Generally, gravity ANOMALY is the difference between the observed acceleration of Earth's gravity and a normal value. Topography (all masses above geoid) plays a main role in definition of the gravity ANOMALY. Based on modeling of the effect of topography, there are different models of gravity ANOMALY such as free-air and BOUGUER ANOMALY. The main goal of the BOUGUER ANOMALY is removing of gravitational effect of all masses above the geoid (topography and atmosphere). This ANOMALY is widely used in exploration geophysics. In geodetic applications, in the absence of topography, BOUGUER gravity ANOMALY is smooth and thus more suitable for interpolation and even stable downward continuation.In the other hand, gravity ANOMALY is the difference between real gravity at a point and normal gravity in corresponding point where the real and normal potentials in both points are the same. In geodesy, the gravity disturbance is defined as the difference between the real gravity observed at a point and normal gravity at the same point. In many geophysics literatures, gravity ANOMALY is replaced by gravity disturbance together a corrective term called geophysical indirect effect. This correction is computed by application of the free-air (and usually the BOUGUER) correction over the geoid–ellipsoid separation. This correction must be computed by application of only free air correction to separation of the real equipotential surface and its equivalence in normal gravity field at gravity observation. The free-air (FA) correction is used to up/downward continuation of normal gravity ANOMALY. In practice, only linear approximation, 0.3086 mGal/m, is used while a second-order FA correction is more realistic than the linear approximation. Note that the FA correction is not a reduction formula for downward continuation of gravity ANOMALY.One of the most ambiguities in definition of BOUGUER effect gravity ANOMALY arises from formulating the effect of topography. The gravitational of topography can be split into BOUGUER term, which is the dominant term, plus minor effect, terrain roughness. In the evaluation of a topographical effect, planar or spherical models of topography can be used. Many studies have shown that planar and spherical model of topography give very different results for BOUGUER anomalies. Also, it was shown that the planar topography model (in form of infinite BOUGUER plate) yields to a mathematically and physically meaningless quantity. To compute the terrain correction in geophysics, the gravitational effect of only masses up to about distance 167 km (Hayford zone) is considered. In principle the domain of computation of the topographical effect is the whole of the Earth. Despite the fact that the gravitational effect decreases with distance, the effect of beyond Hayford zone is large and should be considered.The removal of the topographical masses disturbs the isostasic equilibrium of the crust. As a result, the equipotential surface can be moved up to several hundred meters. The indirect topographic effect is defined as the effect on gravity due to removing the topographical masses. The indirect effect of topography (ITE) in BOUGUER gravity ANOMALY was first introduced by Vanicek, et al (2004). Their computations show that the numerical values of ITE can be reached up to 150 mGal in mountainous area. While, in most studies, ITE does not take into account and only direct topographical effect is considered.In analogy with topographical effect, in the computation of BOUGUER gravity ANOMALY, the direct and indirect effects of atmospheric masses should be considered. Usually the gravity effect of the atmosphere is evaluated by IAG formula. This formula considers only the direct topographical effect as the correction to gravity ANOMALY. The indirect atmospherical effect is not discussed in this context. In this study, the method proposed by Sjoberg (2000) is recommended and applied.In order to investigate differences between classic and new BOUGUER gravity anomalies, numerical calculations were performed in a mountainous area bounded by , where there are 2385 land gravity observation. The classic planar BOUGUER anomalies were computed from where g and are observed and normal gravity, H is the orthometric height of point and is the terrain correction computed up to Hayford zone. The new spherical BOUGUER anomalies were computed from where FA is second-order free-air correction, DTE is the direct topographical effect (spherical shell + terrain roughness), ITE is the indirect topographical effect, DAE is the direct atmospherical effect and, IAE is the indirect Atmospherical effect. The results indicate that there are large differences (over 100 mGal) between classical and new BOUGUER anomalies. The new BOUGUER anomalies are less correlated with terrain heights. Therefore the planar model cannot completely remove the gravitational effect of topography.

