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Department of Laser Measurement and Navigation Systems St.-Petersburg Electrotechnical University St.-Petersburg, Russia
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- PublicationOpen AccessHorizontal rotation signals detected by “G-Pisa” ring laser for the Mw = 9.0, March 2011 Japan earthquake(2012)
; ; ; ; ; ; ; ; ;Belfi, J.; Department of Physics "Enrico Fermi", Università di Pisa, and CNISM unità di Pisa, Italy ;Beverini, N.; Department of Physics "Enrico Fermi", Università di Pisa, and CNISM unità di Pisa, Italy ;Carelli, G.; Department of Physics "Enrico Fermi", Università di Pisa, and CNISM unità di Pisa, Italy ;Di Virgilio, A.; INFN Sez. di Pisa, Pisa, Italy ;Maccioni, E.; Department of Physics "Enrico Fermi", Università di Pisa, and CNISM unità di Pisa, Italy ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Stefani, F.; Department of Physics "Enrico Fermi", Università di Pisa, and CNISM unità di Pisa, Italy ;Velikoseltzev, A.; Department of Laser Measurement and Navigation Systems St.-Petersburg Electrotechnical University St.-Petersburg, Russia; ; ; ; ; ; ; We report the observation of the ground rotation induced by theMw=9.0, 11th of March 2011, Japan earthquake. The rotation measurements have been conducted with a ring laser gyroscope operating in a vertical plane, thus detecting rotations around the horizontal axis. Comparison of ground rotations with vertical accelerations from a co-located force{balance accelerometer shows excellent ring laser coupling at periods longer than 100s. Under the plane wave assumption, we derive a theoretical relationship between horizontal rotation and vertical acceleration for Rayleigh waves. Due to the oblique mounting of the gyroscope with respect to the wave direction{of{arrival, apparent velocities derived from the acceleration / rotation rate ratio are expected to be always larger than, or equal to the true wave propagation velocity. This hypothesis is con_rmed through comparison with fundamental{mode, Rayleigh wave phase velocities predicted for a standard Earth model.248 212