A Study of Pre-Earthquake Ionospheric Anomaly (PEIA) in Low Latitude/ Equatorial Region TEC Using the Wavelet Power Spectrum Method

Abstract

Earthquakes are major natural hazards that often result in significant loss of life and property. Previous studies indicate that the ionosphere exhibits anomalous behavior prior to seismic events. This study investigates pre-earthquake ionospheric anomalies (PEIA) associated with five earthquakes of magnitude M ≥ 7.0 in the low-latitude/equatorial region using Total Electron Content (TEC) data. Earthquake parameters were obtained from the United States Geological Survey (USGS), while TEC data were sourced from the International GNSS Service (IGS) via Ionolab, covering 10 days before and 5 days after each event. To distinguish seismic effects from external influences, geomagnetic and solar conditions were assessed using Dst, Kp, AE, and F10.7 indices from the OMNI database. Analysis using time series and Wavelet Power Spectrum (WPS) methods revealed significant TEC anomalies up to 10 days before each earthquake. WPS results further showed enhanced power intensity during the pre-earthquake period compared to quiet conditions. These findings demonstrate the role of lithosphere–atmosphere–ionosphere coupling mechanisms prior to major earthquakes, suggesting that PEIA is driven by multiple mechanisms.