Crustal structure, tectonic evolution and seismogenesis in the Northern Apennines (Italy)

The aim of this paper is to illustrate how the time and space relationships between compression and extension in the Northern Apennines can be expressed through three main rules: i) at any time, compression and extension are contemporaneously active, in the foreland and in the hinterland, respectively; ii) at any position, extension follows compression; iii) extension can occur in the uppermost crust at the same time and position of compression at greater depth (lower crust and upper mantle). These rules are always verified, by considering both the long-term evolution of the Apennines, illustrated by the geological data about the age of syntectonic basins, and the short-term, present-day image, highlighted by the instrumental seismicity pattern. A comprehensive review of the geological and geophysical evidence supporting the contemporaneous activity and eastward migration of compression and extension in the Northern Apennines is reported. The main results of the CROP03 project, integrated with new geophysical data sets, are discussed together with the space distribution and kinematics of instrumental seismicity recorded in the last 20 years, that has furnished a present-day, instantaneous image of the evolution of the Northern Apennines. The last part of the paper presents and discusses some relevant and debated topics on the setting and evolution of the Northern Apennines.