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Sample records for bouguer gravity anomalies

  1. Complete Bouguer gravity anomaly map of the state of Colorado

    USGS Publications Warehouse

    Abrams, Gerda A.

    1993-01-01

    The Bouguer gravity anomaly map is part of a folio of maps of Colorado cosponsored by the National Mineral Resources Assessment Program (NAMRAP) and the National Geologic Mapping Program (COGEOMAP) and was produced to assist in studies of the mineral resource potential and tectonic setting of the State. Previous compilations of about 12,000 gravity stations by Behrendt and Bajwa (1974a,b) are updated by this map. The data was reduced at a 2.67 g/cm3 and the grid contoured at 3 mGal intervals. This map will aid in the mineral resource assessment by indicating buried intrusive complexes, volcanic fields, major faults and shear zones, and sedimentary basins; helping to identify concealed geologic units; and identifying localities that might be hydrothermically altered or mineralized.

  2. Optimization schemes for the inversion of Bouguer gravity anomalies

    NASA Astrophysics Data System (ADS)

    Zamora, Azucena

    associated with structural changes [16]; therefore, it complements those geophysical methods with the same depth resolution that sample a different physical property (e.g. electromagnetic surveys sampling electric conductivity) or even those with different depth resolution sampling an alternative physical property (e.g. large scale seismic reflection surveys imaging the crust and top upper mantle using seismic velocity fields). In order to improve the resolution of Bouguer gravity anomalies, and reduce their ambiguity and uncertainty for the modeling of the shallow crust, we propose the implementation of primal-dual interior point methods for the optimization of density structure models through the introduction of physical constraints for transitional areas obtained from previously acquired geophysical data sets. This dissertation presents in Chapter 2 an initial forward model implementation for the calculation of Bouguer gravity anomalies in the Porphyry Copper-Molybdenum (Cu-Mo) Copper Flat Mine region located in Sierra County, New Mexico. In Chapter 3, we present a constrained optimization framework (using interior-point methods) for the inversion of 2-D models of Earth structures delineating density contrasts of anomalous bodies in uniform regions and/or boundaries between layers in layered environments. We implement the proposed algorithm using three different synthetic gravitational data sets with varying complexity. Specifically, we improve the 2-dimensional density structure models by getting rid of unacceptable solutions (geologically unfeasible models or those not satisfying the required constraints) given the reduction of the solution space. Chapter 4 shows the results from the implementation of our algorithm for the inversion of gravitational data obtained from the area surrounding the Porphyry Cu-Mo Cooper Flat Mine in Sierra County, NM. Information obtained from previous induced polarization surveys and core samples served as physical constraints for the

  3. Bouguer Gravity Anomalies Associated with Lunar Craters: Initial Results from the GRAIL Mission

    NASA Astrophysics Data System (ADS)

    Phillips, R. J.; Zuber, M. T.; Smith, D. E.; Konopliv, A. S.; Park, R. S.; Wieczorek, M. A.; Lemoine, F. G.; Neumann, G. A.; Melosh, H. J.; Thomason, C. J.; Egan, A. F.

    2012-12-01

    During its primary mapping phase, the Gravity Recovery and Interior Laboratory (GRAIL) mission has mapped the gravity field of the Moon to unprecedented resolution, providing a spherical harmonic model of degree and order 420 and quantitatively useful results to a spatial resolution of at least 20 km. Anomalies associated with impact craters, from large mascon basins down to crater diameters less than 30 km, are the dominant features of a GRAIL degree (l) 420 free-air gravity map of the Moon. Here we focus on the Bouguer gravity anomalies associated with intermediate-sized craters, in the diameter range of ~30-230 km. Results from Apollo-era gravity and topography data analyses suggested that the behavior of crater Bouguer anomalies is age-dependent, but the crater database used then was extremely sparse (12 craters). With the GRAIL gravity field we have a vastly larger set of craters to work with and to date have examined ~200 craters. We calculate a finite-amplitude Bouguer correction with a semi-analytical spatial Green's function sampling a spherical harmonic representation of the lunar shape matched to the gravity bandwidth used (l = 2-300). The resulting crater Bouguer anomalies, averaged over the inner part of each crater, fall in a range of approximately -40 to +40 mGal. We compare Bouguer anomalies against lunar age, crater diameter, regional elevation, geographical locale, and geological setting. Results are interpreted in terms of processes that have operated in the lunar crust and upper mantle.

  4. Simple Bouguer gravity anomaly field and the inferred crustal structure of continental Ecuador

    NASA Astrophysics Data System (ADS)

    Feininger, Tomas; Seguin, M. K.

    1983-01-01

    The simple Bouguer gravity anomaly field of continental Ecuador corresponds closely to the physiographic provinces of the country. The Sierra, which includes the Andes and their foothills, is characterized by a pronounced low with values to -292 mgal, which reflects the deep Andean root. Bouguer anomalies over the Oriente become less negative away from the Sierra, chiefly in response to progressive thinning of continental crust eastward. The Costa, between the Sierra and the Pacific shore, in the north has the most positive on-land Bouguer anomalies (+162 mgal) so far known in the Western Hemisphere. This part of the Costa is underlain by an ancient oceanic plate now welded to the northwestern corner of the otherwise continental South American plate.

  5. World Gravity Map: a set of global complete spherical Bouguer and isostatic anomaly maps and grids

    NASA Astrophysics Data System (ADS)

    Bonvalot, S.; Balmino, G.; Briais, A.; Kuhn, M.; Peyrefitte, A.; Vales, N.; Biancale, R.; Gabalda, G.; Reinquin, F.

    2012-04-01

    We present here a set of digital maps of the Earth's gravity anomalies (surface free air, Bouguer and isostatic), computed at Bureau Gravimetric International (BGI) as a contribution to the Global Geodetic Observing Systems (GGOS) and to the global geophysical maps published by the Commission for the Geological Map of the World (CGMW) with support of UNESCO and other institutions. The Bouguer anomaly concept is extensively used in geophysical interpretation to investigate the density distributions in the Earth's interior. Complete Bouguer anomalies (including terrain effects) are usually computed at regional scales by integrating the gravity attraction of topography elements over and beyond a given area (under planar or spherical approximations). Here, we developed and applied a worldwide spherical approach aimed to provide a set of homogeneous and high resolution gravity anomaly maps and grids computed at the Earth's surface, taking into account a realistic Earth model and reconciling geophysical and geodetic definitions of gravity anomalies. This first version (1.0) has been computed by spherical harmonics analysis / synthesis of the Earth's topography-bathymetry up to degree 10800. The detailed theory of the spherical harmonics approach is given in Balmino et al., (Journal of Geodesy, 2011). The Bouguer and terrain corrections have thus been computed in spherical geometry at 1'x1' resolution using the ETOPO1 topography/bathymetry, ice surface and bedrock models from the NOAA (National Oceanic and Atmospheric Administration) and taking into account precise characteristics (boundaries and densities) of major lakes, inner seas, polar caps and of land areas below sea level. Isostatic corrections have been computed according to the Airy-Heiskanen model in spherical geometry for a constant depth of compensation of 30km. The gravity information given here is provided by the Earth Geopotential Model (EGM2008), developed at degree 2160 by the National Geospatial

  6. A simple Bouguer gravity anomaly map of southwestern Saudi Arabia and an initial interpretation

    USGS Publications Warehouse

    Gettings, M.E.

    1983-01-01

    Approximately 2,200 gravity stations on a 10-km2 grid were used to construct a simple Bouguer gravity anomaly map at 1:2,000,000 scale along a 150-km-wide by 850-km-long strip of the Arabian Peninsula from Sanam, southwest of Ar Riyad, through the Farasan Islands and including offshore islands, the coastal plain, and the Hijaz-Asir escarpment from Jiddah to the Yemen border. On the Precambrian Arabian Shield, local positive gravity anomalies are associated with greenstone belts, gneiss domes, and the Najd fault zones. Local negative gravity anomalies correlate with granitic plutonic rocks. A steep gravity gradient of as much as 4 mgal-km-1 marks the continental margin on the coastal plain near the southwestern end of the strip. Bouguer gravity anomaly values range from -10 to +40 mgal southwest of this gradient and from -170 to -100 mgal in a 300-km-wide gravity minimum northeast of the gradient. Farther northeast, the minimum is terminated by a regional gradient of about 0.1 mgal-km-1 that increases toward the Arabian Gulf. The regional gravity anomaly pattern has been modeled by using seismic refraction and Raleigh wave studies, heat-flow measurements, and isostatic considerations as constraints. The model is consistent with the hypothesis of upwelling of hot mantle material beneath the Red Sea and lateral mantle flow beneath the Arabian plate. The model yields best-fitting average crustal densities of 2.80 g-cm-3 (0-20 km depth) and 3.00 g-cm-3 (20-40 km depth) southwest of the Nabitah suture zone and 2.74 g-cm-3 (0-20 km depth) and 2.94 g-cm-3 (20-40 km depth) northeast of the suture zone. The gravity model requires that the crust be about 20 km thick at the continental margin and that the lower crust between the margin and Bishah (lat 20? N., long 42.5? E.) be somewhat denser than the lower crust to the northeast. Detailed correlations between 1:250,000- and 1:500,000-scale geologic maps and the gravity anomaly map suggest that the greenstone belts associated

  7. Bouguer gravity anomaly and isostatic residual gravity maps of the Tonopah 1 degree by 2 degrees Quadrangle, central Nevada

    USGS Publications Warehouse

    Plouff, Donald

    1992-01-01

    A residual isostatic gravity map (sheet 2) was prepared so that the regional effect of isostatic compensation present on the Bouguer gravity anomaly map (sheet 1) would be minimized. Isostatic corrections based on the Airy-Heiskanen system (Heiskanen and Vening Meinesz, 1958, p. 135-137) were estimated by using 3-minute topographic digitization and applying the method of Jachens and Roberts (1981). Parameters selected for the isostatic model were 25 km for the normal crustal thickness at sea level, 2.67 g/cm3 for the density of the crust, and 0.4 g/cm3 for the contrast in density between the crust and the upper mantle. These parameters were selected so that the isostatic residual gravity map would be consistent with isostatic residual gravity maps of the adjacent Walker Lake quadrangle (Plouff, 1987) and the state of Nevada (Saltus, 1988c).

  8. Data reduction and tying in regional gravity surveys—results from a new gravity base station network and the Bouguer gravity anomaly map for northeastern Mexico

    NASA Astrophysics Data System (ADS)

    Hurtado-Cardador, Manuel; Urrutia-Fucugauchi, Jaime

    2006-12-01

    Since 1947 Petroleos Mexicanos (Pemex) has conducted oil exploration projects using potential field methods. Geophysical exploration companies under contracts with Pemex carried out gravity anomaly surveys that were referred to different floating data. Each survey comprises observations of gravity stations along highways, roads and trails at intervals of about 500 m. At present, 265 separate gravimeter surveys that cover 60% of the Mexican territory (mainly in the oil producing regions of Mexico) are available. This gravity database represents the largest, highest spatial resolution information, and consequently has been used in the geophysical data compilations for the Mexico and North America gravity anomaly maps. Regional integration of gravimeter surveys generates gradients and spurious anomalies in the Bouguer anomaly maps at the boundaries of the connected surveys due to the different gravity base stations utilized. The main objective of this study is to refer all gravimeter surveys from Pemex to a single new first-order gravity base station network, in order to eliminate problems of gradients and spurious anomalies. A second objective is to establish a network of permanent gravity base stations (BGP), referred to a single base from the World Gravity System. Four regional loops of BGP covering eight States of Mexico were established to support the tie of local gravity base stations from each of the gravimeter surveys located in the vicinity of these loops. The third objective is to add the gravity constants, measured and calculated, for each of the 265 gravimeter surveys to their corresponding files in the Pemex and Instituto Mexicano del Petroleo database. The gravity base used as the common datum is the station SILAG 9135-49 (Latin American System of Gravity) located in the National Observatory of Tacubaya in Mexico City. We present the results of the installation of a new gravity base network in northeastern Mexico, reference of the 43 gravimeter surveys

  9. Recalculation of regional and detailed gravity database from Slovak Republic and qualitative interpretation of new generation Bouguer anomaly map

    NASA Astrophysics Data System (ADS)

    Pasteka, Roman; Zahorec, Pavol; Mikuska, Jan; Szalaiova, Viktoria; Papco, Juraj; Krajnak, Martin; Kusnirak, David; Panisova, Jaroslava; Vajda, Peter; Bielik, Miroslav

    2014-05-01

    In this contribution results of the running project "Bouguer anomalies of new generation and the gravimetrical model of Western Carpathians (APVV-0194-10)" are presented. The existing homogenized regional database (212478 points) was enlarged by approximately 107 500 archive detailed gravity measurements. These added gravity values were measured since the year 1976 to the present, therefore they need to be unified and reprocessed. The improved positions of more than 8500 measured points were acquired by digitizing of archive maps (we recognized some local errors within particular data sets). Besides the local errors (due to the wrong positions, heights or gravity of measured points) we have found some areas of systematic errors probably due to the gravity measurement or processing errors. Some of them were confirmed and consequently corrected by field measurements within the frame of current project. Special attention is paid to the recalculation of the terrain corrections - we have used a new developed software as well as the latest version of digital terrain model of Slovakia DMR-3. Main improvement of the new terrain corrections evaluation algorithm is the possibility to calculate it in the real gravimeter position and involving of 3D polyhedral bodies approximation (accepting the spherical approximation of Earth's curvature). We have realized several tests by means of the introduction of non-standard distant relief effects introduction. A new complete Bouguer anomalies map was constructed and transformed by means of higher derivatives operators (tilt derivatives, TDX, theta-derivatives and the new TDXAS transformation), using the regularization approach. A new interesting regional lineament of probably neotectonic character was recognized in the new map of complete Bouguer anomalies and it was confirmed also by realized in-situ field measurements.

  10. GTeC-A versatile MATLAB® tool for a detailed computation of the terrain correction and Bouguer gravity anomalies

    NASA Astrophysics Data System (ADS)

    Cella, Federico

    2015-11-01

    Gravity Terrain Correction (GTeC) is a versatile MATLAB® code for terrain correction aimed to this purpose and capable of going beyond the limits of other public domain codes targeted to this aim. It runs with input gravity data (absolute measurements or free air anomalies) at the land/sea surface and with one or more DTMs (indifferently gridded or scattered) at different detail levels. Each of them can be used to calculate the gravity contribution of a concentric terrain zone around the point station with increasing resolution toward the center. The user can choose between two alternative algorithms for terrain modeling. The simplest one considers each grid point as the flat top of a squared prism. For areas closer to the point station a second algorithm can be chosen to better approximate the relief, with respect to others formulas, by means of a tessellation based network formed by triangular prisms. A more precise terrain correction is therefore achieved, especially in presence of high topographic gradients or just outside the sea/land boundaries. In the last case a suitable algorithm was expressly devised to fit the tessellation based network to the irregular trend of the coastline. GTeC calculates also free air anomalies and both plate and curvature corrections, providing also a complete graphic output including topography, free air anomalies, plate correction, total terrain correction, Bouguer anomalies and the terrain effect due to each computational zone. GTeC speeds up CPU times taking advantage from the parallel computing functions and from the vectorization code, both exploited in MATLAB®. Two code versions of GTeC (for normal or parallel computation), executable under MATLAB environment (pcode), are fully available as public domain software. The results of a synthetic case, of a real case at the regional scale and of a microgravity survey carried out at a short scale, are here presented.

  11. On the Optimization of the Inverse Problem for Bouguer Gravity Anomalies

    NASA Astrophysics Data System (ADS)

    Zamora, A.; Velasco, A. A.; Gutierrez, A. E.

    2013-12-01

    Inverse modeling of gravity data presents a very ill-posed mathematical problem, given that solutions are non-unique and small changes in parameters (position and density contrast of an anomalous body) can highly impact the resulting Earth's model. Although implementing 2- and 3-Dimensional gravitational inverse problems can determine the structural composition of the Earth, traditional inverse modeling approaches can be very unstable. A model of the shallow substructure is based on the density contrasts of anomalous bodies -with different densities with respect to a uniform region- or the boundaries between layers in a layered environment. We implement an interior-point method constrained optimization technique to improve the 2-D model of the Earth's structure through the use of known density constraints for transitional areas obtained from previous geological observations (e.g. core samples, seismic surveys, etc.). The proposed technique is applied to both synthetic data and gravitational data previously obtained from the Rio Grande Rift and the Cooper Flat Mine region located in Sierra County, New Mexico. We find improvements on the models obtained from this optimization scheme given that getting rid of geologically unacceptable models that would otherwise meet the required geophysical properties reduces the solution space.

  12. On different techniques for the calculation of Bouguer gravity anomalies for joint inversion and model fusion of geophysical data in the Rio Grande Rift

    NASA Astrophysics Data System (ADS)

    Zamora, Azucena

    Density variations in the Earth result from different material properties, which reflect the tectonic processes attributed to a region. Density variations can be identified through measurable material properties, such as seismic velocities, gravity field, magnetic field, etc. Gravity anomaly inversions are particularly sensitive to density variations but suffer from significant non-uniqueness. However, using inverse models with gravity Bouguer anomalies and other geophysical data, we can determine three dimensional structural and geological properties of the given area. We explore different techniques for the calculation of Bouguer gravity anomalies for their use in joint inversion of multiple geophysical data sets and a model fusion scheme to integrate complementary geophysical models. Various 2- and 3- dimensional gravity profile forward modeling programs have been developed as variations of existing algorithms in the last decades. The purpose of this study is to determine the most effective gravity forward modeling method that can be used to combine the information provided by complementary datasets, such as gravity and seismic information, to improve the accuracy and resolution of Earth models obtained for the underlying structure of the Rio Grande Rift. In an effort to determine the most appropriate method to use in a joint inversion algorithm and a model fusion approach currently in development, we test each approach by using a model of the Rio Grande Rift obtained from seismic surface wave dispersion and receiver functions. We find that there are different uncertainties associated with each methodology that affect the accuracy achieved by including gravity profile forward modeling. Moreover, there exists an important amount of assumptions about the regions under study that must be taken into account in order to obtain an accurate model of the gravitational acceleration caused by changes in the density of the material in the substructure of the Earth.

