Blind study site assessment of shear-wave velocity at Kumamoto City, Japan, using direct-fitting SPAC methods

Abstract The study used data acquired by the ESG6 Blind Prediction Step BP1 Working Group for purposes of facilitating a comparison interpretation methods obtaining shear-wave velocity profiles (V s ) from array observations microtremor (passive seismic) noise. This work uses direct-fitting MMSPAC method and krSPAC on passive seismic supplied four seven-station nested triangular arrays with apertures ranging 1 to 962 m, located within Kumamoto City, Japan. allow useful frequency range 38 Hz down 0.3 Hz, giving depth sensitivities 2 m > 1000 m. Results are presented as seven-layer model which has time-averaged shear wave velocities top 30 300 V s30 = 189 m/s s300 584 m/s, respectively. HVSR spectra show two significant peaks at 1.2 0.35 indicative major contrasts depths 26 750 (and its variant) also proved viable one asymmetric where seven stations were corrupted incoherent low-frequency Indications lateral variation in could be detected due non-concentric geometry arrays, variations largest array. Further analysis step 4 blind trials, making use geological Preferred participants, showed apparent discrepancies between our upper 40 PS log appears inconsistent model. At low frequencies 0.5–2.5 dispersion suggest that Rayleigh effective mode is superior fundamental deducing Vs below 100 direct fitting observed SPAC enabled bandwidth 0.5–38 interpretation, wider than achieved other participants alone. Graphical