GNSS-based Ionospheric Observations after the Noto Peninsula Earthquake and Tsunami

On 1 January 2024 a M7.5 earthquake struck the Noto Peninsula of Japan at 2024-01-01 07:10:09 (UTC).We use ground-based Global Navigation Satellite Systems (GNSS) data from GEONET (GNSS Earth Observation Network System) receivers operated by the Geospatial Information Authority of Japan (GSI) and the Continuously Operating Reference Station (CORS) operated by the National Geographic Information Institute (NGII) in South Korea to analyze the ionospheric response to this earthquake and resulting tsunami event.An N-shaped co-seismic ionospheric disturbance is observed in the total electron content (TEC) measurements between eight to fifteen minutes after the earthquake across 91 GSI's GEONET stations and 11 satellites.We observed a variety of coseismic ionospheric disturbance velocities and directions while the event is relatively smaller than other major submarine earthquakes with a depth of 10km.The predominant co-seismic ionospheric disturbances (CSID) propagated from the epicentral area with a velocity of 800 m/s, extending 650 km from the epicenter.A secondary disturbance potentially due to the tsunami is under investigation.