[M-IS09] Interdisciplinary studies on pre-earthquake processes

[MIS09-P03] Study on an optimal short-term earthquake forecast using long-term ionosonde data 1958-2024

*Chinatsu Sasanuma¹, Shunya Mitsuishi¹, Chie Yoshino², Katsumi Hattori^2,4,5, Jann-Yenq LIU³ (1.Department of Earth Sciences, Faculty of Science, Chiba University, 2.Graduate School of Science, Chiba University, 3.Center for Astronautical Physics and Engineering, National Central University, Taiwan, 4.Center for Environmental Remote Sensing, Chiba University, 5.Research Institute of Disaster Medicine, Chiba University)

In recent years, ionospheric disturbances related to earthquakes have been reported and are considered promising for realizing short-term earthquake forecasting.
In the Japan region, analysis of ionosonde data from Kokubunji from 1958-2018 shows a significant anomaly 6-10 days before the earthquakes with epicenter distance 350 km or less, magnitude 5.8 or more, depth 40 km or less in NmF2 (ionospheric maximum electron density).
However, ionospheric disturbances 30 days before the Noto M7.6 of Jan 1, 2024, were reported. Therefore, in this study, we extended the analysis period from 30 days before the earthquake to 45 days and recalculated.
We defined the threshold of the positive anomaly as the value of median + 1.5IQR of the NmF2 at the same time in the previous 15 days and an abnormal day as ten or more hours of the anomalies appear in one day. We performed Superposed Epoch Analysis (SEA) to investigate the statistical significance of the correlation between NmF2 anomalies and earthquakes. We repeated the random SEA test 100,000 times to evaluate the statistical significance.
In addition, we performed Molchan’s Error Diagram (MED) analysis to evaluate the efficiency of NmF2 anomalies for earthquake forecasting.
SEA and MED results suggested a causal relationship between NmF2 anomaly and earthquakes.
The detail will be presented in this presentation.