Reservoir Modeling by Data Integration via Intermediate Spaces and Artificial Intelligence Tools in MPS Simulation Frameworks     

Rouhollah Ahmadi  Ehsan Khamehchi 《Natural Resources Research》2013,22(4):321-336

Conditioning stochastic simulations are very important in many geostatistical applications that call for the introduction of nonlinear and multiple-point data in reservoir modeling. Here, a new methodology is proposed for the incorporation of different data types into multiple-point statistics (MPS) simulation frameworks. Unlike the previous techniques that call for an approximate forward model (filter) for integration of secondary data into geologically constructed models, the proposed approach develops an intermediate space where all the primary and secondary data are easily mapped onto. Definition of the intermediate space, as may be achieved via application of artificial intelligence tools like neural networks and fuzzy inference systems, eliminates the need for using filters as in previous techniques. The applicability of the proposed approach in conditioning MPS simulations to static and geologic data is verified by modeling a real example of discrete fracture networks using conventional well-log data. The training patterns are well reproduced in the realizations, while the model is also consistent with the map of secondary data.  相似文献   

Refining the OSL age of the last earthquake on the Dheshir fault,Central Iran     

M. Fattahi  H. Nazari  M.D. Bateman  B. Meyer  M. Sébrier  M. Talebian  K. Le Dortz  M. Foroutan  F. Ahmadi Givi  M. Ghorashi 《Quaternary Geochronology》2010,5(2-3):286-292

In Central Iran there are several cities along the Dehshir fault, which have similar geological conditions to that of the city of Bam prior to the 2003 earthquake (Mw 6.5), during which more than 30,000 lives were lost. Optical stimulated luminescence (OSL) samples were collected from the Dehshir fault in order to place constraints on its seismic history. The single aliquot regenerative (SAR) dose measurement protocol on coarse grained quartz extracts was used for this study. This SAR protocol had to be optimized for the low OSL sensitivity by varying both the preheat temperatures and test doses used. Dose recovery tests showed that given laboratory dose could be successfully recovered. However, replicate palaeodose (D_e) data were scattered and consequently ages based on mean D_e's had large uncertainties. As this is thought to largely reflect poor bleaching conditions prior to sediment burial at the site, various statistical procedures were employed in conjunction with the stratigraphic knowledge of the site to try and extract more refined burial ages from the samples. From this the timing of the last earthquake was estimated around 2.0 ± 0.2 kyr. This refined age suggests that the earthquake catalogue of Iran is incomplete and more paleoseismological investigation is required to recognize and date the previous events of Dheshir fault.  相似文献   

Correction of Hydrological and Oceanic Effects from GRACE Data by Combination of the Steric Sea Level,Altimetry Data and GLDAS Model     

Farzam Fatolazadeh  Behzad Voosoghi  Mehdi Raoofian Naeeni 《Acta Geophysica》2016,64(4):1193-1210

In this study, a scheme to estimate oceanic and hydrological effects in the GRACE (Gravity Recovery and Climate Experiment) data is presented. The aim is to reveal tectonic signals for the case of the Sumatra earthquake on 26 December 2004. The variations of hydrological and oceanic effects are estimated with the aid of data set of GRACE, altimetry, World Ocean Atlas, and the GLDAS model for a period of January 2003 to December 2006. The time series of computed gravity changes over Sumatra region show some correlations to the deformation resulting from the earthquake occurred in December 2004. The maximum and minimum impacts of hydrological and oceanic effects on gravity changes are about 3 μGal in radial direction and–5 μGal in northward direction. The maximum and minimum amounts of gravitational gradient changes after the correction are 0.2 and–0.25 mE, which indicates the significant influences of hydrological and oceanic sources on the desired signal.  相似文献   

Experimental study on the settlement of marine deposits of Anzali under cyclic loading by laminar box apparatus     

Hadi Ahmadi  Abolfazl Eslami  Mahyar Arabani 《Marine Georesources & Geotechnology》2017,35(3):330-338

The central Alborz mountain range, located in northern Iran, neighboring the Caspian Sea and where the two Persia and Eurasia plates meet, is known as a seismologically active area. In this regard, investigation of the behavior of saturated sand deposits located in this area may be of particular interest. Saturated sand deposits are subjected to instabilities owing to liquefaction or volume change due to earthquake shakings. A particular type of saturated sand deposits is Anzali sand which is abundant in Anzali port and other cities located in this area in northern Iran. This type of sand is a representative for most sands found in this area, i.e., the southern coastal line of Caspian Sea. This research is solely focused on the volume change behavior of marine deposits of Anzali area, often characterized as Anzali sand, in terms of the settlement of a model footing located on the surface of the sand by the aid of a transparent laminar shear box apparatus. Effects of a number of factors such as the frequency of the cyclic loading, the initial density of the sand, and the sample preparation method have been investigated. Observations indicated that the density index and the frequency of loading which are proportional to the energy of an earthquake have direct effects on the accumulation and amount of the final settlement of Anzali sand.  相似文献   

Vulnerability assessment of urban groundwater resources to nitrate: the case study of Mashhad,Iran     

Parisa Asadi  Behzad Ataie-Ashtiani  Aliasghar Beheshti 《Environmental Earth Sciences》2017,76(1):41

