GNGTS 2013 - Atti del 32° Convegno Nazionale

Gargano, and the Doruneh Fault System for Northern Iran. Both test sites are characterized by prevalent transcurrent tectonic regimes with low deformation rates (few mm per yr). We also present some examples of coseismic studies in which the geological field data availability or absence played a fundamental role in the definition of the seismic sources: the 2012 Emilia seismic sequence and the 2008 Baluchistan (Central Pakistan) seismic swarm. For both interseismic and coseismic datasets we performed the data inversions using the elastic model of Okada (1985), with the aim to investigate its applicability in the general context of the study of the earthquake-cycle in different tectonic domains, analyzing the limits of the method and the contribution of surface and deep geological data. Concerning the postseismic deformation, we present results concerning two strong earthquakes affecting the Italian peninsula in the last four years: the 2009 L’Aquila and the 2012 Emilia earthquakes. In this cases we show the fundamental role of geological field data concerning the survey of the afterslip ground faulting with respect to gravitational phenomena (for the L’Aquila event), and the survey of the hydrogeological dynamic and paleo-topography analysis of the epicentral area to discern the tectonic contributions to the ground deformation (for the Emilia events). Results. Ground deformation during the interseismic and preseismic phase. We used multitemporal InSAR techniques for the measurement of low interseismic ground velocities, in particular we studied the interseismic deformation in the Gargano promontory (Southern Italy) and in the Doruneh region (Northern Iran). The Gargano Promontory is an ENE-WSW oriented topographical and structural high representing a portion of the Apulian foreland extending into the Adriatic Sea. This area is characterized by active (instrumental and historical) seismicity that can originate strong earthquakes reaching intensities of XI MCS. The E-WMattinata Fault (MF) has been frequently proposed as a natural candidate to represent the major seismogenic structure in the Gargano area; however the spatial distribution of the recorded seismicity does not concentrate along this structure. Using the SBAS multitemporal DInSAR technique (Berardino et al. , 2002) we analyzed a SAR dataset of 88 descending (from 1992 to 2010) and 46 ascending (from 1995 to 2008) ERS and ENVISAT images to retrieve high resolution, mean velocity maps of the Gargano area (Southern Italy). Combining ascending and descending line of sight velocity maps, we obtained the East and Up component velocity maps (Figs. 1A and 1B). The Up velocity component (Fig. 1B) shows no vertical movement in the inner Gargano, whereas, in the East velocity component (Fig. 1A), we identify a NW-SE oriented maximum gradient of about 0.03 mm yr -1 per km in the inner Gargano, across the MF, in good agreement with GPS data and the main stress axis orientation. We also evaluate a deformation rate of about 40-50 nanostrains yr -1 for the East component in the inner Gargano along E-W oriented velocity profile. These values are higher than the regional ones calculated using GPS, borehole or seismological punctual data. We modeled the MF using the elastic dislocation model proposed by Okada (1985). Our measurements are compatible with a right-lateral kinematics of MF with a slip rate of about 1.5 mm yr -1 to a depth of 15 km, as shown by comparing observed and modeled velocity profile (Profile A of Fig. 1A). Our results confirm the slip rate values proposed by many authors, and the right-lateral geodynamical interpretation of the MF as a fundamental active junction in the dynamic equilibrium between the different motion of the Adria and Apulia microplates. We interpreted the interferometric signal and we inverted the SAR maps using the MF source parameters, subsequently evaluating the inversion goodness by comparing our results with bibliographic data. Without fundamental a priori information about the geometry of the fault, the hypocenter distribution and geological knowledge of the area, it would have been impossible to carry out a correct data interpretation and source modeling. Concerning the Northern Iran site, we used the SBAS DInSAR analysis technique to estimate the interseismic deformation along the western part of the Doruneh fault system (DFS) (Pezzo et al. , 2012). We processed 90 ENVISAT images from four different frames from 96 GNGTS 2013 S essione 1.1