Kyoto University discovers correlation between ionospheric disturbances and crustal movement anomalies immediately before a major earthquake

A research group led by Professor Ken Umeno and Hiroki Tanaka of the Graduate School of Informatics at Kyoto University, announced on September 30 that they successfully detected crustal movement anomalies associated with ionospheric disturbances that occurred 1-2 hours before the 2011 Great East Japan Earthquake. Correlation analysis, a method for detecting ionospheric disturbances before a major earthquake, was applied to high-frequency crustal movement data taken just before the Earthquake. They discovered an anomaly that is believed to be a preslip, causing a shift of about 1 cm in 2 hours. The results are expected to lead to the development of a technology that predicts major earthquakes in advance and were presented at the international conference EMSEV2024 held in Greece on October 7.

The ionosphere exists above the earth and is affected by natural phenomena such as earthquakes and solar flares as well as human-made events such as missiles. Detecting anomalies before major earthquakes by observing the ionospheric electron content has attracted attention since an abnormal increase in the ionospheric electron content was discovered before the main shock of the Great East Japan Earthquake. However, it was unclear whether these ionospheric disturbances were of seismic origin, and there was no evidence of preslip before a major earthquake.

Therefore, the research group employed the correlation analysis method for multipoint observations that they developed in 2016 to the Great East Japan Earthquake. Generally, high-frequency crustal movement data at 5-minute intervals contain a lot of noise. However, this analysis method suppresses this noise and improves the signal-to-noise ratio (SNR), thereby successfully detecting anomalies. As the distance from the epicenter decreases, the correlation value increases correspondingly. The results show a high correlation with earthquake occurrences.

Going forward, the group will continue to link these results to the investigation of other major earthquakes. The researchers plan to make a presentation on the Hyuga-Nada Earthquake in August this year at the meeting of the Seismological Society of Japan in Niigata in October and on the 2016 Kumamoto Earthquake and the Southern Taiwan Earthquake at the American Geophysical Union (AGU) meeting in the United States in December. The presentation will be given priority, followed by the publication of papers. In the future, the researchers aim to build a real-time anomaly detection system that can detect anomalies in real time, up to 1 hour in advance.

Journal Information
Publication: International Journal of Plasma Environmental Science and Technology
Title: A capacitive coupling model between the ionosphere and a fault layer in the crust with supercritical water
DOI: 10.34343/ijpest.2024.18.e01003