Shear Wave Velocity Measurement for Seismic Site Characterization Using Ambient Vibration Tests

This paper describes a series of ambient vibration tests conducted at a designated site in the province of British Columbia, Canada, to measure the shear wave velocity in soil in order to characterize the seismic site according to the seismic provisions in design codes. At the designated site, the vibration recordings were conducted at multiple locations using wireless sensors: single-instrument recordings for site period estimation (single-station test), multi-instrument simultaneous circular array ambient vibration recordings (passive test), and multi-instrument simultaneous linear array recordings with an active source (active test). The recorded data was processed and analyzed in order to characterize the soil conditions. For each location, the ratio of the horizontal to vertical Fourier spectra of ambient noise recorded (typically noted as H/V) was calculated by a three-component sensor to determine the site period. Also, shear wave velocity profile was computed using the dispersion curves obtained from passive or active array tests. The average Vs to a depth of 30 m (Vs30) was then calculated and reported in the results, as it is the current site parameter in the NBCC. This information could be then used for site response analysis and earthquake site amplification prediction.