Measurement network introduction of electric precursors of earthquakes by VAN method in the Northwestern of Iran



Iran is a country in the middle part of the Alp-Himalayan orogeny system that have huge earthquakes. The risk of the earthquakes is the cause of the researches about the precursors. Because earthquakes occur suddenly, often with devastating consequences, earthquake prediction is a matter of great interest among the public and emergency service officials. A few observations suggest that some earthquakes may be preceded by detectable anomalies of geophysical signals as a precursors. One of the successive precursors is Seismic Electric Signals. Seismic Electric Signals (SES) are low frequency electric signals that have been recorded in Greece in first time (e.g. by VAN team at 1984 ) and Japan ( e.g. Uyeda at 2000) to precede earthquakes. Now these signals are recording in NW of Iran (since 2014) for the first time. Varotsosa and his colleagues recording the electrotelluric potential in several stations in Greece and claim that their signals reveal systematic anomalies before major earthquakes. A possible correlation between SES characteristics and earthquake parameters was investigated by some scientists. There are some relationships between VAN seismic electric signals (SES) and earthquake parameters, such as magnitude, current time and location. In this research we install 5 VAN stations in NW of Iran and recording data since Mar 2014, that shown 4 SES. This signals and predicted earthquake parameters, reported to the government (East Azarbaijan disaster management organization) before shake and these earthquakes were successively predicted by this method.
On Jun 19, 2015, an Ms=4.0 earthquake occurred in Basmenj. 13 days before, the our group observed an electrotelluric anomaly (seismiec electric signals (SES) ) at our station of University of Tabriz, located NE of Tabriz. The second SES is recorded 2 days after stop the 1st signal. 13 days after recording of this signal the earthquake Ms=3.7 Kolvanag in the NE of Tabriz recorded. Third SES in 1/2/2015 recorded for 8 days. After 17 days the earthquake Ms=3.3 Khoy in 26/02/2015 is recorded.
For the first time, in Iran for search and capability of recording the SES precursors since Mar 2014 in the NW of Iran installed 6 VAN stations help to recognize more than 6 earthquakes.
3 of the 6 stations by recording the SES, changed to the main sensitive VAN stations in the NW Iran. Search and compatibility of recorded SESs by the results of the VAN group in Greece shown these signals are the same in both countries.
Furthermore selectivity is one of the most important SES physical properties which refers to the experimental fact that a (sensitive) monitoring station is capable to detect SES only from a restricted number of seismic areas. A map showing the seismic areas that emit SES detectable at a given station is called selectivity map of this stations. Now the number of station in the NW of Iran is limited and therefore prediction the location of the earthquakes and make selectivity maps is difficult. Then it is necessary to install more VAN stations to be possible make selectivity map and locating precede earthquakes and their times.


Main Subjects

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