Abstract:Considering the limit of the PCA method in detecting ionospheric anomalies, we propose a detection method that combines PCA and sliding time window. We use three strong earthquakes as examples to test its anomaly detection capability. The results show that this method retains the advantages of each of the two methods. Compared with the sliding time window method, its detection results are more intuitive and concise, and have stronger resistance to environmental disturbances as well as relatively higher confidence and reliability of anomaly detection. Compared with the PCA method, it can be better used for long-time anomaly detection and accurately distinguish between positive and negative anomalies. On this basis, this paper analyzes the anomalous perturbation of the pre-earthquake ionosphere for the 2020 Oaxaca earthquake using this method. The study showed that the TEC anomalies increased 13 days before the earthquake, and decreased 12, 11, 9, and 6 to 4 days before the earthquake in the ionospheric TEC, which is located in the southerly region of the epicenter and mainly manifested as negative anomalies. Finally, combining these four earthquakes, it can be found that the ionospheric anomalies mainly appear in the southerly direction of the epicenter, and most of them are conjugate structures.
XIE Ting,CHEN Biyan,KUANG Cuilin. Study of Ionospheric Anomaly Detection Method Combining PCA and Sliding Time Window[J]. jgg, 2021, 41(10): 1085-1094.