جستجوی مقالات مرتبط با کلیدواژه "north tehran fault" در نشریات گروه "زمین شناسی"

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 abrupt topographical change in northern Tehran divides the Eocene rock formation from Quaternary and Plio-Quaternary alluvial deposits situated in the piedmont and the plain. This phenomenon has been interpreted differently by two Geologists in the 70's and 80's. The term North Tehran Fault (NTF) is the first interpretation of rock-alluvium boundary, coined by Tchalenco (1975). According to this interpretation consist the NTF of the fault system, arranged in an en-echelon manner, not necessarily forming the rock-alluvium boundary in northern Tehran. A later interpretation, by joining all the fault systems, as a single line, called North Tehran Thrust (NTT). According to this interpretation forms (NTT) a single line, defining the boundary of rock-alluvium in northern Tehran (Berberian et al., 1983), not confusing with North Tehran Fault (NTF). The mentioned two interpretations of faulting in northern Tehran include two different faulting mechanisms opposing each other diagonally. By time are the two interpretations wrongly melted together as (NTF) and were used by several authors without paying attention to its original meaning interpreted by Tchalenko (1975).In later works (Langraf et al., 2009; Ritz et al., 2012) is (NTF) the main structure responsible for the rising of highly elevated rock formation in the hanging wall of North Tehran Thrust (NTT).The present study deals strictly with the boundary of rock and alluvium in northern Tehran, which was called (NTT). Kinematic study along the contact of rock and alluvium revealed two characteristic features: 1- Rock-Alluvium boundary occurs not along with a single faulting trend, it is rather arranged along NW-, N-S, E-W, and NE-striking faults. 2- Obtained stress direction associated with fault plane solution show different directions.In many places is the NTT covered by rock slides, obscuring the trace of the rock-alluvium boundary. Older rockslides are thrusted over alluvium units of different ages. The contact of such boundaries shows striations compatible with present-day stress direction. The slow deformation rate in northern Tehran is not concentrated along a single fault. Therefore, it seems that absorbed deformation in northern Tehran is distributed over a wide range adjacent to the rock-alluvium boundary. These observations suggest an unrecognized fault, which needs more careful geological and seismological study.Considering the three different trends of NTT, namely NW-, E-W- and NE-trending, no fold axis run parallel to those trends. The results obtained in this study suggest the NTT is not a major fault and in addition, it could not be regarded as a single fault responsible for the rising of the rock formation on the hanging wall of NTT in northern Tehran.

The capital city of Tehran is located to the south of central Alborz. The North Tehran
fault, as the main structure of this region, perched on the northern part of the city
and separate alluvial fans from volcanic rocks of the Alborz. There are several other
faults within the city which seem to be structurally related to the North Tehran fault.
Geomorphic study of fans and river deposits suggest that most of these faults are active
and taking up both left-lateral and shortening in a wider zone to the south of North
Tehran fault. In addition to faults there is distinct folding within the Tehran plain. Field
observation along road cuts which cross these structures suggest that young folding in
Tehran plain are active and escalate due to the activities of the underlying faults. There is
little evidence of rupture in front of these structures and thus most of them are considered
as blind faulting. The trend of these structures is oblique to the North Tehran fault which
is probably due to distribution of left lateral deformation in wider zone within the Tehran
plain. The distance between active folds and the North Tehran fault increase from west
to east. Analog modelings were carried out to study the effect of thickness and slop of
deposits on position and trend of structures within the Tehran plain. Results from these
experiences show that geometry, orientation and distance between structures is probably
controlled by oblique shortening of the zone, as well as increase in thickness and slope
of the sedimentary deposits.

The North Tehran Fault with a length of about 110 km in North of Tehran and soutern of central Alborz with W-E trend (N25˚E) and dipping (30˚NE) is located in western of Mosha Fault.The branch of Chitgar such as Milad and Vardavard Fault in the form of propagation fault is increased toward south. Previous morphotectonical investigation along the North Tehran Fault show that shear of quaternary sedimentation and pressure mechanism with left-lateral component. Determination of seismic parameter and seismic action that result of this fault movement, need to doing paleoseismological investigation. In this text with using stratigraphy correlation method, estimated of subsidence rate is 0.16 mm/yr and logging with ratio and ortho photography method, 3-6 event is determined with 6.4-7.4 magnitude and recurrence time is 3650 yr at Chitgar trench.