@article { author = {Ashtari Talkhestani, Ahmad and Nabi-Bidhendi, Majid and Jamali, Javad}, title = {Prediction of reservoir porosity distribution from seismic attributes using NEFPROX neuro-fuzzy model in the Gorgan Basin}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {1-15}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Prediction of spatial distribution of porosity in a reservoir is an essential issue for estimating reserves and planning production operations. In most cases, however, lateral variations of porosity cannot be delineated from measurements made at sparsely located wells. The integration of 3D seismic data with petrophysical measurements can significantly improve the spatial description of porosity. In the last two decades, several methods have been developed for the estimation of reservoir porosity. A number of inversion methods are available in the industry to convert seismic amplitude into acoustic impedance. Acoustic impedance is indirectly related to porosity. Alternate integrative approaches for estimating porosity include geo-statistical methods, such as kriging and co-kriging using well and seismic data. One of the most accurate methods for estimating reservoir parameters is the application of seismic attributes by a nonlinear estimator, such as neural network or neuro-fuzzy model. Both neural networks and neuro-fuzzy models can be good estimators but the latter has the benefit of being interpretable. In this study, a neuro-fuzzy model called NEFPROX was used to estimate porosity in a gas reservoir located in the Gorgan Basin. NEFPROX is a Mamdani-type neuro-fuzzy model, so it has an advantage of being interpretable that makes it distinct from other type of neuro-fuzzy models. The time-consuming characteristic of that method is irrelevant in this case because the prediction of porosity is an offline prediction problem. The Gorgan Basin is located in the northern part of Iran, southeast of the Caspian Sea. This area consists mainly of three formations:the upper formation, called Clay-Sand Group I, belongs to quaternary period. Below Clay-Sand Group I is a tertiary formation called Clay-Sand Group II. A formation of Brown Beds is also a tertiary formation that lies below Clay-Sand Group II. All of these formations consist mainly of shale and sand. The discovery of gas in the Brown Beds Formation has persuaded explorationists to increase their activities in the Gorgan Basin. The purpose of this study is to recognize shale and sand bodies in the Brown Beds formation that consists of alternative sand and shale layers with variable thickness. First, a list of 20 seismic attributes was prepared to extract from raw seismic data in the location of wells. Stepwise regression was used to select four appropriate attributes. The maximum number of attributes was set at four to avoid the model complexity. These attributes, in the order of priority, are instantaneous frequency, amplitude weighted frequency, apparent polarity, and second derivative instantaneous amplitude. Then these four selected attributes were introduced into the neuro-fuzzy model as input to predict porosity as an output of the model. The neuro-fuzzy model was trained with the data of well GO3. Based on hydrocarbon core samples obtained from the Brown Beds formation and the potential of this formation as a probable reservoir, the data corresponding to this formation were selected as a training data. A model blind test was also conducted with the data of well GO5. Porosity sections generated as the output of the model showed two low porosity sandy and shaly-sand channels in the Brown Beds formation. Lateral variations of these channels can clearly be recognized in these sections. The core samples available in well GO3 (containing hydrocarbon) confirm the existence of the two inferred channels. This clear image of channels is simply unidentifiable from raw seismic data. Hence, NEFPROX can be very helpful in supplying valuable information about extent, shape and lithological variation of a reservoir. Finally, compared comparison was made between the performance of the neuro-fuzzy model and regular neural networks in estimation of porosity. The comparison indicates that the accuracy of the NEFPROX estimation is equal to that of MLP and is greater than that of RBF.  }, keywords = {porosity,NEFPROX neuro-fuzzy model,Seismic attributes,Gorgan Basin}, title_fa = {برآورد توزیع تخلخل مخزن از نشانگر‌های لرزه‌ای با استفاده از مدل عصبی- فازی NEFPROX در دشت گرگان}, abstract_fa = {برآورد توزیع تخلخل مخزن در فواصل بین چاه‌ها در تعیین دقیق گسترش جانبی مخزن و در نتیجه در برآورد میزان ذخیره هیدروکربوری و برنامه‌ریزی برای بهره‌برداری از مخزن، از اهمیت اساسی برخوردار است. یکی از دقیق‌ترین روش‌هایی که تاکنون برای این منظور به‌کار رفته، استفاده از برآوردگر غیرخطی مانند شبکه عصبی و مدل‌های عصبی- فازی برای برآورد پارامتر پیش‌گفته از نشانگرهای لرزه‌‌ای است. شبکه‌های عصبی و مدل‌های عصبی- فازی هر دو برآورد‌گرهای غیرخطی خوبی هستند، اما مدل‌های عصبی- فازی یک مزیت نسبت به شبکه‌های عصبی دارند و آن تفسیر‌پذیری مدل عصبی- فازی است. در این تحقیق از مدل عصبی- فازی NEFPROX برای برآورد تخلخل در یک مخزن گازی در دشت گرگان استفاده شده است. با توجه به مقاطع تخلخل به‌دست آمده، دو کانال ماسه‌ای و ماسه‌ای- رُسی با تخلخل نسبتاً کم در واحد زمین‌‌شناسی Brown Beds به وضوح قابل تشخیص است و تغییرات جانبی آنها را در این مقاطع می‌توان دنبال کرد. مغزه‌های حاوی هیدروکربن که از چاه GO3 گرفته شده‌اند، وجود دو کانال پیش‌گفته را تأیید می‌‌کنند. نتایج برآورد تخلخل با این مدل‌ عصبی- فازی نشان می‌دهد که دقت آن تقریباً برابر دقت شبکه عصبی MLP برای برآورد تخلخل است ولی از دقت شبکه عصبی RBF برای برآورد تخلخل بیشتر است.}, keywords_fa = {تخلخل,مدل عصبی- فازی NEFPROX,نشانگرهای لرزه‌ای,دشت گرگان}, url = {https://www.ijgeophysics.ir/article_40819.html}, eprint = {https://www.ijgeophysics.ir/article_40819_411c5680c84f44fc17f7c5366a73d9e0.pdf} } @article { author = {Ashrafi, Khosro and Azadi, Majid and Sabetghadam, Samane}, title = {Effects of various digital filter initialization methods on results of weather research and forecasting (WRF) model}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {16-33}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Numerical weather prediction (NWP) models without initialization techniques may be result in unreal and inaccurate data. Many initialization methods, such as linear and nonlinear normal mode initialization, have been developed and applied in the field of NWP by atmospheric researchers and modelers. In application, such techniques are very complex and expensive. One of the most efficient and simple techniques which can be used in operational forecasting is digital filter initialization. Digital filter initialization methods are applied to eliminate non-physical and high frequency waves from NWP models. These unwanted waves can affect the results of the models and cause its results to depart from real world and observed conditions. In this paper, different filters (1- uniform filter, 2- Lanczos filter, 3- Hamming filter, 4- Blackman filter, 5- Kaiser filter, 6- Potter filter, 7- Dolph [Dolph-Chebyshev] window, 8- Dolph filter and 9- Recursive High-Order filter) are theoretically investigated. The theoretical study of these filters shows that the Dolf filter works better than the other filters. This superiority can be verified using a digital filter initialization technique associated with the Dolf filter in