GNGTS 2013 - Atti del 32° Convegno Nazionale

Seismic strain rate variation in the area shocked by the 2012 Emilia seismic sequence S. Barani 1,2 , R. De Ferrari 1,2 1 DISTAV, Università degli Studi di Genova, Italy 2 GEAmb S.r.l., spin-off dell’Università di Genova, Italy Foreword and scope of work. This work draws inspiration from the discussion, taken during the final meeting of the DPC-INGV 2012-2013 projects (https://sites.google.com/site/ progettisismologici/), about seismic strain rate variations in the area shocked by the 2012 Emilia seismic sequence. A further motivation for this work is the evident anomaly (with respect to the neighboring areas) shown in that area by the seismic strain rate map published by Barani et al. (2010), map which is presented also here (Fig. 1). The map clearly shows a deficit in the release of seismic deformation or, more precisely, a deficit in the distribution of the strain rate values in the area between Modena and Ferrara. This pattern is very similar to that observed by Chen et al. (2009) analyzing the distribution of the total amount of seismic moment in the Taiwan region before and after the 1999 Chi-chi earthquake ( M w = 7.6) and to that found by Barani and Eva (2011) in the area stricken by the 2009 L’Aquila earthquake ( M w = 6.3). Both studies have evidenced clear deficits in the total amount of seismic moment, deficits which were then filled following the occurrence of strong earthquakes. The major conclusion from both studies was that, for domains with similar tectonic settings, the analysis of deficit-then-fill patterns may be useful for the inference of future disastrous earthquakes. In this study, the approach for seismic strain rate calculation proposed by Barani et al. (2010) is applied to the area of the 2012 Emilia sequence in order to investigate, in a retrospective way, the anomaly observed in the map in Fig. 1. The study is also important to further test the reliability of the method of Barani et al. (2010) to study seismicity patterns, such as seismic gaps and quiescence periods. Seismotectonic framework. The area struck by the Emilia 2012 seismic sequence is located in the outermost portion of the northern Apennines. The Apennine chain is a post-collisional Fig. 1 – Seismic strain rate map for Northwestern Italy (after Barani et al. , 2010). The map accounts for the contribution of earthquakes occurred between year 1350 and 2006. The dashed square indicates the interpolation area Fig. 2. 210 GNGTS 2013 S essione 1.2