Earthquake-induced paleo-landslides in the Tehran Region and its role in assessing the seismic hazard, Iran

Abstract

In the central portion of the Arabia-Eurasia collision zone, the Tehran domain is positioned at a transitional boundary between seismotectonic zones of the Central Iranian lowland (to the south) and the Alborz highland (to the north). Consequently, numerous destructive seismic events have occurred in this active tectonic domain. This study delves into the tectonic geomorphology of the region within its northern highland domain, specifically focusing on the hanging wall of the E-striking north-dipping North Tehran fault (NTF) zone. Our findings in this northern domain emphasize several prominent topographic scars as significant co-seismic features. These include huge landslides, rockfalls, rock avalanches, and offset geomorphic surfaces and could be present as the main indirect co-seismic morphological features. Within this seismically active region, the extensive dimensions of these geomorphic pieces of evidence reveal the seismic potential of the Tehran Region to experience really strong earthquakes (i.e. M>7.5). These results contrast with the previous Maximum Credible Earthquake (MCE) magnitude estimated for the Tehran Region (i.e. M~7.2) through different approaches in Seismic Hazard Assessments (SHAs). Consequently, the previous SHAs of the Tehran Region might have underestimated the seismic risk, and therefore, it is necessary to conduct an updated and complementary deterministic SHA based on the more detailed seismogenic geological features in this crucial area.