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Seismic shear waves as Foucault pendulum
Author(s) -
Snieder Roel,
SensSchönfelder Christoph,
Ruigrok Elmer,
Shiomi Katsuhiko
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl067598
Subject(s) - physics , polarization (electrochemistry) , earth's rotation , longitudinal wave , rotation (mathematics) , transverse plane , transverse wave , mechanical wave , love wave , wave propagation , classical mechanics , geophysics , optics , geometry , quantum mechanics , chemistry , mathematics , structural engineering , engineering
Earth's rotation causes splitting of normal modes. Wave fronts and rays are, however, not affected by Earth's rotation, as we show theoretically and with observations made with USArray. We derive that the Coriolis force causes a small transverse component for P waves and a small longitudinal component for S waves. More importantly, Earth's rotation leads to a slow rotation of the transverse polarization of S waves; during the propagation of S waves the particle motion behaves just like a Foucault pendulum. The polarization plane of shear waves counteracts Earth's rotation and rotates clockwise in the Northern Hemisphere. The rotation rate is independent of the wave frequency and is purely geometric, like the Berry phase. Using the polarization of S c S and S c S 2 waves, we show that the Foucault‐like rotation of the S wave polarization can be observed. This can affect the determination of source mechanisms and the interpretation of observed S K S splitting.