Investigation of electromagnetic effects of earthquakes
When an Earthquake occurred, different electromagnetic phenomena occur in variety of frequency bands. These effects and their relationship with earthquakes have been reported in many cases. Sine these effects, appear at hours up to several weeks before origin time of an earthquake, they seem appropriate to be investigated as precursors.
Actually the cause of these phenomena is not clear yet, but we can mention some reasons for it. Moving of conductive earth crust in its magnetic field is one of them. One of other possible causes for these phenomena is the effects of electron emission from recently cracked surfaces, with respect to occurrence of microfracturing times before main shock.
These effects have been investigated in different ways. In this study we have tried to not only review the past studies but also make some investigations with use of Tehran magnetic observatory records as much as possible.