JOURNAL OF THE EARTH
Year:2010 | Volume:5 | Issue:1 (SPECIAL EDITION)|Papers Count:12

The purpose of this paper is to present the focal mechanism of earthquakes, in south eastern part of Zagros. In this investigation all earthquakes greater than 4.5 magnitude from 1977 to 2007 were studied.Information of these earthquakes are collected from the Harvard university website (Harvard Centroeid Moment Tensor). On the basis of the primary p-wave polarity, focal mechanisms of earthquakes and main stress axis (T and P), nodal planes were determined.The Focal software has used for determination of the earthquake's focal mechanism. This software determines the primary stress axis (T and P) and nodal planes.Focal mechanisms show that the most earthquake faults in the studied area have compressional or main compressional component and in some cases strike slip component.

Zircon (ZrSiO4) is the most abundant and important mineral that contains Zirconium (Zr). Zirconium and Zirconia (ZrO2) are obtained from Zircon. Zircon is recovered from placer deposits containing heavy minerals.According to surveys, heavy minerals have been deposited in some areas of Caspian Sea southern coast, also these sediments were observed in beach sands of Babolsar- Noor.In this thesis, for determining the provenance and distribution of Zircon, sedimentology and heavy minerals experiments (heavy liquids and magnetic separation) were performed on 17 coastal samples, and by finding the placer of Zircon concentration, sampling and complementary studies were done on other 16 samples along Haraz River and its branches. Samples were studied with binocular microscope. Consequently, origin of Zircons is upstream igneous bodies including Cretaceous diabases, basalts and andesites which were leached by Haraz River and carried to the beach. Were the deposit formed sea placers due to high specific weight of Zircon?

In this paper a case study on ground response analysis of a site in Miyaneh region during the Ardabil earthquake (28 Feb. 1997, Mw 6.1) is presented. The Miyaneh city and its suburban areas are located in the Northwest of Iran in Eastern Azarbayjan province. This area is prone to high seismic risk due to the presence of several active faults. Subsurface soils subjected to strong motion exhibit significant nonlinear behavior. For site characterization, deep site investigations have been undertaken, and a seismic geotechnical procedure for the proposed bridge over the rivers at mentioned site which is performed for Iran railway network, subjected to earthquake provokes has been notified. The effect of nonlinearity on site response analysis for the selected site with assumption of elastic and rigid (viscoelastic) half space bedrock by using of standard hyperbolic model nonlinear approach was evaluated and the results of them were compared to each other. Test of the capability of designed computer code by authors, namely as “Abbas Converter”, description and evaluating the nonlinearity of the subsurface soil conditions encountered at the sites to analyze, evaluate the obtained test, site response and quantify the site effect on the surface over a number of geotechnical areas were the targets of this study. The results clearly showed that the effect of bedrock and local soil conditions on soil behavior under the studied area is one of the main effective factors on computed response spectra in ground response prediction. The key factor in this work was to develop and use “Abbas Converter”. It is worked and installed so quickly, operated as a logic connecter function between the used softwares. Therefore, it can make and render the study easier than previous have done, and take over the encountered problems.

We use core analysis and well testing to determinate the reservoir lithology. Unfortunately, coring from each wells in large oil fields such as Iran oil fields, is very expensive. However, because of the importance of this information which is obtained from lithology, it is necessary to coring from some of the reservoir wells.Purpose of this study is prediction of hydrocarbon reservoir lithology in South Pars field using artificial neural network with back propagation error algorithm (BP) and Trainlm algorithm with Matlab software from wire-line logs including gamma ray, density, neutron, sonic and photoelectric (PE). This method can reduce requirement of coring and reduce the costs. The area we have studied, consist of three lithologies, including Dolomite, shale and Anhydrite. The regression between the predicted and the real values of volume concentrations of Dolomite, shale and Anhydrite are obtained respectively, as 0.87, 0.76 and 0.90. The results show that the neural network gives a reasonable estimation for lithology.

Upper Red Formation (Miocene) in Sharabian area (South-West of Sarab) comprises about 1600 meters of detrital and evaporatic facies. Accurate field and laboratory studies upon detrital layer of Upper Red Formation lead to break up four groups of facies, that showing alluvial fan, braided and Meandring Rivers and playa condition. Lower part of formation the demonstrates braided and meandring rivers settings. Narrow thickness in midle part of formation showing alluvial fan depositional environment and upper part of formation is incorporation of meandring rivers depositional environmental and playa conditions.

South Pars gas field is one of the field in south west of Iran in the Zagros hydrocarbon basin and consist of two reservoirs, Kangan and Upper Dalan. Kangan and Dalan formations which belong to Dehram group are two of the most important gas reservoirs in the Persian Gulf area. The aim of this study is of various petrophysical factors affected on water saturation equations calculation errors Kangan and Dalan formations in-well Sp.x- South Pars field by using Core and wrie line logs. In first, evaluation characters petrophsycal in the well about studying have been done with using from core and logs data. Then with using from water saturation formulas with, the factors of formulas and their numerical range were gained. With the quantity of the variable, the column of variable (consecutive quantities of each factor in its range) is formed. Then by using the column of the each variable, water saturation (the column of Sw) are calculated. Afterwards, the consecutive values of Sw are subtracted from each other and positive values of variation are gained (the column of variation in Sw).Then the chart of variation in Sw was plotted against each parameters and its variations (by use the column of variable and the column of variation in Sw). Also the chart of Sw was plotted for understanding the relation between different factor and water saturation. At last the average of error in all of the formulas was calculated and comparedresult.

