Seismo-Geomagnetic Pulsations Triggered by Rayleigh Waves of the 11 March 2011 M 9.0 Tohoku-Oki Earthquake

  • Author(s): Horng-Yuan Yen, Chun-Rong Chen, Yu-Tsung Lo, Tzay-Chyn Shin, and Qi Li
  • DOI: 10.3319/TAO.2014.10.09.01(T)
  • Keywords: Tohoku-oki earthquake, Rayleigh wave, Magnetic pulsations

This study reports on geomagnetic pulsations excited by traveling Rayleigh waves. The geomagnetic total intensity fields recorded using 12 magnetometers are utilized to examine seismo-magnetic pulsations induced by the 2011 M 9.0 Tohoku-oki earthquake. Geomagnetic data and seismograms from 4 co-located seismometers are examined and cross-compared to deter- mine whether magnetic variations result changes in space weather or traveling Rayleigh waves. A 150 - 250 s band-pass filter was adopted to determine the arrival times and amplitudes of the seismo-magnetic pulsations. Seismo-magnetic pulsations with pronounced periods of about 200 s and amplitudes of 0.2 - 1.2 nT appear at distances ranging from 190 - 4600 km from the epicenter. Pulse speed of 3.8 km s-1 estimated from the epicentral distances and arrival times indicates that the seismo-mag- netic pulsations were induced by Rayleigh waves produced by the Tohoku-oki earthquake. The seismo-magnetic pulsations constantly lag seismic wave pulses by about 6.3 minutes, confirming that ionospheric conductivity affects magnetic fields.

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