جستجوی مقالات مرتبط با کلیدواژه "fault" در نشریات گروه "زمین شناسی"

In gravity earthquakes that are affected by extensional tectonics in the crust, contrary to the dominance of elastic energy over gravity in strike-slip and compressional mechanisms, gravity is responsible for hanging wall collapse and earthquake occurrence. Therefore, in normal faulting, the release of energy in the form of elastic waves after the interseismic period is different from other faulting mechanisms. With the increase in the volume of the involved mass and the dip of the normal fault, the vertical displacement becomes larger, which leads to a larger released seismic energy and, consequently, an increase in the intensity of the earthquake. Although normally, the dip angle of activation of normal faults is considered to be around 60 degrees, if the internal friction of the rock is low, a lower dip is expected. Therefore, in this situation, the released gravitational energy will not have the ability to emit much seismic energy. The natural examples of the numerical model resulting from this study can be compatible with geodynamic situations that are characterized by the broad and well-known activity of extensional tectonics and related earthquakes. In addition, energy partitioning is important in earthquakes, and the potential energy stored by the volume involved during coseismic collapse can be compared and analyzed with the energy deduced from the magnitude of the earthquake. Regardless of the origin of the earthquake, potential energy indicates the energy allocation ratio, i.e., the ratio of the available energy to the energy released by the earthquake waves. Therefore, the issue of energy emission from other geological phenomena can be raised, according to previous studies. In this research, the estimation of the stress required for the occurrence of block collapse in normal faults has been investigated through the modeling of a two-layered block with brittle upper crust conditions. Therefore, the thinning of the lower crust during the interseismic stationary periods has been considered, and therefore, along with the extensional tectonics, continuous shearing deformation has also been applied. By knowing the extension rate in the interseismic stage, the stress required to break the entire thickness of the tested brittle crust is estimated.

In this article, in continuation of Doglioni's work (Doglioni, 2015), assuming the transfer of the constant deformation of the lower ductile crust upwards, but the different characteristics of the rock materials and the brittle range due to expansion in a conjugate wedge with the main active normal fault, the behavior of faults was investigated through block modeling consisting of a simple double layer with brittle upper crust conditions. It is assumed that the lateral changes in mantle deag with viscous-plastic behavior control the tectonic conditions at the plate boundaries and deformation is transferred from the base of the lithosphere to the earth's surface. Due to the brittle behavior of the upper crust, shallow deformation occurs periodically and the energy accumulated over hundreds of years is released in a very short period of time.

In this study, the order of the model elements is based on a non-structured network in such a way that it prevents the influence of the structure of Sparse matrices on the performance of linear algebra operations. While the lower crust continuously has a shearing behavior, the upper brittle crust is locked, and according to the results, an expansion wedge is imagined, and the width of this triangle is depicted here in such a way that it affects the locked fault with a thickness of about 3.5 km. As the ductile lower crust is thinned by viscous flow during the interseismic stationary period, the brittle-ductile transition zone (BDT) is characterized by a pressure gradient, while the viscous-plastic lower crust shows continuous shear deformation.
 

Continuous shear in the lower crust of the finite element model can indicate the locking of the brittle upper crust in the interseismic period of a seismic cycle. By applying tension of 2 mm per year in the interseismic stage, the brittle crust with a thickness of about 12 km needs about 160 MPa to break under tension. Therefore, the increase of accumulated slip from the boundary of two layers, i.e. BDT, towards the mainshock, 50% of the fractures resulting from the interseismic period are closed again (recovery). Considering the lower extension rate in the current model compared to the previous models, the difference in the result of stress required to break the brittle crust can have a significant relationship with the extension rate.

