Seismo ionospheric anomalies before the 2007 M7.7 Chile earthquake from GPS TEC and DEMETER

Abstract

Earthquake (EQ) related variations in the ionosphere may provide some insights to understand the seismo ionospheric coupling and to mitigate the damages of seismic hazards. In this paper, the electromagnetic variations in the ionosphere associated with November 14, 2007, M7.7 Chile EQ are investigated in electron density and electron temperature measurements from ISL (Langmuir Probe) of DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite and TEC (total electron content) estimated from GPS (Global Positioning System). The investigation of temporal and spatial measurements suggests anomalies which are observed within 10 days before the future EQ (i.e. 9 days before on November 5, 2007). The temporal values of daytime DEMETER and diurnal TEC on November 5, 2007 imply abrupt anomalies that are considered to be the fragments of the plasma intensification process in the Southern Hemisphere activated by the rock compression in the quake region. Similarly, spatial maps of TEC and DEMETER (electron density and electron temperature) showed the anomalous configuration of the temporal analysis that may induce by the epicenter. In addition to spatial and temporal analysis, the Index number for the northern and southern sectors of the EQ preparation zone around the epicenter along latitude confirmed the anomalous values of electron density and electron temperature of the DEMETER satellite. Similarly, the comparison of electron density and electron temperature at the epicenter latitude and its conjugate reveals anomalous enhancement over the seismogenic zone on November 5, 2007 (9 days before) prior to the event.