Groundwater vulnerability assessment of urban areas is a challenging task in the fast trend of urbanization around the globe. This study introduces a new approach for modifying well-known parameters of common vulnerability indexes to adjust them for urban areas. The approach is independent of a specific weighting system. The aquifer of Mashhad city, contaminated by domestic wastewater, is selected as a case in this study. In order to evaluate the aquifer vulnerability due to anthropogenic activities, at first, parameters of depth to groundwater, recharge, land use, and soil are modified based on their basic concepts and their influences on contamination attenuation. Then, the modified parameters are used simultaneously in several index methods to investigate the capability of the modified parameters to increase correlation coefficient of all employed index methods with the measured nitrate concentration. Accuracy of the modified methods is evaluated by Spearman nonparametric correlation. It is shown that considering the wastewater discharge into recharge parameter leads to an increase of 20% in correlation coefficient. Also, level difference technique shows that more than 70% of the vulnerable areas are predicted correctly in all utilized methods. The accurate prediction in all employed methods indicates that these modifications are independent of the type of index method. Moreover, sensitivity analysis reveals that the recharge and the land use are both the most significant parameters for evaluating the vulnerability.  相似文献   

Wetland cover change detection using multi-temporal remotely sensed data     

Saeed Ojaghi  Farshid Farnood Ahmadi  Hamid Ebadi  Raechel Bianchetti 《Arabian Journal of Geosciences》2017,10(21):470

Lake Urmia, located in northwest Iran, contains a number of wetlands significantly affecting the environmental, social, and economic conditions of the region. The ecological condition of Lake Urmia has degraded during the past decade, due to climate change, human activities, and unsustainable management. The poor condition of the lake has also affected the surrounding wetlands. This study analyzes the land cover change of one of the wetlands in the southern part of Lake Urmia, known as Ghara-Gheshlagh wetland, in the period 1989–2015 using post-classification change detection and machine learning image classification. For this analysis, three Landsat images, acquired in 1989 (TM), 2001 (TM), and 2015 (Landsat-8), were used for the classification and change detection. Support vector machine learning algorithm, a supervised learning method, is employed, and images are classified into four main land cover classes namely “water,” ”barren,” “salty land,” and “agriculture and grassland.” Change detection was carried out for pairs of years 1989 to 2001 and 2001 until 2015. The results of this classification show that there is a sharp increase in the area of salt-saturated land as well as a decrease in the area of water resources. Overall classification accuracy obtained were high for the individual years: 1989 (91.48%), 2001 (90.63%), and 2015 (88.6%). Also, the Kappa coefficients for individual maps were high: 1989 (0.89), 2001 (0.8742), and 2015 (0.84). After that, the land cover change map of the study area is obtained between 1989 to 2001 and then 2001 to 2015. The results of this analysis suggest that more efforts should be taken to effectively manage water resources in the region and point to potential locations for focused management actions within the wetland area.  相似文献   

Kinematic Evolution Model of Fault-Related Anticline based on the Study of the Striated Pebbles of the Related Growth-Strata: A Case Study of the Es Satah Anticline in Southern Tunisian Atlas,Tunisia     

Khalfi  C.  Ahmadi  R.  Trigui  H.  Ouali  J.  Mercier  E. 《Geotectonics》2019,53(3):419-432

Geotectonics - Through several stations on the forelimb of the Es Satah anticline belonging to Gafsa basin part of the southern Tunisian Atlas, an analysis of the striations encountered on the...  相似文献   

Stability of frames subjected to a white noise base excitation     

Samir Abdel-Rahman  Goodarz Ahmadi 《Soil Dynamics and Earthquake Engineering》1989,8(4):166-175

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Seismic isolation of buildings with sliding concave foundation (SCF)   总被引：1，自引：0，他引：1  

M. Hamidi  M. H. El Naggar  A. Vafai  G. Ahmadi 《地震工程与结构动力学》2003,32(1):15-29

In this paper, a new base isolation system, namely the sliding concave foundation (SCF), is introduced and the behaviour of the buildings using such a system is theoretically investigated. A building supported on the new system behaves like a compound pendulum during seismic excitation. The pendulum behaviour accompanied by the large radius of foundation curvature shifts the fundamental period of the system to a high value (e.g. more than 8sec), in a frequency range where none of the previously recorded earthquakes had considerable energy. This results in a large decrease in the structural responses. Since small friction forces are essential on the contact surfaces, PTFE sheets can be used as sliding surfaces. Although the pure frictional sliding systems have the same efficiency as the SCF, in reducing the responses of the superstructure, the main advantage of the new system is a significant decrease in sliding displacement. The performance of the SCF subjected to a number of harmonic and non‐harmonic base excitations is studied and its ability to reduce the structural responses is examined. Some numerical examples are solved for a single‐degree‐of‐freedom (SDOF) structure and the responses are compared with the responses of the same SDOF structure on a fixed base or a pure frictional sliding support system. The comparisons confirm the effectiveness of the new system. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

A comparative study of performances of various base isolation systems,part II: Sensitivity analysis     

Lin Su  Goodarz Ahmadi  Iradj G. Tadjbakhsh 《地震工程与结构动力学》1990,19(1):21-33

A series of numerical experiments on the performance of different base isolation systems for a non-uniform shear beam structure is carried out. Several base isolation systems are considered and the peak relative displacements and the maximum absolute accelerations of the base-isolated structure and its base raft under a variety of conditions are evaluated. Several sensitivity analyses for variations in properties of the base isolator and the structure are carried out. A number of different earthquake excitations are also used in the study. The results show that performances of the base isolation systems are not sensitive to small variations in their natural period, damping or friction coefficient. The presence of a frictional element in the isolators reduces their sensitivity to severe variations in frequency content and amplitude of the ground acceleration. In particular, the resilient-friction base isolators with or without sliding upper plate perform reasonably well under a variety of loading conditions. The rubber bearing type, however, leads to the lowest peak transmitted accelerations for moderate intensity earthquakes.  相似文献