Cross-sphere Coupling and Source Inversion of Ionospheric Disturbances Associated with the 2025 Myanmar Strike-slip Earthquake from BeiDou GEO and Multi-GNSS Observations

Abstract

Focusing on the M7.9 earthquake in Myanmar in 2025, this study comprehensively utilizes data from BeiDou geostationary satellites of the Chinese Continental Crustal Movement Observation Network and multi-system Global Navigation Satellite Systems (GNSS). The spatiotemporal evolution characteristics and physical mechanisms of pre-seismic ionospheric anomalies and co-seismic ionospheric disturbances were systematically analyzed. By employing the moving interquartile range method combined with solar-terrestrial environmental parameters, a negative Total Electron Content (TEC) anomaly associated with the seismogenic region was identified three days before the earthquake. The equatorial conjugate structure of this TEC anomaly revealed a multi-path coupling effect between the lithosphere, atmosphere, and ionosphere. The extraction of Coherent Ionospheric Disturbance (CID) signals based on wavelet transform and band-pass filtering indicated that the co-seismic ionospheric disturbances were dominated by acoustic-gravity waves in the 2-8 mHz frequency band, propagating at a speed of approximately 1.2 km/s, and exhibiting an asymmetric pattern in the southeast direction. A spatial density-weighted method for locating the source of ionospheric disturbances was proposed, elucidating the joint control mechanism of fault strike-slip motion, geomagnetic field modulation, and equatorial electrojet on the disturbance energy. The results confirm that the high spatiotemporal resolution of BeiDou GEO satellites and multi-system GNSS significantly enhances the capability to capture weak ionospheric anomaly signals associated with earthquakes. These results provide additional observational constraints on space-based Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) processes and may contribute to the development of ionosphere-based earthquake monitoring techniques.

Figures (10)

• Figure 1: Distribution of BeiDou geostationary satellite ionospheric pierce points (IPPs) in the study area. The labels (a)--(i) mark the nine representative IPPs used in the preseismic time-series analysis in Figure \ref{['fig:pre_seismic_tec']}; the remaining symbols show the full set of GEO IPPs in the study region.
• Figure 2: Ionospheric TEC anomalies detected by the BeiDou geostationary satellites before the earthquake. Panels (a)--(i) show detrended TEC time series at the nine representative IPPs. The red line in each panel denotes the 27-day running median, and the shaded band shows the prediction interval (median $\pm$ 1.5 $\times$ IQR). Blue (red) markers indicate data points below (above) this interval. The number followed by "km" in each panel title denotes the horizontal distance between the corresponding IPP and the earthquake epicenter. Panels (j)--(m) display relevant space environment indices, and the light pink shaded areas indicate periods of disturbed solar or geomagnetic activity. Panels (a)--(i) correspond to the IPPs labelled (a)--(i) in Figure \ref{['fig:ipp_distribution']}.
• Figure 3: Distribution of JPL Global Ionosphere Map (GIM) TEC anomalies on March 25. The green star marks the earthquake epicenter, and the black star indicates the magnetic equatorial conjugate point of the epicenter. The solid black line between them represents the magnetic equator.
• Figure 4: (a) Location of the earthquake, with black triangles representing CMONOC sites and red hexagons representing the IPPs of the corresponding BeiDou-5 GEO satellite. (b) Detrended TEC time series (without band-pass filtering) from the BeiDou-5 GEO satellite for the YNWS, YNSM, and YNGM stations together with their wavelet power spectra. The 2--8 mHz band (indicated by dashed lines) is used to design the Butterworth band-pass filter applied in panel (c) and subsequent figures. (c) Time--distance plot of co-seismic ionospheric disturbances detected by the BeiDou-5 GEO satellite, based on 2--8 mHz band-pass filtered TEC.
• Figure 5: Time--distance plots showing co-seismic ionospheric disturbance propagation velocities derived from multi-system GNSS TEC data. The black arrows indicate the apparent propagation directions and velocities and have been drawn with reduced thickness to avoid obscuring the TEC disturbance signals.