Microseisms observations in the Santa Clara Valley, California

We have investigated ground-motion amplification in the Santa Clara Valley (SCV) using microseisms observed during the 1998 deployment of 41 short-period seismometers. The Santa Clara Valley Seismic Experiment (SCVSE) (Lindh et al., 1999; Fletcher et al., 2003) recorded many local, regional, and teleseismic events. In our previous work we investigated the 3D velocity structure of the SCV by modeling the teleseismic P waves recorded during the SCVSE (Dolenc et al., 2005). To complement these results, we now focus on the microseisms that were recorded during the same period and relate these observations to local earthquake wave amplification. It is found that the seismic noise is related to the ocean wave heights measured on the weather buoy west of Half Moon Bay, California. The spectral ratio of the horizontal to vertical (H/V) microseisms at each SCVSE site is stable with time, and the period of the dominant peak in the H/V ratio is related to the basin depth. The results of this study show that seismic noise can be used in the assessment of the effects of deep sediments on long-period earthquake ground motions.