High-frequency P-wave seismic noise driven by ocean winds

Earth's background vibrations at frequencies below about 0.5 Hz have been attributed to ocean-wave energy coupling into the ground and propagating as surface waves and P-waves (compressional waves deep within the Earth). However, the origin and nature of seismic noise on land at frequencies around 1 Hz has not yet been well studied. Using array beamforming, we analyze the seismic noise fields at two remote sites (Parkfield and the Mojave Desert) in California, for durations of one and six months respectively. We find that (1) the seismic background noise at about 0.6-2 Hz consists of a significant amount of continuous P-waves originating offshore, and (2) the power of the P-wave noise is highly correlated with the offshore wind speed, demonstrating that these high-frequency P-waves are excited by distant ocean winds. Our result suggests a land-based seismological proxy for monitoring oceanic weather. Citation: Zhang, J., P. Gerstoft, and P. M. Shearer (2009), High-frequency P-wave seismic noise driven by ocean winds, Geophys. Res. Lett., 36, L09302, doi: 10.1029/2009GL037761.