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Modal propagation of ocean acoustic waves generated by earthquakes
Language
en
Communication dans un congrès avec actes
This item was published in
OCEANS 2019 - Marseille, OCEANS 2019 MTS/IEEE, 2019-06, Marseille. 2019-10-14
English Abstract
The generation of low-frequency (≤ 40 Hz) acoustic waves (T-waves) by undersea earthquakes below a flat abyssal plain is not yet fully understood. To model the generation and propagation of PN-waves (horizontally in the ...Read more >
The generation of low-frequency (≤ 40 Hz) acoustic waves (T-waves) by undersea earthquakes below a flat abyssal plain is not yet fully understood. To model the generation and propagation of PN-waves (horizontally in the crust and vertically in the ocean) and of T-waves over a rough sea bottom, we use a 2D spectral finite-element code (SPECFEM2D). The model includes a solid layer (Earth crust) overlain by a fluid ocean, and separated by a sinusoidal crust/water interface (seafloor roughness). Synthetic T-waves propagate as Rayleigh modes with their expected vertical and long-range horizontal propagation. In the simulated PN-wave spectrum, resonance peaks appear at frequencies predicted by the analytical solution for Rayleigh modes. The same peaks are observed in actual T-wave records from an antenna of two hydrophones at different, generated by a large magnitude earthquake 987 km away. The T-waves spectrum from the shallowest hydrophone shows an energy gap in the 1-4 Hz frequency range that can be explained by modal propagation. The resonance peaks in the observed PN-wave spectrum are also well predicted by the analytical solution.Read less <
English Keywords
Abyssal T-waves
PN-waves
SN-waves
Rayleigh modes
spectral element modeling
Origin
Hal imported