The near-coastal microseism spectrum: Spatial and temporal wave climate relationships

Bromirski, PD, Duennebier FK.  2002.  The near-coastal microseism spectrum: Spatial and temporal wave climate relationships. Journal of Geophysical Research-Solid Earth. 107

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ambient noise, attenuation, depth, microseism propagation characteristics, microseism source areas, microseisms, ocean, ocean bottom, pressure, Rayleigh wave, reflection, sea-floor, seismometer, wave climate


[1] Comparison of the ambient noise data recorded at near-coastal ocean bottom and inland seismic stations at the Oregon coast with both offshore and nearshore buoy data shows that the near-coastal microseism spectrum results primarily from nearshore gravity wave activity. Low double-frequency (DF), microseism energy is observed at near-coastal locations when seas nearby are calm, even when very energetic seas are present at buoys 500 km offshore. At wave periods >8 s, shore reflection is the dominant source of opposing wave components for near-coastal DF microseism generation, with the variation of DF microseism levels poorly correlated with local wind speed. Near-coastal ocean bottom DF levels are consistently similar to20 dB higher than nearby DF levels on land, suggesting that Rayleigh/Stoneley waves with much of the mode energy propagating in the water column dominate the near-coastal ocean bottom microseism spectrum. Monitoring the southward propagation of swell from an extreme storm concentrated at the Oregon coast shows that near-coastal DF microseism levels are dominated by wave activity at the shoreline closest to the seismic station. Microseism attenuation estimates between on-land near-coastal stations and seismic stations similar to150 km inland indicate a zone of higher attenuation along the California coast between San Francisco and the Oregon border.






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