  13. Worldwide complete spherical Bouguer and isostatic anomaly maps

    NASA Astrophysics Data System (ADS)

    Bonvalot, S.; Balmino, G.; Briais, A.; Peyrefitte, A.; Vales, N.; Biancale, R.; Gabalda, G.; Reinquin, F.

    2011-12-01

    We present here a set of digital maps of the Earth's gravity anomalies (surface "free air", Bouguer and isostatic), computed at Bureau Gravimetric International (BGI) as a contribution to the Global Geodetic Observing Systems (GGOS) and to the global geophysical maps published by the Commission for the Geological Map of the World (CGMW). The free air and Bouguer anomaly concept is extensively used in geophysical interpretation to investigate the density distributions in the Earth's interior. Complete Bouguer anomalies (including terrain effects) are usually computed at regional scales by integrating the gravity attraction of topography elements over and beyond a given area (under planar or spherical approximations). Here, we developed and applied a worldwide spherical approach aimed to provide a set of homogeneous and high resolution gravity anomaly maps and grids computed at the Earth's surface, taking into account a realistic Earth model and reconciling geophysical and geodetic definitions of gravity anomalies. This first version (1.0) has been computed by spherical harmonics analysis / synthesis of the Earth's topography-bathymetry up to degree 10800. The detailed theory of the spherical harmonics approach is given in Balmino et al., (Journal of Geodesy, submitted). The Bouguer and terrain corrections have thus been computed in spherical geometry at 1'x1' resolution using the ETOPO1 topography/bathymetry, ice surface and bedrock models from the NOAA (National Oceanic and Atmospheric Administration) and taking into account precise characteristics (boundaries and densities) of major lakes, inner seas, polar caps and of land areas below sea level. Isostatic corrections have been computed according to the Airy Heiskanen model in spherical geometry for a constant depth of compensation of 30km. The gravity information given here is provided by the Earth Geopotential Model (EGM2008), developed at degree 2160 by the National Geospatial Intelligence Agency (NGA) (Pavlis

  14. The origin of lunar mascons - Analysis of the Bouguer gravity associated with Grimaldi

    NASA Astrophysics Data System (ADS)

    Phillips, R. J.; Dvorak, J.

    Grimaldi is a relatively small multi-ringed basin located on the western limb of the moon. Spacecraft free-air gravity data reveal a mascon associated with the inner ring of this structure, and the topographic correction to the local lunar gravity field indicates a maximum Bouguer anomaly of +90 milligals at an altitude of 70 kilometers. Approximately 20% of this positive Bouguer anomaly can be attributed to the mare material lying within the inner ring of this basin. From a consideration of the Bouguer gravity and structure of large lunar craters comparable in size to the central basin of Grimaldi, it is suggested that the remaining positive Bouguer anomaly is due to a centrally uplifted plug of lunar mantle material. The uplift was caused by inward crustal collapse which also resulted in the formation of the concentric outer scarp of Grimaldi. In addition, an annulus of low density material, probably a combination of ejecta and in situ breccia, is required to fully reproduce the Bouguer gravity signature across this basin. It is proposed that Grimaldi supplies a critical test in the theory of mascon formation: crustal collapse by ring faulting and central uplift to depths of the crust-mantle boundary are requisites

  15. The origin of lunar mascons - Analysis of the Bouguer gravity associated with Grimaldi

    NASA Technical Reports Server (NTRS)

    Phillips, R. J.; Dvorak, J.

    1981-01-01

    Grimaldi is a relatively small multi-ringed basin located on the western limb of the moon. Spacecraft free-air gravity data reveal a mascon associated with the inner ring of this structure, and the topographic correction to the local lunar gravity field indicates a maximum Bouguer anomaly of +90 milligals at an altitude of 70 kilometers. Approximately 20% of this positive Bouguer anomaly can be attributed to the mare material lying within the inner ring of this basin. From a consideration of the Bouguer gravity and structure of large lunar craters comparable in size to the central basin of Grimaldi, it is suggested that the remaining positive Bouguer anomaly is due to a centrally uplifted plug of lunar mantle material. The uplift was caused by inward crustal collapse which also resulted in the formation of the concentric outer scarp of Grimaldi. In addition, an annulus of low density material, probably a combination of ejecta and in situ breccia, is required to fully reproduce the Bouguer gravity signature across this basin. It is proposed that Grimaldi supplies a critical test in the theory of mascon formation: crustal collapse by ring faulting and central uplift to depths of the crust-mantle boundary are requisites

  16. Separation of Bouguer anomaly map using cellular neural network

    NASA Astrophysics Data System (ADS)

    Albora, A. Muhittin; Ucan, Osman N.; Ozmen, Atilla; Ozkan, Tulay

    2001-02-01

    In this paper, a modern image-processing technique, the Cellular Neural Network (CNN) has been firstly applied to Bouguer anomaly map of synthetic examples and then to data from the Sivas-Divrigi Akdag region. CNN is an analog parallel computing paradigm defined in space and characterized by the locality of connections between processing neurons. The behaviour of the CNN is defined by two template matrices and a template vector. We have optimised the weight coefficients of these templates using the Recurrent Perceptron Learning Algorithm (RPLA). After testing CNN performance on synthetic examples, the CNN approach has been applied to the Bouguer anomaly of Sivas-Divrigi Akdag region and the results match drilling logs done by Mineral Research and Exploration (MTA).

  17. An updated Bouguer anomaly map of south-central West Africa

    USGS Publications Warehouse

    Hastings, David A.

    1983-01-01

    A new Bouguer gravity anomaly map compiled for western Africa adds data for Ghana, Guinea, and Liberia.The new data add detail to a key part of the Eburnean shield and assist in the development of a model of rifting at the time of the Eburnean orogeny, 2000 million years ago. This model includes a framework for the deposition of the region's mineral deposits. The model and existing field data can be used to guide future minerals exploration in the region.

  18. Spherical harmonic modelling to ultra-high degree of Bouguer and isostatic anomalies

    NASA Astrophysics Data System (ADS)

    Balmino, G.; Vales, N.; Bonvalot, S.; Briais, A.

    2012-07-01

    The availability of high-resolution global digital elevation data sets has raised a growing interest in the feasibility of obtaining their spherical harmonic representation at matching resolution, and from there in the modelling of induced gravity perturbations. We have therefore estimated spherical Bouguer and Airy isostatic anomalies whose spherical harmonic models are derived from the Earth's topography harmonic expansion. These spherical anomalies differ from the classical planar ones and may be used in the context of new applications. We succeeded in meeting a number of challenges to build spherical harmonic models with no theoretical limitation on the resolution. A specific algorithm was developed to enable the computation of associated Legendre functions to any degree and order. It was successfully tested up to degree 32,400. All analyses and syntheses were performed, in 64 bits arithmetic and with semi-empirical control of the significant terms to prevent from calculus underflows and overflows, according to IEEE limitations, also in preserving the speed of a specific regular grid processing scheme. Finally, the continuation from the reference ellipsoid's surface to the Earth's surface was performed by high-order Taylor expansion with all grids of required partial derivatives being computed in parallel. The main application was the production of a 1' × 1' equiangular global Bouguer anomaly grid which was computed by spherical harmonic analysis of the Earth's topography-bathymetry ETOPO1 data set up to degree and order 10,800, taking into account the precise boundaries and densities of major lakes and inner seas, with their own altitude, polar caps with bedrock information, and land areas below sea level. The harmonic coefficients for each entity were derived by analyzing the corresponding ETOPO1 part, and free surface data when required, at one arc minute resolution. The following approximations were made: the land, ocean and ice cap gravity spherical

  19. Processing the Bouguer anomaly map of Biga and the surrounding area by the cellular neural network: application to the southwestern Marmara region

    NASA Astrophysics Data System (ADS)

    Aydogan, D.

    2007-04-01

    An image processing technique called the cellular neural network (CNN) approach is used in this study to locate geological features giving rise to gravity anomalies such as faults or the boundary of two geologic zones. CNN is a stochastic image processing technique based on template optimization using the neighborhood relationships of cells. These cells can be characterized by a functional block diagram that is typical of neural network theory. The functionality of CNN is described in its entirety by a number of small matrices (A, B and I) called the cloning template. CNN can also be considered to be a nonlinear convolution of these matrices. This template describes the strength of the nearest neighbor interconnections in the network. The recurrent perceptron learning algorithm (RPLA) is used in optimization of cloning template. The CNN and standard Canny algorithms were first tested on two sets of synthetic gravity data with the aim of checking the reliability of the proposed approach. The CNN method was compared with classical derivative techniques by applying the cross-correlation method (CC) to the same anomaly map as this latter approach can detect some features that are difficult to identify on the Bouguer anomaly maps. This approach was then applied to the Bouguer anomaly map of Biga and its surrounding area, in Turkey. Structural features in the area between Bandirma, Biga, Yenice and Gonen in the southwest Marmara region are investigated by applying the CNN and CC to the Bouguer anomaly map. Faults identified by these algorithms are generally in accordance with previously mapped surface faults. These examples show that the geologic boundaries can be detected from Bouguer anomaly maps using the cloning template approach. A visual evaluation of the outputs of the CNN and CC approaches is carried out, and the results are compared with each other. This approach provides quantitative solutions based on just a few assumptions, which makes the method more

  20. Band-limited Bouguer gravity identifies new basins on the Moon

    NASA Astrophysics Data System (ADS)

    Featherstone, W. E.; Hirt, C.; Kuhn, M.

    2013-06-01

    Spectral domain forward modeling is used to generate topography-implied gravity for the Moon using data from the Lunar Orbiter Laser Altimeter instrument operated on board the Lunar Reconnaissance Orbiter mission. This is subtracted from Selenological and Engineering Explorer (SELENE)-derived gravity to generate band-limited Bouguer gravity maps of the Moon so as to enhance the gravitational signatures of anomalous mass densities nearer the surface. This procedure adds evidence that two previously postulated basins on the lunar farside, Fitzgerald-Jackson (25°N, 191°E) and to the east of Debye (50°N, 180°E), are indeed real. When applied over the entire lunar surface, band-limited Bouguer gravity reveals the locations of 280 candidate basins that have not been identified when using full-spectrum gravity or topography alone, showing the approach to be of utility. Of the 280 basins, 66 are classified as distinct from their band-limited Bouguer gravity and topographic signatures, making them worthy of further investigation.

  1. Bouguer gravity trends and crustal structure of the Palmyride Mountain belt and surrounding northern Arabian platform in Syria

    SciTech Connect

    Best, J.A.; Barazangi, M. ); Al-Saad, D.; Sawaf, T.; Gebran, A. )

    1990-12-01

    This study examines the crustal structure of the Palmyrides and the northern Arabian platform in Syria by two- and three-dimensional modeling of the Bouguer gravity anomalies. Results of the gravity modeling indicate that (1) western Syria is composed of at least two different crustal blocks, (2) the southern crustal block is penetrated by a series of crustal-scale, high-density intrusive complexes, and (3) short-wavelength gravity anomalies in the southwest part of the mountain belt are clearly related to basement structure. The crustal thickness in Syria, as modeled on the gravity profiles, is approximately 40{plus minus}4 km, which is similar to crustal thicknesses interpreted from refraction data in Jordan and Saudi Arabia. The different crustal blocks and large-scale mafic intrusions are best explained, though not uniquely, by Proterozoic convergence and suturing and early Paleozoic rifting, as interpreted in the exposed rocks of the Arabian shield. These two processes, combined with documented Mesozoic rifting and Cenozoic transpression, compose the crustal evolution of the northern Arabian platform beneath Syria.

  2. New Data Bases and Standards for Gravity Anomalies

    NASA Astrophysics Data System (ADS)

    Keller, G. R.; Hildenbrand (Deceased), T. G.; Webring, M. W.; Hinze, W. J.; Ravat, D.; Li, X.

    2008-12-01

    derive the predicted or modeled gravity, and thus, anomalies of this class are termed planetary. The most primitive version of a gravity anomaly is simply the difference between the value of gravity predicted by the effect of the reference ellipsoid and the observed gravity anomaly. When the height of the gravity station increases, the ellipsoidal gravity anomaly decreases because of the increased distance of measurement from the anomaly- producing masses. The two primary anomalies in geophysics, which are appropriately classified as planetary anomalies, are the Free-air and Bouguer gravity anomalies. They employ models that account for planetary effects on gravity including the topography of the earth. A second class of anomaly, geological anomalies, includes the modeled gravity effect of known or assumed masses leading to the predicted gravity by using geological data such as densities and crustal thickness. The third class of anomaly, filtered anomalies, removes arbitrary gravity effects of largely unknown sources that are empirically or analytically determined from the nature of the gravity anomalies by filtering.

  3. Upward Continuation Apply Newly to Process Gravity Anomaly Data in the East China Sea

    NASA Astrophysics Data System (ADS)

    Han, Bo; Zhang, Xunhua; Jiang, Jinyu

    2014-05-01

    The research area lies in the East China Sea and its adjacent area and the concrete is between 120-130 degree of east longitude and 20-30 degree of north latitude and it also lies between Eurasian Plate and Pacific Plate. The structures of the area transform differently and they are namely Uplifted Zone of Zhejiang-Fujian, East China Sea Shelf Basin, Okinawa Trough Back-arc Basin, Ryukyu Arc, Ryukyu trench and Philippine Sea from west to east. Bouguer gravity anomaly can reflect deep structure characters and it is help to judge deep structures. The bouguer gravity anomalies of the area change differently from west to east. The anomalies increase gradually from land to the middle of Okinawa trough and near land anomaly contour strike accords with coastline and the middle of Okinawa trough reflect the highest anomalies in this area. Gravity anomalies re-increase from Ryukyu fore-arc basin to trench and Ryukyu island arc appears the low anomalies. Philippine Sea appears high gravity anomalies background. Upward continuation method has been used to process original gravity anomaly as a common method and its destination is to weaken local anomaly and at last strengthen deep anomaly and it's important to deep structure study. Upward 5 km, 10 km and 20 km have been used to process data and the results been compared. However, the research area is very large and the deep structure is complex, it isn't suitable to use single height to upward continuation processing bouguer gravity anomaly. Then we propose multiple upward heights continuation to process gravity data respectively in different area. We use upward 20km to process data in the area from land to the slope and upward 10km from Okinawa trough to Ryukyu island arc and upward 5km from Ryukyu trench to Philippine Sea. At last we obtain multiple upward height result and the calculated result confirms that it is fit to use this method. Gravity anomalies contours become smoother than before and the deep structures become

  4. Comparison of onshore Bouguer anomalies with GOCE Satellite Data in two sections of the Andes: at 29°S and at 39°S.

    NASA Astrophysics Data System (ADS)

    Alvarez, O.; Gimenez, M.; Braitenberg, C.; Martinez, P.

    2012-04-01

    In the present work we compare the Bouguer anomaly obtained from onshore measurements with the Bouguer anomaly obtained from satellite GOCE data along two well known sections of the Andes, at 29°18'S and at 38°45'S. The first gravimetric section, published by Martinez et al. (2006), describes a gravity and altimetric profile that extends over a distance surpassing 800km in Argentina, at 29°18'S. Using gravimetric inversion methods a crustal model was obtained which is in accordance with the main regional geologic structures. This model fits with a dominant collision mechanism that affected ancient blocks and is a two-layer crustal model with lateral density variations. The Chilenia, Cuyania, Famatina System, Pampia and River Plate cratons were detected. From the gravimetric signal we identify beyond doubt the suture zone between the Precordillera and the Famatina System Ranges, as well as the shear zone between the latter ranges and the Velasco Range. The maximum crustal thickness determined beneath the Andean Cordillera at this latitude is 69 km, whereas under the Famatina System and the Velasco Ranges the values obtained are, respectively, 56 km and 46.5 km. The second profile was published by Folguera et al., (2008). The western retroarc of the Southern Andes between 38° and 40°S is formed by a NNW-elongated ridge not associated with stacked thrust sheets. On the contrary, during the last 4-3 Ma this ridge was affected by extensional deformation, regional uplift and related folding on a very broad scale. Receiver function analysis shows that the drainage divide area and adjacent retroarc lie over an attenuated crust. Normal crustal thickness at these latitudes is around 42km, whereas in this part of the retroarc the thickness is less than 32km. The causes for such attenuation have been linked to a moderate steepening of the subducted Nazca plate beneath South American plate, which is suggested by a westward shift and narrowing of the arc during the last 5Ma

  5. Interpretation of gravity anomalies in the northwest Adirondack lowlands, northern New York

    SciTech Connect

    Revetta, F.A.; O'Brian, B. . Geology Dept.)

    1993-03-01

    Twelve hundred gravity measurements were made in the Adirondack Highlands and northwest Adirondack Lowlands, New York between 44[degree]15 minutes and 44[degree]30 minutes N. Latitude and 75[degree]00 minutes W. Longitude. A Bouguer gravity map constructed from the gravity measurements includes the Carthage-Colton Mylonite Zone, a major structural boundary between the highlands and lowlands. The gravity map indicates the gravity contours trend parallel to the CCMZ along most of its length however in some areas the contours cross the boundary. No clear-cut relationships exists between the CCMZ and gravity contours. The Bouguer gravity map shows several prominent gravity anomalies which correlate with the geology seismicity and mineral deposits in the area. Gravity lows of 20 to 30 g.u. are centered over the Gouverneur, Hyde and Payne Lake Alaskite gneiss bodies. A gravity high of 20 g.u. occurs over the Pleasant Lake gabbro pluton. Gravity highs of 35 and 100 g.u. occur over the Sylvia Lake Zinc District and marble just north of the district. A gravity high at Russell, N.Y. coincides with a cluster of nine earthquake epicenters. Finally a steep gravity gradient separates high density rocks from lower density rocks along the Black Lake fault. Two-dimensional computer modeling of the geologic features is underway and quantitative models of the structures will be presented.

