults, coinciding with the focal mechanism, location and magnitude of the earthquakes which occurred in August 1962 ( M s = 5.7, 6.1 and 5.4 ). A system for monitoring ground displacements and related seismic activities has been in place since 1982 in this region, and has recently been improved on the basis of our knowledge of the seismic source mechanisms. The aim is to study the stress regime during interseismic phases, to gain a better understanding of the physics of earthquake processes and to discover any patterns in earthquake occurrences in the seismogenetic regions of the Apennines.