TY - JOUR A1 - Ghassemi, Mohammad R. A1 - Fattahi, Morteza A1 - Landgraf, Angela A1 - Ahmadi, Mehdi A1 - Ballato, Paolo A1 - Tabatabaei, Saeid H. T1 - Kinematic links between the Eastern Mosha Fault and the North Tehran Fault, Alborz range, northern Iran JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - Kinematic interaction of faults is an important issue for detailed seismic hazard assessments in seismically active regions. The Eastern Mosha Fault (EMF) and the North Tehran Fault (NTF) are two major active faults of the southern central Alborz mountains, located in proximity of Tehran (population similar to 9 million). We used field, geomorphological and paleoseismological data to explore the kinematic transition between the faults, and compare their short-term and long-term history of activity. We introduce the Niknamdeh segment of the NTF along which the strike-slip kinematics of EMF is transferred onto the NTF, and which is also responsible for the development of a pull-apart basin between the eastern segments of the NTF. The Ira trench site at the linkage zone between the two faults reveals the history of interaction between rock avalanches, active faulting and sag-pond development. The kinematic continuity between the EMF and NTF requires updating of seismic hazard models for the NTF, the most active fault adjacent to the Tehran Metropolis. Study of offsets of large-scale morphological features along the EMF, and comparison with estimated slip rates along the fault indicates that the EMF has started its left-lateral kinematics between 3.2 and 4.7 Ma. According to our paleoseismological data and the morphology of the nearby EMF and NTF, we suggest minimum and maximum values of about 1.8 and 3.0 mm/year for the left-lateral kinematics on the two faults in their linkage zone, averaged over Holocene time scales. Our study provides a partial interpretation, based on available data, for the fault activity in northeastern Tehran region, which may be completed with studies of other active faults of the region to evaluate a more realistic seismic hazard analysis for this heavily populated major city. (C) 2014 Elsevier B.V. All rights reserved. KW - Mosha Fault KW - North Tehran Fault KW - Alborz range KW - Slip rate KW - Fault linkage and interaction KW - Paleoseismology Y1 - 2014 U6 - https://doi.org/10.1016/j.tecto.2014.03.007 SN - 0040-1951 SN - 1879-3266 VL - 622 SP - 81 EP - 95 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ballato, Paolo A1 - Uba, Cornelius Eji A1 - Landgraf, Angela A1 - Strecker, Manfred A1 - Sudo, Masafumi A1 - Stockli, Daniel F. A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. T1 - Arabia-Eurasia continental collision insights from late Tertiary foreland-basin evolution in the Alborz Mountains, northern Iran JF - Geological Society of America bulletin N2 - A poorly understood lag time of 15-20 m.y. exists between the initial Arabia-Eurasia continental collision in late Eocene to early Oligocene time and the acceleration of tectonic and sedimentary processes across the collision zone in the early to late Miocene. The late Eocene to Miocene-Pliocene clastic and shallow-marine sedimentary rocks of the Kond, Eyvanekey, and Semnan Basins in the Alborz Mountains (northern Iran) offer the possibility to track the evolution of this orogen in the framework of collision processes. A transition from volcaniclastic submarine deposits to shallow-marine evaporites and terrestrial sediments occurred shortly after 36 Ma in association with reversals in sediment provenance, strata tilting, and erosional unroofing. These events followed the termination of subduction arc magmatism and marked a changeover from an extensional to a contractional regime in response to initiation of continental collision with the subduction of stretched Arabian lithosphere. This early stage of collision produced topographic relief associated with shallow foreland basins, suggesting that shortening and tectonic loading occurred at low rates. Starting from the early Miocene (17.5 Ma), flexural subsidence in response to foreland basin initiation occurred. Fast sediment accumulation rates and erosional unroofing trends point to acceleration of shortening by the early Miocene. We suggest that the lag time between the initiation of continental collision (36 Ma) and the acceleration of regional deformation (20-17.5 Ma) reflects a two-stage collision process, involving the "soft" collision of stretched lithosphere at first and "hard" collision following the arrival of unstretched Arabian continental litho sphere in the subduction zone. Y1 - 2011 U6 - https://doi.org/10.1130/B30091.1 SN - 0016-7606 VL - 123 IS - 1-2 SP - 106 EP - 131 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Ballato, Paolo A1 - Stockli, Daniel F. A1 - Ghassemi, Mohammad R. A1 - Landgraf, Angela A1 - Strecker, Manfred A1 - Hassanzadeh, Jamshid A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. T1 - Accommodation of transpressional strain in the Arabia-Eurasia collision zone new constraints from (U-Th)/He thermochronology in the Alborz mountains, north Iran JF - Tectonics N2 - The Alborz range of N Iran provides key information on the spatiotemporal evolution