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

Abstract

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.