Descriptions of reservoir parameters are necessary for recognition of hydrocarbon reservoir. According to this fact that the compressional waves data are more available than shear waves data, estimation of shear waves velocity from petrophysical data always is one of the serious challenge in hydrocarbon reservoir description. The significant parameters that affect waves velocity in carbonate rocks are porosity, porosity type, mineralogy, pressure, fluid saturation and temperature. In this paper by using hydraulic flow units based on experimental data, different rock types are studied and then relationship between shear waves velocity and compressional waves velocity is determined in each flow unit. The results represent acceptable match between shear waves velocity and compressional waves velocity in hydralical flow units, so that correlation coefficient in different hydraulic flow units are 0.89, 0.94, 0.84. whereas this coefficient for all samples is 0.58.

Wave velocity and attenuation are among the most important attributes of stress waves that propagate through geomaterials. Utilizing these attributes, it is possible to acquire useful information about porous geomaterials such as soil and rock and also the fluids that saturate the pores of geomaterials. The key point in order to gain these informations is to establish an accurate link between field measurements of wave attributes and physical properties of geomaterials’ skeleton and pore fluid. The pore fluids and their inhomogeneous distribution fluid are among factors that affect wave velocity and attenuation to a considerable extent. Patchy saturation of pores which occurs on the scale larger than grians size but smaller than wavelength is one of the reasons that causes inhomogeneity in pore fluid distirbution. The influence of such inhomogeneity is studied in present paper. Two different attenuation mechanisms including relative movement of fluid with respect to solid phase and also attenuation caused by grain to grain contact are implemented to fully assess wave attenuation. It is observed that the former attenuation is more dominant at higher frequencies compared to the latter attenuation.

Stress waves contain useful information about the properties of porous materials; they can be recovered through different non-destructive testing methods such as crosswell, vertical seismic profile, borehole logging as well as sonic tests. In all these methods, it is crucial to assess the effects of frequency on wave attributes including velocity and intrinsic attenuation. The dependency of permeability on frequency which is known as dynamic permeability and its effects on wave attributes of compressional waves are investigated in the present paper. Utilizing the dispersion relation derived for compressional waves, it is shown how the velocity and intrinsic attenuation of waves propagated in water saturated sand may be influenced by dynamic permeability. In low frequency range (viscous dominated flow regime), the dynamic permeability behaves like Darcy steady-state permeability and its effects on wave attributes are negligible. However, deviations from Darcy permeability start to occur at higher frequencies. Therefore, it is important to know how dynamic permeability controls the behavior of wave velocity and intrinsic attenuation in relatively high frequencies. For example, it is demonstrated that neglecting dynamic permeability results in overestimation of velocities of fast and slow waves in high frequency ranges (inertia dominated flow regime).

Scope of this paper is the application of Krief’s method to petrochemical interpretation of an oil/gas reservoir in southwest of Iran. The base of this method is via shear and compress ional waves. Recent development in oil industry and full-waveform sonic tools have renewed interest in the interpretation of the velocities of compress ional and shear waves and their relationship to the litho logy and the petrochemical parameters of formation. As we know, original researches, such as the Wyllie and the Raymer equations, are currently used in a petrochemical interpretation of formations. But these equations deal only with the compress ional wave. In this paper the Krief’s method would be reviewed and applied to an oil/gas research in southwest of Iran. This method is based on a relationship between the squares of the velocities of the compress ional and shear waves and porosity of a formation, which is derived half theoretically and half empirically. A cross plot of the squares of the velocities of the compress ional and shear waves shows the quasi-linear relationship between the squares of the velocities.

Knowledge about sound transmission in ocean sediments helps oceanographers to study underwater acoustics, especially in seismic wave propagation modeling. In this paper, we study shear and compressional wave velocity in sediments. Because of the absence of related studies in Iranian part of the Persian Gulf and the importance of acoustical oceanography researches in this area, we focused on the calculation of wave velocity. We applied ROPME (Regional Organization for the Protection of Marine Environment) sea area cruise data which were obtained in summer 2001. We used Hamilton geoacoustic model to analyze shear and compressional wave velocity. Sediments in this area are composed of mud and sand. Results show that shear and compressional waves velocity increase when water temperature decreases (which are unlike with variations in sea water) and increase while water density in sediments increases.

