Publication Date:
2024-04-05
Description:
Secondary microseisms recorded by seismic stations are generated in the ocean by the interaction
of ocean gravity waves.We present here the theory for modelling secondary microseismic
noise by normal mode summation.We show that the noise sources can be modelled by vertical
forces and how to derive them from a realistic ocean wave model. We then show how to
compute bathymetry excitation effect in a realistic earth model by using normal modes and
a comparison with Longuet–Higgins approach. The strongest excitation areas in the oceans
depends on the bathymetry and period and are different for each seismic mode. Seismic noise
is then modelled by normal mode summation considering varying bathymetry. We derive an
attenuation model that enables to fit well the vertical component spectra whatever the station
location. We show that the fundamental mode of Rayleigh waves is the dominant signal in
seismic noise. There is a discrepancy between real and synthetic spectra on the horizontal
components that enables to estimate the amount of Love waves for which a different source
mechanism is needed. Finally, we investigate noise generated in all the oceans around Africa
and show that most of noise recorded in Algeria (TAM station) is generated in the Northern
Atlantic and that there is a seasonal variability of the contribution of each ocean and sea.
Description:
Published
Description:
1732-1745
Description:
1T. Geodinamica e interno della Terra
Description:
JCR Journal
Description:
restricted
Keywords:
Surface waves and free oscillations
;
Seismic attenuation
;
Theoretical seismology
;
Wave propagation
;
04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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