مجله ژئوفیزیک ایران
سال یازدهم شماره 2 (پیاپی 34، تابستان 1396)

Two-dimensional shallow water equations are commonly used to study the dynamics of large-scale flows in the atmosphere and oceans that are nearly horizontal. Over the past years, the numerical solution of multi-layer shallow water systems has been widely researched. In stratified geophysical flows, two-layer shallow water equations are proper models for the simulation of certain phenomena in the atmosphere and oceans. In this model, the fluid is assumed to be composed of two shallow layers of immiscible fluids in which the superposed layers differ in velocity and density in a two-dimensional domain. The constant density of upper layer is less than the density of the lower one.
For the solution of shallow water equations, high order compact finite difference schemes have been widely used owing to their good accuracy compared with standard finite difference schemes for a large range of wave numbers and a low numerical diffusion with small dispersion errors.
In this research, fourth-order compact finite-difference method was used for spatial differencing of f-plane two-layer shallow-water equations in the vorticity-divergence formulation for a rectangular domain with periodic boundaries; the results were compared to those of conventional second order finite difference method. For time integration, a three-level semi-implicit formulation was applied with the Robert-Asselin time filter which prevents the numerical instability caused by the computational mode of the three-time-level scheme. The equations were derived in terms of barotropic and baroclinic variables such that they were split into two coupled systems (barotropic and baroclinic systems) consisting of all variables of both upper and lower layers in each system. These systems are different than standard two-layer shallow water systems.
A perturbed unstable zonal jet, in a two-layer shallow-water flow, was considered for initial value problem with baroclinic instabilities. The two-layer baroclinic initial values were extracted from a one-layer initial condition such that the potential vorticity of one-layer initial condition was equal to the upper layer potential vorticity; other initial values of the two-layer shallow water equations were determined by taking the definition of baroclinic initial condition, in the situation where the initial current in the upper layer is opposite to one in the lower layer such that the initial barotropic variables are all zero. Over time, the initial state broke up into smaller barotropic and baroclinic vortices.
To control the numerical nonlinear instability due to the interaction of nonlinear terms of the vorticity equations and subsequently produce the aliasing errors, the barotropic and baroclinic planetary vorticities were explicitly damped by adding the hyperdiffusion operator acting on the same vorticity equations.
There exist myriad methods for assessing the accuracy of numerical schemes such as the conservation of total mass and energy. The ability of each simulation to conserve the total energy on the total layer-depth (i.e. energy error) and mass between isolevels of the potential vorticity (i.e. mass error) within each layer, was measured in order to assess the numerical accuracy. Results showed that this model meets the conservation laws of mass and energy in the test problem considered here. The fourth-order compact finite-difference method entailed less energy error than the second order finite difference method during the time integration of two-layer shallow water equations; additionally, it is more accurate regarding the conservation of mass for a long time integration.

Identification of temperature regimes is very crucial for a better management of energy resources, recreations and truisms as well as for adequately determining agricultural calendars in different parts of the country. Few attempts have been made to adumbrate the Iranian temperature regimes; thus it is necessary to identify the most realistic temperature regimes of Iran using as many available stations across the country as possible. For this purposes, 155 Iranian synoptic stations with a relatively regular distribution across the country, mostly having full data records for the common period of 1990 to 2014, were used for the identification of the temperature regimes. In all stations, the average of the mean monthly temperature was computed in the mentioned period and further employed for the analysis. A principal Component Analysis (PCA) was applied to the inter-stations correlations matrix (155×12) composed of 155 stations and 12 mean monthly temperature values for each station. The computed Kaiser-Meyer-Olkin (KMO) measure of the sampling adequacy indicated that the matrix with the KMO value of 0.87 is useful for a PCA application. The first three leading PCs were considered for further analysis based on the scree plot and the sampling errors of the PCs (North et al., 1982). The remaining PCs were then rotated using varimax orthogonal criterion. The PC scores of both rotated and un-rotated solutions were separately used as inputs for Cluster Analysis (CA) to partition the considered stations into distinctive clusters. Moreover, all agglomerative CA methods as well as K-means CA were examined so as to find out the most appropriate method for partitioning the data. The cophenetic correlation coefficient was employed to measure how well the hierarchical dendrogram of a given CA represents the relationships within the input data. The results indicated that all the clustering approaches properly represented the inherent structure of the input data, yet the Ward method was selected as the most appropriate method since it resulted in much realistic clusters that quite perfectly matched the topographic and geographical features of the country. The correct number of clusters was also selected based on the Silhouette index (Rousseeuw, 1987) that measures how well objects lie within their cluster, and which ones are merely somewhere in between the clusters. The average silhouette width provides an evaluation of clustering validity, and might be used to select an ‘appropriate’ number of clusters. Computing the index for a set of predefined cluster numbers (2 to 15 clusters), it was observed that six is the most appropriate number for clusters for a better representation of the inherent structure of the data. As such, all 155 stations were classified into six clusters applying Ward CA method on the three leading un-rotated PC scores.
