Analyzing GNSS-RO derived ionospheric intensity scintillation preceding earthquakes in the Coral Sea during 2022

Abstract

Lithosphere–atmosphere–ionosphere coupling models have been widely studied as potential earthquake precursors. After the earthquakes, total electron content (TEC) anomalies propagating away from the epicenter have been identified. Recent evidence has also found that electromagnetic phenomena related to earthquakes might also produce ionospheric anomalies before their occurrence. This study analyzes the correlation between ionospheric intensity scintillation, characterized by the S4 index, and seismic activity in the area around the Coral Sea in the year 2022. The S4 intensity scintillation index derived from COSMIC-2 global navigation satellite system radio occultation estimates ionospheric perturbations and identifies anomalies. The methodology involves applying rigorous filters to ensure reliable S4 estimation, including slant TEC thresholding and night-time filtering. To compare the S4 scintillation index with seismic activity, the mean and the 95th percentile of the S4 values are computed at 1-d intervals. Two case studies of earthquakes in 2022 with magnitudes larger than 6 are presented, as well as a statistical analysis based on the calculation of the confusion matrices, and the receiver operating characteristic curves. A positive correlation between the ionospheric intensity scintillation and the occurrence of earthquakes is found, with a probability of detection exceeding 35.7 % and a false alarm rate of 7.1 %