Shear wave velocity ( ) and its average based on travel time from the surface to a depth of 30 m, is known as ( ) are often used in engineering projects to determine soil parameters, evaluate the dynamic properties of the soil and classify it. This quantity is directly related to the important property of soil and rock, i. e., their shear strength. The average shear wave velocity is used in geotechnics to assess soil liquefaction and in earthquake engineering to determine soil period, site amplification coefficient, and determination of attenuation. Usually, the average shear wave velocity is obtained from shear wave refraction survey, PS logging or from shear wave velocity profile obtained by inversion of experimental dispersion curve of surface waves. Surface wave analysis is one of the methods for estimating the profile of shear wave velocity, but inverting of dispersion curve is a time-consuming part of this process and also, the inverse problem has a non-unique solution. This becomes more evident when the goal is to determine a two-or three-dimensional shear wave velocity model. This study provides a method to estimate directly the average shear wave velocity ( ) as well as the average compressional wave velocity ( ) from dispersion curves of surface waves without the need to invert the dispersion curves. For this purpose, we need to exploit the relation between surface wave wavelength and investigation depth. Estimating the wavelength-depth relationship requires access to a shear wave velocity model (a reference model) in the study area, which can be obtained from well data, refraction seismic profiles, or by inverting one of the experimental surface wave dispersion curves. The is then estimated directly from dispersion curve using the wavelength-depth relationship. In addition, due to the dependence of the value of to Poisson's ratio and the sensitivity of the estimated wavelength-depth relationship to this ratio, we estimate the Poisson's ratio profile and average compressional velocity ( ) for the study area, from the. For a given range of Poisson's ratio values, theoretical dispersion curves of the synthetic earth models are determined by forward modeling. Then using these dispersion curves and estimated average shear wave velocity of the model, the wavelength-depth relationship corresponding to each Poisson's ratio is determined. In the next step by comparing experimental and estimated wavelength-depth relationships, one can estimate the Poisson's ratio at each depth. Then the average compressional wave velocity ( ) is estimated using the and the Poisson's ratios. We evaluated the performance of the proposed method by applying on both real MASW seismic data set from USA and synthetic seismic data. The synthetic data collected over synthetic earth model and showed that the average shear and compression waves velocities are estimated with uncertainty of less than 10% in layered earth model with very large lateral variations in shear and compression waves velocities. According to the results, the proposed method can be used to take the non-destructive advantages of the surface wave method in engineering, geotechnical, and earthquake engineering projects to get the average shear wave velocity

In this study the effect of different petrophysical parameters on the velocity of compressional waves has been studied. A coloumn of 70 m height has been selected from the Asmari formation in one of Iranian oil reservoirs. The petrophysical parameters were determined for 150 plug samples. The well logs obtained for desired depths were evaluated and corrected to obtain a correlation between the petrophysical properties and the velocities. The data from petrophysical experiments and well logs were matched.The results show a scattered linear relation between the velocity of compressional waves and porosity values, but the variation of velocity has been formulated as a function of porosity and density. The effect of depth, density, and absolute permeability has also been analyzed.

In this paper, the velocity values of shear and compressional elastic waves of Phyllite limestone samples obtained both theoretically and practically are compared. These rock samples were performed in cubic shape. At the room pressure and temperature, the velocity values for these samples were measured using the first arrival times of elastic waves along the mentioned samples. The frequency of compressional waves was 63 kHz and that for shear waves was 33 kHz. The velocity values of compressional and shear waves for different incident angles such as 0, 30, 45, 60 and 90 degress between the receiver and the transducer were measured. In the theoretical stage, the crack density and dynamically Lama's constants were computed using Budiansky and O'Connell (1974) theory. Then, the theoretical velocity values of the same samples were calculated based on Hudson (1980) theory. The obtained results showed that a good correlation exists between the calculated and the measured data for the samples with low crack density. While for the samples with a high crack density the correlation is poor when the incident angles were at 30, 45 and 60 degrees. This difference between theory and measurements might be attributed to the presence of inclusions and inhomogeneity in the rock samples.

Seismology has an important role in identifying earth structure using seismic waves. The amplitude and frequency of these waves change when they pass into the earth due to anisotropy and heterogeneity. Seismic waves decay as they radiate away from their sources, partly for geometric reasons because their energy is distributed on an expanding wave front, and partly because their energy is absorbed by the material they travel through. The energy absorption depends on the material properties. The amplitude of seismic waves decreases with increasing distance from earthquake, explosion, and impact sources. How this amplitude decrease, occurs, how rapidly it occurs, and how it depends on the frequency of the seismic waves is fundamentally important to the efforts to describe Earth structure and seismic sources. Attenuation of seismic waves is expressed with inverse quality factor (Q-1) and helps us to understand the physical laws governing the propagation of seismic waves in the lithosphere. The observed seismic-wave amplitudes usually decay exponentially with increasing travel distance after the correction for geometrical spreading. These decay rates are proportional to the Q− 1 values which characterize the spatial attenuation of seismic waves. The study area is located in Fariab region, south-east of Sanandaj-Sirjan metamorphic zone and adjacent to the Main Zagros Reverse Fault (MZRF). This rejoin is among the rare regions located in Sanandaj-Sirjan area which has high seismic activity. Seismicity in this area has a north east-south west trend. Depths of events are relatively low, in the range of less than 40 km. The 28 Feb. 2006 earthquake with a magnitude of Mw=6. 0 has taken place in this region. Despite the remarkable magnitude of this earthquake, no significant damage was reported, even for low strength buildings such as clay buildings. This phenomenon may indicate a significant attenuation of the elastic wave in the area. Aftershocks of this event have been recorded by a temporary network. The well-located aftershocks, with hypocentral distances less than 100 km, have been used for estimation of the P-wave quality factor. The attenuation of P-waves has been estimated using waveforms of 431 well-located aftershocks. The attenuation of P-wave (QP-1) has been estimated at 5 frequency bands (1. 5, 3, 6, 12, 24 Hz) using extended coda normalization method. The estimated QP values show highly frequency dependency. The frequency dependent relation for longitudinal waves in the study area has been derived as Qp=23f-0. 78. The QP values have been estimated by using waveforms with two major directions to investigate the probably existed attenuation anisotropy. The frequency dependent relation in two directions of north west-south east and north east-south west were calculated as Qp=10f-0. 94 and Qp=25f-0. 75, respectively. It has been observed that the quality factor value at the reference frequency of 1 Hz is smaller than 200, which is reported for seismically active regions. Therefore it could be concluded that this region is active in terms of seismicity and tectonics. The small values of the quality factor which demonstrates the relatively high attenuation indicate high seismic activity of this region. This is not so compatible with what we expect for the earth’ s crust structure in this area with the metamorphic zone. This high attenuation is probably due to the crushed zone affected by various earthquakes in this region.

