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Although source location based on teleseismic body wave microseisms has a superior spatial resolution because of relatively simple wave propagation, the signals in this frequency range are too weak to use.
A clue for the source localization of primary microseisms is the observation of precursory signals for a CCF between a land station and an ocean floor station, which emerge before the first arrivals when strong localized sources exist in near-shore areas between the pair of stations.
67,102,108) Most studies have shown seasonal variations in the amplitudes of these microseisms.
For example, observations from an ocean-floor seismic station at 4,977 m depth halfway between Hawaii and California showed that secondary microseisms in pelagic and coastal regions depend on their typical frequency.
4 Hz showed not only P- but also S-wave microseisms excited by a severe, distant storm in the Atlantic Ocean (85) (Fig.
For the northern Fennoscandian region, cross-correlation analysis of high-frequency secondary microseisms reveals Moho-reflected body wave (0.
The excited amplitudes of body wave microseisms are smaller than the amplitudes of surface waves in the source area.
Even at coastal stations, overtones and teleseismic body waves become dominant in the frequency range of secondary microseisms when local ocean swell activity is calm and distant swell activity is intense.
In-situ offshore observations of secondary microseisms are indispensable for this estimation.
infragravity wave at the ocean floor for seismic hum, (13,143) and to ocean swell in near-shore areas for primary microseisms.
As pointed out above, backprojection that utilizes teleseismic P-waves of secondary microseisms has superior spatial resolution and localization capability because scattering in the mantle is weaker than the scattering of surface waves in the crust.
First, let us consider the energy partitioning of secondary microseisms with frequencies above 0.