The Ahangaran Pb-Ag (Zn) deposit is located in the Sanandaj-Sirjan zone and in the NW part of the Malayer-Isfahan Metallogenic belt. Mineralization and mineral horizon in this deposit is formed in dolomitic sandstone and dolomitic limestone of Kc3 unit. The aim of this study is structural analysis and investigation of the fault systems affecting the mineralization in the Ahangaran Pb-Zn deposit. For this purpose, field observations, study of satellite images, orthophoto images and digital elevation models have been used. The results of this study indicate that the nappes moving from the NE to the SW caused the orbitulin limestone of the Kl unit to be thrusted over the younger lower Cretaceous units. The Koh-Darrehghar fault with N33°E trend and left-lateral separation has caused a displacement of about 2600 meters in the eastern part of the study area. Fractures in the study area have three main trends including N20°E to N35°E, N02°E to N20°W and N30°W to N60°W. The Darreh-Somagh, Tunnel and East-Road fault zones are the main effective structures that have divided the study area into four structural zones. These faults with normal separation have caused the displacement of mineralized horizons. The Tunnel and East-Road faults with normal separation and dip towards the east have caused downward movement of the Kc3 unit in the hanging wall. Also, Pb-Ag (Zn) mineralization is widely formed in the fractures of the second and third zones.

Based on the solution of mechanisms in this study, Golbaf, Kuhbanan and Rafsanjan faults have a dominant right-lateral mechanism with a reverse component and Sarvestan fault has a pure reverse dominant mechanism. Earthquakes are mostly scattered around the city of Shiraz near the Sabzpooshan fault system and Borazjan fault. Solved mechanisms also show that earthquakes with a dominant right-lateral mechanism are related to the Karebas fault. Some earthquakes, which are related to the Sabzevaran fault are with the dominant mechanism of strike slip. Earthquakes of the Sabzpoushan fault are with the dominant mechanism of strike-slip right-lateral (N-S active plain). Mechanism of some earthquake is not compatible with any known faults in the range. In the interpretation of earthquakes in of all maps, the location error of the seismicity must also be considered. This error can reach up to ten kilometers (in some cases) due to the intermediate distance between the stations of the seismological networks. The mechanism of some of these faults, which were studied in previous works (geologically or seismologically), are consistent with the mechanism solved in this study.

Qeshm Island, with an area of ​​1,486 square kilometers, is located at the southeastern end of the Zagros Belt and at the western end of the Strait of Hormuz. Since the tectonic era, it seems possible to assess the influence of neotectonics and fault dynamics on island morpho-tectonic deformation using basin tectonic indicators. In this research, five indicators are extracted and calculated using satellite images, geological maps, aerial photographs, and a digital elevation model (30 meters) using various software. The smoothness and asymmetry of waterways (AF), watershed shape index (BS), cross-topographic symmetry index (T), river meandering index (S) and their comprehensive evaluation are evaluated in model form (IAT)). It is an index to evaluate the degree of tectonic deformation in the basin, and the obtained results indicate the relative dynamics of various tectonic deformations on the island. Furthermore, based on the IAT index, 26 of the 44 subbasins belong to a very high tectonic layer, consistent with the number of faults, so more active tectonic deformation is observed in the western part of the island.

The study area is located in the south of Qushadagh mountain range, in the north of Asbkhan village, Heris township and in East Azarbaijan province. In terms of structural geology of Iran, this area is located in the main zone of Central Iran and Alborz-Azerbaijan sub-zone. The geological units of the region are including Eocene igneous and pyroclastic rocks with combination of andesitic, Trachyandesitic, basaltic, tuffic and ignembritic. The semi-deep intrusive mass with Oligocene age, with the combination of quartz diorite, diorite and quartz monzonite in the form of stock and dyke is exposed in the area. Structural studies, including fault plates, slickenside on them, and the joints system in various lithologies, indicate at least two general stress directions in the range, Which can be created following one tectonic regime or two tectonic regimes. If we consider the tectonic regime as a phase and consider the tensors with different directions as the result of rotation in the fault plates, We can introduce a general strike-slip regime with a general north-south trend that controls the existing structures of the region. At the same time, the infiltration of intrusive masses has caused the disintegration of these structures and made the issue more complicated. In general, faults with a northwest-southeast trend and a right on strike-slip mechanism, form the main structures of the area.Other faults are controlled by the main structures following the Riddle fractures system. Based on the system of joints in four different lithologies, lithological units from old to new include: basaltic andesite, quartz diorite, quartz monzonite (porphyry mass) and diorite, which from old to new reduces the diversity of the joints system. The northwest-southeast tectonic system has been involved in the development of argillic alteration and the northeast-southwest system has been important in the development of siliceous and mineralized veins.

