GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.2 343 A further insight into the data significance was obtained by inverting the Rayleigh wave ellipticity curves in terms of 1D velocity model for each noise measurement station. In data inversion, the thickness of the first layer was constrained on the basis of the ERT outcome. At a first stage, separate modeling was attempted for the two resonance peaks in the 2-4 and 6-13 Hz band. Starting from the high frequency peak, representative of the most superficial layers, the calculated models can constrain only the surface layers, leaving a major uncertainty about the deeper layers. However, using the low frequency peak, which better controls the velocities at depth, information on the deeper part of the deposit can be inferred, which shows a gradual variation in the material velocity. The inversion revealed a layering of the dam deposit, probably related to the overlapping of the debris of two or more landslides occurred at different times, and also a lateral variation in the surface layer velocity; the later can be linked to a variable amount of rock material within the 2008 landslide deposit. Overall, the layering distinguished through the velocity models agrees quite well with the field observations made along the outcrops of the dam deposit generated by the river incision. References Del Gaudio, V., 2017: Instantaneous polarization analysis of ambient noise recordings in site response investigations . Geophys. J. Int., 210 , 443–464, doi: 10.1093/gji/ggx175. Fan, X.M., Juang, C.H., Wasowski, J., Huang, R.H., Xu, Q., Scaringi, G., van Westen, C.J., Havenith, H.-B., 2018. What we have learned from the 2008 Wenchuan Earthquake and its aftermath: a decade of research and challenges . Eng. Geol. 241 , 25–32. https://doi.org/10.1016/j.enggeo.2018.05.004 Nakamura, Y., 1989: A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface . Q. Report Railway Tech. Res. Inst., 30 , 25–33. Fig. 3 - ERT section showing the resistivity variation along the profile with ambient noise measurements (see Figs. 1-2). Note the thickness of the most resistant surface layer (identified by white vertical segments under each measurement point), interpreted as corresponding to the most recent rock avalanche deposit. FRAMING URBAN LIMIT CONDITIONS THROUGH RESILIENCE DIMENSIONS E. Cianci, C. Fontana Institute of Environmental Geology and Geoengineering (IGAG), Italian National Research Council, (CNR), Rome, Italy Setting the scene. Recent studies on seismic risk reduction and mitigation introduced the Urban Limit Conditions (ULC), as thresholds of physical and functional urban damage caused by a major earthquake. When each of these hypothetical thresholds is reached, depending on the event’s severity, the settlement undergoes significant changes in its functionalities, such as to compromise its maintenance (Bramerini et al. , 2013). In analogy with the definition of limit states for buildings and structures (NTC 2018), the ULC can be different (Fig.1) and correspond