We collected significant wave height recordings measured at buoys deployed by National Ocean and Atmospheric Administration (NOAA) and Japan Meteorological Agency (JMA) on the Pacific for days of 30 through 35 in 2000. The significant wave heights are compared to the variations in the level of seismic amplitude at F-net and BDSN (Figure 13.26).
We computed maximum mean stack amplitude for center period of 240 s and compared the variations in amplitude with significant wave height measured at buoys placed close to the two arrays in Japan (F-net) and California (BDSN). Two significant wave height measurements in different parts of the Pacific show similar trends with two maxima on day 31 and 33. Rough comparison of the onsets of associated maxima in buoy and seismic data for the eastern Pacific shows that the maximum in the seismic data arrives later than that in buoy data on days 31 and 33. It indicates that seismic energy measured at the two arrays had been generated closer to the shore than the location of the buoys and the mechanism of generating continuous long period Rayleigh waves may be similar to the one for the microseisms at short periods. The significant wave heights measured at the buoys placed very close to the Californian coast (46027 in Figure 13.26) show much better agreement with the seismic data at BDSN. It is very difficult to determine similar trends of significant wave heights at eastern and western part of the Pacific are just local phenomena from separate ocean waves or basically initiated by one common origin. Considering long term correlation of seismic amplitudes for both arrays, we prefer one common atmospheric perturbation - that may be very spatially extended - which generates eastward and westward propagating ocean waves.
Berkeley Seismological Laboratory
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