Ionospheric Response of Earthquakes in the Philippines from November to December 2023

Abstract—Ground-based magnetometric measurements were used to study ionospheric disturbances observed from November to December 2023 after a series of fairly strong earthquakes in an area of intense seismic activity in the Philippines. It is shown that a stable pattern of the appearance of magnetic disturbances from events with different magnitudes (from Mw = 6 to Mw = 7.4) is observed, containing short- and long-period disturbances caused by variations in the current systems of the lower ionosphere. It has been established that these variations belong to different branches of atmospheric acoustic-gravity waves: acoustic and internal, respectively. It is shown that the origin of disturbances in the acoustic range may be associated with the arrival of seismic Rayleigh waves, which are a source of acoustic vibrations, while the estimated velocities of atmospheric internal waves correspond to their generation directly at the epicenters of events. Magnetometric measurements have made it possible to record ionospheric disturbances from events with a significantly lower magnitude compared to the radio sounding method using global navigation satellite systems.