Capability of TEC correlation analysis and deceleration at propagation velocities of MSTID: Preseismic ionospheric anomalies before the large earthquakes
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• Ken Umeno,
• Ryo Nakabayashi,
• Takuya Iwata,
• Minghui Kao
Ken Umeno
Kyoto University, Kyoto University
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Ryo Nakabayashi
Kyoto University, Kyoto University
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Takuya Iwata
Kyoto University, Kyoto University
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Minghui Kao

Corresponding Author:kao.minghui.3z@kyoto-u.ac.jp

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## Abstract

Capability of TEC ’s CoRrelation Analysis (CRA) (Iwata and Umeno, 2016) for detecting preseismic anomaly is explained from the view point of the increase in signal-to-noise ratio to {\it amplify} preseismic TEC’s small anomaly signals with multiple sensor data synchronization and correlation to respond to all the criticisms proposed recently by Ikuta et al. 2021. Furthermore, deceleration at propagation velocities of MSTID before the 2016 Kumamoto earthquake firstly observed by CRA as velocity reduction of MSTID propagation in the F Layer of the ionosphere is then elucidated as a candidate of preseismic anomalies. This paper presents three models to explain its physical relationship with preseismic anomalies before large earthquakes. In particular, Model 1 predicts that the 35 m/s change in MSTID propagation velocities estimated by TEC’s CRA requires 0.58*10^{-3} V/m electric field change in the F Layer ionosphere, which is almost consistent with the estimation (Kelley et. al. 2017) in that the E*B/B^2 rift of 12 m/s for dislocations of electrons requires 0.5*10^{-3} V/m electric field in the E Layer to explain Heki’s finding of TEC anomaly behavior before the Tohoku-Oki earthquake. The $$10000$$ times amplified effect of weak signals such as 0.58 mV/m in electrical field to affect MSTID propagation velocity change as is firstly observed by Iwata and Umeno, 2017 by CRA which has significant amplified capability. Contrary to the claim by Ikuta et al. 2021, TEC’s correlation anomalies detected (Iwata and Umeno 2016 and 2017) already provided supporting evidences that physical preseismic anomalies really exist.