Unveiling the vertical ionospheric responses following the 2024 Noto Peninsula Earthquake with an ultra-dense GNSS network

Abstract

This paper leverages total electron content (TEC) perturbations obtained from an ultra-dense Global Navigation Satellite System (GNSS) receiver network across the Japanese archipelago to reconstruct the three-dimensional (3-D) structures of ionospheric responses following the 2024 Noto Peninsula Earthquake (Mw7.5). Reconstructions successfully captured the concentric electron density perturbations extending radially from the epicenter in the horizontal and vertical cross section 9–10 min after the earthquake. At south of the epicenter, in the meridional-vertical cross sections, phases of the electron density perturbations have a tilted structure stretching from north-up to south-down, which gradually becomes more vertical over time. Model calculations indicate that these electron density perturbations are caused by seismic acoustic waves, with sound velocity increasing at higher altitudes. However, the difference between theoretical predictions and reconstruction results may suggest the non-linear propagation of acoustic waves in the ionosphere, and the presence of multiple acoustic wave sources along the fault.