Recent seismicity of Italy: Active tectonics of the central Mediterranean region and seismicity rate changes after the Mw 6.3 L'Aquila earthquake

- New and strongly improved seismicity images of Italy
- New vision on the Alps and Apennines seismotectonics
- Seismicity rate changes after the 2009 L'Aquila earthquake.

In this paper we present a new image of the instrumental seismicity of Italy, obtained by refining hypocentral determinations for about 100,000 earthquakes that occurred in the period 2005-2012. The improved locations yield new constraints on active tectonics of the central Mediterranean area, where prolonged interaction between nested plates and continental slivers led to the development of the Alpine and Apennines systems. Intermediate-depth and deep earthquakes define a lateral heterogeneous process of delamination and sinking of the continental lithosphere active beneath the mountain belts. Shallow seismicity prevalently occurs beneath elevated topography and correlates with low velocity mantle anomalies, suggesting a superposition of gravity-related forces to the Eurasia-Africa plate convergence. The delamination process drives a paired system of compression and extension that stretches the mountain range while shortening the external side of the belts. The updated seismic catalog permits us to resolve a sharp variation of seismic rates that occurred in recent years, timely after the 2009 Mw 6.3 L'Aquila earthquake. The increase of seismic rates is reasonably due to regional-scale perturbation of the stress field induced by fluid flow and pore-pressure variations within the crust, probably related to deep dehydration processes active beneath the mountain belt.