A B S T R A C T Temperature is one of the climate elements that has fluctuated a lot over time. When these fluctuations increase and decrease more than normal and are placed in the upper and lower regions of the statistical distribution, if continued, it can lead to the creation of heating and cooling waves. The purpose of this study is to analyze the temporal and spatial changes in heating and cooling waves in Iran during a period of 50 years. For this purpose, the temperature of 663 synoptic stations from 1962 to 2004 was obtained from the Esfazari database. Then, in order to complete this database, the daily temperature from 2004 to 2011 was obtained from the Meteorological Organization of the country and added to the aforementioned database. In order to perform calculations and draw maps, Matlab, grads and Surfer software have been used. The results of this study showed that the index of cooling waves and heating waves, while having a direct effect on each other, had an increasing trend in most of the area of Iran. The statistical distribution of the index of cooling waves is more heterogeneous than that of the index of heating waves. So that the spatial variation coefficient for cold waves is 84.22%. Also, the index of cooling waves has more spatial variability. The highest common diffraction of the index of heating and cooling waves has been seen in the northwest, east and along the Zagros mountains. Analysis of the indexes trends show that heat waves have intensified in 65.8% of Iran and the intensity of cold waves has decreased in 48.5% of Iran Extended Abstract Introduction Temperature is one of the major climatic variables, which it has a direct impact on different aspects of human life. It plays an essential role in the growth of crops and is considered a key driver of the biological system(Reicosky et al, 1988). It is associated with several types of extremes, for example, heat and cold waves which caused human societies maximum damage. Past occurrences of heat waves hitherto had significant impacts on several aspects of society. Have increased Mortality and morbidity. Ecosystems can be affected, as well as increased pressure on infrastructures that support society, such as water, transportation, and energy(Dewce, 2016). The long-term change of extreme temperatures has a key role in climatic change. The form of statistical distribution and the variability of mean values and also extreme event indicate a change in the region. It can be a small relative change in the mean as a result of a large change in the probability of extreme occurrence. Also, the variation in temperature data variance is significantly more important than the mean, for assessing the extreme occurrence of climate(Toreti and Desiato, 2008). The average surface temperature has increased the world between 0.56 and 0.92 ° C over the past 100 years(IPCC, 2007). Meanwhile, it was in the Middle East, the average daily temperature increased by 0.4-0.5 ° C in decades(Kostopoulou et al, 2014; Tanarhte et al, 2012). Considering that not many studies have been done in the field of spatio-temporal Variations of the heating and cooling waves thresholds in Iran, in this study, the spatio-temporal Variations of the heating and cooling waves thresholds in Iran during 50 years were examined and analyzed.   Methodology The daily temperature from the beginning of the year 21/03/1967 to 19/05/2005 was obtained from the Esfazari database prepared by Dr. Masoudian at the University of Isfahan. In order to increase the time resolution of the mentioned database, the daily temperature of observations from 05/21/2005 to 05/12/2012 has been added to the mentioned database using the same method, and the exact spatial resolution (15 x 15 km) is used as a database. Threshold indices of heating waves are the average numbers between the 95th and 99th percentiles, that is, the extreme hot threshold to the limit of excessively extreme hot. For extreme cool, from the 5th percentile down to zero is used. Of course, a condition was added to these thresholds, which is that these thresholds must be repeated two days in a row. These thresholds were extracted for each day in the 50 years of the study period and used as the original database. In order to analyze the relationship between cooling and heating waves, Pearson's correlation coefficient was used and regression was used to analyze the trend.   Results and discussion The average of cold waves was 5.26 ° C and for the heat waves is 30.20° C. Generally, if the temperature is upper or lower than this threshold, it is considered as hot or cold temperatures. A comparison of the median, mode, and average of cold waves with heat waves shows that the distribution is more heterogeneous for cold waves and its CV is 84.22%. In southern Iran, the average threshold heat waves are higher. This situation can be caused by the effects of subtropical high-pressure radiation, low latitude, and proximity to the sea. Though the threshold is higher in these areas, fewer fluctuations and changes are seen in the area. Heights moderate the temperature so they pose a minimum threshold for heat waves i.e. an iso-threshold of 25 ° C is consistent along the Zagros mountain chains, but in the west and east of Zagros Mountains, the threshold of heat waves is increased. Heat waves have increased in most areas of the country. So nearly 85 percent of the Iran has been an increasing trend, of which 65.8 percent is statistically significant at the 95% confidence level. Still, more areas of the country (60 percent) have a trend between 0.00828 and 0.00161. As can be seen, only 15% of the land area (including the southwest and northwest of the Country) had decreased heat waves. Cold waves, in most parts of the country, have a Positive Trend. However, about 25 percent of the study area's cold waves have a negative trend. they are located in areas higher than Latitude 30°. The largest decline of the wave's trend along the country is highlands. Nowadays, most of the country, has a trend between 0.01494 and 0.00828 ° C, respectively. Conclusion Common changes and effects of heat and cold waves had a direct relationship in many parts of the country. It is remarkable common variance in the East reached 55 percent, according to statistical significance. In some areas of the northwest and southwest, which have been impressive heights, the common variance is 40 percent. This common variance in mountains area has been high values. Investigation of heat waves trend shows that 65.8% of Iran significant positive trend and 7.1% significant negative trend. Also, the cold waves trend has indicated a 48.5% significant positive trend and a 10.8% significant negative trend. Climate change and global warming have changed the frequency and severity of temperature extremes. The present study, by examining the number of warm waves, concluded that the warm waves have increased in magnitude in 65.8% of the Iran zone. Also, the study of the cold waves trend showed that 48.5 percent of Iran had a positive trend, which means that the amount of temperature in the cold waves increased In other words, the severity of the cold has been reduced And only 10.8 percent of Iran had a negative cold wave trend And it shows the intensity of these waves is reduced.   Funding There is no funding support.   Authors’ Contribution The authors contributed equally to the conceptualization and writing of the article. All of the authors approthe contenttent of the manuscript and agreed on all aspects of the work declaration of competing interest none.   Conflict of Interest The authors declared no conflict of interest.   Acknowledgments  We are grateful to all the scientific consultants of this paper.