JOURNAL OF THE EARTH
Year:2010 | Volume:5 | Issue:3|Papers Count:14

Probabilistic methods are helpful for characterizing earthquake prediction. The seismic process can be modeled as a renewal process using a list of strong earthquakes (M³6.5) from 1900 until now which occurred in the Zagros fold-thrust belt. Two renewal models have been used. The model parameters have been specified by the method of moments and the method of maximum likelihood.We conclude that the gamma model gives the better result than the lognormal model. The probability of the occurrence of the next large earthquake during a specified interval of time can be calculated for each model.Also by maximizing the conditional probability for each model, we estimated approximately the recurrence time of the next strong earthquake in this region. The next earthquake with M³6.5 may occur before 2012.577±5.333 (yrs) and 2012.o46±5.25 (yrs) by using the Gamma model and Lognormal Model, respectively.

Significant ground water level changes have been recorded in most earthquakes of the world. Nowadays these are used as powerful tools to predict future earthquake, get information of new water sources and conquer water crisis after earthquake occurrences.Historical and instrumental earthquakes of Iran indicate that most of them were accompanied by considerable ground water level changes in the region. Therefore ground water level changes in Zarand earthquake were examined according to hydro geological data in a 4 year period, between 2002 and 2006. Then, ground water level changes in February 2005, Zarand-Dahuiyeh, earthquake, were analyzed in detail. The results showed that the earthquake caused considerable water level drop in Qanats nearest to earthquake epicenter. In addition to these negligible changes, water level records of nearest piezometers to fault revealed that general trends of changes before and after the earthquake were the same.

One of the linear noise attenuation methods is t-р transform. By transformation of seismic data to t-р domain and applying a filter in this domain, we can attenuate linear noise. Results of this method on synthetic and real data show that t-р transform has good application in linear noise attenuation and when reservoir study is the case, t-р transform is preferred to F-K filter for linear noise attenuation.

Separating upgoing and downgoing waves is so important in the VSP interpretation. In this paper, visualization of eigenimage from SVD is used for separating upgoing and downgoing waves. The results of SVD method on synthetic data are then compared with f-k method. For this purpose, using 2-D Fourier transform requires uniform sampling in both time and space.In applying median filter for separating upgoing and downgoing waves, one of the events must become aligned carefully. According to the obtained results from implementation of SVD method on synthetic data, we can express that because of unneccessity to both uniform sampling and exact alignment, SVD method is prefered. Also, according to theoretical foundations of eigneimages, automatic noise attenuation through the proccessing is another adventage of SVD method.

Quality factor of seismic waves, Q in the lithosphere at high frequencies (1 to 20 Hz) is one of the most useful parameters to explain attenuation of seismic waves as an important property for the study of earth structure which contains meaningful information even in short distances. Many methods have been innovated for measuring Q factor by using natural and artificial data. In this investigation which determines Q for Tehran region we used single back scattering method by Aki and Chouet (1975) using coda wave. The used data in this investigation is from Tehra City Seimogragh Network (TCSN) which contains 13 short period seismographs (1-15 Hz). In this network more than 500 events had been recorded in four year and we could locate 425 events accurately to choose for processing.After processing we proposed a relation for Q in Tehran region as Q=65 ¦ 0.89, that confirms increasing of Q with frequance.

Because of the reflection and refraction of the electromagnetic (EM) waves at both horizontal and vertical interfaces separating the media of different electrical parameters, geoelectromagnetic methods have been developed and employed to recognize the geological features and particularly fault zones in many regions. Due to its lateral resolution and also greater depth penetration, the magnetotelluric (MT) method is one of the most effective EM techniques to image the subsurface structures electrically. During year 2007 wide frequency range magnetotelluric measurements was carried out in Arak area, Iran to understand the crustal electrical conductivity of the region by putting emphasis on relocating the fault zones.The electric and magnetic field components were acquired along a profile across the geological trend at 3 stations. A robust single site processing followed by the inversion and one dimensional as well as two dimensional modeling were performed. The inversion results revealed electrical conductivity structures in good correlation with geological features. As a significant result, true location of a major fault, Talkhab, was recognized in Arak area.

AVO analysis is a technique for studying on pre-stack seismic data. Today, estimation and crossplotting attributes can be used to identify lithologies and pore fluids. In this paper, we study the Poisson reflectivity (PR) and the normal incident reflectivity (NI) for identifying lithologies and pore fluids. Two models are considered as a class II AVO model. They are including water-saturated sand and gas-saturated sand fenced in shale layers. First, we generated a color-coded seismic section using color coding method in NI-PR cross-plot that colors replace the numbers. In this way, we can indicate that the AVO clustering in each time sample and each offset. This technique directly helps to commentator to distinct the AVO class anomalies in special time and location on a stack section. We noticed that the bright spot or the dim spot technique is not successful to infer the class II in NI or NI*PR section. But the (PRÙ2-NIÙ2) /2 attribute generates a section that class II AVO anomalies is mapped as class III AVO anomalies and class III will be associated with the bright spot. Therefore, PR attribute besides NI attribute can be useful to indicate class II AVO anomalies by mapping in class III and the bright spot in a seismic section.

Khatunabad region with 78 square kilometer located NW of Iran. It’s a part of Urumieh–Daughter zone. Morphology is affected completely by main faults with W-E and NW-SE trend. The alteration zones are directly along the faults. Two type of mineralization have been recognized in this zone. The disseminated copper mineralization in volcanic units and copper and molybdenum mineralization in sub volcanic dacite porphyry stocks. The aeromagnetic geophysical and structural and geochemistry data, all shows good relation with mineralization zones.

The Lakarkuh fault is located in north of Kerman province, in the central Iran structural unit. The main objective of this paper is to investigate structural characteristics of the Lakarkuh fault by using morphotectonic and neotectonic indices. The variety of structures indicate that the Lakarkuh fault can be devided into three (northern, middle and southern) segments. In northern and termination splay structures are dominant. Dip of the fault in northern segment is towards southwest, in southern part is towards northeast and in the middle part (towards north) which is mainly mountaineous.

Geological constructors and hydrogeclogical characteristics are amang the effective factors in relation to quality of ground water. In this study in order to investigate ground water qualitatively, a number of water resources have been closen and main onions and cations existent in them were measured and also electrical conductivity, total dissolved solid, sodium adsorption ratio and hardness were measured and differences them were investigated. The investigations show that the water is of sodium bicarbonate type. Also investigations of waters in view of pot ability and suitable for irrigation in view of pot ability is between good to medium level, and in view of being suitable for irrigation more than 60 percent of samples are in category S1C2 and S1C3 show between good to medium level.

This structure is typical of this oil-reach area and is mainly composed of carbonate successions. This reservoir has a matrix with appreciable porosity but low permeability, while fractures have negligible porosity and very high permeability. To achieve maximum recovery during hydrocarbon production, in addition to reservoir geology, changes in the fluids pressures during production history and hydrodynamics should be carefully investigated. To evaluate controlling factors for petroleum recovery from the studied reservoir various data are gathered from this field that include: cores and cuttings, thin sections, electric logs, results of Drill Stem Tests (DST) and as well as production data for history of this field. The more important data in this regard are, Analysis of the reservoir fluids pressures, Gas-oil ratio in production, Production Mechanisms, Reservoir Hydrodynamics, Interpretation of pressure stabilization in the reservoir, Pressure Distribution Patterns in different Sectors and else. Using static pressure data of different wells as well as variations in the pressure distribution patterns and permeability data this oil field is divided into three domains including Northern, Southern and Western sectors. The more important results, Determine Hydrodynamics and production sector was for MDP (Master development Plane).

The Bangestan Group (Middle-Upper Cretaceous) in southwest Iran includes Kazhdumi, Sarvak and Ilam formations. To study facies, depositional environments and sequence stratigraphy of Kazhdumi and Sarvak formations in Fars area, stratigraphic sections of Buzpar well no.1 (Kazhdumi and Sarvak formations), Namak Kangan (Kazhdumi Formation) and Kangan (Sarvak Formation) have been studied.Facies studies of the Kazhdumi Formation led to recognition of siliciclastic and carbonate facies. Sandstones of the Kazhdumi Formation (Quartzarenite) were probably deposited in a beach environment. Carbonate facies of Kazhdumi and Sarvak formations were deposited in open marine (A), barrier (B), lagoon (C) and lower intertidal (D) facies belt.Facies types and their vertical changes and comparision with recent and ancient depositional environments indicate that the facies of the Kazhdumi and Sarvak formations were deposited in a ramp platform.Sequence stratigraphy indicates that Kazhdumi and Sarvak formations in Coastal Fars include two depositional sequences and in Sub-Coastal Fars consist of three depositional sequences. The first sequence (Upper Albian- Lower Cenomanian) in Kangan and Buzpar sections (Coastal Fars and sub- Coastal Fars) includes the Kazhdumi Formation and the lower part of the Sarvak Formation (Lower Madod). The lower boundary of first sequence is a type 1 sequence boundary (SB1). The second sequence (Lower-Middle Cenomanian) includes the middle part of the Sarvak Formation. The contact between the first and second sequence is type 2 sequence boundary (SB2). The upper limit of the second sequence is the laterite horizone related to Cenomanian- Torunian unconformity in Kangan section. The third sequence (Middle Cenomanian) include the upper part of the Sarvak Formation in Buzpar well no.1. The lower boundary of third sequence is a type 2 sequence boundary (SB2) and the upper boundary of this sequence is a type 1 sequence boundary (SB1).

The area under investigation is including some parts of Tehran, Mazandaran and Semnan provinces, with 23985 km area. In this dissertation, geological maps and ETM satellite data used to remote sensing investigation by ENVI.4.0, ER Mapper7.0, ArcView GIS3.3, Tectonics FP, GIS 9.2, PCI Geomatica software. According to this, first geocoding and then filtering and finally, the lineament map has prepared. In the other hand, fault map has prepared, base on geological maps, too. Finally, it has analyzed and compared with the lineament map that caused to introducing several new lineaments.