Ionospheric multiple stratifications and irregularities induced by the 2011 off the Pacific coast of Tohoku Earthquake

Abstract

A strong earthquake with a magnitude of 9.0 occurred at 1446:23 JST on March 11, 2011, in Japan. Ionospheric disturbances were detected at 1500 JST at four ionosonde stations. An irregular distortion of echo trace was observed at Kokubunji, which is the nearest station to the epicenter and is 440 km from it. Multiple-cusp-type trace indicating extra stratification was observed at Wakkanai and Yamagawa, which are 870 and 1410 km away from the epicenter. A small wavy fluctuation was observed at Okinawa 1910 km away from the epicenter. The real height analysis of the ionograms showed a vertical structure with a scale size of 20∼30 km.

The resonant response of the ionosphere imaged after the 2011 off the Pacific coast of Tohoku Earthquake

“…Its propagation speed was estimated to be ∼225 m/s and frequency of about 1.8 mHz. These features are coherent with the observations of Maruyama et al (2011) and Tsai et al (2011) using GPS-TEC technique and the observations of Liu and Sun (2011) in ionogram records. They are corroborated here by normal modes computation.…”

Seismo-traveling ionospheric disturbances of ionograms observed during the 2011 M w 9.0 Tohoku Earthquake

“…Many studies report STIDs triggered by the 11 March, 2011, M 9.0 Tohoku Earthquake by means of TEC (total electron content) derived from ground-based GPS receivers of GEONET (Maruyama et al, 2011;Rolland et al, 2011;Tsai et al, 2011) and ionograms of ionosondes (Maruyama et al, 2011). Three different STIDs are observed by the 5 ionosondes after the earthquake.…”

“…Liu et al (2011) report that STIDs of the GPS TEC first appear near the epicenter about 7 minutes after the Tohoku Earthquake onset, while Tsai et al (2011) find that the STIDs in the GPS TEC triggered by the Rayleigh waves appear 7-8 minutes after the earthquake occurrence. Maruyama et al (2011) further cross-compare concurrent/co-located GPS TECs and ionograms recorded by the 4 ionosondes in Japan during the Tohoku Earthquake. They find the earlier onset of the disturbance in the ionogram than the commencement of the propagating TEC perturbation.…”

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

“…These structures were very dynamic (Liu and Sun, 2011;Maruyama et al, 2011). However, traditionally ionosondes have relatively low (about 15 minutes) temporal resolution, not allowing us to study dynamics of the vertical structure of irregularities.…”