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Vertical velocity of acoustic wave determined from altitudes of TEC disturbances after a foreshock
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  • Yoshihiro Kakinami,
  • Hiroaki Saito,
  • Tetsuo Yamamoto,
  • Chia-Hung Chen,
  • Masa-Yuki Yamamoto,
  • Kensuke Nakajima,
  • Jann-Yenq Liu,
  • Shigeto Watanabe
Yoshihiro Kakinami
Hokkaido Information University

Corresponding Author:[email protected]

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Hiroaki Saito
Kochi University of Technology
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Tetsuo Yamamoto
Hokkaido University
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Chia-Hung Chen
National Cheng Kung University
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Masa-Yuki Yamamoto
Kochi University of Technology
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Kensuke Nakajima
Kyushu University
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Jann-Yenq Liu
National Central University
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Shigeto Watanabe
Hokkaido Information University
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Abstract

We investigate ionospheric disturbances using the total electron content (TEC) data retrieved by the three satellites after the foreshock of the 2011 Tohoku Earthquake on 9 March 2011. Co-seismic ionospheric disturbances (CIDs) appeared to extend from an onset point concentrically in all of the satellite data. We have found, however, that the geographic coordinates of the onset points did not coincide if the observed CIDs were assumed to occur at one altitude. Admitting that the altitudes of the onset points are different, we searched for coinciding geographic coordinates of the onset points using the two data sets by changing the altitudes and identified the altitude of the two onset points at 155.4 and 234.9 km, and the onset time at these altitudes. As a result, the vertical velocity of acoustic wave is estimated to be 1.04 km/s from the travel time between the altitudes of 155.4 and 234.9 km. This is 1.4 times higher than the sound velocity calculated using the empirical model NRLMSISE-00. The present study provides a method of determining the source location of the acoustic wave from the ionospheric TEC analysis without using the seismic data.