  6. Spreading rate dependence of gravity anomalies along oceanic transform faults.

    PubMed

    Gregg, Patricia M; Lin, Jian; Behn, Mark D; Montési, Laurent G J

    2007-07-12

    Mid-ocean ridge morphology and crustal accretion are known to depend on the spreading rate of the ridge. Slow-spreading mid-ocean-ridge segments exhibit significant crustal thinning towards transform and non-transform offsets, which is thought to arise from a three-dimensional process of buoyant mantle upwelling and melt migration focused beneath the centres of ridge segments. In contrast, fast-spreading mid-ocean ridges are characterized by smaller, segment-scale variations in crustal thickness, which reflect more uniform mantle upwelling beneath the ridge axis. Here we present a systematic study of the residual mantle Bouguer gravity anomaly of 19 oceanic transform faults that reveals a strong correlation between gravity signature and spreading rate. Previous studies have shown that slow-slipping transform faults are marked by more positive gravity anomalies than their adjacent ridge segments, but our analysis reveals that intermediate and fast-slipping transform faults exhibit more negative gravity anomalies than their adjacent ridge segments. This finding indicates that there is a mass deficit at intermediate- and fast-slipping transform faults, which could reflect increased rock porosity, serpentinization of mantle peridotite, and/or crustal thickening. The most negative anomalies correspond to topographic highs flanking the transform faults, rather than to transform troughs (where deformation is probably focused and porosity and alteration are expected to be greatest), indicating that crustal thickening could be an important contributor to the negative gravity anomalies observed. This finding in turn suggests that three-dimensional magma accretion may occur near intermediate- and fast-slipping transform faults.

  7. Deformation induced topographic effects in inversion of temporal gravity changes: First look at Free Air and Bouguer terms

    NASA Astrophysics Data System (ADS)

    Vajda, Peter; Zahorec Pavol, Pavol; Papčo, Juraj; Kubová, Anna

    2015-06-01

    We review here the gravitational effects on the temporal (time-lapse) gravity changes induced by the surface deformation (vertical displacements). We focus on two terms, one induced by the displacement of the benchmark (gravity station) in the ambient gravity field, and the other imposed by the attraction of the masses within the topographic deformation rind. The first term, coined often the Free Air Effect (FAE), is the product of the vertical gradient of gravity (VGG) and the vertical displacement of the benchmark. We examine the use of the vertical gradient of normal gravity, typically called the theoretical or normal Free Air Gradient (normal FAG), as a replacement for the true VGG in the FAE, as well as the contribution of the topography to the VGG. We compute a topographic correction to the normal FAG, to offer a better approximation of the VGG, and evaluate its size and shape (spatial behavior) for a volcanic study area selected as the Central Volcanic Complex (CVC) on Tenerife, where this correction reaches 77% of the normal FAG and varies rapidly with terrain. The second term, imposed by the attraction of the vertically displaced topo-masses, referred to here as the Topographic Deformation Effect (TDE) must be computed by numerical evaluation of the Newton volumetric integral. As the effect wanes off quickly with distance, a high resolution DEM is required for its evaluation. In practice this effect is often approximated by the planar or spherical Bouguer deformation effect (BDE). By a synthetic simulation at the CVC of Tenerife we show the difference between the rigorously evaluated TDE and its approximation by the planar BDE. The complete effect, coined here the Deformation Induced Topographic Effect (DITE) is the sum of FAE and TDE. Next we compare by means of synthetic simulations the DITE with two approximations of DITE typically used in practice: one amounting only to the first term in which the VGG is approximated by normal FAG, the other adopting a

  8. The decompensative gravity anomaly and deep structure of the region of the Rio Grande rift

    SciTech Connect

    Cordell, L. ); Zorin, Y.A. ); Keller, G.R. )

    1991-04-10

    An isostatic correction is commonly made to Bouguer anomaly gravity data to remove the gravity effect of isostatic compensation of topographic loads. In the USSR a decompensative correction has then been made to the isostatic gravity anomaly to remove the gravity effect of isostatic compensation of geologic loads as well. The authors employ here calculations in the wave number domain, leading to an efficient and exact solution. In a 1,200 {times} 1,200 km region centered on the Rio Grande rift the decompensative correction ranges from about {minus}35 to +25 mGal. The decompensative anomaly, highlights an arcuate gravity low and a system of gravity highs inferred to reflect prerift welts of mass concentration which have indirectly influenced the position of the rift and its segmentation and zones of accommodation. Under the assumptions made, if the decompensative anomaly is subtracted from the Bouguer anomaly, then the residual is the gravity anomaly field of deep structure, without gravity effects of shallow sources in the upper crust. Using available seismic data to (weakly) constrain the Moho surface, they invert the residual gravity field for topography of the base of the lithosphere. Lithosphere is found to be 200 km thick in the High Plains; 40-50 km in the eastern Great Basin; 75-100 km in the Colorado Plateau, and as thin as 40 km in the southern Rio Grande rift. In the area studied, the thickness of the lithospere is everwhere greater than that of the crust. The separation of gravity effects made possible by the decompensative correction shows how the rift is fundamentally controlled by thinning of the lithosphere, yet in detail is deflected by long-lived tectonic welts in the shallow, brittle crust.

  9. Consistent anomalies of the induced W gravities

    NASA Astrophysics Data System (ADS)

    Abud, Mario; Ader, Jean-Pierre; Cappiello, Luigi

    1996-02-01

    The BRST anomaly which may be present in the induced Wn gravity quantized on the light-cone is evaluated in the geometrical framework of Zucchini. The cocycles linked by the cohomology of the BRST operator to the anomaly are straightforwardly calculated thanks to the analogy between this formulation and the Yang-Mills theory. We give also a conformally covariant formulation of these quantities including the anomaly, which is valid on arbitrary Riemann surfaces. The example of the W3 theory is discussed and a comparison with other candidates for the anomaly available in the literature is presented.

  10. Gravity anomalies, spatial variation of flexural rigidity, and role of inherited crustal structure in the Aquitaine Basin

    NASA Astrophysics Data System (ADS)

    Angrand, Paul; Ford, Mary; Watts, Anthony; Bell, Rebecca E.

    2016-04-01

    The Aquitaine foreland basin developed from Campanian to Miocene by flexure of the upper (European) plate during the Pyrenean orogeny. The foreland basin forms a syn-orogenic sedimentary wedge up to 6 km thick in the south, thinning rapidly north and has a maximum width of 200 km in the west. The flexural basin was superimposed on a lithosphere previously affected by Apto-Albian hyper-extension. What are the effects of an inherited extremely weak and narrow rifted zone on the behavior of a superimposed flexural foreland basin? Coupled with surface and subsurface data, Bouguer gravity anomalies were used to determine the crustal structure of the northern Pyrenean retrowedge and the flexure of the European plate. In the centre, the basin shows a regional Bouguer anomaly pattern typical of foreland basins with the maximum of syn-orogenic deposits corresponding to a low and the forebulge to a high. However, south of the North Pyrenean Frontal Thrust (NPFT) this regional field is overprinted by strong positive Bouguer anomalies, which correspond to high density bodies (mantle or lower crust) transported along the NPFT. Stratigraphy shows that the central basin evolved as a series of narrow, laterally variable depocentres that migrated north. Shortening is accommodated mainly by thick skinned deformation and local reactivation of salt structures. In the east, the Toulouse Fault separates the central and eastern foreland. The eastern foreland shows a broader zone of negative Bouguer values. This foreland is salt-free and stratigraphy records higher subsidence. The easternmost basin is completely overprinted by the opening of the Gulf of Lion. In the west, the foreland does not show a typical regional gravity anomaly pattern due to overprinting by the opening of the Bay of Biscay. Instead, a major gravity high is centered on the northern Landes High, with a second high centered on the Labourd massif south of the NPFT. Neither the Parentis rift basin nor the salt

  11. Magnetic and gravity anomalies in the Americas

    NASA Technical Reports Server (NTRS)

    Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator)

    1981-01-01

    The cleaning and magnetic tape storage of spherical Earth processing programs are reported. These programs include: NVERTSM which inverts total or vector magnetic anomaly data on a distribution of point dipoles in spherical coordinates; SMFLD which utilizes output from NVERTSM to compute total or vector magnetic anomaly fields for a distribution of point dipoles in spherical coordinates; NVERTG; and GFLD. Abstracts are presented for papers dealing with the mapping and modeling of magnetic and gravity anomalies, and with the verification of crustal components in satellite data.

  12. Anomaly freedom in perturbative loop quantum gravity

    SciTech Connect

    Bojowald, Martin; Hossain, Golam Mortuza; Kagan, Mikhail; Shankaranarayanan, S.

    2008-09-15

    A fully consistent linear perturbation theory for cosmology is derived in the presence of quantum corrections as they are suggested by properties of inverse volume operators in loop quantum gravity. The underlying constraints present a consistent deformation of the classical system, which shows that the discreteness in loop quantum gravity can be implemented in effective equations without spoiling space-time covariance. Nevertheless, nontrivial quantum corrections do arise in the constraint algebra. Since correction terms must appear in tightly controlled forms to avoid anomalies, detailed insights for the correct implementation of constraint operators can be gained. The procedures of this article thus provide a clear link between fundamental quantum gravity and phenomenology.

  13. Newberry Combined Gravity 2016

    SciTech Connect

    Kelly Rose

    2016-01-22

    Newberry combined gravity from Zonge Int'l, processed for the EGS stimulation project at well 55-29. Includes data from both Davenport 2006 collection and for OSU/4D EGS monitoring 2012 collection. Locations are NAD83, UTM Zone 10 North, meters. Elevation is NAVD88. Gravity in milligals. Free air and observed gravity are included, along with simple Bouguer anomaly and terrain corrected Bouguer anomaly. SBA230 means simple Bouguer anomaly computed at 2.30 g/cc. CBA230 means terrain corrected Bouguer anomaly at 2.30 g/cc. This suite of densities are included (g/cc): 2.00, 2.10, 2.20, 2.30, 2.40, 2.50, 2.67.

  14. Long wavelength gravity and topography anomalies

    NASA Technical Reports Server (NTRS)

    Watts, A. B.; Daly, S. F.

    1981-01-01

    It is shown that gravity and topography anomalies on the earth's surface may provide new information about deep processes occurring in the earth, such as those associated with mantle convection. Two main reasons are cited for this. The first is the steady improvement that has occurred in the resolution of the long wavelength gravity field, particularly in the wavelength range of a few hundred to a few thousand km, mainly due to increased coverage of terrestrial gravity measurements and the development of radar altimeters in orbiting satellites. The second reason is the large number of numerical and laboratory experiments of convection in the earth, including some with deformable upper and lower boundaries and temperature-dependent viscosity. The oceans are thought to hold the most promise for determining long wavelength gravity and topography anomalies, since their evolution has been relatively simple in comparison with that of the continents. It is also shown that good correlation between long wavelength gravity and topography anomalies exists over some portions of the ocean floor

  15. Topographic gravity modeling for global Bouguer maps to degree 2160: Validation of spectral and spatial domain forward modeling techniques at the 10 microGal level

    NASA Astrophysics Data System (ADS)

    Hirt, Christian; Reußner, Elisabeth; Rexer, Moritz; Kuhn, Michael

    2016-09-01

    Over the past years, spectral techniques have become a standard to model Earth's global gravity field to 10 km scales, with the EGM2008 geopotential model being a prominent example. For some geophysical applications of EGM2008, particularly Bouguer gravity computation with spectral techniques, a topographic potential model of adequate resolution is required. However, current topographic potential models have not yet been successfully validated to degree 2160, and notable discrepancies between spectral modeling and Newtonian (numerical) integration well beyond the 10 mGal level have been reported. Here we accurately compute and validate gravity implied by a degree 2160 model of Earth's topographic masses. Our experiments are based on two key strategies, both of which require advanced computational resources. First, we construct a spectrally complete model of the gravity field which is generated by the degree 2160 Earth topography model. This involves expansion of the topographic potential to the 15th integer power of the topography and modeling of short-scale gravity signals to ultrahigh degree of 21,600, translating into unprecedented fine scales of 1 km. Second, we apply Newtonian integration in the space domain with high spatial resolution to reduce discretization errors. Our numerical study demonstrates excellent agreement (8 μGgal RMS) between gravity from both forward modeling techniques and provides insight into the convergence process associated with spectral modeling of gravity signals at very short scales (few km). As key conclusion, our work successfully validates the spectral domain forward modeling technique for degree 2160 topography and increases the confidence in new high-resolution global Bouguer gravity maps.

  16. Flavorful hybrid anomaly-gravity mediation

    SciTech Connect

    Gross, Christian; Hiller, Gudrun

    2011-05-01

    We consider supersymmetric models where anomaly and gravity mediation give comparable contributions to the soft terms and discuss how this can be realized in a five-dimensional brane world. The gaugino mass pattern of anomaly mediation is preserved in such a hybrid setup. The flavorful gravity-mediated contribution cures the tachyonic slepton problem of anomaly mediation. The supersymmetric flavor puzzle is solved by alignment. We explicitly show how a working flavor-tachyon link can be realized with Abelian flavor symmetries and give the characteristic signatures of the framework, including O(1) slepton mass splittings between different generations and between doublets and singlets. This provides opportunities for same flavor dilepton edge measurements with missing energy at the Large Hadron Collider (LHC). Rare lepton decay rates could be close to their current experimental limit. Compared to pure gravity mediation, the hybrid model is advantageous because it features a heavy gravitino which can avoid the cosmological gravitino problem of gravity-mediated models combined with leptogenesis.

  17. The correspondence analysis of the satellite gravity anomalies with the deep lithosphere structure of the East China Sea

    NASA Astrophysics Data System (ADS)

    Yao, C.; Meng, X.; Guo, W.; Zheng, Y.; Gao, D.; Li, H.; He, H.

    2010-12-01

    Based on the satellite gravity data, and the trial analysis of various parameters, the terrain correction and the correction of sea water are carried out to obtain the Bouguer gravity anomalies of the continental shelf of the East China Sea to the Phillipine Basin. The inversion of gravity anomalies and modeling are developed with the constraints of the results of seismic profiles. To infer the deep lithospheric structure of the East China Sea, the shallow geological structure is firstly analyzed. Finally, a gravity model of explanation is provided to demonstrate the site of subduction of the Phillipine plate toward the Eurasia plat, and to show the variation of the Moho and the changes of thickness of lithosphere.

  18. The Origin of the Rodrigues Depth Anomaly: New constraints from integrated gravity inversion

    NASA Astrophysics Data System (ADS)

    Minakov, Alexander; Gaina, Carmen; Faleide, Jan Inge

    2016-04-01

    This study is focused on the Western Indian Ocean including the Central Indian Ridge. The Rodrigues Ridge is a bathymetric feature (500 km -long and 20 km -wide) situated east of the Mascarene Plateau and Mauritius, with an oblique trend with respect to the underlying seafloor spreading fabric. The trend is also different from the fracture zone and hotspot tracks in this area. The region where the Rodrigues Ridge intersects the Central Indian Ridge is characterized by broad area being shallower than it should be according to standard age-depth relations for oceanic basement. With this contribution we aim to determine key factors controlling the formation of the Rodrigues Ridge and the development of the depth anomaly through time. In order to better constrain the nature and extent of the depth anomaly underlying the Rodrigues Ridge and surrounding region, we have carried out a 3D gravity and bathymetry data analysis. This analysis included an iterative gravity inversion approach linked to the computation of residual topography through the temperature and density model of the crust and upper mantle. We use a refined plate kinematic model of the study area for the time period ca. 30 Ma to the present. The refined kinematic model is an important element for temperature modelling at the ridge-transform intersection. Existing seismological data provide additional constraints for the gravity inversion. The results of the 3D gravity and bathymetry data analysis support the model of enhanced production of crust at the Central Indian Ridge adjacent to the Rodrigues Ridge. The depth anomaly is composed of abrupt Rodrigues Ridge edifice sitting on top a relatively smooth and broad anomaly characterized by crustal thickness between 8 and 13 km. These values are significantly higher than those typical for the crustal thickness generated by slow seafloor spreading at the Central Indian Ridge and other slow spreading ridges. This gives rise to a large negative residual mantle

  19. Trace anomaly and counterterms in designer gravity

    NASA Astrophysics Data System (ADS)

    Anabalón, Andrés; Astefanesei, Dumitru; Choque, David; Martínez, Cristián

    2016-03-01

    We construct concrete counterterms of the Balasubramanian-Kraus type for Einstein-scalar theories with designer gravity boundary conditions in AdS4, so that the total action is finite on-shell and satisfy a well defined variational principle. We focus on scalar fields with the conformal mass m 2 = -2 l -2 and show that the holographic mass matches the Hamiltonian mass for any boundary conditions. We compute the trace anomaly of the dual field theory in the generic case, as well as when there exist logarithmic branches of non-linear origin. As expected, the anomaly vanishes for the boundary conditions that are AdS invariant. When the anomaly does not vanish, the dual stress tensor describes a thermal gas with an equation of state related to the boundary conditions of the scalar field. In the case of a vanishing anomaly, we recover the dual theory of a massless thermal gas. As an application of the formalism, we consider a general family of exact hairy black hole solutions that, for some particular values of the parameters in the moduli potential, contains solutions of four-dimensional gauged {N}=8 supergravity and its ω-deformation. Using the AdS/CFT duality dictionary, they correspond to triple trace deformations of the dual field theory.

  20. Determination of mean gravity anomalies in the Taiwan Island

    NASA Technical Reports Server (NTRS)

    Chang, Ruey-Gang

    1989-01-01

    The fitting and proper regression coefficients were made of one hundred seventeen 10 x 10' blocks with observed gravity data and corresponding elevation in the Taiwan Island. To compare five different predicted models, and the proper one for the mean gravity anomalies were determined. The predicted gravity anomalies of the non-observed gravity blocks were decided when the coefficients obtained through the model with the weighted mean method. It was suggested that the mean gravity anomalies of 10 x 10' blocks should be made when comprehensive the observed and predicted data.

  1. GRAVITY STUDIES IN THE CASCADE RANGE.

    USGS Publications Warehouse

    Finn, Carol; Williams, David

    1983-01-01

    A compatible set of gravity data has been compiled for the entire Cascade Range. From this data set a series of interpretive color gravity maps have been prepared, including a free air anomaly map, Bouguer anomaly map at a principle, and an alternate reduction density, and filtered and derivative versions of the Bouguer anomaly map. The regional anomaly pattern and gradients outline the various geological provinces adjacent to the Cascade Range and delineate major structural elements in the range. The more local anomalies and gradients may delineate low density basin and caldera fill, faults, and shallow plutons. Refs.

  2. Spectral analysis of gravity anomalies and the architecture of tectonic wedging, NE Venezuela and Trinidad

    NASA Astrophysics Data System (ADS)

    Russo, R. M.; Speed, R. C.

