JOURNAL OF THE EARTH
Year:2008 | Volume:3 | Issue:1|Papers Count:11

All materials are anisotropic, Although there can be up to 21 independent elastic constants, any material in which more than two are needed is calledanisotropy. More than two elastic constants mean that the material’s properties differ depending on the direction. Seismic wave through anisotropic materials travel faster or slower depend on their direction. The shear wave can be splitted into two pulses, each with a different polarity and travel at a different speed.This phenomenon is calledshear wave splitting. Shear wave splitting of different shear phases can be applied to determine the anisotropy parameters.Parallel, aligned, fluid-filled cracks and microcracks can cause anisotropy and may be sensitive indicators of stress. Thus, for vertically travelingS waves, j (fast direction) is parallel to the cracks and to the maximum principal stress direction. The fast wave speeds in such a medium are identical to those in the uncracked medium (the fast waves do not “see” the cracks.) In this paper, we attempt to automate the choice of analysis window by performing a grid search over different windows to find stable anisotropy direction with minimum error.Finally, for determining anisotropy direction in the crust of Alborz, we use some events where recorded by IIEES seismic broad band station (DAMV, THKV & CHTH). In this study we find out the fast direction of shear wave velocity.

Static correction is very important for seismic survey in rugged exploration areas. A new reflection static correction technique is proposed in the paper. The technique is precise, convenient and effective for short and longer spatial wavelength statics in rugged exploration areas. The technique is composed of 5 stapes: first arrival picking, selection of selections in first arrivals for static calculation, thickness and velocity inversion, error decomposition and elimination and calculation of static correction value. Two field examples are included in the paper.

Prediction of elastic parameters has an important role in the development of oil field.Elastic parameters are important properties, so by knowing them, we can find some variable parameters in reservoir, like pressure, to find the location of oil. In addition, elastic parameters have an important part in the study of isotropy and anisotropy in the earth.Moreover, elastic parameters are a basic way in computing geomechanics parameters in reservoir. For calculation of elastic parameters, we should know compressional wave velocity, shear wave velocity and total density. However, measuring shear wave is difficult and expensive.Therefore in this study we used artificial neural networks for better result. The neural network, which we used, is a feed forward back propagation with three layers and it is made of four neurons in input layer, twelve neurons in hidden layer and one neuron in output layer.With appropriate correlation coefficient in validation process (R=0.91).We used compressional wave velocity, gamma ray, porosity and density for input and shear wave velocity as output, till our network is trained. Then, we can use every well data for input for estimating shear wave velocity and finally elastic parameters.

The earthquakes in Makran and Oman sea and the historical Tsunamies such as one that happened on 27 November 1945 in Makran coast are main reasons for insecurity because of Tsunamie's wave affected in the mentioned area. Also the geophysical interpretation supports this fact. Because of various seismic in this region; it is divided into two areas in this research.The data of earthquakes were used in the current century and historical earthquakes to estimate the Gutenberg–Rishter parameters and the earthquake cycle (recurrence intervals).The distribution of seismic energy released have been drown and analysed. By depth information, slop state of deposit has been analysed and the speed of Tsunami in different places in comparison with different depths of Oman sea has been evaluated. Landslide possibility and height of Tsunamie's wave have been compared in different coast of the Oman sea.

The area under investigation is, Dezful Embayment, between Kazeron and Hendijan faults and investigation of its tectonic position is the main aim of this study. In order to this, results of previous workers have compiled together. In the other hand, geologic and seismologic data have integrated with geophysical data and interpretations. Therefore, it appears that formation of southern Dezful Embayment is the result of basement configuration and its magnetic anomalies is adapted on structural boundaries. Thus, Khark Mish-Hendijan uplift and Borazjan embayment have introduced as basement uplift and embayment.In the other hand, according to all evidence, Hendijan, Khark Mish, Kazeron, Zagros Frontal Faults and Mountain Front faults are basement faults.

