Earthquake Processes Leave Distinct Imprint on Ionosphere

• 25 Nov 2023

A recent study revealed that earthquake processes, even minor ones, leave their mark on the ionosphere, impacting coseismic ionospheric perturbations (CIP) and suggesting the potential for deciphering earthquake precursors through space-based observations.

Key Points

• Distinctive Influence Factors: Coseismic vertical crustal movements trigger acoustic waves (AWs) in the atmosphere, reaching the ionosphere and causing disturbances in electron numbers.
• Factors such as geomagnetism and line-of-sight geometry contribute to near-field CIP, typically occurring within 500–600 km of the earthquake source.
• Assumptions in Past Studies: Past studies often assumed point sources for direct AWs, modelling near-field CIP based on a single acoustic pulse from the surface.
• However, the research challenges this assumption, especially for large earthquakes involving ruptures of multiple fault segments.
• Verification through February 2023 Turkey Earthquakes: Scientists from the Indian Institute of Geomagnetism (IIG) examined near-field CIP of the 2023 February Turkey Earthquakes (less than 8 Mw) to verify assumptions.
• The earthquakes included a devastating Mw 7.8 (EQ1) near the Turkey-Syria border and a subsequent Mw 7.7 (EQ2) to the north.
• Multiple Sources along Fault: The study demonstrates, for the first time, that ionospheric perturbations generated by relatively small earthquakes can involve contributions from multiple sources along the fault.
• Interference of Acoustic Waves: Interference of acoustic waves (AWs) from these multiple sources creates differences in perturbation amplitudes and periods at Global Navigation Satellite System (GNSS) stations, varying in azimuths from the earthquake epicentre.