NEOTECTONIC MODEL OF EAST (IRANIAN) AZERBAIJAN, INFERRED FROM STRESS SEPARATION ANALYSIS

Northwestern Iran, eastern Turkey and Caucasus correspond to the central part of the Arabia–Eurasia collision. The deformation of the region is mainly accommodated by large NW-SE strike-slip faults in the south and NE-SW shortening through the Caucasus in the north. The seismic activity is high, with a lot of instrumental or historical earthquakes with magnitude greater than Mw = 6. The Iranian Azerbaijan is the easternmost part of this region, located in northwestern Iran, it corresponds to a lozenge limited by the Tabriz fault in the SW, the Aras fault in the NW, the Astara-Ardabil fault in the NE and the Myane-Ardabil fault in the SE.

To better describe the complex tectonic behaviour of the Iranian Azerbaijan, we propose to evaluate the stress state of the region from seismic data and new tectonic data directly collected on the faults. We first compile the seismic and tectonic data to analyse the stress state of the faults individually. Then, the mean stress of the Iranian Azerbaijan is reconstructed by using stress separation analysis. Finally, a tectonic model of the region is reconstructed by integration of the results obtained in this study and structural geology concepts.

First we use the method of Angelier (2002) to analyze the stress tensors in the four major boundaries of the domain. Second we use the method of Angelier (1984) and Angelier (2004) to separate the multiple stresses. This analysis is characterised by 4 separated stress states, the NW-SE (N117°) and NE-SW (N023°) directions of the compression, for 3rd and 4th stress states (R3 and R4) respectively (maximum compressive stress σ₁), where the minimum stress axis being close to vertical for them. And also stress analysis is characterised by NW-SE (N155°) and NE-SW (N077°) directions of the compression, for stress states 1 and 2, respectively (σ₁). However, the intermediate stress axis is close to vertical for them (strike-slip mode) and the minimum stress directions as tension are characterized by the N248° and N347° directions for R1 and R2, respectively. Thus, the calculated stress states indicate a dominating thrusting (R1 and R2 ) and strike-slip (R3 and R4) mode for the E-Azerbaijan region. Two compressive stress systems cause development of the three major tectonic grains, the Arasbaran, the Ahar and the Bozkosh thrust sheets in E-Azarbaijan.