Tehran Region Research Articles

Investigation of surface and subsurface displacements due to multiple tunnels excavation in urban area

Underground structures are currently widely used and are built as urbanism develops. The interactions between perpendicularly crossing and parallel tunnels in the Tehran region are investigated by using a full three-dimensional (3D) finite difference analysis with elastic-plastic material models. Special attention is paid to the effect of subsequent tunneling on the support system, i.e., the shotcrete lining and rock bolts of the existing tunnel. Eventually, as the tunnels are excavated at certain levels, the interaction between the tunnels will certainly have a significant influence on both stress distribution and consequently deformations. Since multilayer tunneling is a three-dimensional phenomenon in nature, 3D numerical solutions must be utilized for analyzing effect of perpendicularly crossing tunnels at various levels. As Tohid twin tunnels and Line 7 pass beneath the Line 4 metro tunnel, changes in stress distribution, deformations, and surface settlements are studied for various conditions and the results are presented in this paper. Consequently, it is shown that there is a significant interaction between tunnels that necessitate certain preventive measures to maintain a stable tunneling operation.

Rapid Estimation of Peak Ground Velocity and Earthquake Location Using Small Magnitude Earthquakes in the Tehran Region, Iran

Online Material: Supplemental tables. The Tehran metropolis is located in an extensive area between the Alborz mountain belt to the north and the central Iranian plateau to the south. Tehran, as the political and economic capital of Iran, is considered one of the most populated cities in the world. From the point of view of vulnerability to natural disasters, Tehran is of great concern because of its basic infrastructures and population concentration. The Alborz mountain belt is a part of the Himalayan–Alps orogenic belt with numerous active faults, including the Mosha reverse fault, the North Tehran thrust fault, the Parchin, the Kahrizak, and the South and North Rey faults, with high seismic potential in the study region (Fig. 1). The Mosha fault is one of the fundamental structures of the central Alborz mountains and is situated north of Tehran. This fault is concave to the north and extends from the edge of the mountain range in the west to the eastern Alborz mountains and can be considered an upthrust in some places and an overthrust in others (Moinfar et al. , 1994; Berberian and Yeats, 1999). The North Tehran fault is the most prominent tectonic structure in the immediate vicinity of Tehran for which the trace is east–west to east‐northeast–west‐southwest and slightly concave to the south (Berberian and Yeats, 1999). The Tehran urban district is extended across thick alluvium layers over bedrock with complex geological structure. Based on historic seismic documents, Tehran is surrounded by several specific faults with return periods of about 150 years, but no damaging earthquake has occurred since 1830 (Moinfar et al. , 1994; Berberian and Yeats, 1999), when an estimated 45,000 …

Seismic Hazard Assessment of the Tehran Region

The region aroundTehranisconsidereda highseismicity area.It shouldarouse moreconcern totheseismic safetyof thiscitygiven that the last damaging earthquake occurred nearly 200 years ago, and the geotechnical condition in the study area possibly could cause site amplification. Therefore, this study presents a new hazard map for the region around Tehran with deterministic seismic hazard analysis. In addition, a procedure to select earthquake time histories is demonstrated. From seismic hazard estimates, to site effect, to engineering risk mit- igation, some discussions about earthquake designs and land uses for Tehran also are given in this paper. DOI: 10.1061/(ASCE)NH.1527- 6996.0000123. © 2014 American Society of Civil Engineers.

Earthquake relocation in the Central Alborz region of Iran using a non-linear probabilistic method

In this study, we calculate accurate absolute locations for nearly 3,000 shallow earthquakes (≤20 km depth) that occurred from 1996 to 2010 in the Central Alborz region of northern Iran using a non-linear probabilistic relocation algorithm on a local scale. We aim to produce a consistent dataset with a realistic assessment of location errors using probabilistic hypocenter probability density functions. Our results indicate significant improvement in hypocenter locations and far less scattering than in the routine earthquake catalog. According to our results, 816 earthquakes have horizontal uncertainties in the 0.5–3.0 km range, and 981 earthquakes are relocated with focal-depth errors less than 3.0 km, even with a suboptimal network geometry. Earthquake relocated are tightly clustered in the eastern Tehran region and are mainly associated with active faults in the study area (the Mosha and Garmsar faults). Strong historical earthquakes have occurred along the Mosha and Garmsar faults, and the relocated earthquakes along these faults show clear north-dipping structures and align along east–west lineations, consistent with the predominant trend of faults within the study region. After event relocation, all seismicity lies in the upper 20 km of the crust, and no deep seismicity (>20 km depth) has been observed. In many circumstances, the seismicity at depth does not correlate with surface faulting, suggesting that the faulting at depth does not directly offset overlying sediments.