Damghan area has been considered by earth scientists due to the existence of numerous active faults. These faults with slow and progressive movements have led to changes in the shape of landforms in the area. Even during the history, the activity of these faults led to major earthquakes such as Qumis earthquake in 856 A.D. This earthquake led to the complete destruction of Qumis province in present-day Damghan. Researchers in the area, including Hollingsworth et al 2010., have concluded that major faults in the area, such as the Astaneh and North Damghan faults, have ruptured during the Qumis earthquake. The changes in landforms and high potential of faults in creating seismic events indicate their continuous activity during Quaternary up to now. To study these changes, we need those features that are sensitive to tectonic and erosive events. Rivers are one of these features that react quickly to active tectonic and erosion changes. The main purpose of this study is investigation of the changes in landforms using anomalies in stream orders. Because there is a hypothesis that claims tectonic and erosive changes lead to irregularity in Strahler orders of streams. In this study we use isobase and differential map method to investigate this hypothesis.

Sensitivity of drainage network to tectonic processes and geological contradictions leads to changes and irregularities in river orders. Isobase maps are extracted from information about the spatial classification of rivers and their elevation information in the environment. In fact, these maps show the relationship between the pattern of waterways and the topography of landscapes. Streams with the same Strahler order are formed by the same geological events, and most likely the same order is the same age. We can draw iso base maps for different stream orders. Early orders (1-3) are mostly more sensitive to tectonic events. These early orders due to flow along seams and fault gaps are representative of neotectonic. Rugged structures in the lithology of the region can limit the evolution and development of the early orders, and therefore in these areas the values of the isobase map increase. But isobase map of evolved orders can represent longer periods, such as the Quaternary or Pleistocene. Because evolved orders are formed over longer periods and are able to show older tectonic and erosive events. Differential maps are obtained from the difference in height between the maps of the evolved orders and the present day topography map.

Examination of the isobase map of the primary orders show that most of the values related to the map can be seen in the west and north of the region. These areas are based on mountainous structures. The high values of the isobase map in these areas indicate that the northern and western parts, affected by neotectonic activities and the development of fault gap and seams, have more primary orders of rivers. Because most of these primary orders are formed and developed along these levels of weakness. Resistant lithology of the area has also prevented the development of these orders. The highest value of them is 3830-2312 meters. The differential map prepared from the study area shows a wide range of positive values indicating uplift and negative values indicating subsidence. By examining these values, we can understand the features related to tectonics and geomorphology of various landforms in the region. The highest values of 1191 to 800 meters are related to the high mountain structures of Eastern Alborz in the north and west of the region. The decrease in the value of the differential map indicates the effect of tectonic subsidence on the morphological landforms of the region. The Astaneh pull apart basin in the western part of the region shows the amount of subsidence between -4 to -1 meters. Also, the southern playa of Damghan in the form of a concave foreland basin affected by active faults in the region shows negative values, which indicates the existence of a submerged basin with high sedimentation potential.

