Ocean‐bottom ultralow‐frequency (ULF) seismo‐acoustic ambient noise: 0.002 to 0.4 Hz

Observed spatial and temporal characteristics of ultralow‐frequency (ULF) ocean‐bottom seismo‐acoustic ambient noise are required in order to construct realistic quantitative predictive models of the phenomena involved. Few such data exist or have been studied, especially for frequencies below about 0.1 Hz. Analysis of noise data is presented in the band 0.002 to 0.4 Hz from a 2‐week period, 11/28–12/12/67, recorded from long‐period, three‐component seismometers and a hydrophone of the Columbia‐Point Arena ocean‐bottom seismic station (OBSS, 38° 09.2’N–124° 54.4’W, 3903‐m depth). Two intense NE Pacific storms with hurricane force winds occurred during the emphasized time period. Time variations of spectra and of amplitude and phase coherencies of the four‐component OBSS data are related to the storm histories and to local weather/wave conditions and are used to identify motion (seismic wave) types and directions of propagation.