(Scientific Information Database) - Tabriz is situated in an active tectonic region of Azerbaijan, a sub province of Central Iran seismic province and surrounded by several active and hazardous faults that most of them especially NTF has experienced several catastrophic historical earthquakes. Seismic & tectonic investigations show a major seismic gap around Tabriz city in the instrumental period. The average Focal depth of earthquakes in the region is 20km, representing shallow earthquake sources for the region. Hazard analyses were performed with probabilistic approach. Seismic zonation is performed in Arc GIS environment by merging tectonic and seismological features layers.
The 1721 Tabriz earthquake occurred on April 26th, with an epicenter near Southeast the city of Tabriz, Iran at approximately 7:00 in the morning, one and a half hours after sunrise. In Tabriz itself the shock ruined about three quarters of the houses. Many prominent mosques and schools in the city were destroyed, resulting in the deaths of tens of thousands of people. Internal evidence suggests that the heaviest destruction occurred within a zone that extended from near Tabriz to the southeast, through Shebli and beyond Qara Baba.
The shock triggered many rock-falls and was associated with a fault break that extended for at least fifty kilometers, from Tekmeh Dash to near Tabriz. The break through Shebli was still visible in 1809, and parts of the fault trace that seems to be connected with this earthquake can be seen today on the ground. The shock seems also to have been strongly felt in the Qazvin region and was followed by many strong aftershocks.
The total number of casualties caused by the earthquake is between 8,000 and 250,000; it was most likely approx. 80,000. At the time that it occurred, the earthquake was popularly interpreted as an omen of misfortune, or a demonstration of Godly wrath. The destruction that the earthquake caused was a significant factor in the successful Ottoman takeover of Tabriz in 1722, as well as contributing to Tabriz's economic difficulties during that period. It also caused the destruction of some of the city's significant historical monuments. Accounts of the earthquake are often confused with descriptions of the 1727 Tabriz earthquake.
There is a notable discrepancy in the mortality figures however, with Mallet giving 8,000 dead as a low figure and Sanioddoleh reporting 250,000 killed. A more credible figure of 80,000 killed in this earthquake is given by a later writer, who derives his figure from a more original and reliable source.