Coseismic deformation pattern of the Emilia 2012 seismic sequence imaged by Radarsat-1 interferometry

On May 20th and 29th, 2012, two earthquakes having magnitude 5.9 and 5.8, respectively, and their aftershocks sequence hit the central Po Plain (Italy), about 40 km north of Bologna, in the northern Apennines. Following the main-shocks, more than 2,000 events were recorded by the INGV National Seismic Network (http://iside.rm.ingv.it/). During the seismic sequence, a pure compressional faulting was generated by the activation of blind thrusts of the western Ferrara Arc, thereby activating a 50 km-long stretch of this buried outer front of the northern Apennines. The focal mechanisms of the larger shocks agree with the compilation of present-day tectonic stress indicators, showing a ca. N-S oriented maximum horizontal stress in the area, i.e. oriented perpendicular to the main structural trends. Most of the seismic sequence was confined between 1 and 12 km depth, above the local basal detachment of the outer thrust front of the northern Apennines. The surface displacement pattern, associated with the mainshocks and some following minor events (some of which above M 5.0), has been measured by applying Interferometric Synthetic Aperture Radar (InSAR) technique to a pair of C-Band Radarsat-1 data. The coseismic movements detected overall the epicentral region have been here used as input information for the source inversion model