Abstract
[1] We report for the first time observations of Earth's toroidal free oscillations recorded on a ring laser system that is sensitive to rotational ground motions around a vertical axis. Because of the high noise level on the horizontal translational components in classical seismometers, long-period toroidal modes are amongst the most challenging observations in seismology. In addition, pure uncontaminated observations of long-period motions are difficult as translational sensors are sensitive to rotational motions also. We show that the toroidal modes associated with rotational motions are complementary to those associated with translations and confirm the relatively spatially compact character of the Mw 9.0 Tohoku-Oki earthquake. The observations presented here complement the translational, strain, and gravitational records. We expect these observations to provide additional constraints on long-wavelength deep Earth structure and earthquake sources.
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.