    1994-06-01

    We have analyzed the spectral content of free air gravity anomalies in the Caribbean-South American plate boundary zone in order to determine better the near-surface (0-120 km) distribution of crustal and upper mantle elements which give rise to the unusual gravity field of this region. The plate boundary zone in northeastern Venezuela and Trinidad is the site of the world's sea level continental minimum of Bouguer gravity anomalies, yet the region is also one of mild topography (mean value 43 m, maximum 1200 m). We find the mean depths to interfaces of significant density contrast at a variety of depths for portions of the plate boundary zone. We interpret interfaces at 30-35 km and 32 km beneath the Guyana Shield and the Aves Ridge, respectively, to be the Moho. Other shallow interfaces (5-14 km) are most likely sediment cover-basement contacts in the Maturin foreland basin and southern Grenada Basin. Deeper interfaces (54-63 km) we associate with loaded and downwarped continental and oceanic South American lithosphere. The deepest boundaries, at depths of 89-120 km, may be related to detached or detaching oceanic lithosphere overridden by continental South America. We use our results to test the tectonic wedging model of the plate boundary zone recently published by Russo and Speed (1992). We find that the tectonic wedging model adequately describes many of the structural boundaries inferable from our analysis of gravity anomalies but that the model must be modified to include a thinner Guyana Shield crust.

  3. Preliminary interpretation of satellite gravity and magnetic anomalies in the region of the Philippine Sea Plate

    NASA Astrophysics Data System (ADS)

    Chen, C.; Hu, Z.; Du, J.; Wang, Q.

    2011-12-01

    The Philippine Sea, situated in the northwestern Pacific, is one of the largest marginal seas on the Earth. Analysis of the Philippine Sea's intraplate fault tectonic systems and lithosphere's density and magnetism structures has a significant contribution to understanding not only the dynamic principles of subduction and convergence zones but also effect of plate subduction on back-arc area. It is also important to have cognizance for structure evolution of the ocean crust, the tension and extending progress of marginal sea basins and the mechanisms of geodynamics. Meanwhile, it can be a significant approach for researching the evolution of the East China Sea and the South China Sea. Using high-precision gravity forwarding method based on spatial domain in spherical coordinate, we have calculated the Bouguer gravity disturbance (BGD) in the Philippine Sea based on the ETOPO1 1 arc-minute topography & bathymetry data and the gravity field model EIGEN-6C. After removing the gravity effect of the sediments and deep abnormal materials, we make spherical cap harmonic analysis of the residual anomaly and obtain the topography of Moho and apparent-density's distribution of our study area by alternate iteration inversion method. Then, we calculate the distributions of the study area's magnetic anomalies based on the Earth magnetic model NGDC720, reduce to the pole of the study area's magnetic anomalies by the equivalent source method based on spherical prism magnetic forwarding, inverse the processed magnetic anomalies with spherical cap harmonic analysis to obtain the topography of Curie surface and the apparent magnetic susceptibility distribution. Finally, we divide the Philippine Sea block into tectonic units and derive the faults distributions through the analysis of gravity magnetic anomalies' linear characteristics. The results show that West Philippine Basin is divided by Central Basin Ridge into two block units, the tectonic trend of the north block is south

  4. Isostatic Model and Isostatic Gravity Anomalies of the Arabian Plate and Surroundings

    NASA Astrophysics Data System (ADS)

    Kaban, Mikhail K.; El Khrepy, Sami; Al-Arifi, Nassir

    2016-04-01

    The isostatic modeling represents one of the most useful "geological" reduction methods of the gravity field. With the isostatic correction, it is possible to remove a significant part of the effect of deep density heterogeneity, which dominates in the Bouguer gravity anomalies. Although there exist several isostatic compensation schemes, it is usually supposed that a choice of the model is not an important factor to first order, since the total weight of compensating masses remains the same. We compare two alternative models for the Arabian plate and surrounding area. The Airy model gives very significant regional isostatic anomalies, which cannot be explained by the upper crust structure or disturbances of the isostatic equilibrium. Also, the predicted "isostatic" Moho is very different from existing seismic observations. The second isostatic model includes the Moho, which is based on seismic determinations. Additional compensation is provided by density variations within the lithosphere (chiefly in the upper mantle). According to this model, the upper mantle under the Arabian Shield is less dense than under the Platform. In the Arabian platform, the maximum density coincides with the Rub' al Khali, one of the richest oil basin in the world. This finding agrees with previous studies, showing that such basins are often underlain by dense mantle, possibly related to an eclogite layer that has caused their subsidence. The mantle density variations might be also a result of variations of the lithosphere thickness. With the combined isostatic model, it is possible to minimize regional anomalies over the Arabian plate. The residual local anomalies correspond well to tectonic structure of the plate. Still very significant anomalies, showing isostatic disturbances of the lithosphere, are associated with the Zagros fold belt, the collision zone of the Arabian and Eurasian plates.

  5. Upgraded gravity anomaly base of the United States

    USGS Publications Warehouse

    Keller, Gordon R.; Hildenbrand, T.G.; Kucks, R.; Roman, D.; Hittelman, A.M.

    2002-01-01

    A concerted effort to compile an upgraded gravity anomaly database, grid, and map for the United States by the end of 2002 is under way. This effort can be considered as the first step in building a data system for gravity measurements, and it builds on existing collaborative efforts. This paper outlines the strategy for assembling the individual map and digital products related to the United States gravity database.

  6. Interpretation of Local Gravity Anomalies in Northern New York

    NASA Astrophysics Data System (ADS)

    Revetta, F. A.

    2004-05-01

    About 10,000 new gravity measurements at a station spacing of 1 to 2 Km were made in the Adirondack Mountains, Lake Champlain Valley, St. Lawrence River Valley and Tug Hill Plateau. These closely spaced gravity measurements were compiled to construct computer contoured gravity maps of the survey areas. The gravity measurements reveal local anomalies related to seismicity, faults, mineral resources and gas fields that are not seen in the regional gravity mapping. In northern New York gravity and seismicity maps indicate epicenters are concentrated in areas of the most pronounced gravity anomalies along steep gravity gradients. Zones of weakness along the contacts of these lithologies of different density could possibly account for the earthquakes in this high stress area. Also, a computer contoured gravity map of the 5.3 magnitude Au Sable Forks earthquake of April 20, 2002 indicates the epicenter lies along a north-south trending gravity gradient produced by a high angle fault structure separating a gravity low in the west from high gravity in the east. In the St. Lawrence Valley, the Carthage-Colton Mylonite Zone, a major northeast trending structural boundary between the Adirondack Highlands and Northwest Lowlands, is represented as a steep gravity gradient extending into the eastern shore of Lake Ontario. At Russell, New York near the CCMZ, a small circular shaped gravity high coincides with a cluster of earthquakes. The coincidence of the epicenters over the high may indicate stress amplification at the boundary of a gabbro pluton. The Morristown fault located in the Morristown Quadrangle in St. Lawrence County produces both gravity and magnetic anomalies due to Precambrian Basement faulting. This faulting indicates control of the Morristown fault in the overlying Paleozoics by the Precambrian faults. Gravity and magnetic anomalies also occur over proposed extensions of the Gloucester and Winchester Springs faults into northern New York. Gravity and magnetic

  7. Lithosphere structure underneath the North China Craton inferred from elevation, gravity and geoid anomalies

    NASA Astrophysics Data System (ADS)

    Wang, K.

    2015-12-01

    The North China Craton (NCC) is a classical example of ancient destroyed cratons. The NCC experienced widespread thermotectonic reactivations in the Phanerozoic. Recent work suggested that the old craton has been significantly modified or destroyed during this process. However, most of the studies were confined to the Eastern NCC, the nature and evolution of the lithosphere beneath the Central and Western NCC was less constrained due to the lack of data. While, recent geodetic data, with the advantages of high resolution and coverage, offers an opportunity to study the deep structure underneath the whole NCC. Here we construct a lithospheric-scale 3D model based on the integration of regional elevation, gravity, geoid and thermal data together with available seismic data. The combined interpretation of these data provides information on the density and temperature distribution at different depth ranges. In the Eastern NCC, a rapid thickness decrease of both crust and lithosphere is reflected, concordant with abrupt changes in surface topography and Bouguer gravity anomaly. Our results together with the widespread magmatic rocks suggest that the Eastern NCC has experienced significant destruction of the lithospheric mantle with substantial modifications and thinning of the crust. In the Central and Western NCC, the generally thick and 'cold' lithosphere suggests that the cratonic mantle root is preserved in the central and western NCC, in agreement with the relatively low heat flow, rare magmatic activity and long-term tectonic stability observed at the surface, with some areas mildly modified as indicated by thin lithosphere.

  8. Detailed gravity anomalies from GEOS-3 satellite altimetry data

    NASA Technical Reports Server (NTRS)

    Gopalapillai, G. S.; Mourad, A. G.

    1978-01-01

    A technique for deriving mean gravity anomalies from dense altimetry data was developed. A combination of both deterministic and statistical techniques was used. The basic mathematical model was based on the Stokes' equation which describes the analytical relationship between mean gravity anomalies and geoid undulations at a point; this undulation is a linear function of the altimetry data at that point. The overdetermined problem resulting from the excessive altimetry data available was solved using Least-Squares principles. These principles enable the simultaneous estimation of the associated standard deviations reflecting the internal consistency based on the accuracy estimates provided for the altimetry data as well as for the terrestrial anomaly data. Several test computations were made of the anomalies and their accuracy estimates using GOES-3 data.

  9. Study of gravity and magnetic anomalies using MAGSAT data

    NASA Technical Reports Server (NTRS)

    Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator)

    1981-01-01

    The results of modeling satellite-elevation magnetic and gravity data using the constraints imposed by near surface data and seismic evidence shows that the magnetic minimum can be accounted for by either an intracrustal lithologic variation or by an upwarp of the Curie point isotherm. The long wavelength anomalies of the NOO's-vector magnetic survey of the conterminous U.S. were contoured and processed by various frequency filters to enhance particular characteristics. A preliminary inversion of the data was completed and the anomaly field calculated at 450 km from the equivalent magnet sources to compare with the POGO satellite data. Considerable progress was made in studing the satellite magnetic data of South America and adjacent marine areas. Preliminary versions of the 1 deg free-air gravity anomaly map (20 m gal contour interval) and the high cut (lambda approximately 8 deg) filtered anomaly maps are included.

  10. Gravity data of Nevada

    USGS Publications Warehouse

    Ponce, David A.

    1997-01-01

    Gravity data for the entire state of Nevada and adjacent parts of California, Utah, and Arizona are available on this CD-ROM. About 80,000 gravity stations were compiled primarily from the National Geophysical Data Center and the U.S. Geological Survey. Gravity data was reduced to the Geodetic Reference System of 1967 and adjusted to the Gravity Standardization Net 1971 gravity datum. Data were processed to complete Bouguer and isostatic gravity anomalies by applying standard gravity corrections including terrain and isostatic corrections. Selected principal fact references and a list of sources for data from the National Geophysical Data Center are included.

  11. Gravity Anomaly Assessment Using Ggms and Airborne Gravity Data Towards Bathymetry Estimation

    NASA Astrophysics Data System (ADS)

    Tugi, A.; Din, A. H. M.; Omar, K. M.; Mardi, A. S.; Som, Z. A. M.; Omar, A. H.; Yahaya, N. A. Z.; Yazid, N.

    2016-09-01

    The Earth's potential information is important for exploration of the Earth's gravity field. The techniques of measuring the Earth's gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE) has introduced a better way in providing the information on the Earth's gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs) has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth's gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R2) and the root mean square error (RMSE) of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R2 and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

  12. Detailed gravity anomalies from Geos 3 satellite altimetry data

    NASA Technical Reports Server (NTRS)

    Gopalapillai, G. S.; Mourad, A. G.

    1979-01-01

    Detailed gravity anomalies are computed from a combination of Geos 3 satellite altimeter and terrestrial gravity data using least-squares principles. The mathematical model used is based on the Stokes' equation modified for a nonglobal solution. Using Geos 3 data in the calibration area, the effects of several anomaly parameter configurations and data densities/distributions on the anomalies and their accuracy estimates are studied. The accuracy estimates for 1 deg x 1 deg mean anomalies from low density altimetry data are of the order of 4 mgal. Comparison of these anomalies with the terrestrial data and also with Rapp's data derived using collocation techniques show rms differences of 7.2 and 4.9 mgal, respectively. Indications are that the anomaly accuracies can be improved to about 2 mgal with high density data. Estimation of 30 in. x 30 in. mean anomalies indicates accuracies of the order of 5 mgal. Proper verification of these results will be possible only when accurate ground truth data become available.

  13. Poisson downward continuation of scattered Helmert's gravity anomalies to mean values on a raster on the geoid using least squares

    NASA Astrophysics Data System (ADS)

    Foroughi, Ismael; Vaníček, Petr; Kingdon, Robert; Novák, Pavel; Sheng, Michael; Santos, Marcelo

    2016-04-01

    .e., around 244000 scattered gravity values, were considered in the context of the target area on the geoid limited by 0gravity anomalies were first transformed into the Helmert space to enable us to continued them down to the geoid. The target area was then broken down into 1 arc-deg squares containing 1 arc-min mean downward continued Helmert's gravity anomalies on the geoid. 36 such squares were finally fused together after testing the fit of continued gravity values along their edges. DC of no-topography (NT) anomalies, a.k.a. spherical complete Bouguer anomalies, will be investigated next.

  14. Gravity anomalies without geomagnetic disturbances interfere with pigeon homing--a GPS tracking study.

    PubMed

    Blaser, Nicole; Guskov, Sergei I; Entin, Vladimir A; Wolfer, David P; Kanevskyi, Valeryi A; Lipp, Hans-Peter

    2014-11-15

    The gravity vector theory postulates that birds determine their position to set a home course by comparing the memorized gravity vector at the home loft with the local gravity vector at the release site, and that they should adjust their flight course to the gravity anomalies encountered. As gravity anomalies are often intermingled with geomagnetic anomalies, we released experienced pigeons from the center of a strong circular gravity anomaly (25 km diameter) not associated with magnetic anomalies and from a geophysical control site, equidistant from the home loft (91 km). After crossing the border zone of the anomaly--expected to be most critical for pigeon navigation--they dispersed significantly more than control birds, except for those having met a gravity anomaly en route. These data increase the credibility of the gravity vector hypothesis.

  15. On global gravity anomalies and two-scale mantle convection

    NASA Technical Reports Server (NTRS)

    Marsh, B. D.; Marsh, J. G.

    1976-01-01

    The two-scale model of mantle convection developed by Richter and Parsons (1975) predicts that if the depth of the convective layer is about 600 km, then for a plate moving at 10 cm/yr, longitudinal convective rolls will be produced in about 50 million years, and the strike of these rolls indicates the direction of motion of the plate relative to the upper mantle. The paper tests these predictions by examining a new global free air gravity model complete to the 30th degree and order. The free air gravity map developed shows a series of linear positive and negative anomalies (with transverse wavelengths of about 2000 km) spanning the Pacific Ocean, crossing the Pacific rise and striking parallel to the Hawaiian seamounts. It is suggested that the pattern of these anomalies may indicate the presence of longitudinal convective rolls beneath the Pacific plates, a result which tends to support the predictions of Richter and Parsons.

  16. Inversion of residual gravity anomalies using tuned PSO

    NASA Astrophysics Data System (ADS)

    Roshan, Ravi; Singh, Upendra Kumar

    2017-02-01

    Many kinds of particle swarm optimization (PSO) techniques are now available and various efforts have been made to solve linear and non-linear problems as well as one-dimensional and multi-dimensional problems of geophysical data. Particle swarm optimization is a metaheuristic optimization method that requires intelligent guesswork and a suitable selection of controlling parameters (i.e. inertia weight and acceleration coefficient) for better convergence at global minima. The proposed technique, tuned PSO, is an improved technique of PSO, in which efforts have been made to choose the controlling parameters, and these parameters have been selected after analysing the responses of various possible exercises using synthetic gravity anomalies over various geological sources. The applicability and efficacy of the proposed method is tested and validated using synthetic gravity anomalies over various source geometries. Finally, tuned PSO is applied over field residual gravity anomalies of two different geological terrains to find the model parameters, namely amplitude coefficient factor (A), shape factor (q) and depth (z). The analysed results have been compared with published results obtained by different methods that show a significantly excellent agreement with real model parameters. The results also show that the proposed approach is not only superior to the other methods but also that the strategy has enhanced the exploration capability of the proposed method. Thus tuned PSO is an efficient and more robust technique to achieve an optimal solution with minimal error.

  17. New analytic solutions for modeling vertical gravity gradient anomalies

    NASA Astrophysics Data System (ADS)

    Kim, Seung-Sep; Wessel, Paul

    2016-05-01

    Modern processing of satellite altimetry for use in marine gravimetry involves computing the along-track slopes of observed sea-surface heights, projecting them into east-west and north-south deflection of the vertical grids, and using Laplace's equation to algebraically obtain a grid of the vertical gravity gradient (VGG). The VGG grid is then integrated via overlapping, flat Earth Fourier transforms to yield a free-air anomaly grid. Because of this integration and associated edge effects, the VGG grid retains more short-wavelength information (e.g., fracture zone and seamount signatures) that is of particular importance for plate tectonic investigations. While modeling of gravity anomalies over arbitrary bodies has long been a standard undertaking, similar modeling of VGG anomalies over oceanic features is not commonplace yet. Here we derive analytic solutions for VGG anomalies over simple bodies and arbitrary 2-D and 3-D sources. We demonstrate their usability in determining mass excess and deficiency across the Mendocino fracture zone (a 2-D feature) and find the best bulk density estimate for Jasper seamount (a 3-D feature). The methodologies used herein are implemented in the Generic Mapping Tools, available from gmt.soest.hawaii.edu.

