Lithosphere Deformation Modelling of the Italian Peninsula: A Tool for Seismic Hazard Assessment
Abstract
Large uncertainties of input data for seismic hazard assessment, like the incompleteness of the historical catalogues, magnitude estimation uncertainties and low reliability of epicentral location forces the adoption of additional information for the characterization of seismicity. Lithosphere deformation measuring and modelling techniques were largely increased and improved during the last decade; the detail and the reliability of the deformation models presently available make possible the development of methodologies for constraining the geodynamical evolution of active areas and particularly of their long term seismotectonic behaviour. In the present work we describe and test a procedure to create a probabilistic hazard source model for some areas of the Italian peninsula by integrating crustal deformation modelling results with historical evidences of earthquake occurrence. This procedure uses a Bayesian approach with geophysical input to define the earthquake occurrence behaviour: historical earthquake data characterize the sample likelihood function while strain derived occurrence rates define prior distribution parameters. Modelled strain rates are calculated by means of a finite element model based on the thin shell scheme of peninsular Italy and central Mediterranean that simulates the effects of Africa-Eurasia convergence and subduction underneath the Calabrian Arc on lithospheric deformation. The computed horizontal velocities and strain rates are compared with their geodetic counterparts retrieved by a network of permanent GPS receivers in the area. In order to reproduce the clockwise rotation in southern Italy from the NNW direction of the NOTO site (south eastern Sicily), envisaging the motion of the Africa plate, to the NNE direction of GPS sites in Calabria and Matera, the effects of the Calabrian subduction must be completed by the effects of the counter-clockwise rotation of the Adria microplate. This kinematics of Adria reproduces the NNE motion of the Camerino GPS site, which is located at 43.1 North latitude, and indicates that the central Apennines are migrating at a rate of some millimetres per year towards Eurasia. The methodology applied allows the description of hazard source models by properly selecting weighting parameters for the prior and likelihood function. In the present case-history the rates computed accounting for modelled crustal deformation show a smoother spatial variation in respect of the ones directly calculated from historical seismicity.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....9208J