Estimation of average S-wave velocity of ground using microtremors at strong-motion sites in Yokohama

First, Average S-wave velocity in the uppermost 30 m (Vs30) obtained from PS-logging data and site amplification factors for peak acceleration and velocity derived from strong motion records are compared at the dense strong-motion network sites in Yokohama (Y-NET). Next, a simple method for estimating Vs30 is examined at Y-NET sites. This method involves placing 3 sensors in the shape of the letter 'L' for simultaneous microtremor observation. Finally, a method to estimate peak ground acceleration and velocity using Vs30 is proposed and its applicability is investigated.