GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 2.2 349 flows mainly northward. Hillslopes are characterised by the presence of landslides of different typology, dimension and state of activity, remnants of hanging relict landscapes, testified also by depositional river terraces and slope-waste deposits; at the junctions of the main tributary streams with the Tronto River well-developed alluvial fan also occur. Adetailed geological survey of the Quaternary continental deposits together with geophysical analysis (e.g. single station HVSR, SSR, MASW, Re.Mi, ERT) is being carried out in order to identify unit areas susceptible to local seismic amplification. Such an amplification can be locally ascribed both to stratigraphic and topographic factors. The narrow Tronto river-valley is prone to 2D amplification effects due to both valley- shape and heterogeneities of the alluvial filling, here mainly composed of gravel and sand. 2D amplification effects due to peculiar landforms, such as narrow ridges and edges of rock-scarps, that host some villages (i.e. Colleposta, Collespada and Cassino) can have a relevant role on local seismic response of the area. Moreover, considering the 24 th August mainshock and the related near fault conditions, the influence on the amplification phenomena due to non-vertical incidence of seismic waves on slopes cannot be neglected. Such conditions can determine wave focusing and effects related to seismic directivity. Geophysical investigations including active and passive multichannel seismic surface-waves analysis, seismic body-wave tomography, H/V spectral ratio inversion, and P- and S- down hole tests, will be performed to estimate 1D and 2D subsurface velocity models and complemented by electrical resistivity tomography and ground probing radar to help defining morphological and constraints for the seismic interpretation. Furthermore, lab tests and geological surveys will be performed to define, more in detail, the engineering geological and seismic models and provide reliable input for the modelling of the expected local seismic amplification. The obtained results have also undoubted scientific implications. References Cacciuni A., Centamore E., Di Stefano R., Dramis F.; 1995: Evoluzione morfotettonica della Conca di Amatrice. Studi Geologici Camerti, Volume Speciale 1995/2, pp. 95-100. EMERGEO Workgroup; 2016: Terremoto di Amatrice del 24 Agosto 2016: Effetti Cosismici. Pierantoni P., Deiana G., Galdenzi S.; 2013: Stratigraphic and structural features of the Sibillini Mountains (Umbria- Marche Apennines, Italy).Ital. J. Geosci. (Boll. Soc. Geol. It.), Vol. 132, No. 3 (2013), pp. 497-520. ReLuis-INGV Workgroup; 2016: Preliminary study of Rieti earthquake ground motion records V2 changes related to seismic activity may control fluid circulation at depth forcing crustal uid to migrate upwards, especially along faults (King, 1986; Ciotoli et al. , 2007). Fluid circulation at depth may alter the geochemical characteristics of the fault core (Annunziatellis et al. , 2008), which in turn can influence soil gas concentrations at the surface (e.g., Baubron et al. , 2002;