The maps of varimax rotated PC scores properly represented areas characterized with seasonal temperature variability. The first and second varimax rotated PC sores respectively display the winter and summer temperature variability across the country. Applying Ward clustering on un-rotated PC scores resulted in seven distinct clusters that appropriately specified the Iranian temperature regimes. It was found that the western and northern mountainous areas have a mountainous temperature regime whereas the central-eastern Iran hosting the Iranian deserts has a plain temperature regime which is considerably warmer than the earlier one. The third temperature regime includes stations scattered across the mountainous region, all of which are characterized with a very high elevation, hence having the coldest winters and the coolest summers in the country. The hot temperature regime which is the warmest temperature regime in the country belonged to the southwest and certain parts of the south. The stations located in the coastal areas of the northern and southern Iran respectively have the Caspian coastal, Persian Gulf coastal and Oman Sea coastal temperature regimes, all with the lowest annual temperature ranges in the country. Four out of the seven Iranian temperature regimes are continental but the two mountainous temperature regimes are the most continental regimes in the country due to their wider temperature ranges. The results conduce to a better management of energy resources, recreations and tourisms as well as an optimal determination of agricultural calendars in different parts of the country.

Presently, seismic hazard assessment (SHA) is highly conducive to seismic-resistant building designs and seismic regulations. Seismic hazard maps and other seismic hazard products such as spectral acceleration (SA) are prerequisites for the preparation of building codes and earthquake risk mitigation plans, which are used in making public decisions and policy. Therefore, it is indispensable to use the best available data and methods in SHA. In cases of incomplete historical records like Iran, and in intracontinental areas like Central-East Iran, where fracture boundaries interact slowly, large earthquakes may recur every 1000–5000 years or even with a longer period. In such areas, it is useful to employ geological inputs like slip rates. In the present paper, the slip rate of the faults is used for the first time, in both direct and indirect approaches in time-independent probabilistic seismic hazard assessment (PSHA), so as to evaluate spectral acceleration (SA). To this end, Kerman region (Southeastern Iran) is selected as an example, and Kerman and Ravar cities located between 54-59° N, and 28.5- 34° E are considered as specific regions to show the effects of slip rate on the seismic hazard. With the purpose of using slip rates in PSHA, indirectly, we have defined a new factor denoted as the fifth factor (K5) to specify the effects of slip rates in calculating spatial distribution function (SDF). On the other hand, the mean annual occurrence rate of each source may be directly calculated based on the slip rate of the faults for a direct use of slip rates in PSHA. In the first time-consuming stage, the slip rates of the faults or fault segments and the seismological data are assembled using available resources and literature. Seismicity parameters in the targeted region are calculated using a unified, homogenized and complete catalog in the method proposed by Kijko and Sellevoll (1992), in which one can consider the magnitude uncertainty and completeness of data in calculations. Through the use of geological maps with scales of 1:100000 and 1:250000, and with the experience of previous studies, we have determined 26 potential seismic sources in the region. The comparison of the SDFs calculated based on four factors (K1-K4) and SDFs calculated based on slip rate factor (the fifth, K5) accompanied with the previous four factors indicates that the most differences occurred for sources No. 111 and 121 for the magnitude of 7

Coastal classification is an effective method for investigating the reaction of coasts against such hydrodynamical factors as waves and tides. This method is also employed in integrated coastal zone management, especially shoreline management. Coastal classification models are of two kinds, equilibrium models, predicting the effects of constant incident waves on nearshore features such as bars and troughs, and morphologic state models, predicting the sequence of bar-trough shapes and scales under the varying influences varying waves. Wright and Short (1984) presented the most widely accepted beach classification scheme where three main beach states are identified, namely dissipative, intermediate, and reflective. Intermediate beaches are divided into four states, low tide terrace, transverse bar rip, rhythmic bar beach, and longshore bar trough.
