Surface-wave site characterization at 52 strong-motion recording stations affected by the Parkfield, California, M6.0 earthquake of 28 September 2004

We present one-dimensional shear-wave velocity (V_S) profiles at 52 strong-motion sites that recorded the 28 September 2004 Magnitude 6.0 Parkfield, Calif., earthquake. We estimate the V_S profiles with the Spectral Analysis of Surface-Waves (SASW) method. The SASW method is a noninvasive method that indirectly estimates the V_S at depth from variations in the Rayleigh wave phase velocity at the surface. To address the uncertainty associated with these measurements, we compare the SASW profiles to surface-source downhole-receiver (SSDR) profiles at four sites. Three of the four SSDR sites are in close agreement with the adjacent SASW site, while the SASW profile is considerably slower than the SSDR profile at one site.