In this research, gravity surveying is used for exploration of petroleum reservoirs in the Chenaran region, northeast of Iran. For this purpose a gravity survey is conducted by making gravimeter readings at 816 sites, located along 26 parallel lines of profiles. The recording sites are at equal distances of I km and the lines of profiles are spaced at equal intervals of 2 km. After estimating the surface density value, two dimensional and three dimensional BOUGUER ANOMALY maps are made in which all the relevant corrections, including the free-air correction, the BOUGUER correction, the latitude correction, the terrain correction, the drift correction, and the tidal correction, have been applied. For interpretation of these maps, local and regional anomalies have been separated by using two of the most widely used schemes that involve computation of weighted averages, namely upward continuation method and the second vertical derivative respectively. The local patterns of BOUGUER gravity variation reveal the presence of buried anticlinal structures and fault zones in the region. Due to the favourable geological conditions for petroleum accumulation in the region, it is very likely that petroleum reservoirs have been trapped by these buried structures. Finally the results indicate that gravity survey, particularly, BOUGUER ANOMALY separation, plays ae important role in petroleum exploration.

The present tectonic structure and high seismicity of the Makran zone is affected by the northward subduction of the Neo-Tethys oceanic plate under the Eurasian plate. According to scientific and historical evidences, the Makran fault has high seismicity and is completely capable of causing tsunami hazard on Iranian southeastern and Pakistanian western coasts. Topography, Free-Air and BOUGUER gravity anomalies show critical changes over this region, which are related to the changes in the Earth deep structures. More negative Free-Air gravity values are observed in the western rather than eastern parts, indicating that the subducting plate beneath the western Makran is steeper than of that beneath the eastern part. Many of the earthquakes of magnitudes greater than 6 in the Makran have occurred in places where the Free-Air gravity changes abruptly from positive to negative values. Such areas could predict, to some extent, large earthquakes. BOUGUER gravity values change from 150 mGal in the oceanic crust of Oman Sea to -90 mGal in the Eurasian continental region. Moho depth is about 14 km beneath the Oman Sea and increases up to 32 km under the Eurasian continental crust. The subducting plate dips around 5.70. Studying and numerical simulation of flooding water due to tsunami, and considering possible earthquakes, is very important. In this research, the run up of tsunami caused by the possible earthquakes of the Makran fault in Sistan and Baluchestan province coastlines (Beris region) has been studied using numerical methods. The scenarios were tested by three earthquakes including an 8-magnitude earthquake, the 1945Pakistan earthquake with a magnitude of 8.5, and 9-magnitude earthquake in Japan, 2010. Results show that the maximum flood height of the model was up to 0.5m (for the 8-magnitudeearthquake), 3.4m (for the 8.5-magnitude earthquake) and 14m (for the 9-magnitude earthquake). The maximum flood width is estimated to be 1.4 km and the arrival time of the first tsunami waves is inferred to be 22 minutes. These results could be useful in determining high risk regions to optimize development planning.

Euler's homogeneity equation for determining the coordinates of the source body especially to estimate the depth (EULDPH) is discussed at this paper. This method is applied to synthetic and high-resolution real data such as gradiometric or microgravity data. Low-quality gravity data especially in the areas with a complex geology structure has rarely been used. The BOUGUER gravity anomalies are computed from absolute gravity data after the required corrections. BOUGUER ANOMALY is transferred to residual gravity ANOMALY. The gravity gradients are estimated from residual ANOMALY values. Then by applying the gravity gradients, using EULDPH, the coordinates of the perturbing body will be determined. Two field examples one in the east of Tehran (Mard Abad) where we would like to determine the location of the ANOMALY (hydrocarbon) and another in the south-east of Iran close to the border with Afghanestan (Nosrat Abad) where we are exploring choromit are presented.

