Özet:

Since earthquakes are seismic activities that various symptoms appear before they occur. One of the effects of seismic activity is known to be on the lower ionosphere layer. For this reason, changes on the ionosphere layer are observed and possible seismic events are tried to be determined. Vibrations caused by crustal movements in the earth cause not only concussion on humans but also some environmental changes that people cannot perceive directly. These changes can be modelled in such a way that different methods and devices can detect them. One of the main parameters in the examination of these methods is the change in Very Low Frequency (VLF) signal values. For this purpose, the changes in the lower ionosphere layer before and after the earthquake can be modelled with the changes obtained from VLF signals and the relationship between them can be used to determine the pre-earthquake ionospheric changes. The use of transient disturbances in this region of the ionosphere in VLF signals and remote sensing systems has been the subject of many studies. In the studies, it is seen that the VLF waves are based on the reflection rule of the ionosphere substrate (from the D region). It shows some observable changes on the electromagnetic waves that the ionosphere provides to be reflected within a few days before earthquakes. Understanding these changes with specific mathematical and statistical models reveals the possible precursors of earthquakes before they occur. In this study, January 17, 1995 Kobe (M = 7.2); January 6, 2008 (M=6.2) Greece Earthquake; April 25, 2015 (M=7.8) Nepal-Gorkha and the aftershocks of this earthquake on May 12, 2015 (M=7.3) Earthquake; January 12, 2010 (M=7.0) Haiti and 11-21 November 2016 Japan (M=6.1 and M=6.9) earthquakes in the lower ionosphere layer emitted as a result of the earthquake precursor results examination was carried out.

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