In this paper, the beach states of the southern coasts (Hormozgan Province) of Iran were classified using Masselink and Short (1993) and Masselink and Hegge (1995) methods. Owing to its location, and abundant oil and gas resources, Persian Gulf is one important military, economic and political interest, hence the necessity of its investigation. We primarily studied different kinds of hydrodynamic forces dominating the beaches of the province. Six stations were chosen throughout the shoreline between 54˚39' 18" latitude and 26˚30' 29" longitude up to 53˚ 9' 39" longitude and 27˚4' 34" latitude. Next, the waves, tides, and sediments were evaluated in different depths in these stations via laboratory actions. We employed the wave data of 2002 from the modeling project (ISWM) which was done in the National Institute of Oceanography, and the sediment data of Hormozgan Province coast were gleaned from the Marine Geological Organization. In order to determine the general slope of the beach by Arc GIS software, hydrographic maps were used with approximately 1/100000, and the slope of each station was calculated. After that, through breaker height (Hb), the tide range (TR), wave period (T) and sediment fall velocity (Ws), two dimensionlessparameters, namely the relative tide range (RTR = TR/ Hb) and the dimensionless fall velocity (Ω = Hb/WsT,) were calculated in each station.
The results indicated that in the southern regions of Iran (Hormozgan Province), due to the tidal effects in and based on (3

Today, it is indispensable to transmit and retain fuels, water and other energy resources by buried pipes, tanks and cables in urban and non-urban areas. Thus, the generation of huge and costly underground networks for this purpose is inevitable. Following the creation of such networks, their maintenance, and prevention from possible destructions are needed. Otherwise, considerable financial losses and irreparable environmental contaminations may occur. Often, a sufficient physical contrast between these installations and their surrounding media exists, and as a result, these installations are considered as suitable targets for detection by ground penetrating radar (GPR) method. In this paper, GPR data, acquired from a GPR survey on buried pipes including metallic pipes for gas transmission, have been processed and interpreted to detect the buried metallic pipes and other subsurface anomalies. To investigate the advantages or efficiency and drawbacks of the GPR method in this application, we have compared the results of the GPR method with the results of the magnetic method performed on the same targets. The results of this comparison are given in the following.
The GPR method provides a higher resolution in comparison to the magnetic method. However, GPR waves in subsurface highly conductive media are intensively attenuated. Hence, the depth of penetration in the latter method is limited. As can be seen from the GPR depth sections obtained from the GPR survey in the study area, the depth of penetration is even less than two meters. The magnetic method, despite its weak resolution, can more successfully detect the targets in highly conductive media provided that there is a good magnetic susceptibility contrast between the target and the surrounding medium. In urban areas, where high noise levels exist magnetic surveys unlike GPR methods via shielded antenna cannot be successfully performed. In this research, first, both the GPR and magnetic surveys have been carried out along survey lines passing the buried gas pipelines and other shallow subsurface targets in Qaleh-Showkat area that is approximately located 10 km to the west of Shahrood city to detect the targets. Then, the results of the GPR and magnetic surveys have been compared. As a result, we have found that the GPR method provided higher resolution in the detection of small anomalies located at shallow depths and near each other. However, in the locations having high electrical conductivities, the GPR method, unlike the magnetic method, could detect very shallow subsurface targets or anomalies even high attenuation of the GPR waves happen in these situations.