Studies conducted on the area show that the two factors including active tectonic and lithology have a great impact on the morphological structures and landforms of the area. The results of isobase map and the differential map show and confirm this issue. The methods used in this study to investigate the tectonic activity of the faults in the area indicate their activity during the Quaternary. These faults have different mechanisms of thrust and streak slip which in some areas also have transtensional and transpressional position; they have created a collection of uplifted or concave landforms in Damghan area. The spatial relationship between different values from north to south in the prepared maps indicates the creation of an equivalent states between topographic growth and its destruction in lower altitudes. Based on the studies, we confirm that the preparation of isobase and differential maps can be a suitable method for studying and examining morphological structures. Also studies related to differential map show anomalies in drainage networks and uplift processes associated with active Quaternary landforms can be quantified by these maps. Using baseline and differential maps is one of the appropriate methods to study the Plio-Quaternary tectonics in an area. This study confirms the work of previous researchers based on the available information and documents related to the study area.

Spring distribution and flow rate are influenced by a variety of factors such as tectonics, climate, geology, distance from the drainage network, geomorphology, etc. The current study aims to determine the effect of structural parameters, lithology, and drainage network on two indicators related to springs, notably number and annual water flow in Kamyaran, Kurdistan province. Correlation relationships have also been investigated between springs in watersheds and hydrometric stations downstream of them. A correlation coefficient of 0.947exists. The correlation between the number of springs and the distance from the river is significant and is around 0.76. But there is no significant relationship between these two parameters with the amount of spring water. The discharge variable has a significant relationship with the formation type, with the sand limestone formation having the most annual drainage and the andesite, micro granite, and silty shales having the least. The results of the correlation between springs and hydrometric stations revealed that there are significant relationships between temperature parameters and annual discharge, but no significant relationships between pH and EC indicators.

Sirjan-Beshneh copper deposit with 0.5 kilometer area is located in Kerman province 80 kilometers west of Sirjan city. The variety of exploration activities including remote-sensing, field traverses, geophysical explorations, surface explorations comprising surface sampling and geochemical analysis of 94 samples, drilling and surveying three trenches with sampling and analysis of six samples as well as drilling of eight deep exploration borehole with the total length of 414.5 meter, have been carried out in the metallic deposit. All faults in the region were mapped based on the remote-sensing and structural geology operations of the region. In the present research, all exploration activities carried out in the Beshneh copper deposit were analyzed through investigating their relationship with the faults in the region. To achieve this goal, various techniques including drawing rose-diagram of faults, processing of resistivity and chargeability data of rectangle survey and smoothed inversion of data for five dipole-dipole profiles, imaging isograde maps for the surface and trench samples as well as 3-D modeling of exploration boreholes assays of the region were employed. The results showed that locations of mineralization related to the fractures and faults present in the region since the trend of most mineralized veins is along the main faults. At the end, in order to complete the explorations of the previous stages to get a better recognition of the deposit, drilling of several new exploration boreholes was proposed based on all performed studies and integrating obtained results as an exploration key.

Kurdistan dam watershed with an area of 120.15 km2is located in the northeast of Saqez city.The purpose of this study is to analyze the tectonic activity of the basin and the relationship between faults and landslide risk using the information value model. First, the region is divided into 15 sub-basins using ArcHydro software and morphotectonic indexes including Stream Length Gradient Index (SL), Asymmetric Factor (AF), Hypsometric Integra (Hi), Transverse Topographic Symmetry Factor (T) and basin shape ratio (Bs) are calculated and the results are calculated. Their evaluation was evaluated with active tectonics index (IAT). In order to evaluate the relationship between faults and landslide risk, first a map of faults and maps of factors affecting landslides were prepared by processing satellite images of Landsat 8 sensor and ENVI software and field observations. Then, using the information value model, landslide hazard map of the basin was prepared and combined with the fault map and the relationship between faults and landslide risk in ArcGIS. 10.3 environment was reviewed. The results of calculating the relative active tectonics indices show that 77.77% of the basin is tectonically active in the active class and in the information value model 55.55% of the occurrence of landslides is in the range of high instability risk. Distance coefficients from faults in both positive models and most landslides occurred at a distance of less than 1000 meters and due to active tectonics there is a significant relationship between faults and areas with high landslide risk in the basin. The results showed that the information value model has better performance for landslide risk zoning. In general, diversity of lithology, topography, abundant national and local faults and climatic conditions can be mentioned as the most important factors in the occurrence and distribution of landslides.

