Statistical Study of North‐South Asymmetry Characteristics in Coseismic Ionospheric Disturbance Over the Chile Subduction Zone

Abstract This study statistically investigates the distribution of the coseismic ionospheric disturbances (CIDs) in the north and south directions and the feature of the north‐south asymmetry of the CID amplitude using total electron content measurements for 13 earthquakes with magnitude 6.7–8.8 in the Chile subduction zone. The relative CID amplitude in the south direction is generally smaller than that in the north direction, but the propagation range of the CID in the south direction is basically consistent with that in the north direction. The north‐south amplitude ratio increases with decreasing epicentral distance. The larger CID amplitude in the north direction and the dependence of the north‐south amplitude ratio on the epicentral distance are found to be mainly associated with the effect of the geomagnetic field. Furthermore, the empirical relationship between the relative CID amplitude and the earthquake magnitude is suggested to consider geomagnetic field‐neutral orientation factor (GNF) for improved accuracy. It is also found that the north‐south amplitude ratio increases with the earthquake magnitude, which cannot be fully explained by the combined effect of GNF, north‐south asymmetry of the seismic energy release, and satellite observation geometry.