Gravity and its usage in gravity interpretation is still a challenging field. It is not easy to compute these gradients especially in the case of noisy data. Analytical signal is one of the new methods that uses gravity gradients to locate the perturbing body. This method had already been used for high-resolution magnetic and gravity data and rarely used for low-quality gravity data. The gravity gradients and analytical signal have been applied in two different areas, Zahedan where we are looking for Choromite anomalies and Tehran (Mard Abad) where we are investigating for low density ANOMALY, Probably hydrocarbon.

Using global free air gravity and topography data, first we have calculated a BOUGUER ANOMALY (BA) map for Iranian plateau and then computed the residual isostasy ANOMALY map under the Airy-Heiskannen assumption. The term residual is used as to reflect the assumption of local isostatic compensation in contrast to a regional isostatic compensation. The value with which the gravity effect of the compensation mass (the root/anti-root in the Airy model) is calculated are chosen under careful considerations as to produce reliable results. The resulting residual isostasy map is then used to qualitatively interpret the isostatic highs and lows corresponding to crustal/lithospheric features of the Iranian plateau. The study area is a complex region as a result of its still active tectonics which is mostly driven by the continent-continent collision of the Arabian and Eurasian plates. The five most important tectonic settings in Iran are Zagros Mountains, an active belt formed as the result of the collision extending from south-west Iran along the Persian Gulf; Alborz Mountains, a young belt with an average topography of 3-5 km extending nearly in east-west direction, Makran, in south-east Iran, north of the Iran-Arabian plate boundary where an active subduction is taking place; Caspian Sea, with an oceanic crust covered with an average 15-20 km sediment layer at the Iran-Eurasia plate boundaries and Kopeh-Dagh mountains, an uplifted region as a consequence of converging continental plates. Our results indicate that the Zagros Mountains have reached an isostatic equilibrium but the scenario is slightly different for the Alborz chain. It seems that the isostatic equilibrium is not fully reached in the Alborz due to the observation of a continuous isostatic high (positive) ANOMALY which extends to north-west Iran, however, it may also be partly caused by a simple folding. In the southern Caspian region, there is an enormous isostatic low (negative), for the cause of which we have considered two possible reasons. First, the effect of the sediment layer on the gravity signal due to its negative density contrast. Second, we considered the deficiency in the rock mass at the base of the lithosphere due to an anti-plume or the downward flow of the lithospheric materials towards the mantle which may also explain the high depth of the southern Caspian Basin. Subduction zones are usually characterized with negative isostatic anomalies, but in the case of the subduction of the oceanic lithosphere of the Caspian under the continental crust of the Eurasia, there is no apparent negative isostatic ANOMALY in our map. We believe that this is probably due to the fact that the subduction is still young while in order to observe a negative effect on the residual isostasy ANOMALY map, the subducting slab must be in a deep position, in other words, be of older age. The subduction of the Makran, on the other hand, has caused a negative isostatic residual ANOMALY. This low ANOMALY is also partly due to the uplift of the Makran area. A high-low (positive-negative) residual isostasy ANOMALY pairs corresponds to suture zones. An example of which is seen for the Zagros-Bitlis suture zone which marks the continental collision of the Arabian-Eurasian plates. Our map also shows a negative residual isostatic ANOMALY in the Kopeh-Dagh Mountains, which we interpret as the uplift caused by the convergence of the Iranian and Eurasian plates. It must be noted that every high/low residual isostatic ANOMALY may not be interpreted as isostatically over/under compensated areas. on the contrary, it could be and usually is related to a geological feature of lithosphere/mantle scale.