the weather research and forecasting (WRF) model and investigating its results. Subsequently, the digital filter initialization methods provided in the WRF model are tested for the region of Iran. Three different digital filter initialization techniques, namely the digital filter launch, diabatic digital filter and twice digital filter initialization, with nine aforementioned filters were prepared in the WRF model. The WRF model was set with a 45-kilometer grid size for the region at 12-50 oN and 12-87 oS. The WRF model was run over this region with and without a digital filter initialization technique. In general, the initialization of the NWP models influences the first hours of prediction of the meteorological parameters. In this study, two parameters, including surface pressure and rainfall, were considered as indicators of the effects of digital filter initialization methods on the results of the WRF model. Therefore, the obtained results are investigated and compared for surface pressure fluctuation and rainfall. All results indicate that applying the digital filter initialization effectively liminates nonphysical waves from surface pressure fields, especially in the first hours of prediction. This was determined by studying three parameters, including surface pressure fluctuation in some points, derivative of surface pressure fluctuation in some points, and integrated derivative of surface pressure. It was found that the twice digital filter initialization associated with the Dolph filter works better than the other techniques and filters. For rainfall, three- and six-hours predictions of cumulative rainfall were investigated. The results of rainfall prediction with WRF model using digital filter initialization were compared with the results of WRF model without digital filter initialization and observed station data. This comparison showed that the twice digital filter initialization associated with the Dolph filter has its maximum effect during first three hours and in the second three hours has a minimum effect among other techniques. This means that unwanted fluctuations are eliminated properly during the first three hours. Also, a comparison of rainfall prediction results with observed station data indicates that the diabatic digital filter initialization associated with the Dolph filter has the minimum root mean square error. Among digital filter initialization techniques studied, the digital filter launch has sudden effects on the amount of rainfall predicted during the first three hours of prediction time, so this can induce significant errors in results of the model.  }, keywords = {Initialization,digital filter,WRF Model,digital filter launch,diabatic digital filter,twice digital filter}, title_fa = {بررسی تأثیر روش‌های گوناگون آغازگری پالایه رقومی بر نتایج مدل‌ WRF}, abstract_fa = {روش‌های پالایه رقومی را برای کاهش یا حذف موج‌هایی غیرفیزیکی با بسامدهای زیاد به‌کار می‌برند. این موج‌های مزاحم ممکن است باعث ناپایداری یا انحراف نتایج  مدل‌های پیش‌بینی عددی وضع هوا از مقادیر درست شوند. در این مقاله در ابتدا روش‌های گوناگون آغازگری پالایه رقومی برای انواع متفاوت پالایه‌ها به لحاظ نظری با یکدیگر مقایسه‌ می‌‌شود و مزایا و معایب هریک مورد بررسی قرار می‌گیرد. در ادامه امکانات موجود در مدل WRF که برای اعمال آغازگری پالایه رقومی درنظر گرفته شده ‌است، بررسی و تشریح می‌شوند. سه روش اصلی آغازگری پالایه رقومی موجود در مدل WRF، آغازگری پالایه رقومی لانچ، آغازگری پالایه رقومی ‌دررو و آغازگری پالایه رقومی دومرتبه‌ای هستند. هریک از این روش‌ها با 9 پالایه متفاوت قابل کاربردند که در متن مقاله مورد ارزیابی قرار گرفته‌اند. مدل WRF برای یک بررسی موردی با و بدون روش آغازگری اجرا شده است و نتایج آن مورد بررسی قرار گرفته‌اند. نتایج نشان می‌دهد که روش آغازگری پالایه رقومی دومرتبه‌ای همراه با پالایه دولف نسبت به سایر روش‌ها مزیت نسبی بیشتری دارد. همچنین نتایج نشان می‌دهد که به‌صورت کلی به‌کار بردن روش‌های آغازگری پالایه رقومی باعث کاهش بسامدهای مزاحم در نوسان‌های مربوط به فشار می‌شود.}, keywords_fa = {آغازگری,پالایه رقومی,مدل WRF,آغازگری پالایه رقومی لانچ,آغازگری پالایه رقومی ‌دررو,آغازگری پالایه رقومی دومرتبه‌ای}, url = {https://www.ijgeophysics.ir/article_40820.html}, eprint = {https://www.ijgeophysics.ir/article_40820_dbb66c3dca9cc4666c63a557c99cd9e7.pdf} } @article { author = {Ansari, Abdolhamid and alamdar, kamal}, title = {Using of remote sensing filters in processing of the potential filed images}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {34-50}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Remote sensing is the science and art of the gathering information about an object, area or phenomena by means of a device that is not in contact with the object, area and phenomena under investigation. In remote sensing, the interaction between an energy source (electromagnetic) and surface features (trees, rocks, soil) is recorded. Image processing can be considered as an image-to-information-mapping procedure, which provides the image for future analysis. Image processing techniques usually employ a filter for selecting desired information. Filters are used for spatial image enhancement, for example, to reduce noise or to sharpen blurred images. Such a processing technique works on pixel values and produces a filtered image which the pixel values of which depend on its former neighbors. In this regard, the sunshading, viewshed, edge enhancement, and majority filters are most commonly used as image processing filters. In contrast with remote sensing, geophysical methods employ human agents for data collection and interpretation. Potential geophysical field data, such as aeromagnetic and gravity data are collected by both government Geological Surveys and mineral exploration companies for a wide range of purposes, including geological mapping and mineral exploration. Since the measured data are presented in the form of a contour map, it can be considered as an image and image processing can apply on it. In addition, these images possess a large number of geological features, such as dykes, faults, and folding, which can disappear with disturbing noises. Consequently, the use of image processing techniques for the purposes of noise reduction and edge enhancement of different geological features is necessary. In geophysical literature, derivative filters and local phase filters are the most applicable filters applied on potential field images. The main intent of this study is to develop remote sensing filters, mentioned above, on potential files images. Sunshading is a process in which the observed data are considered as topography data that is illuminated by a light source, such as sun. The elevation and azimuth of a ‘sun’, or light source, are chosen by the interpreter, and the resulting reflectance from the data surface (the elevations of which are proportional to the values of the data to be interpreted) is calculated. Linear features that lie at 90 degrees of the azimuth are enhanced, while those which lie parallel to it become less apparent. The selection of the azimuth and elevation of the sun is normally done in an interactive manner by the interpreter. There are many different algorithms for determining the reflectance from the surface based on a variety of physical models. In this regard, the Lambertian reflector is most admissible regarding geosciences data is given by   where , ,  is the sun elevation (measured from the vertical), and is the azimuth (measured anticlockwise