Observation of Coriolis coupled modes below 1 mHz
We present observations of spectral energy at toroidal mode frequencies in vertical seismic recordings of the 1998 Balleny Islands earthquake. Since toroidal modes on a spherically symmetric, non-rotating Earth have horizontally polarized particle motion these observations call for an explanation. W...
Published in: | Geophysical Journal International |
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Main Authors: | , , , |
Format: | Text |
Language: | English |
Published: |
Oxford University Press
2000
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Subjects: | |
Online Access: | http://gji.oxfordjournals.org/cgi/content/short/143/1/113 https://doi.org/10.1046/j.1365-246x.2000.00220.x |
Summary: | We present observations of spectral energy at toroidal mode frequencies in vertical seismic recordings of the 1998 Balleny Islands earthquake. Since toroidal modes on a spherically symmetric, non-rotating Earth have horizontally polarized particle motion these observations call for an explanation. We first rule out local and instrumental effects as being responsible for the vertical-component signal of the toroidal modes 0 T 3 (0.59mHz) and 0 T 4 (0.77mHz). The global effects that we consider are general heterogeneous mantle structure, ellipticity of figure and rotation. We find that rotation through Coriolis coupling of low-order spheroidal and toroidal oscillations is the dominant mechanism. |
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