GNGTS 2018 - 37° Convegno Nazionale

100 GNGTS 2018 S essione 1.1 compatible with those observed for other mainshock-aftershock sequences around the world (Brenguier et al. , 2018a; Chen et al. , 2010), and may be explained in terms of more rapid co-seismic damaging of the shallow crust, and slower post-seismic recovery towards the background conditions (Zaccarelli et al. , 2011). We could also create a sequence of maps for the spatial relative velocity variations by interpolating over the surface the single station values at different times. From these images we can observe that the area that shows the most intense variations is not merely restricted around the earthquake occurrences, but it also elongates in the NE direction. This zone corresponds to the gas trapped area of the Apennines (Chiarabba and Chiodini, 2013), thus confirming the findings by Brenguier et al. (2014). Finally, we try to model the post-seismic trend, with a best fit regression. It is noteworthy how our best fit estimate is composed by not only a logarithmic contribution (typical of the post-seismic crustal recovery), but also a linear trend, as already found for the Mw 6.1 L’Aquila sequence by Soldati et al. (2015). References Brenguier F., Campillo M., Hadziioannou C., Shapiro N.M., Nadeau R.M., and LaroseE.; 2008a: Postseismic relaxation along the San Andreas fault at Parkfield from continuous seismological observations , Science, 321 , 1478–1481. Brenguier F., Shapiro N.M., Campillo M., Ferrazzini V., Duputel Z., Coutant O., and Nercessian A.; 2008b: Towards forecasting volcanic eruptions using seismic noise , Nat. Geosci., 1 , 126–130. Brenguier F., Campillo M., Takeda T., Aoki Y., Shapiro N.M. and Briand, X.; 2014: Mapping pressurized volcanic fluids from induced crustal seismic velocity drops , Science, 345 , 80–82. Chen J., Froment H., B., Liu Q. Y., and Campillo M.; 2010: Distribution of seismic wave speed changes associated with the 12 May 2008 Mw 7.9 Wenchuan earthquake , Geophys. Res. Lett., 37 , L18302, doi:10.1029/ 2010GL044582. Chiarabba C., and Chiodini G.; 2013: Continental delamination and mantle dynamics drive topography, extension and fluid discharge in the Apennines , Geology, 41 , 6, 715-718. Chiaraluce L., Di Stefano R., Tinti E., Scognamiglio L., Michele M., Casarotti E., Cattaneo M., De Gori P., Chiarabba C., Monachesi G., Lombardi A., Valoroso L., Latorre D., and Marzorati S.; 2017: The 2016 Central Italy Seismic Sequence: A First Look at the Mainshocks, Aftershocks, and Source Models , Bull. Seismol. Soc. Am., 88 , 3, doi:10.1785/0220160221. Marchetti et al.; 2017: The Italian Seismic Bulletin: strategies, revised pickings and locations of the central Italy seismic sequence , Ann. Geophys. 59 , doi: 10.4401/ag-7169. Marzorati, S., Cattaneo M., Frapiccini M., Monachesi G., and Ladina C.; 2016: Recent seismicity before the 24 August 2016 Mw 6.0 central Italy earthquake as recorded by the ReSIICO seismic network , Ann. Geophys. 59 , doi: 10.4401/ag-7191. Fig. 2 - Relative velocity variations (Δv/v) computed for the 378 station couples along the 2 years of continuous seismic recordings. Each dot is plotted with a different color depending on the number of station couples that intervene in the measurement, this indicates the goodness of the evaluation: the hotter the color the more accurate and stable results. The red vertical lines highlight the time of occurrence of the major (Mw ≥ 5.5) seismic events.