from East). Notably, p and q are any two orthogonal gradients of the data, and may be calculated in either the space or frequency domains. The viewshed of a dataset is the region around a given observation point that is visible from that location. The viewshed is used here as a data enhancement tool to aid in the interpretation of geophysical potential field data. The fraction of the area of a moving window visible from each point on the dataset (considered as if it were topography) is computed. Edge enhancement is particularly suited to the analysis of the potential field data. First, edges are naturally what human eyes focus on in the analysis of any kind of image. Second, edges in a gravity/magnetic map mimic the sketches which geophysicists usually draw on potential field maps to guide their interpretation. Edge enhancement filters are divided on two main groups, including high-pass filters and Laplacian filters. With high-pass filters, the high frequency features are passed and those of low frequency suppressed. Since the edge can be considered as a high frequency feature which occupies a portion of the image densely, this kind of filter is admissible. High-pass filters are capable to run either as directional or perpendicular. In the other hand, Laplacian filters enhance the edge in all directions. These filters are logical filters. The main idea of these filers is to replace the central pixel with the pixel having the maximum observed quantity. In fact, the application of these filters led to removing undesirable features. In this paper, these filters were successfully applied on the synthetic magnetic data from prismatic model. Additionally, filters were applied on gravity and magnetic data from southwest England in which the output results relevant to causative granite bodies have a broad correlation with those from the geological map.    }, keywords = {image processing,Remote Sensing,Potential field,sunshading,viewshed,laplacian filter,southwest England}, title_fa = {استفاده از فیلترهای دورسنجی در پردازش تصاویر میدان پتانسیل}, abstract_fa = {پردازش تصویر را می‌توان درحکم نگاشتی از فضای تصویر به فضای اطلاعات دانست که موجب آماده‌سازی تصویر برای آنالیزهای بعدی می‌شود. این کار با فیلترهای گوناگونی صورت می‌‌گیرد که عمده مزیت آنها نبود نیاز به انتقال داده‌ها از حوزه‌ای به حوزه دیگر است. این فیلترها کاربرد گسترده‌ای در مبحث دورسنجی دارند. از مهم‌ترین این فیلترها می‌توان به فیلترهای سایه‌روشن، حوزه دید و آشکارساز لبه اشاره کرد. عمده مزیت استفاده از این فیلترها نبود برجستگی نوفه‌های محیطی و مصنوعی در تصویر فیلتر شده است. در مورد داده‌های میدان پتانسیل معمولاً از فیلترهای مشتق (مشتق افقی، مشتق قائم) برای پردازش تصاویر استفاده می‌شود و محاسبات مربوط به آن از راه انتقال داده‌ها به حوزه بسامد (فوریه) صورت می‌پذیرد. مشکل این فیلترها، نبود تعادل بین سیگنال و نوفه‌ها در تصویر فیلتر شده است. به عبارت دیگر هم‌زمان با برجسته شدن سیگنال‌‌ها نوفه‌های موجود در تصویر نیز برجسته می‌شوند. در این نوشته کارایی فیلترهای دورسنجی در پردازش تصاویر ژئوفیزیکی از نوع میدان پتانسیل شرح داده می‌شود. این فیلترها روی داده‌‌های مغناطیس مصنوعی مدل منشوری در دو حالت بدون نوفه و با نوفه به کار رفته است. در حالتی که داده‌‌ها به نوفه آلوده شده‌‌اند مهم‌ترین مشکل، نبود تعادل بین نوفه و سیگنال در تصویر فیلتر شده است. همچنین فیلترهای فوق روی داده‌‌های مغناطیس‌‌سنجی و گرانی‌‌سنجی هوایی جنوب غرب انگلستان به کار رفته‌اند.}, keywords_fa = {پردازش تصویر,دورسنجی,میدان پتانسیل,سایه‌‌روشن,حوزه دید,لاپلاس,جنوب غرب انگلستان}, url = {https://www.ijgeophysics.ir/article_40822.html}, eprint = {https://www.ijgeophysics.ir/article_40822_b6af06e8b4666cf80ab7b743884a47e2.pdf} } @article { author = {Meshinchi Asl, Mirsattar and Latifi, Hooman}, title = {An algorithm for the modeling and interpretation of Seismoelectric data}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {51-61}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Seismoelectric modeling is a prospecting method, based on seismic electromagnetism in which seismic sources are used to generate this phenomenon. When seismic waves are released within a fluid-saturated sedimentary material, a small amount of fluid-solid relative motion is induced. The seismic force causes this effect through a combination of relative gradient acceleration fluid and the pressure of seed waves. Most of the surface grain, in contact with a liquid electrolytes, are chemically bound to the surface load. The thin layer of charged fluid around each grain is balanced with a scattered distribution of mobile ions with opposite charges. The scattered ions in this layer are free to move through the fluid so that seismic waves create an electrical current flow. This induced seismic current flow acts as a current source in Maxwell's equations, which is the base of electromagnetic wave coupling with a seismic wave. The peaks and troughs that accumulate are P-type waves. The electric field is produced inside the wave (seismic), which is vertical on the wave sinciput. This flow creates convection. In a homogeneous substance, the current flow is equal to convection so that the overall flow is zero; no magnetic or electromagnetic fields are created independently., Hence, the electric field that exists within the wave moves as a part of the reaction without spreading outside the wave. Therefore, a simple pair of electrodes can act as a geophone to measure the electric field inside the P-wave when it passes throughthem. The S shear wave does not separate charges in a homogeneous substance without divergence, so they cause no fluid repletion. The relative motion of fluid to solid is due to seed accelerations. The induced current flow creates magnetic fields that, in turn, produce a small electric field. Thus, for S waves in a porous and homogeneous environment, a magnetic field is produced that moves as a part of the material reaction. Effluent but electromagnetic waves are not produced independently. Supposedly, a magnetic detector (which is insusceptible to mechanical vibration) can serve as a selector geophone on shear wave action and measure the magnetic field N-S wave when the magnet passes the gauge. The effect of a direct current (DC) electric field on the propagation of seismic waves is modeled in this study by means of the pseudospectral time domain (PSTD) method, based on a set of governing equations for poroelastic media. This study focuses on the more general concept of the siesmoelecric coupling effect and the application of poroelastodynamics and Maxwell's equation to seismic and electromagnetic waves. In this project, the magnitude effects of seismoelectric coupling are found to be characterized by charge density, electric conductivity, dielectric permittivity, fluid viscosity and zeta potential. The simulated poroelastic wave propagation and electric field vary with an existing background. A physical experiment was carried out in an oilfield using a DC electric field and the results were compared with those of the simluation. Estimations for solutions of differential equations are based on the function (or a number of separate estimates for this function) defined by a certain relationship between its various derivatives on a given place or time range along the boundary conditions of this area. Overall, this is a serious problem and only a formula for this solution was analyzed. An alternate method with finite derivatives was used to replace the differential equation. The results show that the seismoelectric coupling in a wide range of the seismic frequency bands generated through a DC electric field can significantly affect the propagation of elastic energy.  }, keywords = {electric field,pseudospectral time domain,poroelastic media,seismoelecric coupling,pore pressure}, title_fa = {پیشنهاد الگوریتمی برای مدل‌سازی و تفسیر داده‌‌های سایزموالکتریک}, abstract_fa = {به طور کلی روش سایزموالکتریک، روشی اکتشافی براساس امواج لرزه‌ای و الکترومغناطیسی است. امواج لرزه‌‌ای ایجاد شده با یک چشمه لرزهای در مرز جدایی دو محیط، حرکت نسبی سیال–جامد را به‌وجود می‌‌آورند که در اثر تقابل خواص کشسانی محیط با سیال اشباع‌‌کننده ایجاد می‌‌شود. هدف از این تحقیق، بررسی تاثیر میدان الکتریکی جریان DC روی انتشار امواج ارتعاشی به روش حوزه زمانی شبه‌‌طیفی (pseudo spectral time domain) است که در اصطلاح کلی‌‌تر، تاثیر اتصال سایزموالکتریک نامیده می‌‌شود. در این تحقیق از معادلات پروالاستودینامیک برای امواج ارتعاشی و معادلات ماکسول برای امواج الکترومغناطیسی استفاده شده و میزان تاثیر اتصال سایزموالکتریک با چگالی بار الکتریکی، قابلیت رسانایی الکتریکی، تابع قابلیت نفوذ دی‌‌الکتریک، گران‌رَوی سیال و پتانسیل زتا تعیین شد . تغییر میدان الکتریکی با جریان الکتریکی DC اعمال شده با نتایج آزمایش فیزیکی در محیط مدلسازی شده مقایسه شد و  نتایج روشن ساخت که میدان الکتریکی DC به طور قابل توجهی روی انتشار انرژی کشسانی از راه اتصال سایزموالکتریک در محدوده وسیعی از پهنای بسامد ارتعاشی تاثیر می‌‌گذارد . همچنین  به کمک مولفه افقی میدان الکتریکی موج الکترومغناطیسی، مرز لایه‌‌های زیر سطح زمین مشخص شد.}, keywords_fa = {میدان الکتریکی,حوزه زمانی شبه‌‌طیفی,محیط پروالاستیک,اتصال سایزموالکتریک,فشار منفذ}, url = {https://www.ijgeophysics.ir/article_40823.html}, eprint = {https://www.ijgeophysics.ir/article_40823_e9ca977918e2a861547e84d90201d07b.pdf} } @article { author = {Ghassem Alaskari, Mohammad Kamal and Kazemi, Malihe Sadat and Piran, Michael and Barat Imamgholi, Javad}, title = {Analysis of fractures using fuzzy logic method}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {62-72}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Many of the problems faced in engineering and science can be effectively modeled mathematically. However, in constructing these models many assumptions have to be made which are often not true in the real world.For some applications, the sets that will have to be defined are easily identifiable. For other applications, they will have to be determined by knowledge acquired from an expert or group of experts. Once the names of fuzzy sets have been established, one must consider their associated membership functions. Development of this idea has led to many successful implementations of fuzzy logic systems, also called Fuzzy Inference Systems (FIS). A Fuzzy Inference System is a system that uses fuzzy sets to make decisions or draw conclusions. The approach adopted for acquiring the shape of any particular membership function is often depend on the application. In some applications, membership functions must be selected directly by a `statistical' approach or by an automatic generation of shapes. The determination of membership functions can be categorized as being either manual or automatic. The manual approaches rely only on the experience of an expert. All of the 'manual' approaches suffer from the fact that they rely on subjective interpretation of words. A new indirect fracture detection technique called Fuzzy Logic Integrated System (FLIS) from well logs is presented in this paper. The FLIS can be widely used for fracture detection with high precision in comparison with image logs in zones of interest. This method is very suitable for multiple well logs, where changes in the log- shapes are affected by the fractures. Therefore, the above method should be used correctly. Fuzzy membership of the log data serves also as an indicator for the classification of results and provides valuable information concerning the reliability of the fracture zones. The procedures of executing the fuzzy logic are as follows: First, based on the RockLog program (Ghassem Alaskari, 2005), the well log data on each zone of interest are analyzed and plotted in the log format. Second, anisotropic parameters necessary for the evaluation of highly fractured zones from image logs are determined and compared with the full data set. Third, using FLIS algorithm written for this purpose, fractures can be identified in each zone of interest. Fourth, the comparison between the results given in the third step with the core samples at the same intervals (the fracture density and fracture types) in each zone can be identified. The above procedure has been used successfully for determining fractured reservoir zones in the South-Pars field from an open-hole well log data. A comparison between core samples and image logs was done for the same intervals detected by this technique. As described earlier, a fuzzy set is fully defined by its membership function. How best to determine the membership function is the main question that needs to be addressed. The degree of applicability of this technique is checked by image logs and core samples for the same region, where a full well data was available.}, keywords = {Fuzzy logic,fracture detection,Well Logs,Fracture Index,image logs,core samples}, title_fa = {تحلیل شکاف‌ها با روش منطق فازی}, abstract_fa = {در این تحقیق روش آشکارسازی غیرمستقیمی به‌نام منطق فازی برای تعیین شکاف‌ها با استفاده از نمودارهای چاه عرضه شده‌است. روش منطق فازی را می‌توان برای تعیین شکاف‌ها به‌صورت کلی با دقت بالایی به‌کار برد. روش ذکر شده با استفاده از نمودارها در حالت‌‌هایی که تغییرات در شکل نمودارها مربوط به تاثیر شکاف‌ها باشد، به‌کار می‌رود. بنابراین برای این منظور باید الگوریتم منطق فازی به‌درستی اعمال شود. تعیین عضویت نمودارها در الگوریتم منطق فازی به‌منزله آشکارسازی دقیق برای رده‌‌بندی شکاف‌ها نیز به‌کار می‌رود، زیرا این روش می‌تواند اطلاعات قابل قبولی برای تعیین شکاف‌ها ارائه دهد. لذا با این روش از طریق نمودارهای تهیه شده در چاه‌های باز، برای تعیین شکاف‌ها در سنگ‌های مخازن شکاف‌دار پارس جنوبی استفاده شد که موفقیت آمیز بوده است. در تأیید این موضوع نمودارهای یکی از چاه‌های مخزن پارس جنوبی با روش فوق بررسی گردید و با مغزه‌های موجود و تصویرگرهای همان چاه در همان فواصل عمقی مقایسه شد. کار‌آیی این روش توسط تصویرگرها برای محدوده‌ای از چاه که مغزه‌ها وجود داشت مورد تأیید قرار گرفت.}, keywords_fa = {منطق فازی,تعیین شکاف‌ها,نمودارهای چاه,شاخص شکستگی,تصویرگرها,مغزه‌ها}, url = {https://www.ijgeophysics.ir/article_40824.html}, eprint = {https://www.ijgeophysics.ir/article_40824_3567f4a33511ef35d8e9f61e92b21702.pdf} } @article { author = {Saghafi, Mohammad Ali and Aliakbari Bidokhti, Abbas Ali}, title = {Study of flow and turbulence in an atmospheric boundary layer in an area with complex topography (Tehran)}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {73-91}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {In this paper, the flow and turbulence structure in the boundary layer of an urbanized region with complex topography (Tehran) was studied using data from a meteorological station, Sodar (PA1 Model) for heights above 50m, on days 13 through 24 of August, 2002, and an ultrasonic anemometer, located in Tehran University Geophysics Institute, in August 2005. Days for observation were selected such that they were without any active synoptic system in the region, the skies were clear, wind speed at 10 m did not exceeded 5 meters per second, and the relative humidity was low. The data used for the