The study area is located in North, North-East of Iran, between Shahrud and Sabzevar cities. The most important village of the area is Abbas Abad, where copper mine are located in north and south.At this paper, generally, we have presented “remote sensing applications”; also proposes and operations which have been done on images of area have been investigated. Thereafter by reviewing the common remote imaging systems, short investigation on include of digital images have done. Finally, we explain some notes about alternations, their minerals, and also how separation of units lithology, structural and tectonic separation of units could be done in area.In general, lithologic units of area are include volcanic, volcanio-sedimentary, sedimentary, and metamorphic rocks which formed in Jurassic, cretaceous, quaternary and tertiary periods.The rest of the rocks unit in the area is formed by volcanic, pyroclastic and cenozoic sedimentary rocks. In addition, basaltic, terachyandesite tuff and breccia are located in vast area in the region. In the southern part of the area, before Jurassic period, metamorphic units are located and also in the eastern part, situate carbonatic formations related to the cretaceous period. In the northern-east of the area ophyolite rocks related to the cretaceous period could be considered which are the continuous of southern ophyolite of Sabzevar area.All of the operation which has been done on the satellite images was due to make clarifying of the properties and extension of geological, lithology and mineralized units.These operation could be done in the exploration phase of geological project which in this way we should identify main controller of mineralized as exploration tracers and by combining with geochemical data and field sampling, preparing thin sections and polish sections and chemical analysis, obtain the best result in shortest time of possible. And also because of this, clarification of images must be done in first level.The area in which the object of the study, is investigated by sampling, field working, and also petrography, petrology, mineralogy and geochemical tests is helped to identify the area.By using the satellite images processing technology and librarian documents, also the area is investigate, at least, these images could be notified in economical and exploration development.

In order to determine the mineralized of base elements in Baidjan region, Mazandaran province, the stream sample have been collected. After preparation of net sampling, 266 with weight of 200 gram from<80 mesh size have been collected. These samples, in order to analyzis of base and pathfinder elemens, were sent to laboratory. Univariable and multivariable statistical analysis have been used for determination of caractristical of elements distribution. Then by using AutoCAD software and after calclulted thershold on the base of standard deviation and median value have drrown. The heavy mineral sample collection is the one of the main part of this research that used for anomaly checking and determination of mineralization phases. The total result of these research with field study showed REE, coper, lead and zinc mineralization can be find in this area.

The Mobark Formation (Lower Carboniferous) in south of Shemshak (north of Tehran) is overlain and underlain with disconformable contacts, by the Dozdband and Jeirud Formations respectively. The thickness of the Mobarak Formation in south of Shemshak is 322 meters and is divided into members 1 and 2. These members consist of various facies related to fairweather conditions, but facies related to storm and turbidity currents are also recognized.These facics, based on their depositional environment, belong to four facies groups related to open marine, barrier, lagoon and tidal flat sub-environments.Facies of member 1 related to open marine, bioclastic barrier and lagoonal subenvironments.Open marine facies, particulary the dark grey shales of the deeper part of this environment, make the main part of member 1. Storm and turbidity current deposits are recognized in this member. The carbonate turbidites indicate that member 1 was deposited in a distally steepened ramp during sea-level highstand, similar to the deep (off bank) of the present day bahamas platform. Facies of member 2 belong to open marine, bioclast/ooid barriers, Lagoon and tidal flat sub-environments. Preservation of the ooids indicate high global sea-level and formation of low- Mg calcite ooids. Rocks of member 2 were deposited in a carbonate ramp similar to the southern part of the Persian Gulf.Field and microscopic studies of the Mobarak Formation have led to recognition of seven sequences (3rd order cycle) and several small scales shallowing upward cycles (parasequence). Member 1 consists of three sequences and member 2 contains four sequences respectively. The lower contact of sequence 1 with the Jeirud Formation, contact between sequences 3 and 4 and the upper contact of sequence 7 with the Dozdband Formation are type 1 unconformity (SB1) and other contacts are type 2 unconformity (SB2). These sequences belong to the upper part of Kaskaskia supersequence.