JOURNAL OF THE EARTH
Year:2012 | Volume:7 | Issue:23|Papers Count:20

Qamishloo area has been selected to study the structure of Sanandaj-Sirjan zone. This area consists of group of sedimentary rocks with age range between middle and upper Cretaceous, underlain unconformaly by recent sediments. Based on the processes of satellite images and field studies, 12 fault were discovered. Some minor faults were also discovered during the field studies.The main objective of this paper is to understand the fault structures and related geometry of faults by using mentional data, attempts have been made to analyze the structural patterns and stress and strain systems of the studied area.

The 28th February, 1997, earthquake is the largest and the most destructive earthquake in Ardabil Province and the largest recorded earthquake in NW Iran since the 1990 Rudbar earthquake. The result of teleseismic waveform modeling in this study, indicates that the source process of this earthquake follows mainly two subevents model and focal mechanism of the mainshock is mainly strike slip. The source time function suggests that the main energy was released during the first 10 seconds, the total seismic moment was calculated to be ƩM0=1.89×1025 dyn-cm, the obtained moment magnitude was Mw=6.2. The calculated maximum dislocation was about 27 cm and the stress drop was estimated to be 149 bar. Rupture during the mainshock initiated around the hypocenter and extended unilaterally to the northwest. The results of this study are in agreement with the result of previous studies.

Instantaneous spectral analysis is a continuous time-frequency analysis technique that provides a frequency spectrum for each time sample of a seismic trace. Spectral analysis is a powerful tool for analysis of seismic data. Fourier transform determines the frequency contents of a signal. But for analysis of non-stationary signals, 1D transform to frequency domain is not sufficient. In early years, transforming of seismic traces into time and frequency domains was done with windowed Fourier transform, called a short time Fourier transform (STFT). In this method, the resolution of the results in the time-frequency domain is controlled by the width of the selected window. Continuous wavelet transform (CWT) is a remedy to solve this problem by using the scalable wavelets. CWT uses dilation and transition of a wavelet to produce a time-scale map. By converting the scale to frequency one can get the time-frequency map which is comparable to the time-frequency map obtained from STFT. Converting a scalogram into a time-frequency spectrum using the center frequency of a scale gives an erroneous attenuation in the spectrum. The time-frequency continuous wavelet transform (TFCWT) overcomes this problem and gives a more robust technique of time-frequency localization. Since TFCWT is fundamentally derived from the continuous-wavelet transform, wavelet dilation and compression effectively provides the optimal window length, depending upon the frequency content of the signal. Thus, it eliminates the subjective choice of a window length and provides an optimal time-frequency spectrum without any erroneous attenuation effect for a nonstationary signal. Instantaneous spectral analysis utilizing TFCWT provides high-frequency resolution at low frequencies and high time resolution at high frequencies. Mapping of a seismic trace into the time-frequency domain produces a two dimensional data set by adding a frequency axis. In a similar way a 2D seismic section will generate a 3D data cube in which the third axis is the frequency up to the Nyquist frequency. Sections of single frequency extracted from the cube are called single frequency seismic section (SFS). Comparison of different SFSs can be utilized to detect low-frequency shadows caused by the presence of the hydrocarbon reservoirs. This method can potentially be utilized as a tool for direct hydrocarbon detection. In this study, we applied TFCWT on 2D seismic sections and extracted a single frequency seismic attribute and instantaneous spectral attributes. The purpose of this study is to detect low-frequency anomalies in the real data is obtained from seismic. Hydrocarbon reservoirs in the path of seismic propagation, including the factors that high-frequency seismic signal components absorb and phenomenon called low-frequency shadows creates in the seismic section. This phenomenon directly indicates the presence of hydrocarbons in the region in seismic. For this purpose, single- frequency seismic sections and instantaneous spectral attributes using time-frequency continuous wavelet transform spectrum are calculated and the results of them used to detect hydrocarbon reservoirs. In the next stage, for increasing computational speed, instantaneous spectral attributes directly determined by time-scale spectrum and results implemented on the same data set.

Most of the megacities are located near the active faults. Ground motions in the vicinity of the active faults are associated with two main phenomena so called rupture directivity and fling effects. Therefore, it is important for earthquake resistance design and seismic hazard mitigation to evaluate the characteristics of near-fault ground motions in the megacities. In this paper, the near-fault ground motion was simulated using kinematic model for Tehran City, the capital of Iran. Tehran city was developed along the North Tehran Fault (NTF), which assumed to be the most probable seismic source for the city. Kinematic models are efficient tools to simulate long-period ground motions including slip heterogeneity (Asperities) on the fault and underground geology. Here, the near-fault ground motions are generated assuming NTF scenario using kinematic finite fault model. Then, the variations of faulting parameters such as rise time, maximum slip, rupture velocity, and site to fault distance on the near-fault pulse characteristics are numerically examined and discussed.