  18. Gravity anomalies in Silurian pinnacle reef trend, southwestern Indiana

    SciTech Connect

    Malinconico, L.L. Jr.; Gognat, T.A.; Scher, P.L. )

    1989-08-01

    Structures produced over the top or along the margins of Silurian Pinnacle reefs have proven to be the source of significant oil production in the eastern Illinois basin. The authors have been able to refine gravity methods that can assist in the exploration of such reef targets. A gravity/density model was developed by combining the 1980 work of Dana at the Wilfred pool (Sullivan County, Indiana) with other lithologic and log data in southwestern Indiana. This model includes the density differences between the reef facies and surrounding lithologies as well as density variations that are the result of compaction of the sedimentary sequence above the reef. The density models suggest that positive gravity anomalies with amplitude between 1.5 to 2.5 mgals might occur over the reefs.

  19. Causal Anomalies in Kaluza-Klein Gravity Theories

    NASA Astrophysics Data System (ADS)

    Rebouças, M. J.; Teixeira, A. F. F.

    Causal anomalies in two Kaluza-Klein gravity theories are examined, particularly as to whether these theories permit solutions in which the causality principle is violated. It is found that similarly to general relativity the field equations of the space-time-mass Kaluza-Klein (STM-KK) gravity theory do not exclude violation of causality of Gödel type, whereas the induced matter Kaluza-Klein (IM-KK) gravity rules out noncausal Gödel-type models. The induced matter version of general relativity is shown to be an efficient therapy for causal anomalies that occurs in a wide class of noncausal geometries. Perfect fluid and dust Gödel-type solutions of the STM-KK field equations are studied. It is shown that every Gödel-type perfect fluid solution is isometric to the unique dust solution of the STM-KK field equations. The question as to whether 5D Gödel-type noncausal geometries induce any physically acceptable 4D energy-momentum tensor is also addressed.

  20. Gravity survey of the southwestern part of the sourthern Utah geothermal belt

    SciTech Connect

    Green, R.T.; Cook, K.L.

    1981-03-01

    A gravity survey covering an area of 6200 km/sup 2/ was made over the southwestern part of the southern Utah geothermal belt. The objective of the gravity survey is to delineate the geologic structures and assist in the understanding of the geothermal potential of the area. A total of 726 new gravity stations together with 205 existing gravity stations, are reduced to give: (1) a complete Bouguer gravity anomaly map, and (2) a fourth-order residual gravity anomaly map; both maps have a 2-mgal contour interval. The complete Bouguer gravity anomaly map shows an east-trending regional gravity belt with a total relief of about 70 mgal which crosses the central portion of the survey area. The gravity belt is attributed to a crustal lateral density variation of 0.1 gm/cc from a depth of 5 to 15 km.

  1. The quest for the perfect gravity anomaly: Part 2 - Mass effects and anomaly inversion

    USGS Publications Warehouse

    Keller, Gordon R.; Hildenbrand, T.G.; Hinze, W. J.; Li, X.; Ravat, D.; Webring, M.

    2006-01-01

    Gravity anomalies have become an important tool for geologic studies since the widespread use of high-precision gravimeters after the Second World War. More recently the development of instrumentation for airborne gravity observations, procedures for acquiring data from satellite platforms, the readily available Global Positioning System for precise vertical and horizontal control, improved global data bases, and enhancement of computational hardware and software have accelerated the use of the gravity method. As a result, efforts are being made to improve the gravity databases that are made available to the geoscience community by broadening their observational holdings and increasing the accuracy and precision of the included data. Currently the North American Gravity Database as well as the individual databases of Canada, Mexico, and the United States of America are being revised using new formats and standards. The objective of this paper is to describe the use of the revised standards for gravity data processing and modeling and there impact on geological interpretations. ?? 2005 Society of Exploration Geophysicists.

  2. Use of MAGSAT anomaly data for crustal structure and mineral resources in the US midcontinent

    NASA Technical Reports Server (NTRS)

    Carmichael, R. S. (Principal Investigator)

    1982-01-01

    Progress in the correlation of MAGSAT anomaly maps with geological and geophysical data sets is reported. An excerpt from Bouguer gravity map of the U.S. was filtered to retain wavelengths of 250 km, thus being physically somewhat analogous to MAGSAT data at 400 km height. Residual anomalies were extracted to compare with the satellite magnetics.

  3. Altered orientation and flight paths of pigeons reared on gravity anomalies: a GPS tracking study.

    PubMed

    Blaser, Nicole; Guskov, Sergei I; Meskenaite, Virginia; Kanevskyi, Valerii A; Lipp, Hans-Peter

    2013-01-01

    The mechanisms of pigeon homing are still not understood, in particular how they determine their position at unfamiliar locations. The "gravity vector" theory holds that pigeons memorize the gravity vector at their home loft and deduct home direction and distance from the angular difference between memorized and actual gravity vector. However, the gravity vector is tilted by different densities in the earth crust leading to gravity anomalies. We predicted that pigeons reared on different gravity anomalies would show different initial orientation and also show changes in their flight path when crossing a gravity anomaly. We reared one group of pigeons in a strong gravity anomaly with a north-to-south gravity gradient, and the other group of pigeons in a normal area but on a spot with a strong local anomaly with a west-to-east gravity gradient. After training over shorter distances, pigeons were released from a gravitationally and geomagnetically normal site 50 km north in the same direction for both home lofts. As expected by the theory, the two groups of pigeons showed divergent initial orientation. In addition, some of the GPS-tracked pigeons also showed changes in their flight paths when crossing gravity anomalies. We conclude that even small local gravity anomalies at the birth place of pigeons may have the potential to bias the map sense of pigeons, while reactivity to gravity gradients during flight was variable and appeared to depend on individual navigational strategies and frequency of position updates.

  4. Altered Orientation and Flight Paths of Pigeons Reared on Gravity Anomalies: A GPS Tracking Study

    PubMed Central

    Blaser, Nicole; Guskov, Sergei I.; Meskenaite, Virginia; Kanevskyi, Valerii A.; Lipp, Hans-Peter

    2013-01-01

    The mechanisms of pigeon homing are still not understood, in particular how they determine their position at unfamiliar locations. The “gravity vector” theory holds that pigeons memorize the gravity vector at their home loft and deduct home direction and distance from the angular difference between memorized and actual gravity vector. However, the gravity vector is tilted by different densities in the earth crust leading to gravity anomalies. We predicted that pigeons reared on different gravity anomalies would show different initial orientation and also show changes in their flight path when crossing a gravity anomaly. We reared one group of pigeons in a strong gravity anomaly with a north-to-south gravity gradient, and the other group of pigeons in a normal area but on a spot with a strong local anomaly with a west-to-east gravity gradient. After training over shorter distances, pigeons were released from a gravitationally and geomagnetically normal site 50 km north in the same direction for both home lofts. As expected by the theory, the two groups of pigeons showed divergent initial orientation. In addition, some of the GPS-tracked pigeons also showed changes in their flight paths when crossing gravity anomalies. We conclude that even small local gravity anomalies at the birth place of pigeons may have the potential to bias the map sense of pigeons, while reactivity to gravity gradients during flight was variable and appeared to depend on individual navigational strategies and frequency of position updates. PMID:24194860

  5. Complex research of the areas of the Moon gravity anomalies.

    NASA Astrophysics Data System (ADS)

    Pugacheva, Svetlana

    The report presents the results of a research study of the lunar surface in the areas of gravity anomalies. The source of gravity anomalies of the Moon are large mascons with a high mass concentration at a depth of volcanic plains and lunar Maria. Formation of mascons is connected with intensive development of basaltic volcanism on the Moon in the early periods of its existence. Many volcanic structures have been found by the Grail spacecraft. These are tectonic structures, basins of impact craters, ancient linear gravity anomalies. The article presents the data of physical and mechanical properties of the surface soil layer of the lunar Maria and gives an assessment of the chemical composition of the soil. All measurements have been performed according to the theoretical models of light scattering on the basis of survey of the lunar surface by in-orbit spacecrafts and analysis of the lunar soil samples. There have been calculated heterogeneity parameters of the surface macro-relief of the lunar Maria: albedo, soil density, average grain diameter of the particles forming the surface layer and the volume fraction occupied by particles. Previous articles showed correlation dependence of the chemical composition of rocks on the macrostructure of the lunar surface. The surface macrostructure was evaluated by comparing the local phase function with the lunar spatial scattering indicatrix. Phase function difference at an 18-degree phase is properly consistent with the chemical composition of the surface layer of soil, in particular with the content of thorium and iron oxide. It can be assumed that mascons include rich KREEP rocks with a high content of thorium and iron oxide. KREEP rocks in the areas of the lunar Maria covered by volcanic lava are probably located on the surface or at a shallow depth.

  6. On estimating gravity anomalies from gradiometer data. [by numerical analysis

    NASA Technical Reports Server (NTRS)

    Argentiero, P.; Garza-Robles, R.

    1976-01-01

    The Gravsat-gradiometer mission involves flying a gradiometer on a gravity satellite (Gravsat) which is in a low, polar, and circular orbit. Results are presented of a numerical simulation of the mission which demonstrates that, if the satellite is in a 250-km orbit, 3- and 5-degree gravity anomalies may be estimated with accuracies of 0.03 and 0.01 mm/square second (3 and 1 mgal), respectively. At an altitude of 350 km, the results are 0.07 and 0.025 mm.square second (7 and 2.5 mgal), respectively. These results assume a rotating type gradiometer with a 0.1 -etvos unit accuracy. The results can readily be scaled to reflect another accuracy level.

  7. Continuity of subsurface fault structure revealed by gravity anomaly: the eastern boundary fault zone of the Niigata plain, central Japan

    NASA Astrophysics Data System (ADS)

    Wada, Shigeki; Sawada, Akihiro; Hiramatsu, Yoshihiro; Matsumoto, Nayuta; Okada, Shinsuke; Tanaka, Toshiyuki; Honda, Ryo

    2017-01-01

    We have investigated gravity anomalies around the Niigata plain, which is a sedimentary basin in central Japan bounded by mountains, to examine the continuity of subsurface fault structures of a large fault zone—the eastern boundary fault zone of the Niigata plain (EBFZNP). The features of the Bouguer anomaly and its first horizontal and vertical derivatives clearly illustrate the EBFZNP. The steep first horizontal derivative and the zero isoline of the vertical derivative are clearly recognized along the entire EBFZNP over an area that shows no surface topographic features of an active fault. Two-dimensional density structure analyses also confirm a relationship between the two first derivatives and the subsurface fault structure. Therefore, we conclude that the length of the EBFZNP as an active fault extends to 56 km, which is longer than previously estimated. This length leads to an estimation of a moment magnitude of 7.4 of an expected earthquake from the EBFZNP.[Figure not available: see fulltext.

  8. Gravity anomalies, forearc morphology and seismicity in subduction zones

    NASA Astrophysics Data System (ADS)

    Bassett, D.; Watts, A. B.; Das, S.

    2012-12-01

    We apply spectral averaging techniques to isolate and remove the long-wavelength large-amplitude trench-normal topographic and free-air gravity anomaly "high" and "low" associated with subduction zones. The residual grids generated illuminate the short-wavelength structure of the forearc. Systematic analysis of all subduction boundaries on Earth has enabled a classification of these grids with particular emphasis placed on topography and gravity anomalies observed in the region above the shallow seismogenic portion of the plate interface. The isostatic compensation of these anomalies is investigated using 3D calculations of the gravitational admittance and coherence. In the shallow region of the megathrust, typically within 100 km from the trench, isolated residual anomalies with amplitudes of up to 2.5 km and 125 mGal are generally interpreted as accreted/subducting relief in the form of seamounts and other bathymetric features. While most of these anomalies, which have radii < 50km, are correlated with areas of reduced seismicity, several in regions such as Japan and Java appear to have influenced the nucleation and/or propagation of large magnitude earthquakes. Long-wavelength (500 - >1000 km) trench-parallel forearc ridges with residual anomalies of up to 1.5 km and 150 mGal are identified in approximately one-third of the subduction zones analyzed. Despite great length along strike, these ridges are less than 100 km wide and several appear uncompensated. A high proportion of arc-normal structure and the truncation/morphological transition of trench-parallel forearc ridges is explained through the identification and tracking of pre-existing structure on the over-riding and subducting plates into the seismogenic portion of the plate boundary. Spatial correlations between regions with well-defined trench-parallel forearc ridges and the occurrence of large magnitude interplate earthquakes, in addition to the uncompensated state of these ridges, suggest links

  9. Depth Estimation for Magnetic/Gravity Anomaly Using Model Correction

    NASA Astrophysics Data System (ADS)

    Liu, Pengfei; Liu, Tianyou; Zhu, Peimin; Yang, Yushan; Zhou, Qiaoli; Zhang, Henglei; Chen, Guoxiong

    2017-03-01

    The Tilt-depth method has been widely used to determinate the source depth of a magnetic anomaly. In the present study, we deduce similar Tilt-depth methods for both magnetic and gravity data based on the contact and sphere models and obtain the same equation for a gravity anomaly as that for a magnetic anomaly. The theoretical equations and the model tests show that the routine Tilt-depth method would result in unreliable depth estimation for deep sources. This is due to that the contact model is no longer valid for causative sources under the condition in which the depths of causative sources are significantly larger than their horizontal lengths. Accordingly, we suggest that the Tilt-depth derived from the contact model can be used to detect a shallow source, whereas the Tilt-depth derived from the sphere model can be used to detect a deep source. We propose a weighting method based on the estimated depths from both the contact model and the sphere model to estimate the depth for real data. The model tests suggest that the determined depths from the contact model and the sphere model are shallower and deeper, respectively, than the real depth, while the estimated depth from the proposed method is more close to the actual depth. In the application to the Weigang iron ore located in Jiangsu province, China, the routine Tilt-depth method results in -76% relative error, whereas the proposed method obtains the reliable depth estimation compared with the drill holes. In addition, the proposed method works well in the application for the Shijiaquan iron ore located in Shandong province, China. These results indicate that the proposed weighting equation is a general improvement.

  10. Improving the geological interpretation of magnetic and gravity satellite anomalies

    NASA Technical Reports Server (NTRS)

    Hinze, William J.; Braile, Lawrence W.; Vonfrese, Ralph R. B.

    1987-01-01

    Quantitative analysis of the geologic component of observed satellite magnetic and gravity fields requires accurate isolation of the geologic component of the observations, theoretically sound and viable inversion techniques, and integration of collateral, constraining geologic and geophysical data. A number of significant contributions were made which make quantitative analysis more accurate. These include procedures for: screening and processing orbital data for lithospheric signals based on signal repeatability and wavelength analysis; producing accurate gridded anomaly values at constant elevations from the orbital data by three-dimensional least squares collocation; increasing the stability of equivalent point source inversion and criteria for the selection of the optimum damping parameter; enhancing inversion techniques through an iterative procedure based on the superposition theorem of potential fields; and modeling efficiently regional-scale lithospheric sources of satellite magnetic anomalies. In addition, these techniques were utilized to investigate regional anomaly sources of North and South America and India and to provide constraints to continental reconstruction. Since the inception of this research study, eleven papers were presented with associated published abstracts, three theses were completed, four papers were published or accepted for publication, and an additional manuscript was submitted for publication.

  11. The 2017 solar eclipse and Majorana & Allais gravity anomalies

    NASA Astrophysics Data System (ADS)

    Munera, Hector A.

    2017-01-01

    Two little known anomalies hint to phenomena beyond current theory. Majorana effect: around 1920 in a series of well-designed experiments with a chemical laboratory balance, Quirino Majorana found in Italy that mercury (Hg) and lead (Pb) might shield terrestrial gravity. Majorana experiments were never repeated by the international scientific community. Instead his results were dismissed on theoretical claims: a) unobserved heating of earth by absorption of gravity, and b) unobserved cyclic lunar perturbation of solar gravity at earth’s surface. However, Majorana critics missed the crucial fact that shielding is not mere absorption, but also scattering, and that atomic number Z of matter in the moon is much lower than Z=80 (Hg) and Z=82 (Pb). From the June 30/1954 solar eclipse onwards, high-quality mechanical gravimeters were used to search for Majorana shielding by the moon. Results are positive, provided that shielding is interpreted as scattering rather than absorption of gravity by moon (H. A. Munera, Physics Essays 24, 428-434, 2011). Allais effect: during the same 1954 eclipse (partial in Paris) Maurice Allais had in operation a sensitive paraconical pendulum for a very different purpose. Surprisingly, the pendulum was perturbed by the eclipse, condition repeated once again in a 1959 solar eclipse, also partial in Paris. During the past sixty years, paraconical, torsion and Foucault pendula, and other mechanical devices, have been used to (dis)confirm Allais effect, but the results are not conclusive thus far. A book edited by this author (Should the laws of gravitation be revised? Apeiron 2011) describes some of those observations. Various unexpected effects, some of them torsional, appear both near the optical shadow, and far away. The Sun-Moon-Earth alignment in a solar eclipse allows detection on the terrestrial surface of the dark matter flow scattered on moon’s surface (flow not hitting earth in other geometries). Rotation of moon may induce

  12. Global correlation of topographic heights and gravity anomalies

    NASA Technical Reports Server (NTRS)

    Roufosse, M. C.

    1977-01-01

    The short wavelength features were obtained by subtracting a calculated 24th-degree-and-order field from observed data written in 1 deg x 1 deg squares. The correlation between the two residual fields was examined by a program of linear regression. When run on a worldwide scale over oceans and continents separately, the program did not exhibit any correlation; this can be explained by the fact that the worldwide autocorrelation function for residual gravity anomalies falls off much faster as a function of distance than does that for residual topographic heights. The situation was different when the program was used in restricted areas, of the order of 5 deg x 5 deg square. For 30% of the world,fair-to-good correlations were observed, mostly over continents. The slopes of the regression lines are proportional to apparent densities, which offer a large spectrum of values that are being interpreted in terms of features in the upper mantle consistent with available heat-flow, gravity, and seismic data.

