GNGTS 2013 - Atti del 32° Convegno Nazionale

We also performed a correction of atmospheric effects correlated with topography, estimated from the SAR data itself in non-deforming areas. The time series analysis in the epicenter area show a typical exponential trend (Fig. 3B), so that we can mainly attribute the deformation pattern to the afterslip occurred along the 06/04/2009 earthquake fault plane. Based on ground based SAR interferometry, some authors have estimated the post seismic deformation along the fault plane trace to be of several centimeters (Wilkinson et al. , 2012, 2010); despite the actual difficulty in field identification of centimetric surface deformation, it appears fundamental, soon after a strong earthquake, to provide a temporally continuous field deformation survey to identify the co and postseismic deforming areas. On the other hand, in addition to the afterslip correlated pattern, the postseismic velocity map shows many other features related to gravity, like deep seated gravitational slope deformations (DSGSD). Thus, a correct interpretation of the postseismic velocity map cannot be carried out without a detailed field investigation. Furthermore, the latter is crucial to correctly interpret possible transient deformation patterns from one tectonic structure to another, as well as the evolution of the seismic sequence (e.g. Pezzo et al. , 2013). As a second test-case, we present a post seismic multitemporal SAR analysis of the 2008 Emilia seismic sequence, in which 15 COSMO-SkyMed stripmap SAR images (Fig. 3C). Also in this case we observe a quasi-exponential afterslip deformation pattern in the epicentral area (Fig. 3D). In addition we detect a velocity pattern not directly attributable to the postseismic phenomena. In fact, local subsidence occurs due to fluid migration and compaction of the Po plain sediments. Moreover, there is a rough correspondence between the growth anticline and the positive (approach to the satellite) velocity values. Vice versa, negative velocity patterns correspond to the locations of the tectonic synclines. Furthermore, we observe a general agreement between the preseismic and postseismic, albeit for the afterslip pattern located in the epicentral area (Figs. 3E and 3F). Thus, only knowledge of the geological setting and active processes, at depth and at the surface, can provide a correct interpretation of all deformation features measured by InSAR space geodesy. Acknowledgements. G. Pezzo was funded by the INGV-ASI MUSA project. The COSMO-SkyMed SAR data are copyright of the Italian Space Agency (ASI), and were provided by the Department of Civil Protection (DPC) in the framework of the ASI-INGV-Space-based Monitoring System for Seismic Risk Management (ASI-INGV SIGRIS) project. The ENVISAT ASAR data are copyrighted by the European Space Agency and were provided through CAT1 proposal 3769. Some figures were prepared using the public-domain GMT software (Wessel and Smith, 1998). The ASTER GDEM is a product of METI and NASA. The author thanks J.P. Merryman Boncori and C. Tolomei for their fundamental support in the SAR data processing; S. Atzori and A. Antonioli for their precious help for the data inversions and CFF analysis and S. Salvi for the fruitful geological discussions and comments. References Ambraseys, N.N. and C.P. Melville; 1982: A History of Persian Earthquakes . Cambridge University Press, Cambridge. Bechor N.B.D. and H.A. Zebker;2006. Measuring two-dimensional movements using a single InSAR pair . Geophys. Res. Lett . , 33 , L16311, doi:10.1029/2006GL026883. Berardino, P., G. Fornaro, R. Lanari and E. Sansosti; 2002: A new algorithm for surface deformation monitoring based on small baseline differential interferograms , IEEE Trans. Geosci. Remote Sensing, vol. 40, pp. 2375-2383. Bigi, G., G. Bonardi, R. Catalano, D. Cosentino, F. Lentini, M. Parotto, R. Sartori, P. Scandone and E. Turco; (Editors; 1983); Structural Model of Italy 1:500,000, CNR Progetto Finalizzato Geodinamica. Boccaletti, M., G. Corti, and L. Martelli; 2010: Recent and active tectonics of the external zone of the Northern Apennines (Italy) , Geol. Rundsch. Z. Allg. Geol. 100, 1331-1348, doi: 10.1007/s00531-010-0545-y. Burrato, P., F. Ciucci and G. Valensise; 2003: An inventory of river anomalies in the Po Plain, Northern Italy: evidence for active blind thrust faulting . Ann. of Geophys. 46 (5), 865-882. Casu, F., M. Manzo and R. Lanari; 2006: A quantitative assessment of the SBAS algorithm performance for surface deformation retrieval from DInSAR data , Remote Sens. Environ., 102, no. 3/4, 195-210. D’Agostino, N., D. Cheloni, G. Fornaro, R. Giuliani, and D. Reale; 2012: Space-time distribution of afterslip following the 2009 L’Aquila earthquake , J. Geophys. Res., 117, B02402, doi:10.1029/2011JB008523. Deng, J., M. Gurnis, H. Kanamori and E. Hauksson; 1998: Viscoelastic flow in the lower crust after the 1992 Landers, California, earthquake , Science, 282, 1689-1692. Farbod, Y., O. Bellier, E. Shabanian, and M.R. Abbassi; 2011: Geomorphic and structural variations along the Doruneh Fault System (central Iran) ,Tectonics, 30, TC6014, doi:10.1029/2011TC002889. 101 GNGTS 2013 S essione 1.1