Ionospheric disturbances detected by GPS total electron content observation after the 2011 off the Pacific coast of Tohoku Earthquake

Abstract

All the details of ionospheric disturbances following the 2011 Tohoku Earthquake were first revealed by the high-resolution GPS total electron content observation in Japan. The initial ionospheric disturbance appeared as sudden depletions following small impulsive TEC enhancements ∼7 minutes after the earthquake onset, near the epicenter. Then, concentric waves appeared to propagate in the radial direction with a velocity of 138-3,457 m/s. Zonally-extended enhancements of the TEC also appeared in the west of Japan. In the vicinity of the epicenter, short-period oscillations with a period of ∼4 minutes were observed. This paper focuses on the concentric waves. The concentric pattern indicates that they had a point source. The center of these structures, termed the "ionospheric epicenter", was located about 170 km from the epicenter in the southeast direction. According to the propagation characteristics, these concentric waves could be caused by atmospheric waves classified into three types: acoustic waves generated from a propagating Rayleigh wave, acoustic waves from the ionospheric epicenter, and atmospheric gravity waves from the ionospheric epicenter. The amplitude of the concentric waves was not uniform and was dependent on the azimuth of their propagation direction, which could not be explained by previously-proposed theory.

Acoustic resonance and plasma depletion detected by GPS total electron content observation after the 2011 off the Pacific coast of Tohoku Earthquake

“…The instrumental biases of the satellites and the receivers were estimated and subtracted from the observed data by the method of Otsuka et al (2002). An outline of the ionospheric variations detected by GEONET after the 2011 off the Pacific coast of Tohoku Earthquake has been given by Tsugawa et al (2011), and the ionospheric variations that propagated over a long distance were studied by Chen et al (2011).…”

“…The outline of the variations and the propagating structures in the wide area have been discussed by Tsugawa et al (2011) and . This paper focuses on the ionospheric variations in the vicinity of the epicenter.…”

Dynamics of vertical ionospheric inhomogeneities over Irkutsk during 06:00–06:20UT 11/03/2011 caused by Tohoku earthquake

“…Ionospheric effects of the Tohoku earthquake are currently the subject of many papers. Above all, it is papers analyzing data from dense networks of GPS-receivers, located on the Asian territory (Akhoondzadeh, 2012;Kakinami et al, 2011;Astafyeva et al, 2013;Hao et al, 2012;Komjathy et al, 2012;Liu, 2012;Occhipinti et al, 2011;Ogawa et al, 2012;Ouzounov et al, 2011;Saito et al, 2011;Tsugawa et al, 2011) and data from the SuperDARN radar, located on the Hokkaido island (Nishitani et al, 2011;Ogawa et al, 2012). These instruments have the best temporal resolution -from several seconds to 2 minutes, enabling to monitor the highly dynamic processes.…”

On the Origin of Mega-thrust Earthquakes

“…Liu et al 2011;Tsugawa et al 2011), may provide important opportunities to understand the deformation processes before the occurrence of the mega-thrust earthquakes.…”