and characteristics of the Arabia-Eurasia continental collision zone. The southwestern Alborz range constitutes a transpressional duplex, which accommodates oblique shortening between Central Iran and the South Caspian Basin. The duplex comprises NW-striking frontal ramps that are kinematically linked to inherited E-W-striking, right-stepping lateral to obliquely oriented ramps. New zircon and apatite (U-Th)/He data provide a high-resolution framework to unravel the evolution of collisional tectonics in this region. Our data record two pulses of fast cooling associated with SW-directed thrusting across the frontal ramps at similar to 18-14 and 9.5-7.5 Ma, resulting in the tectonic repetition of a fossil zircon partial retention zone and a cooling pattern with a half U-shaped geometry. Uniform cooling ages of similar to 7-6 Ma along the southernmost E-W striking oblique ramp and across its associated NW-striking frontal ramps suggests that the ramp was reactivated as a master throughgoing, N-dipping thrust. We interpret this major change in fault kinematics and deformation style to be related to a change in the shortening direction from NE to N/NNE. The reduction in the obliquity of thrusting may indicate the termination of strike-slip faulting (and possibly thrusting) across the Iranian Plateau, which could have been triggered by an increase in elevation. Furthermore, we suggest that similar to 7-6-m.y.-old S-directed thrusting predated inception of the westward motion of the South Caspian Basin. Citation: Ballato, P., D. F. Stockli, M. R. Ghassemi, A. Landgraf, M. R. Strecker, J. Hassanzadeh, A. Friedrich, and S. H. Tabatabaei (2012), Accommodation of transpressional strain in the Arabia-Eurasia collision zone: new constraints from (U-Th)/He thermochronology in the Alborz mountains. Y1 - 2013 U6 - https://doi.org/10.1029/2012TC003159 SN - 0278-7407 VL - 32 IS - 1 SP - 1 EP - 18 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Landgraf, Angela A1 - Ballato, Paolo A1 - Strecker, Manfred A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. A1 - Shahpasandzadeh, Majid T1 - Fault-kinematic and geomorphic observations along the North Tehran Thrust and Mosha Fasham Fault, Alborz mountains Iran : implications for fault-system evolution and interaction in a changing tectonic regime N2 - Neighbouring faults can interact, potentially link up and grow, and consequently increase the seismic and related natural hazards in their vicinity. Despite evidence of Quaternary faulting, the kinematic relationships between the neighbouring Mosha Fasham Fault (MFF) and the North Tehran Thrust (NTT) and their temporal evolution in the Alborz mountains are not well understood. The ENE-striking NTT is a frontal thrust that delimits the Alborz mountains to the south with a 2000 m topographic front with respect to the proximal Tehran plain. However, no large instrumentally recorded earthquakes have been attributed to that fault. In contrast, the sigmoidally shaped MFF is a major strike-slip fault, located within the Alborz Mountains. Sinistral motion along the eastern part of the MFF is corroborated by microseismicity and fault kinematic analysis, which documents recent transtensional deformation associated with NNE-SSW oriented shortening. To better understand the activity of these faults on different timescales, we combined fault- kinematic analysis and geomorphic observations, to infer the kinematic history of these structures. Our fault kinematic study reveals an early dextral shear for the NTT and the central MFF, responsible for dextral strike-slip and oblique reverse faulting during NW-oriented shortening. This deformation regime was superseded by NE-oriented shortening, associated with sinistral-oblique thrusting along the NTT and the central-western MFF, sinistral strike-slip motion along subsidiary faults in the central MFF segment, and folding and tilting of Eocene to Miocene units in the MFF footwall. Continued thrusting along the NTT took place during the Quaternary. However, folding in the hanging wall and sinistral stream-offsets indicate a left-oblique component and Quaternary strike-slip reactivation of the eastern NTT- segment, close to its termination. This complex history of faulting under different stress directions has resulted in a composite landscape with inherited topographic signatures. Our study shows that the topography of the hanging wall of the NTT reflects a segmentation into sectors with semi-independent uplift histories. Areas of high topographic residuals and apparent high uplift underscore the fault kinematics. Combined, our data suggest an early mechanical linkage of the NTT and MFF fault systems during a former dextral transpressional stage, caused by NW-compression. During NE-oriented shortening, the NTT and MFF were reactivated and incorporated into a nascent transpressional duplex. The youngest manifestation of motion in this system is sinistral transtension. However, this deformation is not observed everywhere and has not yet resulted in topographic inversion. Y1 - 2009 UR - http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-246X U6 - https://doi.org/10.1111/j.1365-246X.2009.04089.x SN - 0956-540X ER -