  13. Gravity anomalies of the active mud diapirs off southwest Taiwan

    NASA Astrophysics Data System (ADS)

    Doo, Wen-Bin; Hsu, Shu-Kun; Lo, Chung-Liang; Chen, Song-Chuen; Tsai, Ching-Hui; Lin, Jing-Yi; Huang, Yuan-Ping; Huang, Yin-Sheng; Chiu, Shye-Donq; Ma, Yu-Fang

    2015-12-01

    Overpressure and buoyant effect of underlying sediments are generally used to account for the upward motion or formation of submarine mud volcanoes and mud diapirs. In this study, we process and interpret the gravity anomalies associated with the active mud diapirs off SW Taiwan. Geologically, the mud diapirs are just formed and are still very active, thus we can better understand the initial process of the mud diapirs formation through the gravity analysis. Our results show that the density contrasts of the submarine mud diapirs with respect to the surroundings are generally positive. Because the study area is in a tectonically compressive regime and the gas plume venting from the submarine mud volcanoes is very active, we thus infer that mechanically the mud diapirs off SW Taiwan have been formed mainly due to the tectonic compression on the underlying sediments of high pore-fluid pressure, instead of the buoyancy of the buried sediments. The overpressured sediments and fluid are compressed and pushed upwards to pierce the overlying sediments and form the more compacted mud diapirs. The relatively denser material of the mud diapirs probably constrains the flowing courses of the submarine canyons off SW Taiwan, especially for the upper reaches of the Kaoping and Fangliao submarine canyons.

  14. Gravity fields of the terrestrial planets - Long-wavelength anomalies and tectonics

    NASA Technical Reports Server (NTRS)

    Phillips, R. J.; Lambeck, K.

    1980-01-01

    The paper discusses the gravity and topography data available for four terrestrial planets (earth, moon, Mars, and Venus), with particular emphasis on drawing inferences regarding the relationship of long-wavelength anomalies to tectonics. The discussion covers statistical analyses of global planetary gravity fields, relationship of gravity anomalies to elastic and viscoelastic models, relationship of gravity anomalies to convection models, finite strength, and isostasy (or the state of isostatic compensation). The cases of the earth and the moon are discussed in some detail. A summary of comparative planetology is presented.

  15. Relationship between characteristics of gravity and magnetic anomalies and the earthquakes in the Longmenshan range and adjacent areas

    NASA Astrophysics Data System (ADS)

    Zhang, Jisheng; Gao, Rui; Zeng, Lingsen; Li, Qiusheng; Guan, Ye; He, Rizheng; Wang, Haiyan; Lu, Zhanwu

    2010-08-01

    The 2008 Wenchuan earthquake and aftershocks occurred along the northeast-trending Longmenshan fault zone in the eastern margin of the Tibetan plateau. The Tibetan plateau has the strongest negative Bouguer gravity anomaly zone in China and is surrounded by the great gravity horizontal gradient belt. The horizontal gradient belt of the observed gravity anomaly in the Longmenshan area is a part of this giant gravity gradient belt. The Longmenshan fault zone is located to the east of this belt. The horizontal gradient belt of the residual gravity anomaly, obtained by removing large effects of sedimentary basin and variations in the crustal thickness, well matches the Longmenshan fault zone. But this belt is located to the east of the horizontal gradient belt of the observed gravity anomalies. The deviation of the two horizontal gradient belts increases from the southwest to the northeast with a maximum of about 40-50 km. A significant difference in density exists in the lower crust and the uppermost mantle between the Songpan-Ganzê block and the Sichuan basin block. The Songpan-Ganzê block is less dense than the Sichuan basin block in the lower crust as well as in the uppermost mantle. The boundary between the two blocks is located to the west of the Wenchuan-Maoxian, Yinxiu-Beichuan, and Anxian-Guanxian faults approximately. The fault plane crosses the lower crust and uppermost mantle. The rigid Sichuan basin block acts as a resistant for the pushing from the Songpan-Ganzê block. Far-field effects of the collision between the Indian and Eurasian plates, might lead to thrust of some brittle layers in the upper crust along the detachment, in the middle crust of the Songpan-Ganzê block. When movement on a large and deep crustal mega-thrust occurs, earthquakes strike the Longmen Shan margin of the Tibetan Plateau. In the Guanxian-Beichuan segment in the southern Longmenshan fault zone, push from the Songpan-Ganzê block is perpendicular to the density boundary

  16. Calculating the Marine Gravity Anomaly of the South China Sea based on the Inverse Stokes Formula

    NASA Astrophysics Data System (ADS)

    Liu, Liang; Jiang, Xiaoguang; Liu, Shanwei; Zheng, Lei; Zang, Jinxia; Zhang, Xuehua; Liu, Longfei

    2016-11-01

    Marine gravity field information has a great significance for the resource, environment and military affairs. As a new way to get marine gravity data, the satellite altimetry technique makes up for what ship measuring means lack. The paper carries out the researches on how altimeter data applied for calculating marine gravity anomaly based on inverse Stokes formula. In the article, the editing of 14-track Jason-1 data over South China Sea for 7 years is for collinear processing and cross-point adjustment. The inverse Stokes formula and fast Flourier transform technique are applied to calculate marine gravity anomaly of the region (0°∼23°N, 103°∼120°E), and to draw gravity anomaly map. Compared with the gravity anomaly by ship observation, RMS is 12.6mGal, and single altimetry satellite has a good precision.

  17. Gravity anomalies, caldera structure, and subsurface geology in the Rotorua area, New Zealand

    SciTech Connect

    Hunt, T.M. )

    1992-04-01

    This paper discusses a re-examination of gravity which indicates that Rotorua Caldera does not have the circular, negative gravity anomaly typical of other rhyolitic calderas. New gravity measurements and residual gravity anomalies in Rotorua City are consistent with numerous rhyolite domes and ignimbrite sheets, interbedded with a thick sequence of poorly-compacted sediments. Within the city a gravity high extends from the shore of Lake Rotorua south to Whakarewarewa and is associated with a buried ridge, formed by the coalescing of two rhyolite domes. A gravity low centered near Linton Park suggests that rhyolites are thin or absent in this area and sediments extend to a depth of about 1 km. A quantitative analysis of the residual gravity anomalies was limited by insufficient information about the density, extent, and thickness of the material underlying the rhyolites, and the uncertainty in the distribution and density of silicification within the sediments.

  18. The quest for the perfect gravity anomaly: Part 1 - New calculation standards

    USGS Publications Warehouse

    Li, X.; Hildenbrand, T.G.; Hinze, W. J.; Keller, Gordon R.; Ravat, D.; Webring, M.

    2006-01-01

    The North American gravity database together with databases from Canada, Mexico, and the United States are being revised to improve their coverage, versatility, and accuracy. An important part of this effort is revision of procedures and standards for calculating gravity anomalies taking into account our enhanced computational power, modern satellite-based positioning technology, improved terrain databases, and increased interest in more accurately defining different anomaly components. The most striking revision is the use of one single internationally accepted reference ellipsoid for the horizontal and vertical datums of gravity stations as well as for the computation of the theoretical gravity. The new standards hardly impact the interpretation of local anomalies, but do improve regional anomalies. Most importantly, such new standards can be consistently applied to gravity database compilations of nations, continents, and even the entire world. ?? 2005 Society of Exploration Geophysicists.

  19. Gravity anomalies over the Central Indian Ridge between 3∘S and 11∘S, Indian Ocean: Segmentation and crustal structure

    NASA Astrophysics Data System (ADS)

    Samudrala, Kiranmai; Kamesh Raju, K. A.; Rao, P. Rama

    2016-12-01

    High-resolution shipboard geophysical investigations along the Indian Ocean ridge system are sparse especially over the Carlsberg and Central Indian ridges. In the present study, the shipboard gravity and multibeam bathymetry data acquired over a 750 km long section of the Central Indian Ridge between 3 ∘S and 11 ∘S have been analysed to understand the crustal structure and the ridge segmentation pattern. The mantle Bouguer anomalies (MBA) and the residual mantle Bouguer anomalies (RMBA) computed in the study area have shown significant variations along the ridge segments that are separated by transform and non-transform discontinuities. The MBA lows observed over the linear ridge segments bounded by well-defined transform faults are attributed to the thickening of the crust at the middle portions of the ridge segments. The estimates of crustal thickness from the RMBA shows an average of 5.2 km thick crust in the axial part of the ridge segments. The MBA and relative RMBA highs along the two non-transform discontinuities suggests a thinner crust of up to 4.0 km. The most significant MBA and RMBA highs were observed over the Vema transform fault suggesting thin crust of 4 km in the deepest part of the transform fault where bathymetry is more than 6000 m. The identified megamullion structures have relative MBA highs suggesting thinner crust. Besides MBA lows along the ridge axis, significant off-axis MBA lows have been noticed, suggesting off-axis mantle upwelling zones indicative of thickening of the crust. The rift valley morphology varies from the typical V-shaped valley to the shallow valley floor with undulations on the inner valley floor. Segments with shallow rift valley floor have depicted well-defined circular MBA lows with persistent RMBA low, suggesting modulation of the valley floor morphology due to the variations in crustal thickness and the mantle temperature. These are supported by thicker crust and weaker lithospheric mantle.

  20. High-resolution airborne gravity imaging over James Ross Island (West Antarctica)

    USGS Publications Warehouse

    Jordan, T.A.; Ferraccioli, F.; Jones, P.C.; Smellie, J.L.; Ghidella, M.; Corr, H. F. J.; Zakrajsek, A.F.

    2007-01-01

    James Ross Island (JRI) exposes a Miocene-Recent alkaline basaltic volcanic complex that developed in a back-arc, east of the northern Antarctic Peninsula. JRI has been the focus of several geological studies because it provides a window on Neogene magmatic processes and paleoenvironments. However, little is known about its internal structure. New airborne gravity data were collected as part of the first high-resolution aerogeophysical survey flown over the island and reveal a prominent negative Bouguer gravity anomaly over Mt Haddington. This is intriguing as basaltic volcanoes are typically associated with positive Bouguer anomalies, linked to underlying mafic intrusions. The negative Bouguer anomaly may be associated with a hitherto unrecognised low-density sub-surface body, such as a breccia-filled caldera, or a partially molten magma chamber.

  1. Procedures and results related to the direct determination of gravity anomalies from satellite and terrestrial gravity data

    NASA Technical Reports Server (NTRS)

    Rapp, R. H.

    1974-01-01

    The equations needed for the incorporation of gravity anomalies as unknown parameters in an orbit determination program are described. These equations were implemented in the Geodyn computer program which was used to process optical satellite observations. The arc dependent parameter unknowns, 184 unknown 15 deg and coordinates of 7 tracking stations were considered. Up to 39 arcs (5 to 7 days) involving 10 different satellites, were processed. An anomaly solution from the satellite data and a combination solution with 15 deg terrestrial anomalies were made. The limited data samples indicate that the method works. The 15 deg anomalies from various solutions and the potential coefficients implied by the different solutions are reported.

  2. Oxygen isotope, aeromagnetic, and gravity anomalies associated with hydrothermally altered zones in the Yankee Fork mining district, Custer County, Idaho.

    USGS Publications Warehouse

    Criss, R.E.; Champion, D.E.; McIntyre, D.H.

    1985-01-01

    Anomalous geochemical and geophysical properties correlate spatially with epithermal Ag-Au deposits in altered volcanic rocks. Areas of low 18O, low magnetic susceptibilities, low remanent magnetizations and relatively high rock densities are much larger than the zones of obvious (not shown) hydrothermal alteration. Low aeromagnetic intensities and positive Bouguer anomalies are also associated with the altered rock, as which has delta 18O <6per mille. The altering and mineralizing fluids were Tertiary meteoric waters.-G.J.N.

  3. Analysis of gravity anomaly over coral-reef oil field: Wilfred Pool, Sullivan County, Indiana

    SciTech Connect

    Dana, S.W.

    1980-03-01

    To compare the measured and theoretical gravity anomaly of a typical coral-reef oil field, data were collected from the wilfred Pool, Sullivan County, Indiana. Densities of available core samples from the field were determined and the anomaly was calculated, taking into account the lateral and vertical variation of density and the geologic structure known from core studies and drilling-log records of lithologic types penetrated by the wells. Comparison of the theoretical and actual anomalies indicated a rough correspondence except for several sharp negative anomalies on the flanks of the measured gravity anomaly. Further studies indicated that the negative anomalies are possibly due to fluvial erosion that produced, on the surface of the youngest Pennsylvanian sediments, channels which were later filled with glacial till of lower density than the sediments. 13 figures.

  4. Gravity anomalies, plate tectonics and the lateral growth of Precambrian North America

    NASA Technical Reports Server (NTRS)

    Thomas, M. D.; Grieve, R. A. F.; Sharpton, V. L.

    1988-01-01

    The widespread gravity coverage of North America provides a picture of the gross structural fabric of the continent via the trends of gravity anomalies. The structural picture so obtained reveals a mosaic of gravity trend domains, many of which correlate closely with structural provinces and orogenic terranes. The gravity trend map, interpreted in the light of plate-tectonic theory, thus provides a new perspective for examining the mode of assembly and growth of North America. Suture zones, palaeosubduction directions, and perhaps, contrasting tectonic histories may be identified using gravity patterns.

  5. Improving the geological interpretation of magnetic and gravity satellite anomalies

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Braile, L. W. (Principal Investigator); Vonfrese, R. R. B.

    1985-01-01

    Current limitations in the quantitative interpretation of satellite-elevation geopotential field data and magnetic anomaly data were investigated along with techniques to overcome them. A major result was the preparation of an improved scalar magnetic anomaly map of South America and adjacent marine areas directly from the original MAGSAT data. In addition, comparisons of South American and Euro-African data show a strong correlation of anomalies along the Atlantic rifted margins of the continents.

  6. An Automatic Method of Direct Interpretation of Residual Gravity Anomaly Profiles due to Spheres and Cylinders

    NASA Astrophysics Data System (ADS)

    Asfahani, J.; Tlas, M.

    2008-05-01

    We have developed a least-squares minimization approach to determine the depth and the amplitude coefficient of a buried structure from residual gravity anomaly profile. This approach is basically based on application of Werner deconvolution method to gravity formulas due to spheres and cylinders, and solving a set of algebraic linear equations to estimate the two-model parameters. The validity of this new method is demonstrated through studying and analyzing two synthetic gravity anomalies, using simulated data generated from a known model with different random error components and a known statistical distribution. After being theoretically proven, this approach was applied on two real field gravity anomalies from Cuba and Sweden. The agreement between the results obtained by the proposed method and those obtained by other interpretation methods is good and comparable. Moreover, the depth obtained by the proposed approach is found to be in very good agreement with that obtained from drilling information.

  7. Lithospheric structure across the central Tien Shan constrained by gravity anomalies and joint inversions of receiver function and Rayleigh wave dispersion

    NASA Astrophysics Data System (ADS)

    Li, Yonghua; Shi, Lei; Gao, Jiayi

    2016-07-01

    Shear wave velocity structure across the central Tien Shan orogeny was generated by jointly inverting Rayleigh wave phase and group velocity with teleseismic P-wave receiver functions at 40 broadband seismic stations. The inferred seismic structure was validated by forward modeling of the complete Bouguer anomaly data. The joint inversion result reveals larger crust thicknesses beneath the Kokshaal (∼68-72 km) and Kyrgyz ranges (∼62-64 km), while other units have crustal thicknesses between 48 and 58 km. A fast velocity layer (Vs = 3.6-3.9 km/s) in the upper crust is found in some seismic stations within the Kazakh Shield. Our models show the presence of high velocity and density layers in the lowermost crust throughout the region, consistent with the presence of mafic/ultramafic lithologies. The large crustal thickness is associated with a thickened mafic layer in the lower crust, indicating that the thickened crust may be partly caused by magmatic underplating. The low velocity and density anomaly in the middle crust, and low upper mantle velocity observed in our model beneath the middle Tien Shan reflect the presence of partial melt in the crust due to the intrusion of hot mantle material. The lack of correlation between Moho depth and topography, together with the gravity results, suggests that the topographic compensation in the central Tien Shan is not confined to the crust. This requires significant support from the mantle to account for the relative high elevation of the middle Tien Shan.

  8. Gravity data from the San Pedro River Basin, Cochise County, Arizona

    USGS Publications Warehouse

    Kennedy, Jeffrey R.; Winester, Daniel

    2011-01-01

    The U.S. Geological Survey, Arizona Water Science Center in cooperation with the National Oceanic and Atmospheric Administration, National Geodetic Survey has collected relative and absolute gravity data at 321 stations in the San Pedro River Basin of southeastern Arizona since 2000. Data are of three types: observed gravity values and associated free-air, simple Bouguer, and complete Bouguer anomaly values, useful for subsurface-density modeling; high-precision relative-gravity surveys repeated over time, useful for aquifer-storage-change monitoring; and absolute-gravity values, useful as base stations for relative-gravity surveys and for monitoring gravity change over time. The data are compiled, without interpretation, in three spreadsheet files. Gravity values, GPS locations, and driving directions for absolute-gravity base stations are presented as National Geodetic Survey site descriptions.

  9. GEOS 3 data processing for the recovery of geoid undulations and gravity anomalies

    NASA Technical Reports Server (NTRS)

    Rapp, R. H.

    1979-01-01

    The paper discusses the analysis of GEOS 3 altimeter data for the determination of geoid heights and point and mean gravity anomalies. Methods are presented for determining the mean anomalies and mean undulations from the GEOS 3 altimeter data available by the end of September 1977 without having a complete set of precise orbits. The editing of the data is extensive to remove questionable data, although no filtering of the data is carried out. An adjustment process is carried out to eliminate orbit error and altimeter bias. Representative point anomaly values are computed to investigate anomaly behavior across the Bonin Trench and over the Patton seamounts.

  10. The computation of 15 deg and 10 deg equal area block terrestrial free air gravity anomalies

    NASA Technical Reports Server (NTRS)

    Hajela, D. P.

    1973-01-01

    Starting with the set of 23,355 1 deg x 1 deg mean free air gravity anomalies used in Rapp (1972) to form a 5 deg equal area block terrestrial gravity field, the computation of 15 deg equal area block mean free air gravity anomalies is described along with estimates of their standard deviations. A new scheme of an integral division of a 15 deg block into 9 component 300 n. m. blocks, and each 300 n. m. block being subdivided into 25 60 n.mi. blocks, is used. This insures that there is no loss in accuracy, which would have resulted if proportional values according to area were taken of the 5 deg equal area anomalies to form the 15 deg block anomalies. A similar scheme is used for the computation of 10 deg equal area block mean free air gravity anomalies with estimates of their standard deviations. The scheme is general enough to be used for a 30 deg equal area block terrestrial gravity field.

