Fault interactons on different time and length scales: the North-Tehran-Thrust (NTT) and the Mosha-Fasham-Fault (MFF), Alborz mountains, Nothern Iran

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Fault propagation patterns and interaction of neighbouring fault segments in compressional environments are not well understood. Importantly, the analysis of fault activity, slip rates, and kinematics has often resulted in contradictory assessments that call for a rigorous, quantitative assessment of these issues on different timescales. The North Tehran Thrust (NTT) and the sinsitral Mosha Fasham Fault (MFF) are neighbouring faults in the Alborz Mountains, northern Iran, which accommodate oblique shortening of the Arabia-Eurasia collision. The close proximity of both fault systems offers the unique opportunity to study the interaction of fault segments on different time and length scales and evaluate their possible linkage. In particular, geometry, kinematics, segmentation, and lateral propagation along both faults can be assessed. To decipher spatial and temporal fault behavior we propose geotectonic field mapping, supported by air photos, high-resolution satellite imagery, and digital elevation models. To develop a chronology of faulting and migration of deformation in the southern Alborz foreland, we will study clastic units with magnetostratigraphy, 40Ar/39Ar dating of tephra, and cosmogenic nuclide-dating (36Cl) of geomorphic surfaces. Our work will thus help to resolve discrepancies between measured geodetic and geologically derived deformation rates and contribute toward an assessment of the source of destructive earthquakes, and thus help to evaluate and mitigate seismic and related natural hazards.