Himalayan Geology, Vol. 42 (1), 2021, pp. 125-136, Printed in India
Late Pleistocene-Holocene activity of the North Tehran Fault Zone, Tehran, Iran
ASL. Z. MOHAMMADI1*, M.R. ABBASSI2
1Department of Geophysics, Graduate School of Science, Kyoto University, Kyoto, 6068502, Japan
2International Institute of Earthquake Engineering and Seismology, Tehran, Iran
*Email (Corresponding author): z_mohammadiasl@yahoo.com; mohammadi.zara.37c @kugi.kyoto-u.ac.jp
Abstract: North Tehran Fault (NTF) is one of the most distinguished tectonic structures in the southernmost piedmont of the central Alborz Mountains, characterized by its vigorous historical seismicity and topographic relief, with a length of 110 km, striking generally N 100° E and dipping toward N, in the north of Tehran, Iran. This is an important potential seismic source that threatens the Tehran metropolis, which encompasses a population of greater than 15 million. Field investigations are based on the interpretations of three-dimensional (3D) topographic images processed by high-resolution remote sensing image with digital elevation model (DEM) data, and radiocarbon dating. Our results revealed that: i) the NTF, with a distinct fault scarp up to 3.4 m, on QuaternaryHolocene alluvial deposits, is dominated by the thrust mechanism. In addition, witnessing several horizontal striations that are developed in a fault gouge, a sinistral strike-slip component is shown for the NTF, and thus oblique thrust fault; ii) the quantitative estimate of slip rate across the active NTF has shown a net slip rate of 1.72 mm/yr and it is similar to the previous study, and iii) Quaternary and Holocene fluvial terraces are divided into three levels: (T0 (lower surface), T1 (middle surface) and T2 (high surface)), and sedimentation rate of T2 was estimated 0.42 mm/yr. According to the results, the NTF indicated a relatively high slip rate, which has a great impact on the earthquake hazard in the densely-populated Tehran city.
Keywords: Slip rate; Tehran city; Alborz Mountains; North Tehran Fault (NTF).