The Mahi-Dasht aquifer located in Kermanshah province, west part of Iran. Water resources planning, development and management of Mahi-Dasht area has become inerasably complex as many factors, such as population growth and increasing demand on existing water supplies. To overcome the water shortage and increase water supply during critical demand period, interaction of surface water and groundwater has been investigated. For these reason two models, with and without interaction of groundwater and surface water were developed. These conceptual models (with/without feed from river) were developed in the groundwater MODFLOW PMWIN 5.3 model. Then the groundwater level and volume of aquifer were compared. The results shows that the groundwater level increase in wells near to the river, also the aquifer volume increasing too. Too increase the groundwater level as well as the aquifer volume, it is recommend that during the wet season, the flow of river can be used as recharge of groundwater.

Southern Caspian Sea is almost an active block in Alpine-Himalayan Belt that is surrounded by active and Seismic Belts such as Kopeh Dogh, Talesh and Mid-Caspian. The region that is being discussed here is located at 36 to 42 degree northern latitude and 48 to 57 degree eastern longitude. Because of various seismic activities in this region, it is divided into seven areas in this research. The data of earthquakes were used in the current century and historical earthquakes to estimate the Gutenberg-Richter parameters and the earthquake cycle (recurrence intervals) .The distribution of seismic energy released have been drown and analyzed. Evaluation of all these values has shown a high seismic activity in this region.

According to geological division of Iran, quotation of Nabavi the researched area is located in the part of central Alborz in the zone of Alborz-Azarbaijan. Base on country division this area is considered as dependencies of Noor in Mazandaran province. The researched area has 2 km2 extent. This area is located in the eastern corner 1:100000 of Marzan Abad and the coordinates of it is 51o27’6’ eastern length and 36o14’49’ north width.Deserts evidence and microscope investigation demonstrate the presence of one vein deposit sulphide with the hostess of carbonate.Just as the study of sections shows copper is considered as one of the important element in these veins that are shown in the form of sulphide and it is visible by chalcopyrite. As the analysis of ICP-OES copper element is realized more than back ground and shows the importance of it in this area.According to correlation coefficient the result shows that Cu principle as one of the important principle of mine has high correlation with Zn, As, Cd, Sb, S and U, Rb principles and in some extent Mo, Pb, Sn don't have any correlation with none of principles.

The studied area (1:50000 sheet of Toot is located in 45 km Northeast of Ardakan from Yazd province) is between longitudes 54o15’ to 54o30’ and latitudes 32o30’ to 32o45’ Geochemical samples, 118 Heavy mineral samples, 11Rock samples were taken in this area. They proceed after chemical analyzing and Anomaly maps illustrated. However after finding Control anomaly areas, Heavy mineral and Mineralization samples were taken. So we can illustrate Anomaly areas with studying on Heavy minerals and Rock samples analyzing. According to frequency of Iron and Cobalt and overlapping between Air born Geophysics and Fault Density maps and Result of Heavy mineral samples in their Potential areas, some deposits of Magnetite were identified. Consequently, after that, field proved it.

In this paper, we use a new method called Forced Neural Networks (FNN) to find the parameters of buried deposit in geophysical section respect to gravity anomaly assuming the prismatic model. The aim of the geological modeling is to find the shape and location of underground structures in 2-D cross section. Here, one neuron network and back propagation algoritm are applied to fined out the density difference. The method is used for noise-free and noise-corruption synthetic data, and then the Dehloran bitumen field map in Iran is chosen as a real data.

Carbonate deposits of the west of Khosravan village (In Dmavand area) belongs to the Upper Jurassic-Lower Cretaceous. The studied rocks with a thickness of 275 meters are the result of the deposition of laminar to massive carbonates. The lower boundary of the section is continuous and the upper boundary is disconformed. The field and laboratory study of these sediments has led to identifying 5 facies groups including: open marine facies (A), barrier (B), lagoon (C), intertidal (D) and supratidal (E). Comparing the studied facies with ancient and modern environments along with studying the lateral and vertical changes of the facies shows that the mentioned facies in the studied area have been deposited in a carbonated platform of homoclinal ramp type.

Northeast heights of Rafsanjan are directed from northwest to southeast and are situated in Central Iran south border. In this region, we can find Quaternary deposits in form of non fold layer. Availability of folded sediments of Pliocene in this region shows active stresses in last period of Neogen which is along with other stresses in last period of Cenozoic and mostly has the highest effect in the present morphology of the region. The major fault of the region is Davaran Fault which holds right lateral strike slip with pressure factor. It is evident that this fault is the most important factor for deformation of the region. Contemporary activity and clear appearance of the region faults in the processing satellite images are the reason of continuation of stresses up to present time. These structures are due to important Alpine tectonic movements and especially tectonic movement of the last period of Cenozoic. Field observations and digital processing of satellite data have prove the conformity of faults in study area with expected fractures in a shear zone. These fractures including parallel faults with major fault (Y), conjugated faults of Riedel and Anti-Riedel (R, R'), parallel approximate faults with major fault (P) and normal faults (T), These conformities and availability of right handed Enechelon folds approve a dominant convergent strike slip in the region. With study of the region and joint study show that the maximum stress in this area is in northeast direction which is due to movement of Arabia plate toward Iran plate.

Sedimental-structural area of Alborz consists of altitudes of northern Iranian plateau, which are ranging from Azarbaijan to Khorasan in a general E-W direction, in the form of a composite anticline.In the western part, structures trend to be NW-SE while in the eastern part they trend to be NE-SW. They both meet each other just in the Central Alborz.The history of the seismicity of Alborz stresses the fact that the Central Alborz area has great potential for seismicity. According to the major faults, located in the Central Alborz area with a seismic background as well as nearness of the metropolis Tehran to the verge of them, the study of local and regional faults is of great importance.Last studies demonstrate that Purkan-Vardij fault is a thrust fault but new studies shows that this fault is an old steep fault partly with a strike-slip component which does not affect the quaternary plain in the area and the strike-slip movement effects appear in the direction of fault activity. It’s essential to mention that the study of this fault has not been seriously conducted before, so the mechanism of the fault and the history of its likely seismicity are not basically clear. Considering data analysis as well as drawing them on the diagrams, Purkan-Vardij fault illustrates a right lateral movement with a compression component. Also a detailed examination of local joints suggests a dominant N-S stress in the area.

Anzali lagoon’s basin is located on the southwest part of the Caspian Sea. This lagoon is connected by the Ghazian channel to the sea. The level of the underground water in this basin is low. And in the most area of there the depth of underground water is lower than 5 meters. The study of the pollution of this area has been done by the comparison of the result of the analysis of 20 elements in 6 wheals (named Khavchkin, from Rasht to Khomam). Between the period of 1377 to 1383, and then the in relation with lagoons ecosystem were analyzed. Graph of the changes and polluting elements drowned. (According to date, year, place average mathematical of them) and then the result of sampling.

Today, Study of structural fractured and faults using remote sensing techniques have been greatly considered by researchers. Such researches are important for brittle regions and alluviums in covered areas. Nayband fault zone is an area with the above mentioned conditions. With considering morphologies related with faulting, the several image (159-37, 159-38, 159-39, 160-37, 160-38, 160-39) taken by Landsat ETM+ images (Nayband Zone located in the middle of images) were used. then for better observation of lithological cutting caused by fault movement, different RGB color composite were applied and for finding the optimum RGB color composite, the OIF (Optimum Index Factor) was calculate. This image was also merged with Landsat ETM+ Panchromatic band for increasing the spatial resolution. The next used technique was Sunangle and Edges enhancement filters to detect of sharp edges and boundaries related to the fractures and faults. In the next step in order to detect valleys and ridges, the DEM (Digital Elevation Model) images was virtually shined Sun light from the one direction. The final Technique, Band Ratio, was used in two ways. First, using for Grayscale images. Second, on a proper RGB colored image. This technique was used for identifying more faults in understudy area. Finally, The Structural Fractures Map of Nayband Zone was drawn using the fractures detected by the foregoing techniques. In the northern part of Nayband fault system, horsetail structures were determined and studied. The faults have been created along the North West-South East. The results indicate that mainly horsetail have reverse displacement and also important effects in morphological features.

In this study, Dariyan formation in three selected wells of the South pars field was evaluated using well log data. Probabilistic method was used for petrophysical evaluation provided by Geolog 6.6 software. According to this evaluation Dariyan formation is mainly composed of Lithology investigation with use of cross plot shows that the formation is basically limestone and in some parts it is dolomite, and using Schlumberger standard charts clay mineral was determined as illite. Analysis of wire line data shows that this formation has a high porosity. As results porosity (PHIE) and water saturation (SWE) were obtained 23.62% and 30.5% in average, respectively.

The Ruteh Formation in the North of Shalamzar is one of the fossiliferous Permian deposits in Central Alborz. Based on the lithological characteristics, this formation mainly consists of alternations of grey, medium to thick-bedded, fossiliferous limestones with cherts nodules, and can be subdivided into six rock units. This formation overlies unconformably the Dorud Formation and is covered disconformably by the Nesen Formation. According to international conodont biozone, two conodont biozones have been identified as follow:1) Sweetognathus whitei Zone (Artinskian=Yakhtashian).2) Ellisonia-Merilina Assemblage Zone (Early Artinskian-Late Murgabian).Sweetognathus whitei Zone can be coralated with international conodont biozonation (Wang Cheng et al., 1987).