vertical profiles are 12-day averages for 4 local hours, namely: 09:30, 15:30, 21:30 and 03:30. The study of turbulence using the gradient Richardson number shows that, during the day, the boundary layer is generally turbulent while, at nights, in addition to the reduction of turbulence intensity, the depth of the turbulent region of the boundary layer also decreases. Tests done by Monti et al. (2002) have shown that theis not sensitive to the time of averaging in range. The Sodar data are also 15 minutes averaged of the   measurements. Additionally, Sodar data are spatial average of 25-meter, and so this averaging may filter out some turbulent layers in the profiles. This averaging may cause large Richardson numbers. Graphs of, and show that nearly continuous turbulence occurs during the night, but the values are weaker with respect to daytime turbulence. The  diagram shows that this quantity has a daytime maximum value and a nighttime minimum, indicating the effect of stability on turbulence generation. Turbulent intensity components and are almost the same, and are also four times that of during the night and nearly three times of during the day. This shows that turbulent kinetic energy production is a combination of buoyancy and shear effects during the day and is mostly due to the effects of shear during the night. A study of the behavior of turbulent quantity, in association with buoyancy and mechanical turbulent kinetic energy source production terms, explains the thermal and roughness effects on the characteristics of . Values of diurnal  are reduced relative to height at different hours due to the increased production of mechanical and buoyancy turbulence in the surface layer. Values of these quantities are low even in the presence of wind shear that can be due to radiation-induced effects on these quantities during the day, especially in relatively low wind conditions. Wavelet analysis of wind speed using ultrasonic anemometer data with one-minute averaging in the surface layer shows mostly wavy and continuous structures with periods of 6 to 90 minutes that are related to turbulent fluctuations and both regular and irregular internal waves. It seems that the topography-induced flows (down slope, upslope and drainage flows) and urban effects (flows from thermal islands and their interactions with artificial topography such as high buildings, roads and vegetation) cause important changes in the circulation of the wind flows of the region when synoptic systems are absent. Local flows in the region with the effects of complex terrains are generated by pressure gradients and thermal forcing. Urban flows span a wide range of space and time scales. These factors change turbulence and vertical wind profiles. The time series of various quantities show approximately diurnal variations. Vertical profiles of turbulent quantities show that the flow is stratified in the lower section of the boundary layer (under 500m). The depth over which the katabatic flow occurs reaches about 200 meters. This stratified lower section of the boundary layer possibly caused by the effects of complex topography, the urbanization of the region and their circulation interactions (especially during the night, when they reinforce each other). The height of this layer doubles during daytime. The layering of the wind profile may be due to air intrusion from various slopes originating from different sources according to Monti et al. (2002), or to the structure of generated internal waves.}, keywords = {Turbulence,urban area,Sodar,internal waves,complex topography}, title_fa = {بررسی شارش و تلاطم در لایه مرزی جو یک منطقه با توپوگرافی پیچیده (تهران)}, abstract_fa = {هدف از این تحقیق، بررسی ساختار قائم و تغییرات زمانی (شبانه‌روزی) شارش و تلاطم در لایه مرزی منطقة شهری با توپوگرافی پیچیده (تهران) است. به‌این‌‌منظور از داده‌های دستگاه سودار (Sodar) مدلPA1 برای ارتفاع‌های 50 متر به بالا، داده‌های ایستگاه هواشناسی به‌‌منزلة مرجع سطح زمین در تاریخ‌های 13 تا 24 اوت 2002 و داده‌های دستگاه بادسنج فوق‌‌صوتی ماه اوت 2005 مؤسسة ژئوفیزیک دانشگاه تهران استفاده شده است. روزهایی انتخاب شده‌اند که سامانه همدیدی در منطقه وجود نداشته، آسمان تقریباً صاف (حضور ابرهای کومه‌ای در برخی ساعت‌ها در چند روز) و باد سطح 10 متر از 5 فراتر نرفته (میانگین حدود3) و رطوبت نسبی کم (میانگین حدود 25%) باشد؛ طوری‌که گردش‌های محلی  اثر غالب داشته باشند. داده‌های به‌کار رفته برای رسم نمایه‌های قائم کمیت‌ها، میانگین 12 روزه (13-24 اوت 2002) برای 4 ساعت 09:30، 15:30، 21:30 و 03:30 محلی هستند. با توجه به نمودارها، کمیت‌های متفاوت، تقریباً تغییرات شبانه‌روزی از خود نشان می‌دهند. نمودارهای ، و  ( به‌ترتیب نشانگر انحراف معیار مؤلفه‌‌های افقی سرعت باد ( و ) و مؤلفه قائم سرعت باد ()) نشان می‌دهند که تلاطم طی شب تقریباً پیوسته است، ولی نسبت به روز تضعیف شده‌ است. نمودار انرژی جنبشی تلاطمی () نشان می‌دهد که هنگام روز این کمیت بیشینه و در شب کمینه مقدارش را دارد که بیانگر افزایش انرژی جنبشی تلاطمی هنگام روز و کاهش آن طی دوره پایدار شبانه است. داده‌های سودار، متوسط‌های فضایی 25 متری هستند که حذف لایه‌های تلاطمی احتمالی موجود در این محدوده متوسط‌گیری‌ را در پی خواهد داشت. این متوسط‌گیری، سبب ایجاد اعداد ریچاردسن بزرگ خواهد شد که در نمودار مربوط به مشاهده می‌شود. مؤلفه‌های شدت تلاطم و، تقریباً برابرند و طی شب تقریباً چهار برابر و در روز تقریباً سه برابر هستند. این موضوع نشان‌دهنده آن است که در روز، تولید انرژی جنبشی تلاطمی، ترکیبی از اثرات شناوری و برشی و طی شب، بیشتر ناشی از اثرات برشی است. بررسی رفتار کمیت تلاطمی  که مرتبط با جمله‌های تولید سرچشمه شناوری و مکانیکی انرژی جنبشی تلاطم است، تأثیر ترمال‌ها (thermal) و زبری را بر ویژگی‌های  توضیح می‌دهد. مقادیر  در ساعت‌های متفاوت با ارتفاع کاهش می‌یابد که ناشی از افزایش تولید مکانیکی و شناوری تلاطم در لایه سطحی است. هنگام شب مقادیر این کمیت حتی در حضور برش باد کمتر است که  این می‌تواند ناشی از اثر تابش کلی بر این کمیت در هنگام روز، به‌ویژه در شرایط باد نسبتاً کم باشد. تحلیل موجک تندی باد با استفاده از داده‌های متوسط‌گیری شده یک دقیقه‌ای بادسنج فوق‌‌صوتی در لایه سطحی، ساختاری تقریباً موجی و پیوسته و با دوره تناوب 6 تا 90 دقیقه نشان می‌دهد که ممکن است مربوط به نوسان‌های تلاطمی و امواج  نامنظم و منظم درونی باشد.}, keywords_fa = {توپوگرافی پیچیده,منطقه شهری,سودار,تلاطم,امواج درونی}, url = {https://www.ijgeophysics.ir/article_40826.html}, eprint = {https://www.ijgeophysics.ir/article_40826_7c69d72ab6fb1fc36d322419b76ddab6.pdf} } @article { author = {Abedi, Maysam and Afshar, Ahmad and Ebrahimzade Ardestani, Vahid and Norouzi, Gholam Hossain}, title = {2D modeling of gravity data with the compact inversion method and density variation as a stopping criterion}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {92-108}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Potential field data (gravity and magnetic data) are usually analyzed by means of linear transformations, spectral methods, inversion techniques and analytic signal methods. Nowadays, there are diverse methods of modeling the gravity data, but each has some limitations. One of the limitations of these methods is the assumption of a simple shape for buried structures, whereas the actual shape could be entirely different. The present study uses two-dimensional 4-sided polygons (prisms) to resolve these limitations, because with these it is possible to make any shape for an unknown underground structure by arranging these prisms.  