  11. Pioneer Anomaly and Space Accelerometer for Gravity Test

    NASA Astrophysics Data System (ADS)

    Levy, Agnès; Christophe, Bruno; Reynaud, Serge

    2006-06-01

    The Pioneer 10 and 11 spacecraft are subject to an unexplained acceleration which has a constant value of (8.74 1.33) \\cdot 10-10 m\\cdot s-2 and seems to be directed toward the sun. The hypotheses to explain this anomaly are either technical artifacts or new physics. This presentation deals with the unfolding of two aspects of my thesis: Doppler and telemetry data analysis with the objective to investigate the nature of the anomaly, and adapation of an ONERA accelerometer for a future mission in which the anomaly will be confirmed and more precisely measured. The presence of an accelerometer is mandatory for the identification of the anomaly's origin.

  12. South China Sea crustal thickness and lithosphere thinning from satellite gravity inversion incorporating a lithospheric thermal gravity anomaly correction

    NASA Astrophysics Data System (ADS)

    Kusznir, Nick; Gozzard, Simon; Alvey, Andy

    2016-04-01

    The distribution of ocean crust and lithosphere within the South China Sea (SCS) are controversial. Sea-floor spreading re-orientation and ridge jumps during the Oligocene-Miocene formation of the South China Sea led to the present complex distribution of oceanic crust, thinned continental crust, micro-continents and volcanic ridges. We determine Moho depth, crustal thickness and continental lithosphere thinning (1- 1/beta) for the South China Sea using a gravity inversion method which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir, 2008). The gravity inversion method provides a prediction of ocean-continent transition structure and continent-ocean boundary location which is independent of ocean isochron information. A correction is required for the lithosphere thermal gravity anomaly in order to determine Moho depth accurately from gravity inversion; the elevated lithosphere geotherm of the young oceanic and rifted continental margin lithosphere of the South China Sea produces a large lithosphere thermal gravity anomaly which in places exceeds -150 mGal. The gravity anomaly inversion is carried out in the 3D spectral domain (using Parker 1972) to determine 3D Moho geometry and invokes Smith's uniqueness theorem. The gravity anomaly contribution from sediments assumes a compaction controlled sediment density increase with depth. The gravity inversion includes a parameterization of the decompression melting model of White & McKenzie (1999) to predict volcanic addition generated during continental breakup lithosphere thinning and seafloor spreading. Public domain free air gravity anomaly, bathymetry and sediment thickness data are used in this gravity inversion. Using crustal thickness and continental lithosphere thinning factor maps with superimposed shaded-relief free-air gravity anomaly, we improve the determination of pre-breakup rifted margin conjugacy, rift orientation and sea-floor spreading trajectory. SCS conjugate margins

  13. Anomaly-free cosmological perturbations in effective canonical quantum gravity

    SciTech Connect

    Barrau, Aurelien; Calcagni, Gianluca; Grain, Julien E-mail: bojowald@gravity.psu.edu E-mail: julien.grain@ias.u-psud.fr

    2015-05-01

    This article lays out a complete framework for an effective theory of cosmological perturbations with corrections from canonical quantum gravity. Since several examples exist for quantum-gravity effects that change the structure of space-time, the classical perturbative treatment must be rethought carefully. The present discussion provides a unified picture of several previous works, together with new treatments of higher-order perturbations and the specification of initial states.

  14. Investigation of urban faults in Shenzhen using wavelet multi-scale analysis and modeling of gravity observations

    NASA Astrophysics Data System (ADS)

    Xu, Chuang; Chen, Liang; Liu, Xi-kai

    2016-04-01

    Urban faults in Shenzhen are potential threat to the city security and sustainable development. To improve the knowledge of the Shenzhen fault zone, interpretation and inversion of gravity data were carried out. Bouguer gravity covering the whole Shenzhen city was calculated with a resolution of 1kmx1km. Wavelet multi-scale analysis (MSA) was applied to the Bouguer gravity data to obtain the multilayer residual anomalies corresponding to different depths. In addition, 2D gravity models were constructed along three profiles. The Bouguer gravity anomaly shows a NE-striking high-low-high pattern from northwest to southeast, strongly related to the main faults. According to the result of MSA, the correlation between gravity anomaly and faults is particularly significant from 4 to 12 km depth. The residual gravity with small amplitude in each layer indicates weak tectonic activity in the crust. In the upper layers, positive anomalies along most of faults reveal the upwelling of high-density materials during the past tectonic movements. The multilayer residual anomalies also implicate important information about the faults, such as the vertical extension and the dip direction. The maximum depth of the faults is about 20km. In general, NE-striking faults extend deeper than NW-striking Faults and have a larger dip angle. This study is supported by the National Natural Science Foundation of China (Grant No.41504015) and China Postdoctoral Science Foundation (Grant No.2015M572146).

  15. On the recovery of gravity anomalies from high precision altimeter data

    NASA Technical Reports Server (NTRS)

    Lelgemann, D.

    1976-01-01

    A model for the recovery of gravity anomalies from high precision altimeter data is derived which consists of small correction terms to the inverse Stokes' formula. The influence of unknown sea surface topography in the case of meandering currents such as the Gulf Stream is discussed. A formula was derived in order to estimate the accuracy of the gravity anomalies from the known accuracy of the altimeter data. It is shown that for the case of known harmonic coefficients of lower order the range of integration in Stokes inverse formula can be reduced very much.

  16. Gravity anomalies of irregularly shaped two-dimensional bodies with constant horizontal density gradient

    USGS Publications Warehouse

    Pan, Jeng-Jong

    1989-01-01

    An equation to compute the gravity anomalies of two-dimensional (2-D) bodies with density contrast varying with depth (z axis) was developed by Murthy and Rao (1979). I develop an equation for computing the gravity anomalies of 2-D bodies with constant horizontal density gradient. By combining this equation with the equation of Murthy and Rao, I estimate the depth of the sedimentary basin which is adjacent to the master fault associated with the Rio Grande rift in New Mexico, where the density is assumed to decrease basinward from the fault (Cordell, 1979).

  17. Mafic and ultramafic rocks of the northwestern Brooks Range of Alaska produce nearly symmetric gravity anomalies

    SciTech Connect

    Morin, R.L. )

    1993-04-01

    An arc of mafic and ultramafic rocks is mapped from Asik Mountain to Siniktanneyak Mountain in the northwestern Brooks Range of Alaska. Gravity data, although not very detailed, have been collected over the region and show some very conspicuous circular or oval gravity highs over portions of the mapped mafic-ultramafic bodies. Bodies which have large associated gravity anomalies are Asik Mountain (80 mGal), Avon Hills (20 mGal), Misheguk Mountain (30 mGal), and Siniktanneyak Mountain (20 mGal). Gabbros of the Siniktanneyak Mountain complex, where the gravity coverage is best, have densities of about 3.0 g/cm[sup 3] while the densities of the surrounding sedimentary rocks are about 2.6 g/cm[sup 3]. Volcanic rocks in the area have average densities of about 2.7 g/cm[sup 3]. Three-dimensional modeling indicates that the largest anomaly, on the southwestern part of the complex, could be caused by a polygonal prism of gabbro with vertical sides, about 6 km across and about 4.5 km deep. A smaller lobe of the anomaly on the northeast of the complex could be caused by another oblong polygonal prism about 4 km long and 2 km wide trending northeast and about 1.5 km deep. Modeling this anomaly with densities lower than gabbro would require greater thicknesses to produce the same anomaly. Modeling each anomaly along this arc in 2 1/2-dimensions shows many possible solutions using different body shapes and different density contrasts. There are several other gravity anomalies in this vicinity which could represent unexposed high density rocks. One such anomaly is in the Maiyumerak Mountains northeast of Asik Mountain (30 mGal). Another anomaly is to the northwest of Asik Mountain (20 mGal). There is also an anomaly at Uchugrak (20 mGal) east of Avan Hills. Although many of the anomalies in this region are poorly controlled, an attempt has been made to interpret the data to show possible solutions.

  18. The relationship between mean anomaly block sizes and spherical harmonic representations. [of earth gravity

    NASA Technical Reports Server (NTRS)

    Rapp, R. H.

    1977-01-01

    The frequently used rule specifying the relationship between a mean gravity anomaly in a block whose side length is theta degrees and a spherical harmonic representation of these data to degree l-bar is examined in light of the smoothing parameter used by Pellinen (1966). It is found that if the smoothing parameter is not considered, mean anomalies computed from potential coefficients can be in error by about 30% of the rms anomaly value. It is suggested that the above mentioned rule should be considered only a crude approximation.

  19. Detailed Gravity and Magnetic Survey of the Taylorsville Triassic Basin

    SciTech Connect

    Leftwich, John; Nowroozi, Ali, A.

    1999-10-01

    This work reports the progress on collecting existing gravity data in a rectangular area covering the Richmond and Taylorsville Basins and its vicinity. The area covers one-degree latitude and one degree longitude, starting at 37 North, 77 West and ending at 38 North, 78 West. Dr. David Daniels of the United State Geological Survey supplied us with more than 4900 Bouguer gravity anomalies in this area. The purpose of this report is to present the data in form of several maps and discuss its relation to the geology of the Triassic Basins and its vicinity. Johnson and others (1985) also presented a map of the Bouguer gravity anomaly of this area. However, their map covers a smaller area, and it is based on smaller number of observations.

  20. Gravity investigation of the Manson impact structure, Iowa

    NASA Technical Reports Server (NTRS)

    Plescia, J. B.

    1993-01-01

    The Manson crater, of probable Cretaceous/Tertiary age, is located in northwestern Iowa (center at 42 deg. 34.44 min N; 94 deg. 33.60 min W). A seismic reflection profile along an east west line across the crater and drill hole data indicate a crater about 35 km in diameter having the classic form for an impact crater, an uplifted central peak composed of uplifted Proterozoic crystalline bedrock, surrounded by a 'moat' filled with impact produced breccia and a ring graben zone composed of tilted fault blocks of the Proterozoic and Paleozoic country rocks. The structure has been significantly eroded. This geologic structure would be expected to produce a significant gravity signature and study of that signature would shed additional light on the details of the crater structure. A gravity study was undertaken to better resolve the crustal structure. The regional Bouguer gravity field is characterized by a southeastward decreasing field. To first order, the Bouguer gravity field can be understood in the context of the geology of the Precambrian basement. The high gravity at the southeast corner is associated with the mid-continent gravity high; the adjacent low to the northwest results from a basin containing low-density clastic sediments shed from the basement high. Modeling of a simple basin and adjacent high predicts much of the observed Bouguer gravity signature. A gravity signature due to structure associated with the Manson impact is not apparent in the Bouguer data. To resolve the gravity signature of the impact, a series of polynomial surfaces were fit to the Bouguer gravity field to isolate the small wavelength residual anomalies. The residual gravity obtained after subtracting a 5th- or 6th-order polynomial seems to remove most of the regional effects and isolate local anomalies. The pattern resolved in the residual gravity is one of a gravity high surrounded by gravity lows and in turn surrounded by isolated gravity highs. The central portion of the crater

  1. Spherical earth gravity and magnetic anomaly analysis by equivalent point source inversion

    NASA Technical Reports Server (NTRS)

    Von Frese, R. R. B.; Hinze, W. J.; Braile, L. W.

    1981-01-01

    To facilitate geologic interpretation of satellite elevation potential field data, analysis techniques are developed and verified in the spherical domain that are commensurate with conventional flat earth methods of potential field interpretation. A powerful approach to the spherical earth problem relates potential field anomalies to a distribution of equivalent point sources by least squares matrix inversion. Linear transformations of the equivalent source field lead to corresponding geoidal anomalies, pseudo-anomalies, vector anomaly components, spatial derivatives, continuations, and differential magnetic pole reductions. A number of examples using 1 deg-averaged surface free-air gravity anomalies of POGO satellite magnetometer data for the United States, Mexico, and Central America illustrate the capabilities of the method.

  2. Gravity and geoid anomalies of the Philippine Sea: Evidence on the depth of compensation for the negative residual water depth anomaly

    NASA Technical Reports Server (NTRS)

    Bowin, C.

    1982-01-01

    A negative free-air gravity anomaly which occurs in the central part of the Philippine Sea was examined to determine the distribution and nature of possible regional mass excesses or deficiencies. Geoid anomalies from GEOS-3 observation were positive. A negative residual geoid anomaly consistent with the area of negative free-air gravity anomalies were found. Theoretical gravity-topography and geoid-topography admittance functions indicated that high density mantle at about 60 km dept could account for the magnitudes of the gravity and residual geoid anomaly and the 1 km residual water depth anomaly in the Philippine Sea. The negative residual depth anomaly may be compensated for by excess density in the uppermost mantle, but the residual geoid and regional free-air gravity anomalies and a slow surface wave velocity structure might result from low-density warm upper mantle material lying beneath the zone of high-density uppermost mantle. From a horizontal disk approximation, the depth of the low-density warm mantle was estimated to be on the order of 200 km.

  3. An analysis of the gravity field and tectonic evaluation of the northwestern part of Bangladesh

    NASA Astrophysics Data System (ADS)

    Khan, A. A.; Rahman, T.

    1992-06-01

    The total Bouguer anomaly values of the northwestern part of Bangladesh have been analysed on the basis of the trend, shape and magnitude of the anomaly values. Residual gravity and the second vertical derivatives of gravity show only two near-surface features, viz. the Nilphamari and Rangpur highs. Geological models of the two highs have been constructed on the basis of gravity modelling. Gravity data, in conjunction with aeromagnetic and bore hole data, enable us to propose four tectonic elements of the northwestern part of Bangladesh: the Northern Slope of the Platform, the Stable Platform, the Nawabganj-Gaibandha Intracratonic High and the Southern Part of the Platform.

  4. The estimation of 550 km x 550 km mean gravity anomalies. [from free atmosphere gravimetry data

    NASA Technical Reports Server (NTRS)

    Williamson, M. R.; Gaposchkin, E. M.

    1975-01-01

    The calculation of 550 km X 550 km mean gravity anomalies from 1 degree X 1 degree mean free-air gravimetry data is discussed. The block estimate procedure developed by Kaula was used, and estimates for 1452 of the 1654 blocks were obtained.

  5. Direct recovery of mean gravity anomalies from satellite to satellite tracking

    NASA Technical Reports Server (NTRS)

    Hajela, D. P.

    1974-01-01

    The direct recovery was investigated of mean gravity anomalies from summed range rate observations, the signal path being ground station to a geosynchronous relay satellite to a close satellite significantly perturbed by the short wave features of the earth's gravitational field. To ensure realistic observations, these were simulated with the nominal orbital elements for the relay satellite corresponding to ATS-6, and for two different close satellites (one at about 250 km height, and the other at about 900 km height) corresponding to the nominal values for GEOS-C. The earth's gravitational field was represented by a reference set of potential coefficients up to degree and order 12, considered as known values, and by residual gravity anomalies obtained by subtracting the anomalies, implied by the potential coefficients, from their terrestrial estimates. It was found that gravity anomalies could be recovered from strong signal without using any a-priori terrestrial information, i.e. considering their initial values as zero and also assigning them a zero weight matrix. While recovering them from weak signal, it was necessary to use the a-priori estimate of the standard deviation of the anomalies to form their a-priori diagonal weight matrix.

  6. Using Grail Data to Assess the Effect of Porosity and Dilatancy on the Gravity Signature of Impact Craters on the Moon

    NASA Astrophysics Data System (ADS)

    Milbury, C.; Johnson, B. C.; Melosh, J., IV; Collins, G. S.; Blair, D. M.; Soderblom, J. M.; Zuber, M. T.

    2014-12-01

    NASA's dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft have globally mapped the lunar gravity field at unprecedented resolution; this has enabled the study of craters of all sizes and ages. Soderblom et al. [2014, LPSC abstract #1777] calculated the residual Bouguer anomalies for ~2700 craters 27-184 km in diameter (D). They found that the residual Bouguer anomaly over craters smaller than D~100 km is essentially 0±50 mGal, there is a transition for D~100-150 km, and craters larger than 184 km have a positive residual Bouguer anomaly that increases with increasing crater size. We use the iSALE shock physics hydrocode to model crater formation, including the effect of porosity and dilatancy (shear bulking). We use strength parameters of gabbroic anorthosite for the crust and dunite for the mantle. Our impactor sizes range from 6-30 km, which produce craters between 86-450 km in diameter for pre-impact target porosities of 0, 6.8, and 13.6%. We calculate the free-air and Bouguer gravity anomalies from our models and compare them to gravity data from GRAIL. We find that target porosity has the greatest effect on the gravity signature of lunar craters and can explain the observed ±50 mGal scatter in the residual Bouguer anomaly. We investigate variations of impact velocity, crustal thickness, and dilatancy angle; we find that these parameters do not affect the gravity as significantly as target porosity does. We find that the crater diameter at which mantle uplift dominates the crater gravity is dependent on target porosity, and that it occurs at a crater diameter that is close to the complex crater to peak-ring basin transition.

  7. 3D Inversion of Gravity Anomalies for the Interpretation of Sedimentary Basins using Variable Density Contrast

    NASA Astrophysics Data System (ADS)

    Ekinci, Yunus Levent; Ertekin, Can

    2015-04-01

    Concern about sedimentary basins is generally related to their genetic and economic significance. Analysis of sedimentary basins requires the acquisition of data through outcrop studies and subsurface investigations that encompass drilling and geophysics. These data are commonly analysed by computer-assisted techniques. One of these methods is based on analysing gravity anomalies to compute the depth of sedimentary basin-basement rock interface. Sedimentary basins produce negative gravity anomalies, because they have mostly lower densities than that of the surrounding basement rocks. Density variations in a sedimentary fill increase rapidly at shallower depths then gradually reach the density of surrounding basement rocks due to the geostatic pressure i.e. compaction. The decrease of the density contrast can be easily estimated by a quadratic function. Hence, if the densities are chosen properly and the regional background is removed correctly, the topographical relief of the sedimentary basin-basement rock interface might be estimated by the inversion of the gravity data using an exponential density-depth relation. Three dimensional forward modelling procedure can be carried out by introducing a Cartesian coordinate system, and placing vertical prisms just below observation points on the grid plane. Depth to the basement, namely depths to the bottom of the vertical prisms are adjusted in an iterative manner by minimizing the differences between measured and calculated residual gravity anomalies. In this study, we present a MATLAB-based inversion code for the interpretation of sedimentary basins by approximating the topographical relief of sedimentary basin-basement rock interfaces. For a given gridded residual gravity anomaly map, the procedure estimates the bottom depths of vertical prisms by considering some published formulas and assumptions. The utility of the developed inversion code was successfully tested on theoretically produced gridded gravity data set

  8. Principal facts of gravity stations with gravity and magnetic profiles from the Southwest Nevada Test Site, Nye County, Nevada, as of January, 1982

    USGS Publications Warehouse

    Jansma, P.E.; Snyder, D.B.; Ponce, David A.

