GNGTS 2017 - 36° Convegno Nazionale

60 GNGTS 2017 S essione 1.1 Nappi R., Alessio G., Bellucci Sessa E., ; 2010: A case study comparing landscape metrics to geologic and seismic data from the Ischia Island (Southern Italy) . Applied Geomatics, DOI: 10.1007/s12518-010- 0023 z. Orsi G., Gallo G., Zanchi A. ;1991: Simple-shearing block resurgence in caldera depression. A model from Pantelleria and Ischia. J. Volcan Geotherm Res 47:1-11. Orsi G., de Vita, S., Di Vito M., Isaia R., Nave R., Heiken G.; 2003: Facing volcanic and related hazards in the Neapolitan area. In: Heiken, G., Fakundiny, R, Sutter, J. (Eds) Earth Sciences in Cities, American Geophysical Union (Special Publication), Washington, 121-170. Rovida A., Locati M., Camassi R., Lolli B., Gasperini P. (eds); 2016: CPTI15, the 2015 version of the Parametric Catalogue of Italian Earthquakes . Istituto Nazionale di Geofisica e Vulcanologia. doi :http://doi.org/10.6092/ INGV.IT -CPTI15. Vezzoli L.; 1988: Island of Ischia . In: Vezzoli L (ed) CNR Quaderni de “La ricerca scientifica”, 114-10, 122 pp. Violante C., Budillon E., Esposito E., Porfido S., Vittori E.; 2003: Submerged hummocky topographies and relations with land-slides on the northwestern flank of Ischia Island, Southern Italy. In: Piccarelli L (ed) Proc. Int. Workshop on Occurrence and mechanisms of flow-like landslides in natural slopes and earthfills, Sorrento, pp. 309-315. COMPUTING SLIP INVERSION AND COULOMB FAILURE FUNCTION CHANGES IN A LAYERED CRUST: THE 2012 EMILIA ROMAGNA SEISMIC SEQUENCE M. Nespoli 1 , M.E. Belardinelli 1 , L. Anderlini 2 , M. Bonafede 1 , G. Pezzo 3 , M. Todesco 4 , A.P. Rinaldi 5 1 Department of Physics and Astronomy, University of Bologna, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Centro Nazionale Terremoti, Bologna, Italy 3 Istituto Nazionale di Geofisica e Vulcanologia, Centro Nazionale Terremoti, Roma, Italy 4 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Italy 5 Swiss Seismological Service, Swiss Federal Institute of Technology, Zürich, Switzerland Introduction. The first mainshock of the 2012 Emilia Romagna seismic sequence (Mw 6.1) occurred on May 20 at 4:04 AM and it was followed by a second mainshock 9 days later (i.e. May 29) at 9:00 AM. The relocation of the seismic sequence performed by Govoni et al. (2014) suggests the activation of almost two faults: the May 20 mainshock occurred on the Ferrara fault, while the May 29 mainshock occurred on the Mirandola fault, west from the May 20 epicenter location. Due to both temporal and spatial proximity of the two mainshocks the Emilia Romagna seismic sequence is a good candidate for the study of the mechanical interaction of the two faults. Furthermore, the seismic sequence was located in the Po River alluvial plain, where, according to several crustal models available for the region, there are important elastic discontinuities in the first 3.5 km of depth. Therefore, this sequence is also well suited to study the effects of a layered elastic half-space both on the coseismic slip distribution (obtained by inverting the geodetic data, GPS and InSAR ) and the CFF changes. Model andmethods. We performed the inversion ( d = Gs where d is the geodetic data vector, G is the kernel and s is the slip solution vector) of the geodetic data in both an homogeneous (HOM) and a layered (LAY) half space, for both mainshocks. In the HOM case we assumed a uniform Poisson number, υ = 0.25 and a rigidity μ=30 GPa, while for the LAY case we considered three different layering based on three different crustal models available for the region: CRUST1.0 (Laske et al. , 2013), Govoni et al. (2014) and MAMBO (Molinari et al. , 2015). We followed the inversion procedure proposed by Hearn and Bürgmann (2005): in order to compute the kernel G we used the EDGRN-EDCMP software (Wang et al. , 2003). We considered a simple fault geometry (with uniform dip angle) for both the Ferrara and the Mirandola faults, that was constrained on the basis of the relocated seismicity and discretized into uniform slip patches. Our choice relies on the preferability of the simplest geometrical model that explains all the data with the same accuracy as previous studies (e.g. Serpelloni et al. , 2012, Pezzo et al. , 2013, Cheloni et al. , 2016). The rake angle of the faults is kept fixed for all the patches belonging to the same fault, but, to choose its best value, we performed several inversions varying the rake angle in the range indicative for a mostly inverse-slip fault solution.