Character of the stress field in the Calabrian Arc and Southern Apennines (Italy) as deduced by geological, seismological and volcanological information

Three crustal sections, located in key zones of the Calabrian Arc and Southern Apennines, have been drawn on the basis of the available geological, geophysical, seismological and volcanological data. The purpose is to gather information on the state of stress at different crustal levels and to test to which extent data sampled at different time intervals may be consistently compared. The analysis allows for the individualization of the following sectors: (1) Peri-Tyrrhenian belt, marked by a tensional state of stress down to the Moho depth;

(2) Apenninic chain, subjected to tension only in its shallow portions and to a compressive regime at depth;

(3) external chain-internal foretrough, characterized by a deep compressive regime which is expressed at the surface in its outermost zone only;

(4) external foretrough-foreland, with tensional processes in the whole crust.

Compressional processes are linked to the activity of a deep shear zone which causes the thrusting of the Tyrrhenian crust over the Adriatic crust and which seems to control the present distortion of the Calabrian Arc. The analysis suggests a change in the stress field and deformation mechanisms from the uppermost to the lowermost levels of the crust and an eastward migration with time of the compressional events. These facts would explain the contrasting evidence sometimes given by stress constraints derived from geological, seismological and volcanological data.