The Emaft fluorite mine is located in 20 km on south east of Pole Sefid city in Mazandaran province. Structurally the studied area is in the form of a perche syncline and its axial surface trends NE-SW. The Emaft syncline is very important for having fluorite ore because the Kerman and Emaft mines that are located in Lar and Tizkouh Formations are located in the core of this syncline. On the other hand, on the southern limb of syncline and around Elika Formation, fluorite may be found and explored. The structural studies in the area began by measuring the bedding layers, fractures and folds of the area. Then, the data extracted were analyzed by computer (Tectonics Fp1.62 software) and finally the tectonic interplay of the ore-deposit was established. The coordinates of syncline axis in Emaft is 14-N024 that indicates a low plunge of the axis of syncline. The trend of syncline axial surface is N028 and dip is 73NW. The consideration of Emaf fluorite mine shows that the said veins have a trend approaching the axial surface (ranging from 30° to 50° of northeastern). The dips of veins are nearly between 70° to 80° towards northwest the axial surface. According to the data obtained, we find that folding in this region caused linear fractures and the fractures were filled with fluorite solution.

In recent years, wavelet transform was used as a method for interpretation of potential fields. In the potential field theory there are some special groups of wavelets that remain unchanged under the influence of upward continuation operator. These groups of wavelets can produce related wavelet transforms which simplify analyzing of source characteristics like location, depth and etc. Applying poisson wavelet which is equivalent to upward continuation of analytic signal, will help us to determine depth and natural geometry of the homogenous sources in the form of structural index.In this research, we decide to estimate structural index and depth by using the ratio of poisson wavelet coefficients of first and second order. To implement this technique, we used some synthetic models like step and dyke, as well as the real gravity data. The structural index and depth were estimated for these synthetic models by using of analytical and numerical method and compared with each other. Curves of these two parameters shows that results of these two techniques are equivalent at low dilations, but not for high dilations. For simple point sources, it is quite sufficient to investigate this ratio at one level, but for 2-D finite sources, it is necessary to use it at several different levels.

Various converted-wave binning methods (CMP, asymptotic CCP, depth variant CCP, and PSV DMO) were applied to a synthetic PSV seismic data set. The effect of reversing the polarity of the trailing spread is also considered. It is found that depth-variant CCP binning and PSV DMO give the best results. Asymptotic CCP binning, with reversal of the trailing spread, is better than CMP binning with no polarity reversals, while being quicker than depth-variant CCP binning and PSV DMO.

Many studies have been performed on lateral discontinuities such as faults and dikes by means of resistivity Method. Several methods have been proposed to determine potential difference and therefore apparent resistivity.One of the simple methods to determine apparent Resistivity is the Electric Current Image Theory which is only applicable in specific cases like plane boundary or sphere conditions.In the present study, Image Theory has been utilized to location and detects the position of thin vertical dikes and lateral changes in resistivity have been assessed by obtained results. The profiling operation itself has been assessed by means of Wenner, Schlumberger, Half-Schlumberger and Dipole-Dipole Arrays.In the present study, primarily, potential have been calculated for different electrode positions and consequently a MATLAB code has been written to derive apparent resistivity which plots variation in apparent resistivity versus the distances from midpoint of potential electrods to that of the center of dike for different values of K (reflection coefficients). Finally, detection of the dike has been examined and compared for different resistivities.Obtained results show that the Electric Current Image Theory exhibits remarkable results in detecting the position of thin vertical dike in a way that different arrays show different levels of sensitivity. The revealed differences depend on the position of electrodes, width of the dyke and electrodes resolution. In general, the obtained results display the remarkable capability of all four arrays in detection of the dike.

Bam earthquake occured in the southeastern part of Iran in 26 Dec, 2003.The aim of this study is the investigation of correlation between resistivity and seismic refraction in Bam city. The geophysical investigation consisted of 11 electrical profiles including 213 sounding for measurement of resistivity and 80 seismic stations for measurement of P and S-wave velocities.Using IPI2WIN and ARCGIS softwares, image contours up to 30 meters occuring at different depths were prepared. The correlation coefficient between electrical resistivity and elastic wave for depth less than 5m is 0.2 for 5m to 10m is 0.5 also for 10m to 20m is 0.3 and for depth 20m to 30m is 0.04. The correlation coefficient between electrical resistivity and P-wave velocities is 0.0001 and correlation coefficient for total depth between electrical resistivity and S-wave velocities is 0.0007.The main conclusion from our findings is that we cannot estimate elastic wave velocities on the basis of electrical resistivity because there are various grain size distributions and humidities at different depths.

Spatial aliasing is unavoidable in some seismic data acquisitions and has serious adverse impacts on the performance of multichannel data processing and interpretation. So far, many methods have been used for removing spatial aliasing, such as interpolation methods of seismic traces by various transforms like Radon transform. In this paper, a new method for complete removal of spatial aliasing using stationary wavelet transform is presented. Our method has several advantages over previous ones such as, fixing the number of traces, avoiding transfiguration of wavelet shape that constructs the traces, minimizing the phase shift in seismic events, and reducing the run time.