Within the context of this study, the 2D inversion method proposed by Last and Kubik (1983) is reused. For this purpose, a Matlab-based 2D inversion code was developed. This code uses an iterative least squares procedure, which allows the weights to depend on the densities of the previous iteration. Therefore, the solution minimizes both the area of the underground structures or deposits and the weighted sum of squared residuals.   According to Last and Kubik, the iterative procedure stops when a minimum area of the density distribution is reached. The stopping criteria in inversion algorithms are usually based on the fit between the observed data and theoretical data produced by the proposed model. Typically, a misfit function estimator is used. In the inversion of potential field data, the number of observations is often less than the number of unknowns (underdetermined problem). To overcome this problem, this study uses a new method proposed by Ekinci, wherein the density variation is used as a new stopping criterion to find the required number of iterations for convergence the model. The focusing inversion method proposed by Last and Kubik was modified in order to produce a compact final model. For this model, the difference between the block densities at the last successive iteration is minimal. This method minimizes the volume of deposit, which is equivalent to maximizing its compactness. Here, the method for noise-free and noise-corruption synthetic data was used and after obtaining satisfactory results it was applied to real data. The Dehloran Bitumen map in Iran is chosen as a real data application. The area under consideration is located in the Zagros tectonic zone, in western Iran, where a search for Bitumen is under way. Layers of medium bedded limestone with intermediate marl-limestone are the dominant formations in the area, and the hydrocarbon zone is one of the most important characteristics of the area. By using the method for noise-free and noise-corruption synthetic data, the present study produced a program for the Dehloran Bitumen map. Anomaly modeling was used because the anomaly value of the cross section, which is taken from the gravity anomaly map of Dehloran Bitumen, is very close to those obtained from this method. The final result of these methods shows that the deposit starts from the depth of 10 meters to about 35 meters. This modeling was a satisfactory representation of the results of actual drilling in the region. The results of the drillings show that the lowest depth of the deposit varies from 7 to 10 meters. This 2D modeling of gravity data with the compact inversion method and density variation can easily be applied for gravity, microgravity and magnetic data.  }, keywords = {Compact inversion modeling,syntheticmodels,gravity data,Dehloran bitumen}, title_fa = {مدل‌سازی دوبُعدی داده‌های گرانی‌ با استفاده از روش معکوس‌سازی فشرده و معیار توقف تغییر چگالی}, abstract_fa = {اکثر روش‌های مدل‌سازی دارای محدودیت‌اند و این محدودیت برای مدل‌سازی داده‌های پتانسیل نیز وجود دارد. به دلیل پیچیدگی روش‌های مدل‌سازی نهشته‌های با شکل نامشخص، معمولاً سعی می‌شود که این ساختارهای زیرزمینی با شکل‌های ساده شده‌ای شبیه‌سازی شوند. با استفاده از این شبیه‌سازی صورت گرفته، می‌توان پارامترهایی مثل عمق و محدوده نهشته‌ها را برآورد کرد. اما نکته این است که شکل واقعی نهشته می‌تواند کاملاً، متفاوت از شکل ساده شبیه‌سازی شده باشد. بنابراین برای رفع این محدودیت، سطح زیر زمین را با استفاده از منشورهای دوبُعدی چهارگوش تقسیم‌بندی و روش‌های مدل‌سازی را پیاده می‌کنند. در این مقاله با فرض ساختار نامشخص هندسی برای نهشته‌، از روش اصلاح شده مدل‌سازی معکوس فشرده برای داده‌های گرانی‌سنجی استفاده شده است. این روش حجم نهشته ایجاد کننده بی‌هنجاری را حداقل می‌کند که این امر معادل بیشینه کردن فشردگی نهشته است. در اینجا برای به دست آوردن تعداد تکرار مناسب برای همگرایی مدل، از معیار توقف جدید تغییر چگالی استفاده شده است. این روش روی داده‌های مصنوعی بدون نوفه و نوفه‌دار آزمایش شد؛ سپس روی داده‌های واقعی یعنی زغال‌های بیتومینه دهلران به کار رفت. نتیجه نهایی حاکی از لایه‌ای از زغال با عمق بالایی 10 متر است که تا عمق 35 متر گسترش دارد. نتایج حفاری نشان از لایه‌ای از زغال با عمق بالایی حدود 7 تا 10 متر است.}, keywords_fa = {مدل‌سازی معکوس فشرده,مدل‌های مصنوعی,داده‌های گرانی‌سنجی,زغال بیتومینه دهلران}, url = {https://www.ijgeophysics.ir/article_40827.html}, eprint = {https://www.ijgeophysics.ir/article_40827_aade9c5fb471b0410fc678b05667b01e.pdf} } @article { author = {Mirzaei, Mohammad and Mohebalhojeh, Alireza and Ahmadi Givi, Farhang}, title = {Sensitivity of the inertia–gravity waves generation to the degree of baroclinicty}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {109-123}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {The generation of inertia–gravity waves (IGWs) in the idealized simulation of vortical flows is investigated using the isentropic two-layer, primitive-equation model on the sphere. The contour-advective semi-Lagrangian (CASL) algorithm is used to solve the primitive equations in potential vorticity, velocity divergence, and acceleration divergence representation. The CASL algorithm consists of both Lagrangian and Eulerian parts. The Lagrangian part addresses the potential vorticity equation, which is solved by contour advection. The Eulerian part addresses the remainder of the model including the prognostic and diagnostic equations for the grid-based variables of velocity divergence, acceleration divergence and the depth. The Eulerian part is solved by the spectral transform in longitude, the forth-order compact differencing in latitude, and a three-time-level semi-implicit scheme in time. The power of CASL rests in its ability to represent the fine-scale structures in potential vorticity. Therefore, using CASL, it is possible to determine more precisely the generation and propagation of the IGWs generated by vortical flows. The initial state of the numerical experiments is comprised of a balanced, zonal jet with a very small perturbation added to trigger instability. With regard to the balanced initial conditions used, the IGWs are generated mainly through spontaneous-adjustment emission. To determine the sensitivity of the IGWs generated to the degree of baroclinicty, four experiments were carried out in which the upper-layer potential temperature was set to 310, 315, 320, and 325K from the first to the fourth experiment, respectively. The lower-layer potential temperature was set to 280K in all of the experiments. As a result of increasing the upper-layer potential temperature, the static stability increased and thus the baroclinicity decreased from the first to the fourth experiment. To identify the IGWs accurately, the Bolin–Charney potential vorticity inversion was used to decompose the flow into a balanced part representing vortical flow and an unbalanced part representing free IGWs. The analysis of the average growth rate of the baroclinic waves shows that the first experiment has the maximum average growth rate among the four experiments. Increase in static stability from the first to the fourth experiment led to a decrease in the average growth rate, but the time of occurrence of the peak in growth rate increased. The investigation of the unbalanced velocity divergence shows the generation of two wave packets of IGWs during the evolution of the vortical flow in the first experiment; one wave packet on the downstream side of the trough, similar to the mesoscale waves described by Zhang (2004), and the other wave packet on the upstream side of the trough, similar to the wave packet