Ionospheric Signature Recorded on the Hawaii GPS Network of the Mw 6.9 Earthquake and Tsunami
Résumé
On 4 May 2018, a Mw 6.9 earthquake ruptured on the south flank of the Kilauea volcano, Hawaii. The rupture of this largest earthquake in the Hawaii region since 1975 extended offshore and a small tsunami was identified on regional tide gauges. Then we expect a significant shaking of the ionosphere, the ionized layer of the Earth's atmosphere located from 80 km to 2000 km of altitude. This ionization affects Global Positioning System (GPS) signals and these perturbations can be used to image the ionosphere response triggered by large (Mw > 6.5) and shallow earthquakes. Here, we analyze data collected by receivers of the permanent GPS network of Hawaii. While no clear disturbance was detected after the 1 May 2018 crater collapse, we observe clear disturbances in the Total Electron Content (TEC) directly above the rupture area. These fluctuations are consistent with an acoustic wave originating from the rupture area of the earthquake. We investigate the solid/ocean/atmosphere coupling efficiency using a spectral element modeling approach. We then conduct an acoustic ray tracing-based modeling to reconstruct the observed perturbations and relate them to the seafloor static deformation reconstructed using conventional data.