The geological and tectonic background of the Sabalan area in NW Iran and its present-day surface processes make it ideal for examining the effects of tectonic processes in shaping the Earth's crust. As a result of the intense distribution of pre-Quaternary and Quaternary structures (e.g., faults, joints and folds), most of the drainage basins in the southern and central parts of the study area have developed under tectonic-dominated conditions, whereas the effects of erosional processes are greater in the north and east. An evaluation of the geomorphic indices using the index of active tectonics (IAT) and analytical hierarchy process (AHP) methods shows that the AHP results are more reliable than the IAT results and are coherent with the geological and structural conditions of the study area. The geomorphic results are highly consistent with the intensity and distribution of fractures. The majority of fractures have developed in a NW–SE direction, indicating antithetic R′ Riedel fractures to the main NE-SW-trending faults. However, a significant number of the fractures in the study area are NNE–SSW- and NE–SW-oriented R and P fractures and NNW–SSE-oriented tension fractures. Palaeostress analysis of the fault data shows at least two faulting events in the pre-Quaternary and Quaternary, respectively. The pre-Quaternary NNW–SSE-striking dextral strike-slip faults experienced post-Eocene 25–30° clockwise rotation and re-activated as NE–SW-striking sinistral faults during the Quaternary. Although seismic activity is currently low, the consistency of our results with the regional stress data show that the study area is still tectonically active.

Geophysical, structural, geomorphological, topographical and bathymetric data from the Hurd Peninsula area, Livingston Island, South Shetland archipelago, suggest that an extensional fault system, orientated NW–SE, together with a conjugate group of NE–SW normal oblique-slip faults, control the landforms in this area. These structures separate fault-bounded blocks of different heights, giving rise to a horstgraben structure. The depressed blocks were filled by glaciers and flooded in part by the sea. The recent movement of these faults can be established from the calculated isopachs of a small Quaternary sedimentary basin, related to this extensional fault system, which shows that sedimentary bed thickness is controlled mainly by the NE–SW fault system. Geomorphological analysis also shows that the NW–SE faults control the main morphostructures of this region. The character of the recent stress tensor has been established from fault-slip data, taking into account only those faults that are related to morphostructures. The calculated palaeostress tensor is extensional, with a N46°E main extension direction, and an average stress ratio of 0.17.