    1983-01-01

    Three gravity profiles and principal facts of 2,604 gravity stations in the southwest quadrant of the Nevada Test Site are documented in this data report. The residual gravity profiles show the gravity measurements and the smoothed curves derived from these points that were used in geophysical interpretations. The principal facts include station label, latitude, longitude, elevation, observed gravity value, and terrain correction for each station as well as the derived complete Bouguer and isostatic anomalies, reduced at 2.67 g/cm 3. Accuracy codes, where available, further document the data.

  9. Oceanwide gravity anomalies from Geos-3, Seasat and Geosat altimeter data

    NASA Technical Reports Server (NTRS)

    Rapp, Richard H.; Basic, Tomislav

    1992-01-01

    Three kinds of satellite altimeter data have been combined, along with 5 x 5 arcmin bathymetric data, to calculate a 0.125 deg ocean wide gridded set of 2.3 x 10 exp 6 free-air gravity anomalies. The procedure used was least squares collocation that yields the predicted anomaly and standard deviation. The value of including the bathymetric data was shown in a test around the Dowd Seamount where the root mean square (rms) difference between ship gravity measurements decreased from +/- 40 mgal to +/- 20 mgal when the bathymetry was included. Comparisons between the predicted anomalies and ship gravity data is described in three cases. In the Banda Sea the rms differences were +/- 20 mgal for two lines. In the South Atlantic rms differences over lines of 2000 km in length were +/- 7 mgal. For cruise data in the Antarctica region the discrepancies were +/- 12 mgal. Comparisons of anomalies derived from the Geosat geodetic mission data by Marks and McAdoo (1992) with ship dta gave differences of +/- 6 mgal showing the value of the much denser Geosat geodetic mission altimeter data.

  10. Gravity Anomalies of Arbitrary 3D Polyhedral Bodies with Horizontal and Vertical Mass Contrasts

    NASA Astrophysics Data System (ADS)

    Ren, Zhengyong; Chen, Chaojian; Pan, Kejia; Kalscheuer, Thomas; Maurer, Hansruedi; Tang, Jingtian

    2017-03-01

    During the last 15 years, more attention has been paid to derive analytic formulae for the gravitational potential and field of polyhedral mass bodies with complicated polynomial density contrasts, because such formulae can be more suitable to approximate the true mass density variations of the earth (e.g., sedimentary basins and bedrock topography) than methods that use finer volume discretization and constant density contrasts. In this study, we derive analytic formulae for gravity anomalies of arbitrary polyhedral bodies with complicated polynomial density contrasts in 3D space. The anomalous mass density is allowed to vary in both horizontal and vertical directions in a polynomial form of λ =ax^m+by^n+cz^t, where m, n, t are nonnegative integers and a, b, c are coefficients of mass density. First, the singular volume integrals of the gravity anomalies are transformed to regular or weakly singular surface integrals over each polygon of the polyhedral body. Then, in terms of the derived singularity-free analytic formulae of these surface integrals, singularity-free analytic formulae for gravity anomalies of arbitrary polyhedral bodies with horizontal and vertical polynomial density contrasts are obtained. For an arbitrary polyhedron, we successfully derived analytic formulae of the gravity potential and the gravity field in the case of m≤ 1, n≤ 1, t≤ 1, and an analytic formula of the gravity potential in the case of m=n=t=2. For a rectangular prism, we derive an analytic formula of the gravity potential for m≤ 3, n≤ 3 and t≤ 3 and closed forms of the gravity field are presented for m≤ 1, n≤ 1 and t≤ 4. Besides generalizing previously published closed-form solutions for cases of constant and linear mass density contrasts to higher polynomial order, to our best knowledge, this is the first time that closed-form solutions are presented for the gravitational potential of a general polyhedral body with quadratic density contrast in all spatial

  11. Gravity Anomalies of Arbitrary 3D Polyhedral Bodies with Horizontal and Vertical Mass Contrasts

    NASA Astrophysics Data System (ADS)

    Ren, Zhengyong; Chen, Chaojian; Pan, Kejia; Kalscheuer, Thomas; Maurer, Hansruedi; Tang, Jingtian

    2016-11-01

    During the last 15 years, more attention has been paid to derive analytic formulae for the gravitational potential and field of polyhedral mass bodies with complicated polynomial density contrasts, because such formulae can be more suitable to approximate the true mass density variations of the earth (e.g., sedimentary basins and bedrock topography) than methods that use finer volume discretization and constant density contrasts. In this study, we derive analytic formulae for gravity anomalies of arbitrary polyhedral bodies with complicated polynomial density contrasts in 3D space. The anomalous mass density is allowed to vary in both horizontal and vertical directions in a polynomial form of λ =ax^m+by^n+cz^t , where m, n, t are nonnegative integers and a, b, c are coefficients of mass density. First, the singular volume integrals of the gravity anomalies are transformed to regular or weakly singular surface integrals over each polygon of the polyhedral body. Then, in terms of the derived singularity-free analytic formulae of these surface integrals, singularity-free analytic formulae for gravity anomalies of arbitrary polyhedral bodies with horizontal and vertical polynomial density contrasts are obtained. For an arbitrary polyhedron, we successfully derived analytic formulae of the gravity potential and the gravity field in the case of m≤ 1 , n≤ 1 , t≤ 1 , and an analytic formula of the gravity potential in the case of m=n=t=2 . For a rectangular prism, we derive an analytic formula of the gravity potential for m≤ 3 , n≤ 3 and t≤ 3 and closed forms of the gravity field are presented for m≤ 1 , n≤ 1 and t≤ 4 . Besides generalizing previously published closed-form solutions for cases of constant and linear mass density contrasts to higher polynomial order, to our best knowledge, this is the first time that closed-form solutions are presented for the gravitational potential of a general polyhedral body with quadratic density contrast in all

  12. Structure of La Primavera caldera, Jalisco, Mexico, deduced from gravity anomalies and drilling results

    NASA Astrophysics Data System (ADS)

    Yokoyama, I.; Mena, M.

    1991-07-01

    Previous studies of La Primavera caldera have mostly been based on surface geology and topography. Since 1980, many wells, exploring for geothermal energy, have reached depths of about 2 to 3 km at the center of the caldera. The results of the drillings, together with those of the gravity surveys, provide information about the subsurface structure of the caldera, and shed light on its formation. The drilling results and gravity anomalies at La Primavera caldera and San Marcos, located at about 40 km distance from the caldera, suggest that regional gravity anomalies can be interpreted in terms of depths of the granitic basements: the basement beneath La Primavera caldera is about 3 km deep and consists of roughly the same horizon as that beneath San Marcos. The drilling results within the caldera reveal that the depth of the caldera fills ranges from 0.3 to 1 km at the drilling sites. The andesite basement, about 1 km deep, remains approximately horizontal, and the granitic basement has a depth of about 3 km. The surface topographies, such as the postcaldera domes, scarcely disturb the subsurface strata. The local gravity anomalies show two lows within the caldera reflecting the configuration of caldera bottom, two funnel-shaped depressions, one of which corresponds to a vent of the Tala tuff deduced from geological observations. The mass deficiency within the caldera estimated from the gravity anomaly, satisfies the general relationship that the mass deficiency is proportional to the caldera diameter cubed. This means that caldera structure is three-dimensional: the larger the diameter, the deeper the funnel-shape. At present this argument may be limited to funnel-shaped calderas.

  13. Application of Magsat lithospheric modeling in South America. Part 1: Processing and interpretation of magnetic and gravity anomaly data

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Braile, L. W.; Vonfrese, R. R. B. (Principal Investigator); Keller, G. R.; Lidiak, E. G.

    1984-01-01

    Scalar magnetic anomaly data from MAGSAT, reduced to vertical polarization and long wavelength pass filtered free air gravity anomaly data of South America and the Caribbean are compared to major crustal features. The continental shields generally are more magnetic than adjacent basins, oceans and orogenic belts. In contrast, the major aulacogens are characterized by negative anomalies. Spherical earth magnetic modeling of the Amazon River and Takatu aulacogens in northeastern South America indicates a less magnetic crust associated with the aulacogens. Spherical earth modeling of both positive gravity and negative magnetic anomalies observed over the Mississippi Embayment indicate the presence of a nonmagnetic zone of high density material within the lower crust associated with the aulacogen. The MAGSAT scalar magnetic anomaly data and available free air gravity anomalies over Euro-Africa indicate several similar relationships.

  14. Lithospheric structure across the central Tien Shan constrained by gravity anomalies and joint inversions of receiver function and Rayleigh group velocity data

    NASA Astrophysics Data System (ADS)

    Li, Yonghua; Shi, Lei; Gao, Jiayi

    2016-04-01

    Shear wave velocity structure across the central Tien Shan orogeny was generated by jointly inverting Rayleigh wave phase and group velocity with teleseismic P-wave receiver functions at 40 broad band seismic stations of the MANAS project. The inferred seismic structure was validated by forward modeling of the complete Bouguer anomaly data. The joint inversion result reveals larger crust thicknesses beneath the Kokshaal (~68-72 km) and Kyrgyz ranges (~62-64 km), while other units have crustal thicknesses between 48 and 58 km. A fast velocity layer (Vs = 3.6-3.9 km/s) in the upper crust is found in some seismic stations within the Kazakh Shield. Our models show the presence of high velocity and density layers in the lowermost crust throughout the region, consistent with the presence of mafic/ultramafic lithologies. The large crustal thickness is associated with a thickened mafic layer in the lower crust, indicating that the thickened crust may be partly caused by magmatic underplating. The low velocity and density anomaly in the middle crust, and low upper mantle velocity observed in our model beneath the middle Tien Shan reflects the presence of partial melt in the crust due to the intrusion of hot mantle material. The lack of correlation between Moho depth and topography, together with the gravity results, suggests that the topographic compensation in the central Tien Shan is not confined to the crust. This requires significant support from the mantle to account for the relative high elevation of the middle Tien Shan.

  15. Disturbance vector in space from surface gravity anomalies using complementary models

    NASA Astrophysics Data System (ADS)

    Cruz, J. Y.

    1985-12-01

    This modeling of the external disturbance vector of the Earth from surface gravity anomaly data is discussed. The low frequency features of the signal are represented in spherical harmonic series. The recovery of the coefficients of the series from the given gravity anomalies is discussed focusing on the use of analytical continuation and ellipsoidal corrections to account for the Earth's topography and ellipticity. The spectrum and data response of the spatial disturbance vector are studied to aid the design of models and experiments. The local models studied to complement the globally valid spherical harmonic model are: (1) the residual topographic model (RTM), (2) the classical integral model, (3) three versions of the Dirac approach to collocation, and finally (4) two versions of the least squares collocation approach.

  16. Anomalies and Hawking fluxes from the black holes of topologically massive gravity

    NASA Astrophysics Data System (ADS)

    Porfyriadis, Achilleas P.

    2009-05-01

    The anomaly cancelation method proposed by Wilczek et al. is applied to the black holes of topologically massive gravity (TMG) and topologically massive gravito-electrodynamics (TMGE). Thus the Hawking temperature and fluxes of the ACL and ACGL black holes are found. The Hawking temperatures obtained agree with the surface gravity formula. Both black holes are rotating and this gives rise to appropriate terms in the effective U (1) gauge field of the reduced (1 + 1)-dimensional theory. It is found that the terms in this U (1) gauge field correspond exactly to the correct angular velocities on the horizon of both black holes as well as the correct electrostatic potential of the ACGL black hole. So the results for the Hawking fluxes derived here from the anomaly cancelation method, are in complete agreement with the ones obtained from integrating the Planck distribution.

  17. Observation of Wood's anomalies on surface gravity waves propagating on a channel.

    PubMed

    Schmessane, Andrea

    2016-09-01

    I report on experiments demonstrating the appearance of Wood's anomalies in surface gravity waves propagating along a channel with a submerged obstacle. Space-time measurements of surface gravity waves allow one to compute the stationary complex field of the wave and the amplitude growth of localized and propagative modes over all the entire channel, including the scattering region. This allows one to access the near and far field dynamics, which constitute a new and complementary way of observation of mode resonances of the incoming wave displaying Wood's anomalies. Transmission coefficient, dispersion relations and normalized wave energy of the incoming wave and the excited mode are measured and found to be in good agreement with theoretical predictions.

  18. Joint Interpretation of Bathymetric and Gravity Anomaly Maps Using Cross and Dot-Products.

    NASA Astrophysics Data System (ADS)

    Jilinski, Pavel; Fontes, Sergio Luiz

    2010-05-01

    0.1 Summary We present the results of joint map interpretation technique based on cross and dot-products applied to bathymetric and gravity anomaly gradients maps. According to the theory (Gallardo, Meju, 2004) joint interpretation of different gradient characteristics help to localize and empathize patterns unseen on one image interpretation and gives information about the correlation of different spatial data. Values of angles between gradients and their cross and dot-product were used. This technique helps to map unseen relations between bathymetric and gravity anomaly maps if they are analyzed separately. According to the method applied for the southern segment of Eastern-Brazilian coast bathymetrical and gravity anomaly gradients indicates a strong source-effect relation between them. The details of the method and the obtained results are discussed. 0.2 Introduction We applied this method to investigate the correlation between bathymetric and gravity anomalies at the southern segment of the Eastern-Brazilian coast. Gridded satellite global marine gravity data and bathymetrical data were used. The studied area is located at the Eastern- Brazilian coast between the 20° W and 30° W meridians and 15° S and 25° S parallels. The volcanic events responsible for the uncommon width of the continental shelf at the Abrolhos bank also were responsible for the formation of the Abrolhos islands and seamounts including the major Vitoria-Trindade chain. According to the literature this volcanic structures are expected to have a corresponding gravity anomaly (McKenzie, 1976, Zembruscki, S.G. 1979). The main objective of this study is to develop and test joint image interpretation method to compare spatial data and analyze its relations. 0.3 Theory and Method 0.3.1 Data sources The bathymetrical satellite data were derived bathymetry 2-minute grid of the ETOPO2v2 obtained from NOAA's National Geophysical Data Center (http://www.ngdc.noaa.gov). The satellite marine gravity 1

  19. Preparation of Residual Gravity Maps for the Southern Cascade Mountains, Washington Using Fourier Analysis

    SciTech Connect

    Dishberger, Debra McLean

    1983-04-01

    This report represents a continuation of gravity work in the Cascade Mountains of Washington supported by the Division of Geology and Earth Resources since 1974. The purpose of this research has been collection of baseline gravity data for use in geothermal resource evaluation. Results of the Division's gravity studies to date are given in Danes and Phillips (1983a, 1983b). One of the problems encountered when analyzing gravity data is distinguishing between those parts of the data that represent geologic structures of interest, and those that do not. In many cases, the features of interest are relatively small, near-surface features, such as those sought in mineral, petroleum, or geothermal exploration. Gravity anomalies caused by such structures may be distorted or masked by anomalies caused by larger, deeper geologic structures. Gravity anomalies caused by relatively shallow, small geologic structures are termed residual anomalies. Those due to broad, deep-seated features can be described as regional anomalies. The purpose of this report is to describe a Fourier analysis method for separating residual and regional gravity anomalies from a complete Bouguer gravity anomaly field. The technique has been applied to gravity data from the Southern Cascade Mountains, Washington. Residual gravity anomaly maps at a scale of 1:250,000 are presented for various regional wavelength filters, and a power spectrum of the frequency components in the South Cascade gravity data is displayed. No attempt is made to interpret the results of this study in terms of geologic structures.

  20. Improved gravity anomaly fields from retracked multimission satellite radar altimetry observations over the Persian Gulf and the Caspian Sea

    NASA Astrophysics Data System (ADS)

    Khaki, M.; Forootan, E.; Sharifi, M. A.; Awange, J.; Kuhn, M.

    2015-09-01

    Satellite radar altimetry observations are used to derive short wavelength gravity anomaly fields over the Persian Gulf and the Caspian Sea, where in situ and ship-borne gravity measurements have limited spatial coverage. In this study the retracking algorithm `Extrema Retracking' (ExtR) was employed to improve sea surface height (SSH) measurements that are highly biased in the study regions due to land contaminations in the footprints of the satellite altimetry observations. ExtR was applied to the waveforms sampled by the five satellite radar altimetry missions: TOPEX/POSEIDON, JASON-1, JASON-2, GFO and ERS-1. Along-track slopes have been estimated from the improved SSH measurements and used in an iterative process to estimate deflections of the vertical, and subsequently, the desired gravity anomalies. The main steps of the gravity anomaly computations involve estimating improved SSH using the ExtR technique, computing deflections of the vertical from interpolated SSHs on a regular grid using a biharmonic spline interpolation and finally estimating gridded gravity anomalies. A remove-compute-restore algorithm, based on the fast Fourier transform, has been applied to convert deflections of the vertical into gravity anomalies. Finally, spline interpolation has been used to estimate regular gravity anomaly grids over the two study regions. Results were evaluated by comparing the estimated altimetry-derived gravity anomalies (with and without implementing the ExtR algorithm) with ship-borne free air gravity anomaly observations, and free air gravity anomalies from the Earth Gravitational Model 2008 (EGM2008). The comparison indicates a range of 3-5 mGal in the residuals, which were computed by taking the differences between the retracked altimetry-derived gravity anomaly and the ship-borne data. The comparison of retracked data with ship-borne data indicates a range in the root-mean-square-error (RMSE) between approximately 1.8 and 4.4 mGal and a bias between 0

  1. Joint Inversion and Forward Modeling of Gravity and Magnetic Data in the Ismenius Region of Mars

    NASA Technical Reports Server (NTRS)

    Milbury, C. A.; Raymond, C. A.; Jewell, J. B.; Smrekar, S. E.; Schubert, G.

    2005-01-01

    The unexpected discovery of remanent crustal magnetism on Mars was one of the most intriguing results from the Mars Global Surveyor mission. The origin of the pattern of magnetization remains elusive. