Pre-earthquake Electric Field Disturbances and Interference Analysis Based on CSES-01 Satellite Observations

Abstract. Anomalous electromagnetic phenomena in the ionosphere before and after seismic activity have been identified as potential indicators for earthquake early warning. Data from the CSES-01 satellite were analyzed using the STL decomposition method to break down electric field time series into longitudinal, latitudinal, and residual components. The longitudinal and latitudinal components reveal the electric field's double periodicity, characterized by a V-shape from south to north and a bimodal shape from east to west. After isolating conventional periodic disturbances with a strength of 0.87, unconventional disturbances in the residual component were examined to identify seismic precursor anomalies. Electric field power density disturbances associated with the May 11, 2023, Tonga Islands magnitude 7.6 earthquake were extracted. Multiple significant anomalies in the ionospheric electric field were detected within 20 days prior to the earthquake: an initial anomaly with a C-value exceeding 3.5 appeared 20 days before; a persistent anomaly with a peak C-value of 3.9 occurred 13 to 11 days prior; a sharp increase to a peak C-value of 4.4, three times the standard deviation, was observed seven days prior; disturbances decreased until a resurgence four days prior, with a peak C-value of 3.5 lasting two days; the C-value returned to baseline one day before the earthquake. The STL-C method effectively differentiates various causal disturbances in the ionospheric electric field, offering novel approaches and insights for studying seismic precursors.