GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 1.2 233 Fig. 2 shows the velocity (a,b) and diffusivity distribution (c,d) in the shallowest (a,c) and deepest layer (b,d). The shallowest layer shows the highest values for both parameters, in agreement with a higher fracturing degree. In the deepest layer, the highest values are observed to the SE of the source, in the direction of the Dinaric structures. Conclusions. The values of the propagation velocity and the hydraulic diffusivity are compatible with the hypothesis of a porosity wave diffusion, from a source in the neighboring of the 2004 Bovec hypocenter. It could have been generated if we hypothesize a fault valve- behavior (Sibson, 1992) of the NW tip of the Ravne fault, responsible for the Bovec-Krn earthquakes (Kastelic et al. , 2008). A fault-sliding, probably a-seismic, could have broken an impermeable barrier and caused the upward migration of the underlying over-pressurized fluids, along the faults and following the permeability heterogeneities. Acknowledgements. Thanks to G. Bressan and G. Bohm, for the suggestions and comments. OGS manages FReDNet with the support of the Friuli Venezia Giulia Civil Protection; we also thank the Friuli Venezia Giulia Department for Environment and Territory for the Marussi network data availability. References Altamimi, Z., L. Metivier, and X. Collilieux; 2012): ITRF2008 plate motion model , J. Geophys. Res., 117 , B07402, doi:10.1029/2011JB008930. Böhm, G., Rossi, G. e Vesnaver, A.; 1999: Minimum-time ray-tracing for 3-D irregular grids. Journal of Seismic Exploration, 8 , 117-131. Brauchler, R., Böhm, G., Leven, C., Dietrich, P., Sauter, M.; 2013: A laboratory study of tracer tomography . Hydrogeology Journal, 21 (6), 1265-1274, doi:10.1007/s10040-013-1006-z. Brückl, E., Bleibinhaus, F., Gosar, A., Grad, M., Guterch, A., Hrubcova, P., Keller, G.R., Majdański, M., Šumanovac, F.S., Tiira, T., Ylinemi, J., Hegedüs, E., Thybo, H.; 2007: Crustal structure due to collisional and escape tectonics in the Eastern Alps region based on profiles Alp01 and Alp02 from the ALP 2002 seismic experiment . Journal of Geophysical Research, 112 , B06308, doi:10.1029/2006JB004687. Fig. 2 – Results of the tomographic analyses on a schematic map of the region: a) and b) propagation velocity from traveltime tomography; c) and d) hydraulic diffusivity from hydraulic tomography. Shallowest layer (a, c) and deepest layer (b, d). Fair blue: transient source location.