Analysis of Ionospheric Disturbances Potentially Associated with the Maduo Ms7.4 Earthquake on 22 May 2021 in China Using GIM-TEC Data

On May 22, 2021, a magnitude 7.4 earthquake struck Maduo County in Guoluo Prefecture, Qinghai Province, China, with an epicenter at 34.59°N latitude and 98.34°E longitude and a focal depth of 17 kilometers.

Ionospheric disturbances related to this earthquake are analyzed using Global Ionospheric Map Total Electron Content (GIM-TEC) data from May 1 to May 31, 2021. We employ the LSTM-LUBE method, an advanced deep learning model for dynamic range prediction, to detect and analyze anomalies in the GIM-TEC data across both temporal and spatial scales. The core idea of the LSTM-LUBE method is to predict the dynamic range of the input TEC data through a neural network, rather than providing a single point estimate. Data points falling outside the predicted dynamic range are considered anomalies. To ensure the accuracy of the results, disturbances caused by solar activity and geomagnetic fluctuations are excluded. Temporal analysis reveals significant TEC anomalies between May 3 and May 8, as well as a notable TEC anomaly on the day before the earthquake, May 21. From the GIM-TEC spatiotemporal difference maps, conjugate TEC negative disturbances are observed in the earthquake preparation zone and its magnetic conjugate region during UT 6:00-8:00 on May 3. Additionally, conjugate TEC disturbances, characterized by initial positive perturbations followed by negative perturbations, are detected in the Maduo earthquake preparation zone and its magnetic conjugate region during UT 8:00-12:00 and UT 18:00-22:00 on May 5.

This study demonstrates the potential of ionospheric TEC data in earthquake prediction by utilizing the LSTM-LUBE deep learning network to extract TEC anomalies.

Fig. 1. Two typical grid points' TEC time series and difference plots are shown (The red solid line represents ΔTEC, the gray shaded area indicates the dynamic TEC range, and the blue solid line represents the true TEC values). After excluding disturbances from geomagnetic and solar activities, the anomalies observed on May 3, May 5, May 7, May 8, and May 21 may be attributed to earthquake activity.

Fig. 2. On May 3, during UT 6:00-8:00, negative ionospheric disturbances are observed in both the earthquake preparation zone and its magnetic conjugate region in the spatiotemporal difference maps (The red circle represents the preparation zone of the Maduo earthquake epicenter, and the green circle represents the magnetic conjugate region).

Fig. 3. On May 5, during UT 8:00-12:00 and UT 18:00-22:00, anomalous TEC disturbances characterized by initial positive perturbations followed by negative perturbations are observed in both the earthquake preparation zone and its magnetic conjugate region (The red circle represents the preparation zone of the Maduo earthquake epicenter, and the green circle represents the magnetic conjugate region).