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

[MIS09-P04] Statistical Analysis of Ionospheric Total Electron Content Anomalies Associated with large earthquakes (M>7) in globe during 2000-2024 Using GNSS Data

Kento Enomoto¹, *Chinatsu Sasanuma¹, Chie Yoshino², Katsumi Hattori^2,3,4 (1.Department of Earth Sciences, Faculty of Science, Chiba University, 2.Graduate School of Science, Chiba University, 3.Center for Environmental Remote Sensing, Chiba University, 4.Research Institute of Disaster Medicine, Chiba University)

Short-term forecast is important for mitigating damage from earthquakes, and electromagnetic phenomena related to earthquakes are attracting attention as an indicator of such phenomena. Among them, the study of anomalies of TEC before earthquakes is considered to be promising. The number of earthquakes per region is too small to cover large earthquakes (For example, earthquakes of M>7.0 that occurred between 2000 and 2024, 369 in the world and 26 in Japan). Therefore, the purpose of this study is to investigate ionospheric anomalies preceding earthquakes by case/statistical analysis for earthquakes of M>7.0, D<60 km that occurred in the world during 2000-2024. Earthquake catalogs were from the USGS (United States Geological Survey). GIM, a global grid of TEC data published by CODE (Center for Orbit Determination in Europe), was used for the analysis. As a indicator of anomaly, GIM-TEC** was defined by normalizing GIM-TEC at a given time by the median of the same time over the previous 15 days. Values exceeding the median +1.5 IQR were considered anomalies, and days with anomalies exceeding 10 hours per day were considered anomalous days. In the statistical analysis, using the SEA (Superposed Epoch Analysis) method, anomalous days were accumulated for 45 days before and after the earthquake occurrence day. To verify the significance of the anomalies, the same number of days as the earthquake occurrence was randomly selected from the analysis period 10000 times (random SEA), and the process was performed on the grid including the epicenter and the surrounding. Details of the results will be given in the presentation.