One of the hazardous area in Golestan province is Vatan-Farsian area which selected as case study. In this research, main and minor faults were determined by using Remote Sensing techniques together field surveys and then, mapped in GIS environment. The Geohazards were distinguished and categorized into: Faulting, Seismicity, Landslides, Slope movements and Erosion. The location of Geohazards were defined by image processing together field surveys and enter to GIS environment as data layers. Then, these layers overlaid on extracted faults and finally, the relationship between them are investigated. The results shown that maximum density of fractures occurred along fault zones. Also, the faults have potential to occurred earthquakes with magnitude < 4. Many of landslides aligned as wide strip with East-West trend between Tilabad and Susara faults. Some rock falls taken placed along Qeshlaq and Vatan faults. Many of sliding occurred in floor of fault scarps. But, the creeps have weaken relationship with fault zones. The weathering shown in Qeshlaq, Farsian faults and in a fault which controlled the Tillabad river trend. Sloppy erosions show in fault scarps. River erosions haven’t any direct relationship with faults. So, the result shown that faults caused to taken placed and/or defined the location of Geohazards.

The Takab-Qorveh magmatic lineament between the Urumieh-Dokhtar and the Sanandaj-Sirjan zones contains important gold mines such as Dashkasan and Zarshuran. The Dashkasan deposit is located in the Kurdistan province and is one of the largest gold deposits in the Middle East domain. The gold is mainly hosted by porphyritic dacite and breccia. In spite of detailed previous studies, there is still debate regarding the genesis of the Dashkasan. Herein, this study present the source and evolution of the mineralizing fluids using the fluid inclusion and stable isotopic investigations. At Dashkasan, the breccia and mineralization are constrained by the steep NNE-SSW-trending faults. Alteration zones on the surface are phyllic, silicification, tourmalinization, argillic and minor propylitic. Sulfide minerals consist of pyrite, marcasite, arseno-pyrite, stibnite, chalcopyrite and to lesser amounts of bornite, sphalerite and galena associated with quartz, tourmaline, sericite, calcite and chalcedony. Result of microthermometry measurements shows a range of homogenization temperatures between 183-260 °C with salinities of 15.97 to 17.06 wt % NaCl equiv. The oxygen isotope composition of fluid in quartz ranges from 6.6 to 9.9 ‰, while, the tourmaline has δ18Ofluid values are in the ranges of 8.5 to 12.3‰. Also, the δDfluid values of the quartz and tourmaline ranges between -51 to -81 and -93 to -111‰, respectively. Integrating with previous studies, all these data, suggest a migration from a porphyry gold system (stage-I) with a magmatic source to a low-sulphidation epithermal (stage-III). Stage-II occurred simultaneously with the collapse and eruption of crater.

In this study, a range of 50 km radius of Semirom city for the seismotectonic and seismicity evaluataion is selected. A list of earthquakes happening in the area is prepared including 156 instrumental earthquakes with magnitudes of the unit Mw ≥ 3 since 1973 to 2018. Based on obtained results, due to the location of the study area in the Zagros Zone, seismotectonical mechanisms and structures of Semirom city influenced by this zone. Also, most earthquakes in the range of radius 50 km of Semirom region under the action of the Zagros reverse faults. The seismicity of the studied area from the north and northeast to the southwest is increased. Finally, by Kijko (2003) method, seismicity parameters, the annual rate of occurance and earthquake return possiblility for studied area is calculated.