Magnitude-scaling relations using period parameters τc and τpmax, for Tehran region, Iran

In this study, the first step towards establishing an onsite earthquake early warning system (EWS) in the Tehran region is presented. The system uses the period parameters tau(max)(p) and tau(c) from the first 3 s of the vertical and horizontal components of a P wave, separately and combined. Various regression relations between the magnitude and period parameters were determined for different seismic networks operating in the study area. The data set used in this study contains small ground motions including 194 events with magnitudes between M-L 2.5 and 4.6 located within approximately 80 km from the epicentre in the Tehran region. The SDs of the magnitude-scaling relations for all the component categories (vertical, horizontal and total components) based on the tau(max)(p) and tau(c) approaches were estimated to be on the order of +/- 1.0 and +/- 1.1 unit of magnitude, respectively. These relations were determined from the small magnitude range of the velocity records (M-L 2.5-4.6) as input seismograms. Additional tests were conducted to verify the reliability and robustness of the determined magnitude-scaling relations using acceleration records from the 2002 June 22, M-L 6.5 Changureh-Avaj earthquake; 2004 May 28, M-L 6.1 Firoozabad-Koojour earthquake; 2009 October 17, M-L 3.9 Shahre-Rey earthquake and 2011 February 20, M-L 4.1 Sharif-Abad earthquake; the first two events (Changureh-Avaj and Firoozabad-Koojour) occurred outside the study area. Among the various regression scaling relations obtained, the estimated magnitude based on the tau(max)(p) approach using the vertical components yielded the most stable and reliable results of 6.4 (+/- 0.4), 5.9 (+/- 0.4), 3.3 (+/- 0.5) and 3.8 (+/- 0.3) for the Changureh-Avaj, Firoozabad-Koojour, Shahre-Rey and Sharif-Abad earthquakes, respectively. The magnitudes estimated using the tau(c) method exhibited more scatter with higher SDs than those using the vertical components using the tau(max)(p) approach. Our results also indicate that using the horizontal components produces larger SDs, which may be attributed to the larger site effects; however, the horizontal components can be used as auxiliary available data to provide more constrained information for a multilevels pilot alarm system and to reduce the number of missed or false alarms. The main uncertainties in the proposed magnitude-scaling relations result from the absence of any large earthquakes and poor station distributions in the study area. However, the results presented in this study can be used as a pilot onsite earthquake EWS in the Tehran region.

Sensitivity of ground-motion scenarios to earthquake source parameters in the Tehran metropolitan area, Iran

The northern Tehran fault (NTF) is a principal active fault of the Alborz mountain belt in the northern Iran. The fault is located north of the highly populated Metropolitan Area of Tehran. Historical records and paleoseismological studies have shown that the NTF poses a high seismic risk for the Tehran region and the surrounding cities (e.g. Karaj). A series of ground-motion simulations are carried out using a hybrid kinematic-stochastic model to calculate broadband (0.1–20Hz) ground-motion time histories for deterministic earthquake scenarios (M7.2) on the NTF. We will describe the source characteristics of the target event to develop a list of scenario earthquakes that are probably similar to a large earthquake on the NTF. The effect of varying different rupture parameters such as rupture velocity and rise time on the resulting broadband strong motions has been investigated to evaluate the range of uncertainty in seismic scenarios. The most significant parameters in terms of ground-shaking level are the rise time and the value of the rupture velocity. For the worst-case scenario, the maximum expected horizontal acceleration, and velocity at rock sites in Tehran range between 128 and 1315cm/s/s and 11–191cm/s, respectively. For the lowest scenario, the corresponding values range between 102 and 776cm/s/s and 12 to 81cm/s. Nonlinear soil effects may change these results but are not accounted for in this study. The largest variability of ground motion is observed in neighborhood of asperity and also in the direction of rupture propagation. The calculated standard deviation of all ground-motion scenarios is less than 30% of the mean. The capability of the simulation method to synthesize expected ground motions and the appropriateness of the key parameters used in the simulations are confirmed by comparing the synthetic peak ground motions (PGA, PGV and response spectra) with empirical ground-motion prediction equations.

Ambient Noise Rayleigh Wave Shallow Tomography in the Tehran Region, Central Alborz, Iran

The Tehran region is one of the most densely concentrated areas of seismic activity in northern Iran. This region is dominated by the central Alborz Mountains belt and a large composite cone, the Damavand volcano. Located in the foothills of the Alborz Mountains, the city of Tehran, with a population of ∼15 million, is subject to high seismic risk (Jackson 2006; Berberian 2005). It is also surrounded by many active faults that have caused destructive earthquakes in the past (Berberian and Yeats 2001). Recent seismicity studies ( e.g. , Mottaghi et al. 2010) indicate that this region is under t|he threat of some major and yet unresolved active faults. Strong ground motion due to amplification of seismic energy by shallow velocity structure can be responsible for serious property damage (German and Beroza 2008). In order to accurately predict ground motion through waveform modeling, it is necessary to accurately image the shallow crustal seismic velocity. The local tomographic images available in the Tehran area come from body-wave earthquake tomography ( e.g. , Mostafanejad et al. 2011) and do not allow precise control of the near-surface (depth < 5 km) velocity structure. Furthermore, this model is affected by a variety of factors such as the effect of uneven source (or station) distribution and potential errors in identifiable seismic sources. We address these limitations by using the information extracted from ambient seismic noise. The present study uses continuous data recorded at a variety of sensors to investigate shallow crustal structure surrounding Tehran. We extract inter-station Green’s functions (GFs), with Rayleigh waves as the largest component, from beams of ambient noise cross-correlations at stations in and around the city of Tehran. We first estimate group velocity dispersion curves in the period band between 2 and 4 sec for each station-pair to invert for the 2D …

Planetary and tidal wave‐type oscillations in the ionospheric sporadic E layers over Tehran region

It is believed that in the lower ionosphere, particularly in the ionospheric sporadic E (Es) layers (90–130 km), the planetary and tidal wave‐type oscillations in the ionized component indicate the planetary and tidal waves in the neutral atmosphere. In the present work, the presence of wave‐type oscillations, including planetary and tidal waves in the ionospheric sporadic E layers over Tehran region is examined. Data measured by a digital ionosonde at the ionospheric station of the Institute of Geophysics, University of Tehran, from July 2006 to June 2007 are used to investigate seasonal variations of planetary and tidal waves activities. For the purpose of accurate comparison between different seasons, wavelet transform is applied to time series of foEs and h′Es, namely, the critical frequency and virtual height of Es layers, respectively. The results show that the sporadic E layers over Tehran region are strongly under the influence of upward propagation of waves from below. More specifically, among diverse range of periodicities in the sporadic E layers, we found that diurnal (24 hours) and semidiurnal (12 hours) oscillations in all seasons for both parameters. Moreover, terdiurnal (8 hours) tide‐like variation is observed during spring and summer for foEs parameter and summer and winter for h′Es. Furthermore, the results show that diurnal tidal waves obtain their maximum activities during autumn and winter seasons, and their activities decrease during the late spring and summer. In addition, periods of about 2, 4, 6, 10, 14, and 16 days in our observation verifies the hypothesis of upward propagation of planetary waves from lower atmosphere to the ionosphere. Moreover, planetary waves have their maximum activities during equinox.

Adaptive neuro-fuzzy inference systems for semi-automatic discrimination between seismic events: a study in Tehran region

Thisarticle presents an adaptive neuro-fuzzy inference system (ANFIS) for classification of low magnitude seismic events reported in Iran by the network of Tehran Disaster Mitigation and Management Organization (TDMMO). ANFIS classifiers were used to detect seismic events using six inputs that defined the seismic events. Neuro-fuzzy coding was applied using the six extracted features as ANFIS inputs. Two types of events were defined: weak earthquakes and mining blasts. The data comprised 748 events (6289 signals) ranging from magnitude 1.1 to 4.6 recorded at 13 seismic stations between 2004 and 2009. We surveyed that there are almost 223 earthquakes with M ≤ 2.2 included in this database. Data sets from the south, east, and southeast of the city of Tehran were used to evaluate the best short period seismic discriminants, and features as inputs such as origin time of event, distance (source to station), latitude of epicenter, longitude of epicenter, magnitude, and spectral analysis (fc of the Pg wave) were used, increasing the rate of correct classification and decreasing the confusion rate between weak earthquakes and quarry blasts. The performance of the ANFIS model was evaluated for training and classification accuracy. The results confirmed that the proposed ANFIS model has good potential for determining seismic events.

Analysis and modeling of rail maintenance costs

Article history: Received July 10, 2011 Received in Revised form September, 12, 2011 Accepted 25 September 2011 Available online 30 September 2011 Railroad maintenance engineering plays an important role on availability of roads and reducing the cost of railroad incidents. Rail is of the most important parts of railroad industry, which needs regular maintenance since it covers a significant part of total maintenance cost. Any attempt on optimizing total cost of maintenance could substantially reduce the cost of railroad system and it can reduce total cost of the industry. The paper presents a new method to estimate the cost of rail failure using different cost components such as cost of inspection and cost of risk associated with possible accidents. The proposed model of this paper is used for a realworld case study of railroad transportation of Tehran region and the results have been analyzed. © 2012 Growing Science Ltd. All rights reserved.

Comparison of peak characteristics of F2 ionospheric layer over Tehran region at a low solar activity period with IRI-2001 and IRI-2007 models predictions

In the present work values of peak electron density (NmF2) and height of F2 ionospheric layer (hmF2) over Tehran region at a low solar activity period are compared with the predictions of the International Reference Ionosphere models (IRI-2001 and IRI-2007). Data measured by a digital ionosonde at the ionospheric station of the Institute of Geophysics, University of Tehran from July 2006 to June 2007 are used to perform the calculations. Formulations proposed by Shimazaki (1955) and Bilitza et al. (1979) are utilized to calculate the hmF2. The International Union of Radio Science (URSI) and International Radio Consultative Committee (CCIR) options are employed to run the IRI-2001 and IRI-2007 models. Results show that both IRI-2007 and IRI-2001 can successfully predict the NmF2 and hmF2 over Tehran region. In addition, the study shows that predictions of IRI-2007 model with CCIR coefficient has closer values to the observations. Furthermore, it is found that the monthly average of the percentage deviation between the IRI models predictions and the values of hmF2 and NmF2 parameters are less than 10% and 21%, respectively.

Risk factors for abortion in dairy cows from commercial Holstein dairy herds in the Tehran region

In last decade, pregnancy loss in dairy cattle has had an upward trend bringing difficulties for breeders: the annual cost is estimated around 396 billion Rials (i.e. around 40 million US$) for the Iranian dairy industry. The present study was conducted to determine the influence of maternal factors on abortion and to predict the probability of abortion as well as the effect of these factors on the fetal lifetime in Holstein dairy cattle. Data from 44,629 established pregnancies that included 14,226 heifers and 30,403 pregnancies from 12,265 parous cows in nine industrial dairy herds around Tehran were used. Overall, 4871 pregnancies of parous cows resulted in abortion. Prediction of the probability of abortion (PPA) was estimated by a logistic regression model. Survival analysis was performed using an accelerated failure time (AFT) model assuming a multi-modal hazard function. Effective factors included age of dam at conception, gravidity, open days, number of previous abortion(s), abortion before/after 60 days of gestation in previous conception, herd and season of insemination. The PPA decreased with increasing open days, increasing gravidity and no previous abortion. In addition, the PPA was greater for cows which had been inseminated during summer versus winter. However, the difference between autumn and spring was not significant. Overall, 25 sires out of 695 from which sperm was collected for artificial insemination (AI) had significantly higher risk of abortion, with odds ratios ranging between 1.44 and 4.73 compared to the average. The survival probability increased slightly during gestation as gravidity increased for cows that had a previous abortion. Cows that had aborted before 60 days of gestation in previous conception tended to abort later in their next conceptions.

Integrated geophysical methods for determining geometry of the Kahrizak Fault, Tehran, Iran

Historical studies and geologic investigations show that the Kahrizak fault located at the southern foot of the central Alborz Mountains poses a high seismic risk for the Tehran region. However, little is known about the geometry and mechanism of movement along this seismogenic fault. This paper uses three different geophysical methods namely, seismic refraction, electrical resistivity and magnetic techniques to investigate geometry and sense of motion across the Kahrizak fault in southern Tehran. Although the geoelectric measurements do not show clear anomaly across the fault deep down into the ground, it reveals an obvious anomaly in shallow depths. However, looking at the seismic refraction and magnetic profiles across the Kahrizak scarp, we identified a high angle fault dipping south. This result in conjunction with the local relief across the fault scarp would suggest that the southern block is downthrown with respect to the northern block across a normal fault. Such knowledge can contribute to better evaluate the seismic hazard potential of one of the main seismogenic faults in the Tehran area.

Dietary patterns by reduced rank regression predicting changes in obesity indices in a cohort study: Tehran Lipid and Glucose Study.

To examine the association between dietary patterns and obesity indices (BMI, WC, WHR) among Tehranian adults in a 6-year follow-up study. Within frame of a cohort study in Tehran (mean follow up 6.6+/-0.9 years), 141 adults were recruited with: two 24 hour dietary recalls at the beginning, as well as obesity indices at the beginning and end of the study period. Dietary intakes were converted into grams of intakes of food items and categorized into 16 groups. Reduced rank regression analysis derived five patterns with total and polyunsaturated-to-saturated fat intake, cholesterol, fiber and calcium intake as response variables. Factors (dietary patterns) were generated retaining a corresponding factor loading > or = |0.17| on the food groups. Changes in obesity indices were scrutinized within quintiles of factor scores. There were high loadings on refined carbohydrates, whole grain, starchy vegetables, other vegetables, red and refined meat, saturated/trans fat, and egg for the first factor named "traditional". All obesity indices had increasing trend across quintiles of pattern score. The fifth pattern (namely egg pattern) had high loading for eggs, salty snacks, as well as fruits and dry fruits, and negative loadings for red and processed meat, saturated and trans fat, plant oils, and dairy products. This pattern showed increasing trends for WC and WHR after adjustment for potential confounders. Other patterns showed non-significant trends for obesity indices. The results were indicative of a traditional pattern which is dominated in the Tehran region and associated with increase in obesity indices.

Morphological and palaeoseismological analysis along the Taleghan fault (Central Alborz, Iran)

SUMMARY The Taleghan fault (TF) is a major active fault of the Central Alborz mountain range in Iran. Located 50 km northwestwards of Tehran, this 80-km-long fault represents one of the major structures threatening 15 million people living in the capital of Iran and the surrounding cities (e.g. Karaj). The TF could be the source of some of the strongest historical earthquakes recorded in the Tehran region, notably the 958 AD event (estimated magnitude M 7.7). To characterize the kinematics and activity of the fault, we carried out a detailed morphological and palaeoseismological study combining aerial photographs, digital elevation models and fieldwork. We show that, unliked described so far, the TF is not a reverse fault but a left-lateral strike-slip fault with a normal component. Its strike, dip and rake within its eastern part are 105, 60 and –20/–40, respectively. Our palaeoseismological analysis shows that a sequence of 2–3 events with magnitudes Mw ≥ 7 occurred during the past 5300 years. If we consider a three-event scenario, the average recurrence interval is ∼2000 years, and the most recent event is younger than 80 AD. If we consider a two-event scenario, the time interval between the second and the first events ranges between 3760 and 830 years, and the elapsed time since the last event ranges between 3529 and 1599 years. Combined with morphotectonics data, our palaeoseismological analysis allows estimating a minimum horizontal slip rate of 0.6–1.6 mm yr −1 and a minimum vertical slip rate of ∼0.5 mm yr −1 . Taking the ∼450-m total vertical displacement observed across the fault, we conclude that the kinematical change along the TF (from reverse to left-lateral + normal) occurred ∼ 1M a.

Assessment of the groundwater salinity monitoring network of the Tehran region: application of the discrete entropy theory

In this paper, a new entropy-based approach is developed for assessing the location of salinity monitoring stations in the Tehran Aquifer, Tehran, Iran. To find the optimal distance among stations, the measure of Transinformation in the Entropy Theory is used. Then a Transinformation-Distance (T-D) curve is developed and used in a multi-objective GA-based optimization model, which provides the best locations for monitoring stations. Because of the large area of the Tehran aquifer and significant spatial variations of the Electrical Conductivity (EC) of the groundwater in the study area, the C-means clustering method is used to classify the study area to some homogenous zones. The optimization model is applied to each zone to find the optimal location of monitoring stations. The results show the applicability and the efficiency of the model in assessing the groundwater monitoring systems.

The addition of geotechnical properties to a geological classification of coarse-grained alluvium in apediment zone

The city of Tehran is founded on Quaternary alluvium, which has been geologically classified by Rieben. The city is located at the foot of the Alborz Mountain Range, which is basically composed of Eocene pyroclastic deposits (green tuff) and other volcanic rocks. The geology and the morphology of the Tehran region is similar to that for other cities located at the foot of mountains. Rieben divided the Tehran alluvia into four categories, identified as A, B, C and D (from oldest to youngest). In the Rieben geological classification system, which is widely used in Iran, the age and general geological characteristics of alluvia are considered, rather than engineering properties. The Rieben and other geological classification systems are described in this paper and geological factors that affect the geotechnical characterization of the Tehran alluvium are discussed. Because of the nature of the Tehran soils, undisturbed samples for laboratory testing are difficult to obtain and the execution of large-scale in situ tests is difficult, expensive and not practical for the majority of construction sites. Accordingly, a geological–geotechnical classification system is required to assess the engineering properties of coarse-grained soils for use in small to medium-sized construction projects. To determine the geotechnical properties of the Tehran alluvia, a number of in situ tests have been undertaken. The test results have been compared with published research results and the Rieben classification system has been extended to cover geotechnical properties. A similar framework could be used to create local geotechnical–geological classification systems of other coarse alluvia in other locations.

The dsRNA Electrophoretype of Some Isolated Iranian Calf Rotaviruses

Summary A rapid and simple technique for diagnosis of rotaviral diarrhea is polyacrylamide gel electrophoresis (PAGE) of dsRNA extracted from fecal samples. To determine the electrophoretype of Iranian calf rotavirus, 23 rotaviral positive fecal samples from diarrheic Holstein calves at the age of less than one month in Tehran region were examined. The viral dsRNA was extracted with phenol-chloroform, and analyzed by PAGE and silver staining. According to PAGE all of the electrophoretypes were identified as long genome electrophoretypes, characteristic of animal group A rotavirus. There was not any unusual segment rearrangement.

Effect of sowing time on the essential oil content and composition of Agastache foeniculum

The research was carried out during the 2001 at Paykan Shahr (Iran). The results of hydro distillation of the herb and GC and GC/MS of the oils of Agastache foeniculum showed that oil and its compositions were affected by sowing times. The highest oil content (2%) was extracted from the herb of plants were cultivated on 5 and 20 of March. Three constituents of the oil of plants were p-cymen, limonen and methyl chavicol were sown from 5 of March to 20 of May by GC and GC/MS analyses. But five components have been identified (p-cymen, limonene , methyl chavicol cis-limonene oxide and carvone) from the oil of plants were cultivated on 5 and 20 of June. It could be concluded that the most suitable time for sowing of A. foeniculum as a potential source of methyl chavicol (92.12%), in Tehran region of Iran was the first of spring 20 of March.

Crust and uppermost mantle structure of Tehran region from analysis of teleseismic P-waveform receiver functions

Teleseismic P-waveform receiver function analysis has been used to estimate the main features of the crust and uppermost mantle structure of the Tehran region. In this study, 20 teleseismic earthquakes that were recorded at the seven stations of Iranian Long Period Array (ILPA) were used to calculate receiver functions. The radial receiver functions are analysed through inverse modelling and forward modelling. The results of modelling show a good match between observed radial receiver functions and synthetic radial receiver functions up to 30 s. Based on this study, the crustal structure of this area is characterised by three main layers: The upper crust has a P-wave velocity between 4 and 5.8 km/s and a 14-km thickness. The results representing the uppermost crustal structure indicate a strong dependency on the lithology around each station. The middle crust has a positive P-wave velocity gradient from 6 to 6.4 km/s down to ∼30 km depth. A P-wave velocity gradient from 6.4 to 7.5 km/s characterises the lower crust with Moho at 46±2 km at this area. A low-velocity mantle, with velocity gradually increasing with depth down to ∼60 km depth, has been revealed beneath the Tehran region.