The presence of hot springs, travertine outcrops, hydrothermal altered area and active tectonic in the north-east of Takab city in the West Azarbayjan province indicate that there is a geothermal system in the area. In order to characterize the geological structures associated to the geothermal system in the region, a gravity survey was carried out in 140 stations which covered an area about 600 km2. Necessary modifications such as BOUGUER, topography and free air were applied over data to obtain complete BOUGUER ANOMALY field. Then, residual gravity ANOMALY field was calculated by subtracting the regional gravity field from complete BOUGUER field. The regional gravity field was calculated by fitting a three-order polynomials surface over the complete BOUGUER field. The calculated residual gravity map shows two negative ANOMALY zones (A1 and A2) in the study area. In geothermal exploration, negative gravity anomalies are considered as probable reservoir of geothermal systems. The horizontal and vertical derivative maps show complicated fracture zones in the study area. To obtain more information, the depth estimation carried out using Euler method. Estimated depth for the top of negative ANOMALY source in zone 1 is between 1000 and 2000 m. Finally, 3D inversion of the data was performed using Li and Oldenburg algorithm to show an image of the reservoir in the depth. The results of 3D inversion show a significant negative density contrast that occurred only in zone 1. Therefore, the reservoir of the Takab geothermal system is located in the depths between 3000 and 5000 m in A1 ANOMALY zone.

Potential field data is the assembled of effects of all underground sources. Computing regional-residual ANOMALY is a critical step in modeling and inversion in the gravity method. Existence quantitative noise in corrected gravity data is unavoidable. In this paper, we present a novel separation method based on a Singular Value Decomposition (SVD) analysis of gravity dataset. With the SVD, a matrix of BOUGUER gravity data can be decomposed to a series of eigenimages. The number of required eigenimages or threshold for the reconstruction of the regional and residual (local) anomalies maps and noise distribution map from BOUGUER ANOMALY is determined based on the derived singular values by SVD. To reconstruct the data set by eigenimages may lose negligible information. We have considered which this value is equivalent with the mean of the variance of the resulted matrixes by eigenimages. The efficiency of the Singular Value Decomposition method was tested with the noisy synthetic gravity data of a hybrid model of the sphere as a local ANOMALY and deep-seated sloping plane as a regional ANOMALY. The separation results are satisfactory. The proposed method was applied on gravity field dataset of the Qom area, Iran.

Structural analysis of remotely sensed data provides a method of assessing the structural significance of regional metallogenesis in the Dehaj area as the northwestern part of the Kerman porphyry Cu belt. This belt is consisted of dominant Eocene volcanics and the Dehaj type subvolcanic intrusives. In the study area, geologically, Cu-mineralization is hosted by the Kuh-e-Panj type subvolcanic intrusives. Photogeological analysis of the Landsat imagery reveals a pattern of mainly NW-SE oriented linear structures which were apparently generated in response to crustal thickening and lineament reactivations during the generation of a huge stratovolcanoes. A comparison of lineament map generated from Landsat ETM+ image indicates that the locations of some of the deposits, magmatic and hydrothermal centers are at/or close to the intersections of linear structures. This study deals also with the irrefutable genetic links between some small circular features and copper mineralization that has not been previously examined. It is proposed that the circular features are superficial expressions of intruded stocks or bodies in subvolcanic levels without remarkable volcanic equivalents. Of particular matter in this framework is the possible genetic/age relationship between the linear structures and the circular features. These small circular features are thought, in some cases, as having been formed due to development of the local extensional points near the intersection of the linear structures in a regional, tectonically, compressive environment. Regionally, plotting the residual ANOMALY and BOUGUER ANOMALY maps of the region provides, geophysically, a lucid explanation as to how the small circles came into existence.

In exploratory geophysics, main and primary purposes are determination of researching targets densities, which have a particular density difference with that of the host rock. In this study, hence, we introduce new method for density determination, called "variogram method", which is based on the fractal geometry. It is based on minimizing the BOUGUER ANOMALY surface roughness in which fractal dimension of the surface is used as BOUGUER ANOMALY surface roughness criterion. Through this method, we can determine the optimum density of charak in the South Hormozgan, which is utilized in order to accomplish some corrections and review their results about isostatic circumstances of those regions. There are various methods to illustrate the bedrock topography and we will explain one of these methods at the present paper. The calculation is dome in the Fournier domain. The method mentioned above was implemented to detect the bedrock topography and the results were compatible to the region geology.