Decoding multiple source signatures in coseismic ionospheric disturbances of the 2024 January Mw7.5 Noto-Peninsula earthquake, Central Japan

•Comprehensive study of coseismic ionospheric disturbance by the 2024 Jan. Noto-Peninsula earthquake.•Multiple acoustic wave sources caused complicated waveforms and azimuthal dependences.•Ionosphere recorded possible slow earthquake signals following the mainshock.•Medium scale traveling ionospheric disturbance enhanced the coseismic signals. Vertical crustal movements associated with large earthquakes excite various kinds of atmospheric waves. They propagate upward and often disturb ionosphere. Here, I report a case for the 2024 January 1 Mw7.5 earthquake that occurred in the northern tip of the Noto Peninsula, Central Japan, using a dense network of multi-GNSS receivers. A rectangular-shaped positive anomaly of ionospheric total electron content emerged ∼9 min after the mainshock. The initial sharp peak was composed of two acoustic wave pulses excited at the two ends of the fault spanning ∼100 km. It was followed by a series of smaller-amplitude broad peaks, the largest of which was possibly excited by a slow fault rupture near the NE edge of the fault ∼8 min after the mainshock. These signatures become large where the wavefronts overlap with those of medium-scale traveling ionospheric disturbances, suggesting possible enhancement of the coseismic signals by downward displacements of high electron density regions in the ionosphere.