One of the essential studies in exploration, exploitation and development of hydrocarbon fields is to evaluate the fault and fracture systems and the role that they can play in reservoir quality and geometry. If the hydrocarbon reservoir is a fractured carbonate reservoir, assessing the mentioned properties is of great importance. Assessment of the structures should be done simultaneously because of their close relations, and the their probable genesis connection should be revealed. In this research, subsurface data including 2D seismic profiles, underground contour maps and FMI log and eventually analogue modeling have been used for evaluation of probable scenarios explaining formation of faults and fractures. The studied area is located at the front of Zagros deformation belt and the Zagros stresses have apparently not affected it. Two sets of faults of different geometry and role have been detected; the first reverse set (N-S trending) was apparently controller of the reservoir geometry in the structure; the second normal set (NW-SE trending) are most likely causative of the main fractures in the field. It is likely that positive inversion tectonic of the basin led to the development of this field in form of a pop-up structure. Based on the interpretations, the internal normal faults have been formed probably by the rise of Hormuz salt or by local stretching due to left-lateral component of the boundary reverse faults. Using interpretation of drilling-induced fractures and break-outs derived from FMI, trends of the Shmax and Shmin are determined. Also it was revealed that the natural fractures and the main set 2 of faults are sub-parallel with the fractures induced by drilling. Therefore, the compatibility between trends of the natural fractures, breakouts and local normal faults can suggest a tectonic origin for the natural fractures.

The Ghir fault zone is a thrust zone in the Zagros foreland folded belt that is located in the south of Sabz-Pushan shear zone and southeast of the Kar-e-Bas strike-slip fault zone. It is a moderately-dipping fault zone oriented parallel to the general trend of folds and thrusts in the Zagros foreland folded belt. In this study, two methods using fault slip data and focal mechanism of earthquakes were analyzed using the stress inversion method in order to reconstruct the paleostress and recent stress orientations, respectively. The results show a transpressional deformation with current compression direction along N05°E and the mean paleo-compression direction alongN33°E. Both are consistent with the general direction of compression in Zagros due to convergence of the Arabian and Iranian plates, and indicate an anticlockwise change in the compression direction over time and the Mohr circle patterns show an active transpressional zone. The stress ratio of 0.88 obtained from inversion of earthquake focal mechanism data indicates that the shape of stress ellipsoid is oblate. However, a ratioof 0.2 for obtained from inversion of fault slip data indicates a prolate shape of stress ellipsoid.

Faults are among the most important geological events for hydrocarbon and mineral exploration and geological studies. They are considered as the major hydrocarbon traps whose detection in seismic reflection data have important roles in hydrocarbon reservoir characterization and geomechanical studies of reservoirs. According to previous studies, approximately 75% of the oil fields are associated with faults. Faults can influence the efficiency of hydrocarbon reservoirs by improving the permeability of a porous medium. Faults are defined as a discontinuity along a geological layer or geological event which is the result of the failure of that layer or event against the tension exerted on it.
Reflection seismology is one of the best geophysical methods for hydrocarbon exploration. Various methods have been introduced to identify faults in seismic reflection data. In seismic reflection data, faults can be seen as discontinuities along the reflectors. One of the conventional methods of interpretation of the faults is a manual interpretation of seismic horizons which is a highly time-consuming process. Due to the nature of the seismic data, identification of faults plane in this data is a difficult process.
Seismic attributes are considered as useful tools that will reveal hidden information in seismic data which can help the interpreters to detect faults. In fact, a seismic attribute can be used as a filter that makes the structural and stratigraphic information more apparent from the seismic data. There are several seismic attributes for faults detection in reflection seismic data such as coherency, curvature, chaos, and variance. The seismic coherence attribute is one of the most common attributes for fault detection. This attribute is calculated by different criteria such as cross-correlation, semblance, eigenstructure, gradient structure tensor.
In this paper, we used a new form of a seismic attribute for edge detection. It is the Sobel filter which is a widely used tool in image processing, computer vision, and edge detection problems. It is the first derivative of the image and is sensitive to amplitude changes. It is a discrete differentiation operator, computing an approximation of the gradient of the image intensity function by convolving the isotropic operators. These operators are extensible to higher sizes and dimensions. Therefore, the Sobel attributes can be used in two- and three-dimensional seismic data. It can be used in seismic data for identification of the geological events such as faults, salt dome, and buried channels.
The efficiency of dip guided Sobel attribute is evaluated by applying it to both synthetic and real seismic data. We compared the obtained results with the results of conventional seismic coherency attributes. In this paper, we used the eigenstructure-based coherency attribute. Comparison of the results of synthetic models in both noise-free and noisy cases in two and three dimensions show that the dip guided Sobel filter can be a good alternative for coherence attributes. In comparison with the coherence attributes, dip guided Sobel attribute is a short run time process and has large stability against noise. In real seismic tests in two and three dimensions, the obtained results from two attributes show that the dip guided Sobel attribute performs better than the eigenstructure-based coherency attribute.

