ali saket

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.

The analysis of the basic parameters of the foreshocks is one of the most applied researches for risk reduction of earthquakes. Because identification of behavioral pattern of foreshocks can help researchers in detection of the active fault conditions in different areas. Also accurate analysis of these parameters help to study of earthquake prediction as more effective. In this study, we study about behavioral pattern of foreshocks in different tectonic zons in Iran. This research was conducted for prediction of probability the earthquakes with M>5 in Iran. According to this research, accurate analysis of the basic seismic parameters of foreshocks (including: relationship between depth and magnitude of foreshocks) is studied with target for the prediction of big earthquake in various zons for a ten-year period (from 2007 until 2017). The results of this research suggest that there are certain similarities in the magnitude-depth models for the one zone and also different for various zones. Therefore, this can be used as a precursor in earthquake prediction with Magnitude>5 for different zones in Iran. The important results presented in this article can be presented in the following cases:- Investigation of the information of seismicity parameters of foreshocks regarding the relationship between the focal depth of the main earthquake and the frequency of the foreshocks that used in some parts of the world as a precursor of earthquake suggested that main shocks with M>5 and shallow depth have more foreshocks abundances (Fig 2). - Due to the relationship between the type of fault with the occurrence and non-occurrence of aftershocks in different parts of the world, in the case of earthquakes greater than 5 in Iran, in earthquakes with reverse faults have relatively more aftershocks recorded compared to strike-slip faults.- The results of the statistical study conducted in this study show that for earthquakes with reverse fault, the frequency of foreshocks increases with magnitude. However, we do not see such conditions for earthquakes with faults of strike-slip.- The result of this study shows that more earthquake especially in Zagros zone and near salt domes happened without foreshocks. The reason for this is related to effect of salt dome on movement fault from slide to creep. The creep is a gradual movement and it is not usually accompanied by rapid movement such as slides that lead to large and recordable earthquakes.- Based on the present study on earthquakes, for the Zagros (especially in the northern and central part) and Central Iran and Sanandaj-Sirjan, can be used more confidently as a precursor of earthquake because in this zones earthquakes happened with more foreshocks.- In Zagros and Iran Markazi zone the relationship between variations of the depth and magnitude of foreshocks is fruitful for predicting of the main shocks.- For other zones we need to have more complete data bank that has earthquakes with higher frequency of foreshocks. Based on this data bank we can present suitable relations and models for the study of foreshock with the aim of predicting the big earthquakes.

Examining experiences related to past earthquakes, especially in developing countries suggest that in addition to fatalities and injuries caused by the main earthquake the large aftershocks also have effect to increasing the mentioned consequences. In this Research has presented a practical method in predicting the large aftershocks with the aim of reducing fatalities and injuries caused by their occurrence.

The survey method used in this study is based on statistical analysis related to basic parameters of the primary aftershocks such as: time occurrence, magnitude with aim of prediction of time the large aftershock for alarm and evacuation to people from non-resistant buildings. In this research has used seismic quiescence theory (time distance between aftershocks event) and analysis of the normalized data of depth and magnitude of primary aftershocks for the prediction of time and vulnerability level caused of the large aftershocks in Sefidsang earthquake in northeast of Iran.

Data analysis suggests that there is the definite relationship between magnitude and seismic quiescence of primary aftershocks that this relationship can be base of analysis for prediction of the time of the large aftershocks.

The results of this study indicate that predicting the time and the rate of vulnerability of the large aftershocks can be obtained by combining the outputs of the two aforementioned analyzes.