Statistical Seismo-Ionospheric Influence with the Focal Mechanism under Consideration

This research aims to statistically investigate seismo-ionospheric influence related to strong earthquakes with different focal mechanisms. The nighttime O+ density and electron density, measured by the CSES satellite for about 3 years and by the DEMETER satellite for 6 years, were utilized to globally search for ionospheric perturbations with different datasets. Data on strong M ≥ 6.0 earthquakes with focal mechanism information within a ±45° geographic latitude were collected during the periods considered. A comparison was automatically performed using software to correlate these ionospheric variations and earthquakes under the condition that a perturbation occurred at a horizontal distance less than 1500 km from the epicenter and up to 15 days before the earthquake. The Kp index was maintained as less than 3 in this timeframe to reduce the effects of geomagnetic activities. Combined with statistical results provided by four groups of rupture and strike-slip earthquakes corresponding to both satellites, it was shown that the averaged ionospheric number of rupture earthquakes is slightly higher than that obtained from strike-slip events, on which basis it seems that, averagely, rupture earthquakes tend to give rise to a heavier influence on the ionosphere than strike-slip ones. Furthermore, this conclusion was comparatively confirmed by commonly detected earthquakes and random events completely for the CSES satellite and partly for the DEMETER satellite. At the same time, we did not gain a firm conclusion regarding the detection rates corresponding to these two types of earthquakes. Thus, further investigations will be necessary as more data are collected.