GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.2 365 prevention. In particular, in the high seismic risk areas, it is highly suggested to: ( i ) perform high- LOD seismic risk analysis, and ( ii ) improve the definition of the exposed assets characteristics by gathering data through fieldwork, different databases and remote sensing information. Acknowledgements. The ReLUIS 2019-2021 project is acknowledged for the financial support given to this study. The authors are grateful to “ Agenzia delle Entrate ” for providing data analyzed in this study. References Buratti N., Minghini F., Ongaretto E., Savoia M., and Tullini N.; 2017: Empirical seismic fragility for the precast RC industrial buildings damaged by the 2012 Emilia (Italy) earthquakes , Earthquake Engineering & Structural Dynamics, 14 (46), 2317-2335. Crowley H., Colombi M., Borzi B., Faravelli M., Onida M., Lopez M., Polli D., Meroni F., and Pinho R.; 2009: A comparison of seismic risk maps for Italy , Bull. of Earthquake Engineering, 1 (7), 149-180. Frolova N.I., Larionov V.I., Bonnin J., Sushchev S.P., Ugarov A.N., and Kozlov M.A.; 2017: Seismic risk assessment and mapping at different levels , Natural Hazards, 1 (88), 43-62. ISO; 2009: ISO, 31010: Risk management-Risk assessment techniques , Event (London). Geneva 552. Michelini A., Faenza L., Lauciani V., and Malagnini L.; 2008: ShakeMap implementation in Italy , Seismological Research Letters, 5 (79), 688-697. MIT; 2018: Ministerial Decree: “NTC 2018 - Norme tecniche per le costruzioni (In Italian) ” . Xiong C., Lu X., Huang J., and Guan H.; 2018: Multi-LOD seismic-damage simulation of urban buildings and case study in Beijing CBD , Bulletin of Earthquake Engineering, 1-21. NEAR-SURFACE Q P AND Q S ESTIMATION BY DOWNHOLE-VSP SURVEYS F.S. Desideri, M. Cercato “Sapienza” University of Rome – DICEA, Area Geofisica, Rome, Italy Introduction. Seismic attenuation represents the loss of elastic energy contained in a seismic wave, as it propagates. We used two well-established methods for Q (quality factor) estimation: The Spectral Ratio and the Rise time methods. In the Spectral Ratio (SR) method, the determination of attenuation is based on the standard assumption of exponential amplitude decay in the frequency domain. When Q is considered to be frequency-independent, the inverse problem is generally stable, and it can be linearized and solved for all of these three parameters: ln[ A ( ω )/ A 0 ( ω )] = – π Δ tf / Q + ln [ PG ] (1-1) Where A 0 ( ω ) and A ( ω ) are the amplitude spctrum of two seismic traces. The left-hand side of the equation is called Reduced Spectral Ratio. The slope term, γ ( ω ) = π Δ tf / Q , is called Differential Attenuation (Teng, 1968), τ = ( t – t 0 ) is the time delay between two first arrival at two different distance (depths) z and z 0 and f is the frequency in Hz. The Rise Time (RT) method is based on the assumption that the pulse rise time increase linearly with the distance of propagation (Gladwin & Stacey, 1974). An attenuative impulse will satisfy the equation: τ = Ct* (1-2) where τ is the rise time of the resultant pulse and C is a constant. Survey design and acquisition parameters. The data set for determining Q are field data from a profile located in Rieti, Central Italy, as part of the investigation and study activities related to the level III Seismic Microzonation (MS) of the Municipality of Rieti (RI). At the investigation site, a continuous core drilling was carried out, up to 45 meters, and equipped for the Downhole geophysical test. Tab 1 describes the borehole characteristics and acquisition geometry: