Search for: earthquakes
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    Simulation of earthquake records using time-varying ARMA (2,1) model

    , Article Probabilistic Engineering Mechanics ; Volume 17, Issue 1 , 2001 , Pages 15-34 ; 02668920 (ISSN) Mobarakeh, A. A ; Rofooei, F. R ; Ahmadi, G ; Sharif University of Technology
    In this paper, the time-varying auto regressive moving average (ARMA) process is used as a simple yet efficient method for simulating earthquake ground motions. This model is capable of reproducing the nonstationary amplitude as well as the frequency content of the earthquake ground accelerations. The moving time-window technique is used to estimate the time variation of the model parameters from the actual earthquake records. The method is applied to synthesize the near field earthquakes, Naghan 1977, Tabas 1978, and Manjil 1990 recorded on dense soils in Iran, as well as the Mexico City 1985 earthquake recorded on a site with soft soil. It is shown that the selected ARMA (2,1) model and... 

    Generation of artificial earthquake records with a nonstationary Kanai-Tajimi model

    , Article Engineering Structures ; Volume 23, Issue 7 , 2001 , Pages 827-837 ; 01410296 (ISSN) Rofooei, F. R ; Mobarake, A ; Ahmadi, G ; Sharif University of Technology
    The generalized nonstationary Kanai-Tajimi model is used to describe and simulate the ground motion time histories. Both amplitude and frequency nonstationarities are incorporated in the model. The moving time-window technique is used to evaluate the time varying parameters of the model using actual earthquake records. Application of the model for several Iranian earthquakes Naghan (1977), Tabas (1978) and Manjil (1990) are presented. It is shown that the model and identification algorithms are able to accurately capture the nonstationary features of these earthquake accelerograms. The statistical characteristics of the spectral response curves of the simulated accelerograms are compared... 

    Detection of thermal infrared (TIR) anomalies related to the M s=5.1 earthquake on Oct. 14, 2004 near Ravar (SE Iran)

    , Article Journal of the Earth and Space Physics ; Volume 35, Issue 4 , 2010 ; 03781046 (ISSN) Askari, Gh ; Hafezi, N ; Rahimi Tabar, M. R ; Ansari, A. R ; Sharif University of Technology
    Over the last two decades there have been numerous reports from different seismically active regions of the world that thermal infrared (TIR) anomalies can be identified around the epicentral areas before major earthquakes [e.g. (Tronin et al., 2002)]. The TIR anomalies reportedly appear as early as 14 to 7 days before the seismic events and affect areas as large as 1000s to 100,000s km2 in size. Our case study for detection of TIRs using NOAA-AVHRR data(Band 4) is an Ms = 5.1 earthquake that occurred on 14th October 2004 near Ravar in Kerman province located in Loot and Tabas deserts, southeast-central Iran. The area is part of the Golbaf-Sirj seismogenic zone. It includes major faults... 

    A system dynamics approach to the seismic resilience enhancement of hospitals

    , Article International Journal of Disaster Risk Reduction ; Volume 31 , 2018 , Pages 220-233 ; 22124209 (ISSN) Khanmohammadi, S ; Farahmand, H ; Kashani, H ; Sharif University of Technology
    Elsevier Ltd  2018
    In the aftermath of earthquakes, hospitals serve the critical role of treating casualties. In many cases, the key components of a hospital (i.e., the building, staff, medicine inventory, technical systems, and medical equipment) are affected by an earthquake. To handle the demand surge, affected hospitals should recover in an effective manner. Hospital recovery is a complex and dynamic process because each component requires specific types and amount of resources to recover. Furthermore, the recovery of each component not only affects its performance but also plays a role in the overall hospital recovery. Hospital administrators need to model the complex recovery process after a future... 

    Seismic analysis of a system of dam-massed foundation-reservoir under inclined excitation

    , Article JVC/Journal of Vibration and Control ; 2021 ; 10775463 (ISSN) Sotoudeh, P ; Ghaemian, M ; Sharif University of Technology
    SAGE Publications Inc  2021
    One of the acceptable assumptions in engineering practice is vertical propagation of earthquake waves. When the source of earthquake is located very deep in the ground, this assumption is valid, but for sources located in shallow ground, it loses its viability. In this study, linear seismic analysis of a system of concrete dam-massed foundation-reservoir is performed under inclined earthquake excitation. Both P- and SV-type earthquakes are considered for the purpose of the seismic analysis. To consider the effects of inhomogeneous waves for the case of SV wave propagation, post-critical angles are also considered in the analysis. To investigate the effects of earthquake frequency content on... 

    Short-term prediction of medium-and large-size earthquakes based on Markov and extended self-similarity analysis of seismic data

    , Article Lecture Notes in Physics ; Volume 705 , 2006 , Pages 281-301 ; 00758450 (ISSN) ; 3540353739 (ISBN); 9783540353737 (ISBN) Rahimi Tabar, M. R ; Sahimi, M ; Ghasemi, F ; Kaviani, K ; Allamehzadeh, M ; Peinke, J ; Mokhtari, M ; Vesaghi, M ; Niry, M. D ; Bahraminasab, A ; Tabatabai, S ; Fayazbakhsh, S ; Akbari, M ; Sharif University of Technology
    We propose a novel method for analyzing precursory seismic data before an earthquake that treats them as a Markov process and distinguishes the background noise from real fluctuations due to an earthquake. A short time (on the order of several hours) before an earthquake the Markov time scale tM increases sharply, hence providing an alarm for an impending earthquake. To distinguish a false alarm from a reliable one, we compute a second quantity, T1, based on the concept of extended self-similarity of the data. T1 also changes strongly before an earthquake occurs. An alarm is accepted if both tM and T1 indicate it simultaneously. Calibrating the method with the data for one region provides a... 

    A multi-agent optimization formulation of earthquake disaster prevention and management

    , Article European Journal of Operational Research ; Volume 229, Issue 1 , 2013 , Pages 261-275 ; 03772217 (ISSN) Edrissi, A ; Poorzahedy, H ; Nassiri, H ; Nourinejad, M ; Sharif University of Technology
    Natural earthquake disasters are unprecedented incidents which take many lives as a consequence and cause major damages to lifeline infrastructures. Various agencies in a country are responsible for reducing such adverse impacts within specific budgets. These responsibilities range from before to after the incident, targeting one of the main phases of disaster management (mitigation, preparedness, and response). Use of OR in disaster management and coordination of its phases has been mostly ignored and highly recommended in former reviews. This paper presents a formulation to coordinate three main agencies and proposes a heuristic approach to solve the different introduced sub-problems. The... 

    Statistical evaluation and probabilistic modeling of aftershock sequences of Iranian plateau

    , Article Journal of Seismology ; Volume 22, Issue 5 , 2018 , Pages 1249-1261 ; 13834649 (ISSN) Khansefid, A ; Bakhshi, A ; Sharif University of Technology
    Springer Netherlands  2018
    The present research focuses on the statistical evaluation of Iranian plateau aftershocks from an engineering perspective and presents probabilistic models applicable for generating random earthquake scenarios. Accordingly, a comprehensive earthquake data catalog including the period from 1964 to 2016 is prepared. Data are declustered into 37 separate mainshock-aftershock sequences by considering the completeness moment magnitude of the database. The well-known modified Omori occurrence rate formula is adopted to determine the recurrence time of the events, considering the effect of secondary aftershocks. In addition to computing the probability density functions of the parameters of the... 

    Designing possibility of a seismometer using fiber bragg grating and metal bellows

    , Article Journal of the Earth and Space Physics ; Volume 42, Issue 3 , 2016 , Pages 487-498 ; 03781046 (ISSN) Khaje Gowki, F ; Taraz, M ; Nemati, M ; Bahrampor, A. R ; Sharif University of Technology
    Institute of Geophysics 
    In this study, we have theoretically investigated designing possibility of a seismometer using Fiber Bragg Grating (FBG) and Metal Bellows pairs attached on a mechanical system. This new seismometer can record earthquakes according to sensitivity of fiber optic to changes in physical parameters such as stress and strain. Firstly, in order to understand the quantity and quality of sensor performance, with a mathematically brief description, the effect of stress and strain on the FBG reflection spectrum is examined. FBG is an intrinsic sensing element which can be photoinscribed into a silica fiber. The basic principle of this operation commonly uses FBG based sensor system. The operation is... 

    Experimental study of burial depth effect on embedded pipe deformations in sandy slopes under dynamic landsliding

    , Article Soil Dynamics and Earthquake Engineering ; Volume 114 , 2018 , Pages 281-297 ; 02677261 (ISSN) Farahi Jahromi, H ; Jafarzadeh, F ; Samadian Zakaria, M ; Sharif University of Technology
    Elsevier Ltd  2018
    This paper studies the influence of burial depth on slope response and pipe performance under earthquake induced landslide. Three physical models are constructed and tested using 1 g shaking table device. The slope is divided into four sections as toe, lower and upper sections of the slope face and crest. The pips which perpendicularly cross the slope are embedded at these positions in three burial depths to demonstrate burial depth effect in each section. According to the experiments, dynamic slope response which moderately develops at deeper depths at toe and lower section, displays a clear downtrend at upper section and crest. Also, the pipe response depends on pipe route and slope... 

    Applicability of rigid block based approaches in predicting sandy slope displacements by 1g shaking table tests

    , Article Soil Dynamics and Earthquake Engineering ; Volume 126 , 2019 ; 02677261 (ISSN) Jafarzadeh, F ; Farahi Jahromi, H ; Rajabigol, M ; Sharif University of Technology
    Elsevier Ltd  2019
    Various approaches have been developed by researchers to predict earthquake induced landslide displacements. This study evaluates the applicability of these approaches on sandy slopes. For this purpose, nine physical models are constructed inside a rigid box and thirty-six shaking table tests are conducted. Dynamic responses are then converted to the full scale model by applying similitude laws. Five statistical criteria are applied to compare the measured and predicted displacements and evaluate the precision of the approaches. By combining the outcomes and using a scoring procedure, the approaches are scored. Consequently, the approaches of Fotopoulou and Pitilakis [23] and Hsieh and Lee... 

    A decision support model for robust allocation and routing of search and rescue resources after earthquake: a case study

    , Article Operational Research ; 2020 Ahmadi, G ; Tavakkoli Moghaddam, R ; Baboli, A ; Najafi, M ; Sharif University of Technology
    Springer  2020
    The efficient planning of search and rescue (SAR) operations is highly impactful in the disaster response phase, which offers a limited time window with a declining chance for saving trapped people. The present paper introduces a new robust decision support framework for planning SAR resource deployment in post-disaster districts. A two-stage decomposition approach is applied to formulate the problem as iterative interrelated stages of mixed-integer programming (MIP) models. The first stage presents a robust multi-period allocation model for maximizing fair and effective demand coverage in the affected districts during the entire planning horizon. It takes into account the time-sensitiveness... 

    Design method and feasibility study of fully actively controlled frames

    , Article Scientia Iranica ; Volume 11, Issue 1-2 , 2004 , Pages 50-59 ; 10263098 (ISSN) Joghataie, A ; Asbmarz, M. M ; Sharif University of Technology
    Sharif University of Technology  2004
    In this paper, results of a preliminary study on the feasibility of using an Active Tendon Control (ATC) mechanism for frame structures subject to earthquakes is presented. So far, the ATC mechanism has mainly been considered as a means for installation on structures to mitigate their response under severe loading. In this study, it is desired to evaluate the possibility of using the ATC mechanism to serve as the main means for the stability of frames against earthquakes. Hence, a methodology is presented for the integrated design of frames with ATC mechanisms, which is tested numerically. A number of five-, ten-, fifteen- and twenty-story steel frames are used for this purpose. To this end,... 

    Optimal design and fabrication of "CEDRA" rescue robot using genetic algorithm

    , Article 2004 ASME Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Salt Lake City, UT, 28 September 2004 through 2 October 2004 ; Volume 2 A , 2004 , Pages 541-548 Meghdari, A ; Pishkenari, H. N ; Gaskarimahalle, A. L ; Mahboobi, S. H ; Karimi, R ; Sharif University of Technology
    American Society of Mechanical Engineers  2004
    This article presents an overview of the mechanical design features, fabrication and control of a Rescue Robot (CEDRA) for operation in unstructured environments. As a preliminary step, the essential characteristics of a robot in damaged and unstable situations have been established. According to these features and kinematical equations of the robot, design parameters are optimized by means of Genetic Algorithm. Optimum parameters are then utilized in construction. Upon fabrication, this unit has been tested in clean laboratory environment, as well as, ill-conditioned arenas similar to earthquake zones. The obtained results have been satisfactory in all aspects, and improvements are... 

    Simulation the Near-Fault Velocity Pulses from Form and Intensity Point of View

    , M.Sc. Thesis Sharif University of Technology Waezi, Zakariya (Author) ; Rahimzadeh Rofooei, Fayaz (Supervisor)
    Near-Field earthquakes have gained so much attention through their catastrophic consequences on structures in the vicinity of seismic sources during recent events. Based on recorded data, it is understood that these kinds of phenomena are often accompanied with a large energy pulse at the first times of record whose impulsive characteristic is primarily caused by “forward directivity”. Incapability of response spectra for depicting great demand for energy dissipation disqualifies this method for utilization. Thus it seems inevitable to analyze the models prone to this kind of hazard using time-history based analysis. Being simple enough in time domain, raises hopes for finding a mathematical... 

    Estimation of stress drop for some large shallow earthquakes using stochastic point source and finite fault modeling

    , Article Scientia Iranica ; Volume 17, Issue 3 A , JUNE , 2010 , Pages 217-235 ; 10263098 (ISSN) Moghaddam, H ; Fanaie, N ; Motazedian, D ; Sharif University of Technology
    Using stochastic point source and finite fault modeling, the stochastic stress drop is estimated for 52 large shallow earthquakes listed in the 'Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation of Ground Motions (NGA)' database. The Pseudo Spectral Acceleration (PSA) of 541 accelerograms, recorded at National Earthquake Hazards Reduction Program (NEHRP) C-class sites from 52 earthquakes are simulated and compared with the PSA listed in the PEER NGA database. The magnitude of the analyzed earthquakes ranged from M4:4 to M7:6. The stress drop is calibrated by trial and error and based on the analysis of residuals where the residual is defined as the log of the... 

    A novel double slip loads friction damper to control the seismic response of structures

    , Article Engineering Structures ; Volume 225 , 2020 Ghorbani, H. R ; Rofooei, F. R ; Sharif University of Technology
    Elsevier Ltd  2020
    In this study, the performance of a proposed friction damper with two slip loads in controlling the seismic response of steel moment resisting buildings structures under moderate and intense earthquake excitations is investigated. The proposed friction damper initially operates with a smaller slip load and could shift to the higher slip load after a certain amount of slippage when subjected to intense ground motions. In this regard, the hysteresis behavior of the proposed double slip loads (DSL) friction damper is modeled and after necessary verifications is imported to the material library of OpenSees software to be used for parametric study. To evaluate the performance of the proposed DSL... 

    Performance evaluation of masonry buildings using a probabilistic approach

    , Article Scientia Iranica ; Volume 15, Issue 3 , 2008 , Pages 295-307 ; 10263098 (ISSN) Bakhshi, A ; Karimi, K ; Sharif University of Technology
    Sharif University of Technology  2008
    In many countries, there are traditional houses made of stone, adobe and brick, which perform relatively weakly in earthquakes. To mitigate casualties in future earthquakes, it is necessary to evaluate the current status of these buildings and propose effective methods to retrofit them. One method of evaluating the performance of buildings in earthquakes is through the use of fragility curves. These diagrams show the probability of exceeding a specific state of damage versus seismic intensity parameters, such as PGA, MMI, la, CAV etc. Fragility curves will provide an important basis for analytical methods, based on probabilistic approaches. Much work has been done on bridges, concrete and... 

    A multi-objective robust optimization model for logistics planning in the earthquake response phase

    , Article Transportation Research Part E: Logistics and Transportation Review ; Volume 49, Issue 1 , 2013 , Pages 217-249 ; 13665545 (ISSN) Najafi, M ; Eshghi, K ; Dullaert, W ; Sharif University of Technology
    Usually, resources are short in supply when earthquakes occur. In such emergency situations, disaster relief organizations must use these scarce resources efficiently to achieve the best possible emergency relief. This paper therefore proposes a multi-objective, multi-mode, multi-commodity, and multi-period stochastic model to manage the logistics of both commodities and injured people in the earthquake response. Also, a robust approach is developed and used to make sure that the distribution plan performs well under the various situations that can follow an earthquake. Afterwards, it proposes a solution methodology according to hierarchical objective functions and uses it to illustrate the... 

    Determination of target time for endurance time method at different seismic hazard levels

    , Article Scientia Iranica ; Volume 25, Issue 1 , 2018 , Pages 33-49 ; 10263098 (ISSN) Bazmooneh, A. A ; Esmaeilpour Estekanchi, H ; Sharif University of Technology
    Sharif University of Technology  2018
    Various durations of Endurance Time Acceleration Functions (ETAFs) associated with different seismic hazard levels are presented to enable Endurance Time (ET) method for use in probabilistic seismic demand assessment studies. Various Intensity Measures (IMs) were, first, considered for establishing multiple "IM-duration" relationships. A set of 30 RC moment resisting frames were, then, subjected to IDA analysis using 44 ground motion records and the median IM values corresponding to different structural response levels were extracted. These values were compared with the ET-derived IMs by computing the errors corresponding to various demand levels and summating these errors over a complete...