بررسی و تحلیل فعالیت های نوزمین ساختی و لرزه زمین ساختی در منطقه ارومیه

Abstract:

The presence of the geological, geomorphological, archaeological, historical, and seismological evidence in the Urumieh area, west of Urumieh Lake (NW, Iran), indicates that the whole area is tectonically active, however, the activity is not uniform everywhere.  In the central part of the area, which is a vast alluvial plain (Urumieh Plain), the neotectonic activity is not considerable, whereas, in the surrounding mountainous parts, especially in the north and south, the activity is remarkably higher.

 

Since the surface distribution of the earthquake epicenters in these two northern and southern parts has a linear, NE-SW trending alignment, and the position of these lines coincides with the location of several large-scale, right-lateral strike-slip faults with dip-slip reverse component, it can be argued that these two linear alignments of earthquakes are the indications of two en echelon right-lateral strike-slip fault zones of dip-slip reverse component, which form a conjugate fault set with the Tabriz fault zone (i.e. a left-lateral strike-slip fault zone of dip-slip reverse component, extending from Maku to Tabriz in NW-SE direction).

 

It can be also argued that, since the anti-clockwise rotational motion of the Arabian plate is considered to be responsible for the present neotectonic activity, and the orientation of the resultant maximum compressional stress in the Urumieh area is appropriate for the reactivation of most of the present faults, the northern and southern parts of the Urumieh area due to presence of several large-scale, strike-slip faults of dip-slip reverse component, the earthquake risk is high, and in the central part, due to the lack of these types of faults, the earthquake risk is considerably lower.