ESG6 BLIND PREDICTION. STEP1 BY INGV AND ENEA TEAM

Abstract

This paper describes the analysis performed within the ESG6 blind prediction step 1, devoted to the retrieval of the shear-wave velocity (Vs) structure at a target site in Kumamoto city. Ambient vibration data were analysed by different techniques. Horizontal-to-vertical spectral ratios were calculated showing resonance peaks around 0.3 and 1.1 Hz. Three methods were applied for surface-wave dispersion curve (DC) retrieval: cross-correlation (CC), modified spac (MSPAC) and high resolution F-K (RTBF). Vertical components were analysed to retrieve fundamental Rayleigh-wave DCs while horizontal motions allowed to extract Love-wave DC by RTBF. The Rayleigh-wave DCs from all methods are in good agreement. They were used as a target for numerical inversion jointly with Love-wave DC and Rayleigh-wave ellipticity curve obtained for one station. The retrieved Vs profiles are presented, and the comparison of our results with the best Vs model provided by the ESG6 committee is also discussed.