Abstract
On a rotating, aspherical earth, coupling between spheroidal and toroidal seismic free oscillations is manifested in the time domain as a slow alternation of the oscillation envelope between the transverse and the radial and/or vertical motion components. Using a narrow-band smooth envelope estimator, we have observed this behavior in data from the MS = 8.1 Macquarie Ridge earthquake of 5/23/89. Rotational coupling is the principal cause of mixed-type coupling for f < 4.2 mHz. However, envelope perturbations consistent with mixed-type coupling are observed for 0S38-0T36 and 0S37-0T35, which do not couple through rotation, and couple only weakly through smooth upper mantle velocity models. Such envelope perturbations can bias estimates of modal Q, and suggest that scattering may play a role in the attenuation of long-period surface waves.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