Sangan iron deposit is a magnetite iron skarn. Magnetometry is the most common method for the exploration of such kinds of deposits based on the magnetic properties of these minerals. This method specifies the depth, dip, shape, and strike of the sources causing the anomaly. Many explorations of this ilk have been done of which giant Gol e Gohar in Iran is an example. Based on geology and following magnetometry, a massive iron deposit was predicted during Sangan iron exploration, where 558 boreholes in 50×50 m net were designed and drilled in the west ore body, revealing very useful subsurface information. Intrusive bodies are mainly granitic and oxidant types which, because of the presence of fine grain and disseminated magnetite, have higher magnetic susceptibility (K) in comparison to other granites. These bodies are considered as source rocks for the creation of gigantic Sangan mines. Multiphase ground magnetic survey points (19376) with different specifications were equalized and interpreted in this study. The causative sources of most magnetic anomalies in the rotation to the pole (RTP) map were magnetite mineralization, confirmed by the drilling data. In this research, filters of first vertical gradient and upward continuation were used to guide drilling owing to the presence of the remnant magnetism in the magnetite skarn and the unavailability of such measurements that are necessary for specifying the accurate depth of the magnetic anomaly sources. The information pertaining to vertical gradient and upward continued maps correlated well with the depth obtained from drilling and 3D block modelling. The amount of ore reserve and its depth increased from the western anomaly (A') to the central anomaly (C) and had a dip direction to the east. Such change in the depth of mineralization correlated with upward continued responses which represent the central magnetic anomaly (C) as the deepest anomaly in Sangan iron ore deposit. Magnetic responses of the Upward continuation to 1000 m of this magnetic anomaly can be related to either the high depth of the mineralization (620 m drilled so far) or the deeper intrusive body which needed deeper drilling (more than 1000 m) for confirmation.

Seismology has an important role in identifying earth structure by studying seismic waves. The amplitude and frequency of these waves change when they pass into the earth due to various parameters including 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 and 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 understand the physical laws governing the propagation of seismic waves in the lithosphere.
The observed seismic-wave amplitudes usually decay exponentially with increasing traveled distance after the correction for geometrical spreading, and decay rates is proportional to Q−1 which characterizes the spatial attenuation for P-wave.
An earthquake with magnitude Mw 5.8 occurred on Qeshm Island, on the western edge of the Strait of Hormuz in SE Zagros, on November 27, 2005. From 2005 December 2 to 2006 February 26, a dense seismological network of 17 stations was installed in the epicentral region of the 2005 November 27 Qeshm sequence.
In this study, 661 aftershocks were selected to estimate the frequency dependence relationship of the quality factor of P-wave with coda normalization method. The coda normalization method was used for the estimation of the quality factor of the longitudinal waves at 9 frequency band (the central frequency: 1.5, 2.5, 3.5, 5, 7, 10, 14, 19, 24). The frequency dependence relationship for the longitudinal waves are Qp = 0.059f -0.94 in the study area. As reported from other parts of world and Iran, the high value of attenuation in Qeshm may be because of the presence of some soft sediments such as a salt dome. Another reason for this high attenuation, probably due to using aftershocks data. After main shocks occurred, the medium must smash and cracked, and as a result, more heterogeneity and consequently, attenuation increase. The quality factor at a reference frequency of 1.0 Hz is less than 200. Therefore, it can be concluded the area is very active in terms of tectonic plates and seismicity which represents the accumulation of salt domes in this part of Zagros.

A tailing dam or confining embankment is constructed to enable the deposited tailings to settle and retain processed water. Tailing dams are susceptible to different kinds of pressures such as water pressure and the load of the tailings themselves. Miduk tailing dam was originally constructed with a fine silty sand layer to retain water covered by coarse grains. It was constructed in stages according to the downstream method, filter and support fill.
Tailing dams and downstream areas must be monitored as they undergo internal erosion, during which, the fine grains in the core of a dam are flushed away by seeping water and, as a consequence, the hydraulic conductivity in the remaining material increases. High velocity flows through the dam embankment can cause progressive erosion and piping. Moreover, the saturation of embankment soils, abutments, differential settlements in foundations, local stress relaxation in the soil and locally increased hydraulic gradient generally reduce soil strengths. The seepage issue in a tailing dam is the cause of reservoir loss to groundwater . Furthermore, it causes environmental problems such as the diffusion of heavy metals, acid drainage and so forth. Reversed water from the tailing dam is particularly important in desert areas.
Resistivity and self-potential (SP) monitoring has been widely applied for solving environmental and engineering problems of embankment dams by studying the changes in the subsurface properties with time. SP changes are caused by water movements through (or under) the dam and resistivity changes reflect the changes in the electrical properties of the dam materials.
Self-potential (SP) is a method where naturally occurring electrical potentials are measured. There are a number of different electro-chemical processes that can create such potentials. The type that is of interest in dam investigations is the so-called streaming potential which is the voltage difference parallel to the direction of flow. The streaming potential is manifested by a shearing of the diffuse layer caused by the hydraulic gradient. The field equipment for SP measurements is simple and inexpensive. It requires a pair of non-polarized electrodes, a high impedance voltmeter and t cables to connect them. Electrode drifts were controlled during SP measurements. Electrode drift is primarily caused by variations in temperature or soil moisture or by contamination of the electrolyte by ions introduced from the soil. Changes in the telluric currents induce substantial changes in the potential distribution in the subsurface, an effect accounted for by making regular measurements of the SP difference between the reference point and the base point within the survey area.
The Resistivity method involves the measurement of the apparent resistivity of soil and rocks as a function of depth or position. The resistivity of the ground is measured by injecting a current with two electrodes and measuring the resulting potential difference with two other electrodes. The readings are usually converted into an apparent resistivity of the sub-surface. From these measurements, the true resistivity of the subsurface can be estimated. The investigated volume can be changed by moving the electrodes. The data are usually inverted to a vertical resistivity section, assuming a 2D geometry perpendicular to the profile. Most commonly, the local variability is minimized, resulting in smooth models compatible with the measured data, meaning that sharp resistivity borders such as the ground water surface is visualized as a smooth transition in such inverted sections.
The principle objective of the present study was to evaluate the electrical resistivity and the self-potential methods used to detect anomalous seepage through mine tailing dams. In this regard, field measurements of resistivity and self-potential were carried out on the downstream grounds of tailing dam so as to identify the SP-responses related to seepage. The hydro-stratigraphy was mapped with the resistivity data (4 profiles of ERT) and groundwater flow patterns were specified with self-potential data (208 SP measurement points). The groundwater flow pattern was controlled by the geological and tectonic history of bedrock and the preferential flow pathway existing beneath the dam.

Although cloud properties and precipitation formation are primarily affected by atmospheric dynamics, cloud microphysical features also play key roles. The aerosol number concentration strongly influences cloud microphysics and precipitation formation, mainly through affecting the formation of cloud droplets and ice crystals.
In the current research, using the Thompson aerosol-aware microphysics scheme implemented on the Weather Research and Forecasting (WRF) model, the effects of aerosol number concentration was investigated on the precipitation formation of a heavy rainfall in Tehran. The aerosol number concentrations were obtained from the Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model, while the National Center for Environmental Prediction Final Analysis (NCEP/FNL) dataset was used for the initial and lateral boundary conditions. Two numerical simulations were conducted, referred to as the clean and polluted experiments. The initial hygroscopic aerosol number concentrations, compared to the values obtained from the GOCART model, were reduced to one-fifth and increased by a factor of 5 in the clean and polluted experiments, respectively. The model simulations were run with three nested domains, with horizontal resolutions of 21, 7 and 2.3333 km, and 45 levels in the vertical position, reaching up to the 50 hPa level. Simulations were conducted for 30 hours, starting from 18:00 UTC April 13, 2012, from which, the first 6 hours were considered as the model spin-up. The Rapid Radiative Transfer Model (RRTM; Mlawer et al., 1997) was used for the shortwave and longwave radiation, respectively. The land surface scheme and surface layer scheme were based on the five-layer thermal diffusion and the revised MM5 similarity theory, respectively (Zhang and Anthes, 1982). The non-local Yonsei University (YSU) scheme was employed for the parameterizations of the boundary layer processes (Hong et al., 2006). The Kain-Fritsch scheme (Kain, 2004) was used to parameterize moist convection in the mother and first nested domains, while it was explicitly modelled in the innermost domain.
Results indicated that changes in the aerosol number concentration are associated with changes in the spatial distribution of precipitation. Stronger updraft cores were found in the polluted experiment, entailing higher precipitation, longer growth times, and larger sizes of hydrometeor; accordingly, more raindrops survived from the evaporation after falling from the cloud base, increasing the surface precipitation. On the other hand, surface precipitation decreased in the downstream, primarily due to the decrease in the effective radii of ice crystals, reducing the riming processes and the amounts of graupels. Results further indicated that the increase in the aerosol number concentration is associated with the increase in the rate of precipitation under high relative humidities, while the reverse is true when the available water vapour is relatively low.

Iran is one of the seismically active areas of the world because it is located in the Alpine-Himalayan orogenic belt, at a 1000-km-wide zone of the compression between the colliding Eurasian and Arabian continents. Studying the crust velocity structure and Moho discontinuity in Iranian plateau is conducive to an understanding of its evolution and the tectonic history of its seismotectonic zones. Nowadays, it is indispensable to acquire sufficient and accurate data from the crust and upper mantle velocity structure or its specification.
To specify the receiver functions with an iterative approach, we made use of a two-year teleseismic data (with epicentral distance 25o-90o) recorded by six seismic stations located in the southeast Zagros (BNDS, NIAN and GENO), Makran (CHBR) and eastern Iran (SZD1 and ZHSF) . In order to delete high frequencies, Gaussian parameter 1.0 was used. So as to augment the signal to noise ratio, RFs were clustered in 10˚ azimuthal and less than 15˚ epicentral distance ranges. Finally, the RFs were stacked.
Receiver functions (RFs) show Earth’s local structure response to P-wave vertical arrival approximately beneath a three-component seismometer; these functions are sensitive to shear-wave velocity impedance. Depth-velocity trade-off in RFs information poses inversion non-uniqueness issues, but a combined inversion of receiver functions and surface wave dispersion increases the uniqueness of the solution over separate inversions, further facilitating the explicit parameterization of layer thickness in the model space, providing more exact constraints as to the crustal structure. Surface wave velocity dispersion depends more on S wave velocity than on P wave velocity, and its dependence on density is slight. In previous studies, it has been shown that it improves the inversions of receiver functions for crustal structures (Julia et al. 2000). Surface wave velocity dispersion provides information as to the absolute seismic shear velocity, yet is relatively insensitive to sharp velocity changes. The group velocities were incorporated into our joint inversion scheme from an independent surface wave tomography study by Rham (2009). Group velocities from regional events, recorded at permanent and broadband stations, were measured for fundamental mode Rayleigh waves within 10–100s period range. The region was parameterized using a uniform, 1×1°, grid of constant slowness cells. The dispersion curve is the result of separate tomographic imaging for each period. Fundamental mode Rayleigh wave group velocities are taken from the corresponding tomographic cell containing the stations. The joint inversion of the two independent data sets was performed considering a proper combination of weighting parameters done by Herrmann and Ammon’s program (2003). Minimizing the standard error between the real and predicted data is the criterion for the desired final model which is close to Earth’s real model.
Models resulting from joint inversion in the south-east Zagros (Hormozgan province) suggest that Moho discontinuity depths beneath BNDS, GENO and NIAN stations are about 54, 54 and 48 kilometers, respectively, while the average depth of Moho discontinuity in the region is about 52±2 kilometers. In the Makran’s seismotectonic state, the resulted models pertaining to single station in the region (CHBR, near the city of Chabahar) show that the average depth of Moho discontinuity in this region is about 28 kilometers and thickness of the sediments is about 10 km, consistent with the shallow subduction of a high-velocity oceanic crust of Arabian plate beneath the southern side of Makran. In the Flysch zone (eastern Iran), the models of the two stations (SZD1, ZHSF) show that the average depth of Moho is about 40±2 kilometers.