In this study, we tried to dentify the fractures and faults of Khaviz Anticline, north of Behbahan, by using the ETM satellite images and the Digital Elevation Model (DEM) in the ENVI 4.8 and Arc GIS software environments. Therefore, the lineaments were identified using the linear filters in different directions and the hillShade map constructed from the DEM. Subsequently, the lineaments were compared with the constructed band combinations and the geological map to separate the fractures and faults. Based on the findings, the dominant direction of the fractures and faults follow the northwest-southeast (NW-SE) trend along Khaviz Anticline. Assessment the ISODENSITY map of the faults and fractures indicates that there is the utmost accumulation of the fault and fractures is in the south limb of Khaviz Anticline, Then by considering the important role of fractures and faults in migration of hydrocarbons, the southern flank of this anticline can acts as a suitable area for accumulation of hydrocarbons

In this study، horizontal gradient and analytic signal methods have been applied to the reduced aeromagnetic data poled to Iran، to explore subsurface structures in the region. By using these two methods، it is possible to present a map of major geologic-magnetic structures especially large-scale faults displaying magnetic signal in the region. Qualitative and quantitative results of this study were then prepared as maps and compared with previous studies. Finally، the agreements and disagreements observed against the previous studies were explained.

The main objective of interpretation of acquired gravity data on the Earth''s surface is to determine the contrasts in density or shape/dimension of mass anomalies. Interpretation of gravity data can be done through an inversion process. In this research، a block model has been considered for the subsurface anomalous mass. By considering a constant initial density (about 2. 6 gr/cm3) for all blocks and by using inversion method، distribution of density of the anomalous mass was estimated and interpreted. In this research، Occam method is used to invert 246 gravity data collected in 2007. Results of the gravity data inversion show sufficient fit between observed and calculated gravity data. Using this inversion method، distribution of density in the subsurface layers related to sediments and basement are estimated in this area. Since there is a density contrast between sedimentary layers and basement، the estimated density distribution can help to explore the lithology of formations as well as the discontinuities in them. Densities less than 2 gr/cm3 in horizontal and vertical sections obtained from the inversion are attributed to the alluviums. The depth of these sediments، which include sand، silt and clay of different percentages، is estimated to be less than about 200 m. Unequal density distribution along the layers is taken to indicate fractures. In fact، these fractures are associated with part of the Tabarteh fault in this area، which caused numerous earthquakes (but less than 5 Richters in magnitude) around the Arak and Dawood Abad cities in past years.

Kabir-Kuh and Chenareh anticlines are located in the Lurestan Province of the Zagros fold-thrust belt. The geometry and kinematic evolution of folds in the Zagros fold-thrust belt are controlled by thrust faults. In this paper, the geometry of the Kabir-Kuh and Chenareh anticlines is investigated in order to analyze their deformation style. To analyze the deformation style of these anticlines, five structural cross-sections were measured perpendicular to the axial surface trace of the anticlines. Based on geometric and kinematic analysis, Kabir-Kuh and Chenareh anticlines have a geometry similar to faulted-detachment folds with multi-detachment levels. The detachment level above which the folds formed is probably located in the Lower Paleozoic series. Also structural cross-sections represent an important contribution of the Dashtak Formation as intermediate level in the development of deformation in this part of the Lurestan Province.