described by Plougonven and Snyder (2007) in idealized simulations of baroclinic life cycle dominated by cyclonic behavior. The intrinsic frequency of both wave packets is close to that found by Wang and Zhang (2007) for the low static-stability experiment. The upstream wave packet appears in the second experiment, but failed to reach noticeable amplitude in the third and fourth experiments. The effect of increasing static stability is even more dramatic on the downstream wave packet, which is identifiable only in the first experiment. Unbalanced linearized available energy (LAE) is used to quantify the strength of the IGWs. The results show that, consistent with the formation of two wave packets, only the first experiment that reached the maximum value of the unbalanced LAE. Due to increased static stability, there is a considerable reduction in peak value of unbalanced LAE. For example, the ratio of the peak of unbalanced LAE in the first experiment is 86 times as great as that of the fourth experiment. Another way to observe the substantial differences in the strength of the IGWs is to measure the maximum norm of the unbalanced velocity divergence. Before and after reaching the peak of the unbalanced LAE, the maximum norms of the unbalanced velocity divergence in the first experiment were between 15 and 21 times as great as the corresponding values in the fourth experiment.  }, keywords = {Inertia–gravity waves,vortical flow,growth rate,static stability}, title_fa = {حساسیت تولید امواج گرانی- لختی به درجه کژفشاری در مدل دولایه‌ای روی کره}, abstract_fa = {در این مقاله، شبیه‌سازی ایده‌آلی از تولید امواج گرانی– لختی در‌ شارش تاواری در یک مدل عددی شامل معادلات بسیط روی کره با دو لایه هم‌دمای پتانسیلی و کاربست الگوریتم عددی فرابرد پربندی نیمه‌لاگرانژی برای حل معادلات، صورت می‌گیرد. شرایط اولیه مدل برای چهار آزمایش شامل یک جت متوازن با دمای پتانسیلی یکسان در لایه زیرین و دمای پتانسیلی متفاوت در لایه بالایی است. نتایج بیانگر آن است که بیشینه میانگین آهنگ رشد ناپایداری در آزمایش اول رخ می‌دهد و با افزایش پایداری ایستایی، میانگین آهنگ رشد کاهش می‌یابد. همچنین در آزمایش اول، تولید دو بسته موج گرانی– لختی یکی در پایین‌دست ناوه و دومی در بالادست آن مشاهده می‌شود؛ درحالی‌که در آزمایش دوم، فقط تولید بسته‌موج بالادست ناوه وجود دارد و در آزمایش‌های سوم و چهارم، دیگر نشانی از تولید دو بسته‌موج فوق نیست. قله انرژی در دسترس نامتوازن نیز بیشینه مقدار را در آزمایش اول دارد و با افزایش پایداری ایستایی، از مقدار آن کاسته می‌شود.}, keywords_fa = {امواج گرانی– لختی,شارش تاواری,آهنگ رشد,پایداری ایستایی}, url = {https://www.ijgeophysics.ir/article_40830.html}, eprint = {https://www.ijgeophysics.ir/article_40830_3d82488f9f014841de13c265aea1432e.pdf} } @article { author = {Rajab-Baiky, Fatemeh and Afsari, Narges and Taghizadeh-Farahmand, Fataneh and Gheitanchi, Mohammad Reza}, title = {Variations of the Moho depth and Vp/Vs ratio beneath East Iran (Birjand) using P receiver function method}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {124-138}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Characterization of the detailed structure of the crust and upper mantel is an important continuing goal of geophysical studies. There are a variety of geophysical methods (seismic refraction, seismic vertical reflection and seismic tomography) to investigate subsurfaces. The teleseismic P Receiver Function (RF) method has become a popular technique to constrain crustal and upper mantle velocity under a seismic station. Teleseismic body waveforms recorded at a 3-component (Z, N-S, E-W) seismic station contain a wealth of information on the earthquake source, the earth structure in the vicinity of both the source and receiver, and mantle propagation effects. The resulting RF is obtained by removing the effects of the source and mantle path. The basic aspect of this method is that a small percentage of the incident P wave energy from teleseismic events with significant and relatively sharp velocity discontinuities in the crust and upper mantle will be converted to S wave (Ps), and arrive at the station within the P wave coda directly after the direct P wave. To obtain P-RF, the following steps are generally used: to utilize data recorded with different types of seismometers, the instrument responses have to be deconvolved from the original records. ZNE components are then rotated into the local LQT ray-based coordinate system (using the theoretical back azimuth and incidence angle).To eliminate the influence of the source and ray path, an equalization procedure is applied by deconvolving the Q component seismogram with the P signal on the L component. The resulting Q component data are named P-RF. An advantages of the RF method is that, because the P-to-S conversion point is close to the station (usually within 10 km laterally), the estimation is less affected by lateral velocity variations. The estimation provides a good point measurement at the station because of the steep incidence angle of the teleseismic P wave. Since the direct P arrival is used as a reference time, it can be shown that the result is not sensitive to crustal P velocity. We compute P receiver functions to investigate the crustal thickness and Vp/Vs ratio beneath the East of Iran (Birjand) and map out the lateral variation of Moho depth under this region. We selected data from teleseismic events (Mb ≥ 5.5, 30˚<Δ<95˚), recorded from 2005 to 2009 at 4 three-component short period stations from Birjand Seismic Telemetry Network. These stations are equipped with SS-1 seismometers with a natural frequency of 1 HZ. The data is recorded at 50-samples-per-second. First of all, is calculated 247 P-RFs for TEG, KOO and DAH stations and then estimated the Moho depth solely from the delay time of the Moho P-to-S conversion phases. Then, we used an H-Vp/Vs stacking algorithm to estimate crustal thickness and the Vp/Vs ratio under each station. The best value for the H and Vp/Vs ratio are found when the three phases (Ps and crustal multiples) are stacked coherently. The results obtained from the P receiver functions indicate clear conversions at the Moho boundary. A notable feature, which can be observed underneath all stations, is the presence of a significant sedimentary layer at about 0.7-1s delay time. The middle crustal layer at about 1.9-3.3s delay time can also be seen beneath all stations. The most coherent conversion, however, is the conversion at the Moho boundary arriving between 4.7-5.4s delay time. As a result of measurements using the Zhu and Kanamori (2000) method, the average Moho depth is found to be approximately 41 km and to vary from 38.5 to 44 km. The crust is relatively thin beneath the DAH station, whereas the thickest crust was observed beneath the KOO station, located southwest of the study area. The crust of Eastern Iran has an average Vp/Vs ratio of 1.76, with a higher ratio of 1.84 in the TEG station and lower ratio of 1.76 in the KOO station.    }, keywords = {P receiver functions,Teleseismic,Crust,Eastern Iran,Vp/Vs Ratio}, title_fa = {تغییرات عمق موهو و نسبت Vp/Vs زیر شرق ایران (بیرجند) با استفاده از روش تابع گیرنده P}, abstract_fa = {مشخص کردن جزئیات پوسته و گوشته بالایی، یکی از اهداف مهم تحقیقات ژئوفیزیکی است. در این تحقیق به کمک تحلیل تابع گیرنده P، ضخامت پوسته و نسبت Vp/Vs از دو روش محاسبه شد. ابتدا با استفاده از تأخیر زمانی بین موج مستقیم P فرودی به زیر ایستگاه و امواج تبدیل یافته Ps از ناپیوستگی موهو و با استفاده از مدل سرعتی مرجع IASP91 (73/1= Vp/Vs وkm/s3/6= Vp)، عمق موهو در زیر هریک از ایستگاه‌‌ها برآورد شد. سپس برای برآورد هم‌‌زمان عمق موهو و نسبت Vp/Vs در پوسته از روش زو و کاناموری (2000) استفاده شد. در این روش به دنبال H و Vp/Vs ای هستیم که به ازای آنها برانبارش دامنه‌‌های فاز تبدیل یافته و بازتاب های چندگانه در زمان رسیدهای پیش‌‌بینی شده، به بیشینه مقدار خود برسد. به‌‌همین‌‌منظور داده‌های بیش از300 زمین لرزه دورلرز ثبت شده توسط 4 ایستگاه ثابت کوتاه‌‌دوره شبکه لرزه‌‌نگاری بیرجند واقع در شرق ایران از 2005 تا  2009 با بزرگای 5/5≤ Mb و در فاصله رومرکزی˚95 >r>˚30 مورد پردازش قرار گرفت. تعداد 247 تابع گیرنده در زیر سه ایستگاه تجگ، کوه شاه و دهنه چاه محاسبه شد. با اعمال روش برآورد هم‌‌زمان عمق موهو و نسبت Vp/Vs، ضخامت متوسط پوسته در منطقه حدود 41 کیلومتر به دست آمد، کمترین ضخامت پوسته 5/38 کیلومتر در زیر ایستگاه دهنه چاه و بیشترین ضخامت پوسته 44 کیلومتر زیر ایستگاه کوه شاه، که در جنوب غرب منطقه مورد بررسی واقع است به دست آمد، همچنین نسبت Vp/Vs به طور متوسط برای منطقه 79/1، که حدود تغییرات Vp/Vs بین 76/1 تا 84/1 است. به‌‌زیرراندگی پوسته اقیانوسی در منطقه بخیه‌‌ای سیستان، حاکی از کاهش ضخامت پوسته در منطقه شرق ایران است که با نتایج به دست آمده هم‌‌خوانی دارد.  }, keywords_fa = {توابع گیرنده,دورلرز,پوسته,شرق ایران,نسبت Vp/Vs}, url = {https://www.ijgeophysics.ir/article_40834.html}, eprint = {https://www.ijgeophysics.ir/article_40834_8b7385ce29f5fee331708c7fbc18c719.pdf} } @article { author = {Kazemi, Malihe Sadat and Ghassem Alaskari, Mohamad Kamal}, title = {Estimation of anisotropy parameter γ in Kangan and Dalan Formations by DSI in a well at South Pars field}, journal = {Iranian Journal of Geophysics}, volume = {5}, number = {1}, pages = {139-150}, year = {2016}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Anisotropy has an important role in exploration and reservoir characterization. In practice, the determination of seismic anisotropy is not easy, but it has important consequences in enhancement of seismic data recording and processing. Anisotropy interacts with reflection seismology, acquisition, processing and interpretation. Ignoring anisotropy can lead to poor seismic imaging, misleading the seismic reflector responses, inaccurate location of well-ties, and incorrect interpretation of seismic arrival times and amplitudes for the determination of lithology and fluid content. Shear wave velocity anisotropy is commonly referred to as shear wave splitting, because a shear wave traveling in an heteregeneous medium splits into two shear waves. At a given receiver, shear waves are characterized by their orthogonal polarization directions (fast and slow) and a delay between their arrival times. The most common anisotropic models have been related to the framework of transverse isotropy or a hexagonal isotropy system. When the symmetry axis is aligned with the vertical axis, the model is called vertical transverse isotropy or VTI. For a VTI medium, there are five stiffness coefficients and three independent phase velocities. Thomsen (1986) replaced these stiffness coefficients with two vertical velocities (Vp0 and VS0) and three dimensionless anisotropy parameters (namely, ε, γ and δ). Anisotropy parameters can be determined in several ways, including velocity measurements on core samples in a laboratory or from field data in a VSP experiment. A common form of anisotropy observed in many geological area (thinly horizontal layers or fractures). This involves the reference axis of symmetry being normal to the bedding surfaces. Thomsen (1986) introduced three anisotropic parameters (ε, γ and δ) to describe weak anisotropy, which is believed to be the simple model of anisotropy. Thomsen parameters can be computed with the stiffness tensor considered in anisotropic media. Alkhalifah and Tsvankin (1995) showed that, for P-wave Moveout, there exists a range of kinematically equivalent models which are governed by the stacking velocity and introduced by the parameter η. The Dipole Shear Sonic Imager (DSI) is an example of devices that are used to obtain and analyze sonic measurements of formations surrounding a borehole. The DSI Imager can measure the components of shear slownesses in many directions in a plane perpendicular to a borehole axis. The DSI tool is a full waveform acoustic tool that delivers measurements of sonic waves in a wide variety of formations. In the conventional DSI logging tool, one can present compressional slowness, Δtc, shear slownesses, Δts, and Stoneley slowness, Δtst, each as a function of depth. The DSI tool can estimate the orientation and magnitude of stress from velocity dispersion. By inverting the dispersion curves from DSI logs, one can estimate the horizontal stresses. One type of these special dipole modes enables the recording of both inline and crossline (perpendicular) waveforms. These modes, both called cross receivers (BCR) which are used for anisotropy evaluation. In this paper, one of the anisotropy parameters of Thomsen (γ) was determined by the use of S-wave velocities and their relationship with the DSI tool used in the Kangan and Dalan gas zones of the South Pars field. Subsequently, the γ parameter was compared with the Gamma Ray log in depth. The results show anisotropy behavior in shaly zones of Kangan and Dalan Formations. It is found that the average of the γ parameter for the Kangan and Dalan Formations are 0.015 and 0.02, respectively. Also, this parameter was compared with slowness based on anisotropy. A good correlation was observed between anisotropy parameter γ and the slowness based on anisotropy (slowness vector).}, keywords = {Anisotropy,dipole shear sonic imager,γ parameter,Shear waves slowness,Kangan and Dalan Formations}, title_fa = {برآورد پارامتر ناهمسانگردی γ در سازندهای کنگان و دالان با استفاده از نگاره صوتی برشی دوقطبی در یکی از چاه‌های میدان پارس جنوبی}, abstract_fa = {تعیین ناهمسانگردی در ژئوفیزیک اکتشافی و ژئوفیزیک مخزن نقش مهمی ایفا می‌کند. نادیده گرفتن تأثیر ناهمسانگردی، عدم تشخیص پارامترهای لرزه‌ای بازتابی و رخساره‌های سنگی را به‌همراه دارد. در محیط ناهمسانگرد یک موج برشی به دو مولفه برشی عمود بر هم تبدیل می‌شود. یکی از معمول‌ترین روش‌ها برای تعیین ناهمسانگردی، بررسی سرعت های امواج برشی در جهت‌های مختلف است.  امروزه  نیاز به تعیین ناهمسانگردی لرزه‌ای به‌طور قابل ملاحظه‌ای افزایش یافته‌است. با نگاره‌های صوتی برشی دوقطبی (DSI) می‌توان سرعت امواج برشی را تعیین کرد. ابزار صوتی برشی دوقطبی، کُندی امواج برشی را در دو جهت روی صفحه عمود بر محور چاه اندازه‌گیری می‌کند. پارامترهای ناهمسانگردی با اندازه‌گیری مولفه‌های سرعت از نمونه‌های مغزه در آزمایشگاه، داده‌های لرزه ای سه بعدی و داده‌های لرزه‌ای قائم آزیموتی تعیین می‌شوند. در این مقاله، پارامتر ناهمسانگردی γ با استفاده از نگاره‌های صوتی برشی دوقطبی محاسبه شده است. این پارامتر در سازندهای کنگان و دالان، در مجاورت یک چاه اکتشافی در میدان پارس جنوبیتعیین گردید. همچنین پارامتر γ با نمودارهای پرتو گاما برای سازندهای کنگان و دالان مقایسه و میزان ناهمسانگردی به‌دلیل وجود شیل تعیین شد. ضمناً پارامتر γ با پارامتر ناهمسانگردی بر‌حسب کُندی (αDT) مقایسه شد. در این تحقیق همبستگی خوبی بین پارامترهای γ و ناهمسانگردی برحسب کُندی به‌دست آمد. با توجه به نتایج به‌دست آمده، میانگین پارامتر γ، در سازند کنگان 015/0 و در سازند دالان 020/0 محاسبه شد.}, keywords_fa = {ناهمسانگردی,نگاره صوتی برشی دوقطبی,پارامتر γ,کُندی امواج برشی,سازندهای کنگان و دالان}, url = {https://www.ijgeophysics.ir/article_40836.html}, eprint = {https://www.ijgeophysics.ir/article_40836_d58034b37f6f8487a395dc2856821fac.pdf} }