A critique on the problem of the fault zone regulatory act in Iran; An overview of the surface rupture hazard caused by earthquake faulting in the northern zone of Tehran metropolis, Central Alborz, Iran

The megacity of Tehran, Iran's capital, is positioned on the southern slope of the central part of the Alborz Mountain range. This range displays active tectonics, resulting in a history of destructive earthquakes, quaternary deformation, massive ancient landslides, and geodetic phenomena. Earthquake movement and deformation can lead to the emergence of numerous secondary geological and non-geological hazards. This article presents a revised map showcasing the fault distribution in the northern region of the Tehran megacity, based on a synthesis of both current and novel information.

This study entails the formulation of a fault map encompassing the northern sector of Tehran city, employing a cartographic scale exceeding 1:20000. This endeavor capitalizes on geological maps, historical as well as instrumental seismic records, and both extant and novel fault-related insights extrapolated from satellite image scrutiny, aerial photography archives dating back to 1955, and comprehensive field investigations. Subsequently, instances of quaternary faulting have been delineated for salient fault lines. Through a comprehensive examination of strategies aimed at mitigating the risk posed by surface rupture events, heightened attention has been accorded to, and an evaluation has been undertaken of this peril within the delineated study expanse. Elaborated information is expounded upon within the corresponding Persian manuscript.

Figure 1 illustrates the revised cartographic representation delineating the geographic positioning of pivotal faults situated within the northern precinct of Tehran. Of paramount significance within this cartographic presentation is the discernment of fault line continuities previously introduced but whose terminal extents remained obscure. Moreover, an expansive network of fractures or subsidiary faults aligned with the North Tehran fault system has been meticulously charted, particularly in the hangingwall segment thereof, hitherto unreported in extant literature.The North Tehran fault, alongside the Pardisan, Niavaran, Mahmoudieh, Davoodieh, and Kan faults, the latter boasting the most extensive reach, collectively constitute the foremost fault trends imparting significant geological risk within the confines of Tehran city. Creating comprehensive geoscience data systems tailored to urban scales emerges as a viable solution to address myriad requisites, encompassing the effective management of contemporary urban risks.Preliminary inquiries substantiate the assertion that a minimum of twenty prominent public and private hospitals within Tehran directly confront the hazard of surface rupture events.Fig. 1. The updated map of the faults in the northern zone of Tehran city is placed on the digital elevation model. The fault information is from Berberian et al. (2014), Abbasi and Farbad (2009), Talebian et al. (2017) and other sources, along with observations made and the analysis of satellite images and aerial photographs in this research. At the base of the map, the built areas of Tehran are based on 1:25,000 topographic maps of the country's mapping organization, which do not show the full extent of the current city of Tehran.

Contemporary perspectives pertaining to the computation and observation of fault setbacks underscore the imperative of meticulous fault location mapping prior to urban development. While subsurface methodologies hold promise for generating these highly accurate maps within regions characterized by youthful sedimentary deposits, historical data gleaned from fault observations provide valuable context. Given sufficient financial resources, such historical data can corroborate or negate the veracity of known fault lines. Absent such resources, judicious evaluation compels the prioritization of fault line delineation and the concomitant alignment of construction codes therewith.Of paramount import within the context of the presented map is the recognition of fault trend continuities previously introduced, the onward trajectory of which remained enigmatic. Additionally, an extensive matrix of fractures or attendant subsidiary faults inherent to the North Tehran fault system has been methodically charted, with a notable focus on its hanging wall portion hitherto unpublished.The Northern Tehran fault, in conjunction with the Pardisan, Niavaran, Mahmoudieh, Davoodieh, and Kan faults, the latter exhibiting the most expansive extent, collectively constitute the preeminent fault trends engendering pronounced geological risk within the confines of Tehran city. It is noteworthy that although faults such as the Mosha fault, situated at a minimum distance of 30 km from Tehran city, are acknowledged as influential seismic sources for the city, the paramount concern lies in the evaluation of surface rupture hazard, wherein those faults positioned within the urban area assume a markedly more critical role.