We have been examined a method to infer S-wave velocty of deep sediments by an array measurement of microtremors in the period range longer than one second. This paper describes an application of this method to Teriary strata. In January 1995, an array measurement of long period microtremors was performed in Tomioka Town in Fukushima Prefecture. Rayleigh wave phase velocity of fundamental mode was estimated. S-wave velocity was presumed by an inversion analysis of the phase velocity using genetic algorithms. The result is consistent with the boring data near the array and seismic profile. We concluded that the array method of microtremors is applicable for the evaluation of S-wave velocities of Tertiary strata.
