GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione A matrice 23 Tali analisi sembrano indicare l’attivazione di una sorgente sismogenica con strike e dip variabile da sud a nord e non permettono di escludere un possibile ruolo del thrust dei Sibillini durante l’evento principale. Nonostante la natura preliminare dei dati analizzati non consenta di proporre una visione definitiva e convincente sul ruolo del Thurst dei Sibillini nel corso dell’evento principale della sequenza sismica di Amatrice, il solo fatto che sia stata testimoniata una sua riattivazione in senso estensionale nel corso della sequenza sismica pone nuovi interrogativi sul ruolo delle strutture ereditate nel contesto sismotettonico dell’Appennino. Bibliografia Bigi, S., P. Casero and G. Ciotoli (2011). Seismic interpretation of the Laga basin; constraints on the structural setting and kinematics of the Central Apennines, Journal of the Geological Society, 168, 179-190, doi: 10.1144/0016- 76492010-084. Emergeo Working Group (2016). Coseismic effects of the 2016 Amatrice 1 seismic sequence: first geological results. Annals of Geophysics, The Amatrice seismic sequence: preliminary data and results, Fast Track. Michele, M., R. Di Stefano, L. Chiaraluce, M. Cattaneo, P. De Gori, G. Monachesi, D. Latorre, S. Marzorati L. Valoroso, C. Ladina, C. Chiarabba, V. Lauciani and M. Fares (2016). The Amatrice 2016 seismic sequence: a preliminary look to the mainshock and aftershocks distribution, Annals of Geophysics Fast Track, The Amatrice seismic sequence: preliminary data and results. Pierantoni, P., G. Deiana and S. Galdenzi (2013). Stratigraphic and structural features of the Sibillini Mountains (Umbria-Marche Apennines, Italy), Italian Journal of Geosciences, 132(3), 497-520, doi: 10.3301/IJG.2013.08. Tinti, E., L. Scognamiglio, A. Michelini and M. Cocco (2016). Slip heterogeneity and directivity of the ML 6.0, 2016, Amatrice earthquake estimated with rapid finite-fault inversion, submitted to GRL. Analysis of time series of permanent GNSS sites in the area of the Amatrice earthquake A. Caporali, J. Zurutuza Department of Geosciences, University of Padova, Italy Introduction. The network of 600+ permanent GNSS sites processed daily at the University of Padova includes 22 sites within 100 km of the epicenter of the August 24, 2016 event. The station AMAT (Amatrice) is located less than 10 km from the epicenter. To best detect 3D displacements in the epicentral area we used ADDNQ2 of Bernese Software 5.2 (Dach et al. , 2015) and IGS/EUREF processing guidelines (Bruyninx et al. , 2013) to stack daily normal equations of the national network, and extracted time series of sites nearest to the epicenter, after a Helmert transformation of the daily solution on the cumulative solution. Prior to the event we observe in the coordinate time series no particular systematic or sudden motion, within the measurement uncertainty (< 0.5 mm 1 sigma formal error). Likewise the postseismic time series at this time do not show any systematic trend which could lead to make hypotheses about postseismic relaxation. However a more conclusive statement requires several months of postseismic data and is therefore premature. Assuming a purely elastic rheology and a brittle failure model, we compare the geodetic displacements with those predicted from the published fault plane solutions, using the Okada model. We consider the cumulative effect of the Mw=6.2 at 01:36 and of Mw=5.5 at 02:33. The best fit to the geodetic data gives 4 mm rms horizontal and 5 mm rms vertical (INGV TDM solution). State of deformation of the epicentral area. The state of strain rate from GNSS data is presented in Fig. 1. The details of the generation of this map are discussed elsewhere (Caporali et al. , 2016). According to our data the epicentral area is subject to a relatively low strain rate (9 ±8 nstrain/yr) with the extensional eigenvector very nearly perpendicular to the strike