GNGTS 2017 - 36° Convegno Nazionale

122 GNGTS 2017 S essione 1.2 The added value, we believe, is represented by the development of a multi-expertise coordinated working group, formally organized, in which the different teams operate in a harmonized frame to gain altogether a shared result. Being this result achieved in the frame of the Civil Protection field of interests, it has not only a scientific value, but also a societal one. Moreover, the large number of involved investigators from several research institutes makes the obtained result much more easily usable for civil protection purposes, representing not the idea of a single research group, but of a large and qualified community. The Department of Civil Protection guarantees the equilibrium among the Competence Centers within the working group, allowing for a harmonized development of the activities and of the working flow. This organization represents therefore a “ready tool” that could be easily employed for the achievement of similar outcomes in others areas of our country. A QUANTITATIVE APPROACH TO THE LOADING RATE OF SEISMOGENIC SOURCES IN ITALY A. Caporali 1 , C. Braitenberg 2 , P. Montone 3 , G. Rossi 4 , G. Valensise 3 , A. Viganò 5 , J. Zurutuza 1 1 Department of Geosciences, University of Padova, Italy 2 Department of Mathematics and Geosciences, University of Trieste, Italy 3 Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy 4 Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Trieste, Italy 5 Servizio Sismico, Provincia autonoma di Trento, Italy Introduction. To investigate the transfer of elastic energy between a regional stress field and a set of localized faults we project the stress rate tensor inferred from the Italian GNSS velocity field onto fault planes selected from the Database of Individual Seismogenic Sources (DISS 3.2.0). For given Lamé constants and friction coefficient we compute the loading rate on each fault in terms of the Coulomb Failure Function (CFF) rate. By varying the strike, dip and rake angles around the nominal values listed in the DISS, we also estimate optimally oriented fault planes, i.e. planes oriented for maximal CFF rate. Out of 86 Individual Seismogenic Sources (ISSs), all well covered by GNSS data, 78 to 81 (depending on the assumed friction coefficient) load energy at a rate of 0-4 kPa/yr. The sources with larger CFF rate (4 to 6 ± 1 kPa/yr) are all deep (>10 km) faults located in the central Apennine and are all characterized by a significant strike-slip component. We also find that the loading rate of 75% of the examined sources is less than 1 kPa/yr lower than that of optimally oriented faults. We also analyzed the two Mw 6.0-6.5 earthquakes that struck the central Apennine in 2016. The strike of their causative faults based on seismological and tectonic data and the geodetically inferred strike differ by < 30°. Some sources exhibit a strike oblique to the direction of maximum strain rate, suggesting that in some instances the present-day stress acts on inherited faults. The choice of the friction coefficient only marginally affects this result. Computing the loading rate. The knowledge of current deformation rates at the Earth’s surface represents a significant boundary condition for modeling seismogenic processes in most of the Italian region where the typical hypocentral depth is in the order of 5 to 20 km. A few recent papers have proposed the combination of geophysical and geodetic data to infer properties of the crust-mantle coupling (e.g. Palano, 2015) or to constrain finite element models where the deformation is driven by large-scale forces (e.g. Carafa et al. , 2015). Such regional models provide fundamental insight for investigating large-scale geodynamic processes but are too coarse to be used for determining the relative state of stress of adjacent faults.