Seismic-ionospheric perturbations in ionospheric TEC and plasma parameters associated with the 14 July 2019 Mw7.2 Laiwui earthquake detected by the GPS and CSES

Abstract

In this study, with cross-valid analysis of total electron content (TEC) data of the global ionospheric map (GIM) from GPS and plasma parameters data recorded by China Seismo-Electromagnetic Satellite (CSES), signatures of seismic-ionospheric perturbations related to the 14 July 2019 Mw 7.2 Laiwui earthquake were detected. After distinguishing the solar and geomagnetic activities, three positive temporal anomalies were found around the epicenter 1 day, 3 days and 8 days before the earthquake (14 July 2019) along with a negative anomaly 6 days after the earthquake, which also agrees well with the TEC spatial variations in latitude-longitude-time (LLT) maps. To further confirm the anomalies, the ionospheric plasma parameters (electron, O+ and He+ densities) recorded by the Langmuir probe (LAP) and Plasma Analyzer Package (PAP) onboard CSES were analyzed by using the moving mean method (MMM), which also presented remarkable enhancements along the orbits around the epicenter on day 2, day 4 and day 7 before the earthquake. To make the investigations more convincing, the disturbed orbits were compared with their corresponding four nearest revisiting orbits, whose results indeed indicate the existence of plasma parameters anomalies associated with the Laiwui earthquake. All these results illustrated that the GPS and CSES observed unusual ionospheric perturbations are highly associated with the Mw 7.2 Laiwui earthquake, which also strongly indicates the existence of pre-seismic ionospheric anomalies over the earthquake region.