Atmospheric and ionospheric precursors associated with Mw ≥ 6.5 earthquakes from multiple satellites

Abstract

The ionospheric monitoring satellites aid in correlating the lithospheric variation in ionosphere through Lithosphere-Atmosphere-Ionosphere coupling (LAIC) over the epicenter of future earthquake (EQ). In the present paper, we studied variations in ionosphere associated to two large magnitude EQs (Mw ≥ 6.5) and low epicentral depth EQs of less than 12 km in Plasma Density (PD), Slant Total Electron Content (STEC) and Electron Temperature (ET) of European Space Agency's (ESA) Swarm-three satellites (Swarm-A, -B, and –C). These anomalies are investigated in the Swarm data for 60 days before/after each main shock. The anomalies are detected by statistically implemented median (M) and standard deviation (σ) method within the Dobrovolsky's area. In order to exclude the geomagnetic perturbations, we have selected the ionospheric data in quiet geomagnetic conditions. Anomalous variations in Swarm-A data occur in ET and STEC for the USA event, and similarly, significant perturbation is clear in STEC of Swarm-B before the Mw 6.5, USA. In case of Swarm-C, no clear anomalies associated with the USA event. Furthermore, Swarm-A, -B and –C have abnormal post-seismic PD, STEC and ET responses to the Mw 6.7 Turkey EQ in the form intensive perturbations beyond the upper bound. We also study the atmospheric data over the epicenters in the form of Outgoing Longwave Radiation (OLR), Relative Humidity (RH), Surface Temperature (ST), and Air Temperature (AT) to support the Swarm observations. RH and ST show pre-seismic atmospheric anomalies before the USA EQ in the same anomalous time period as Swarm satellites. While, OLR, ST and AT have post-seismic atmospheric anomalies after the Turkey EQ within 15–20-day period. The precursors chain from the lithosphere to the atmosphere, followed by the ionosphere are highlighted at different altitudes. The variations window for Swarm satellites and atmospheric indices are 5 days prior to USA main shock and one month after the Turkish EQ. Moreover, this study also aims to study the caliber of Swarm satellites for indicating seismo-ionospheric irregularities, which need more studies to delineate the LAIC hypothesis for future EQ.