Morphological and palaeoseismological analysis along the Taleghan fault (Central Alborz, Iran)

Abstract

International audienceThe Taleghan fault (TF) is a major active fault of the Central Alborz mountain range in Iran. Located 50 km northwestwards of Tehran, this 80-km-long fault represents one of the major structures threatening 15 million people living in the capital of Iran and the surrounding cities (e.g. Karaj). The TF could be the source of some of the strongest historical earthquakes recorded in the Tehran region, notably the 958 AD event (estimated magnitude M 7.7). To characterize the kinematics and activity of the fault, we carried out a detailed morphological and palaeoseismological study combining aerial photographs, digital elevation models and fieldwork. We show that, unliked described so far, the TF is not a reverse fault but a left-lateral strike-slip fault with a normal component. Its strike, dip and rake within its eastern part are 105, 60 and -20/-40, respectively. Our palaeoseismological analysis shows that a sequence of 2-3 events with magnitudes M-w >= 7 occurred during the past 5300 years. If we consider a three-event scenario, the average recurrence interval is similar to 2000 years, and the most recent event is younger than 80 AD. If we consider a two-event scenario, the time interval between the second and the first events ranges between 3760 and 830 years, and the elapsed time since the last event ranges between 3529 and 1599 years. Combined with morphotectonics data, our palaeoseismological analysis allows estimating a minimum horizontal slip rate of 0.6-1.6 mm yr(-1) and a minimum vertical slip rate of similar to 0.5 mm yr(-1). Taking the similar to 450-m total vertical displacement observed across the fault, we conclude that the kinematical change along the TF (from reverse to left-lateral + normal) occurred similar to 1 Ma

Fault kinematics and active tectonics at the southeastern boundary of the eastern Alborz (Abr and Khij fault zones): Geodynamic implications for NNE Iran

“…Table 1 for details). and qualifying the deformation of this complex zone (e.g., Axen et al, 2001;Jackson et al, 2002;Allen et al, 2003a;Masson et al, 2006Masson et al, , 2007Guest et al, 2006aGuest et al, ,b, 2007Ritz et al, 2006;Ritz, 2009;Tatar et al, 2007;Ballato et al, 2008;Landgraf et al, 2009;Nazari et al, 2009;Hollingsworth et al, 2010;Solaymani Azad et al, 2011). The N-S convergence of Central Iran together with the SW-ward motion of the SCB toward Central Iran results in a NNE-trending transpressional tectonic regime in the Alborz mountain range.…”

Active faulting within a megacity: the geometry and slip rate of the Pardisan thrust in central Tehran, Iran

“…Fig. 1; Ambraseys & Melville 1982;Berberian & Yeats 1999;Nazari et al 2009;Ritz et al 2012). However, earthquakes in 312-280 B.C., 855 A.D., 1177 A.D. were located further south, within the Tehran plain, and their sources are not known with certainty, although palaeoseismic events on the North Tehran Fault (NTF; Ritz et al 2012; Fig.…”

Active tectonics within the NW and SE extensions of the Pambak-Sevan-Syunik fault: Implications for the present geodynamics of Armenia

“…13a). This suggests that the height of the fault scarp reached at least 1e1.5 m (eg McCalpin, 1996;Philip et al, 2001;Nazari et al, 2009). This yields a minimum Moment Magnitude (Mw) of~7 after Wells and Coppersmith (1994)'s functions.…”

“…Combining the geometry of the fault and the displacements (e.g. Nazari et al, 2009) allows calculating a rake of À105 for the slip vector.…”