Characterizing the Complex Two N-Wave Ionospheric Signature of the 2016 Kaikoura Earthquake

Abstract

Major earthquakes (>∼6.5 Mw) can generate observable waves which propagate not only through the Earth but also through the Earth's ionosphere. These traveling ionospheric disturbances can be observed using multifrequency GPS receivers to measure the ensuing perturbations in the Total Electron Content of the ionosphere. Assisted by a statistical approach we developed to indicate the occurrence of a significant TEC perturbation from the normal background behavior, we detect a traveling ionospheric disturbance generated by the 2016 7.8 Mw Kaikoura earthquake occurring in New Zealand on the 13th of November. The disturbance was detected ∼8 min after the earthquake, propagating toward the equator at ∼1 km/s with a peak-to-peak amplitude of ∼0.22 Total Electron Content units. The coseismic waveform exhibits complex structure unlike that of the expected N-wave for coseismic ionospheric disturbances, with observations of oscillations with 4-min periodicity and of two N-waves. This observed complexity in the ionosphere likely reflects the impact of the complex, multifault structure of the earthquake.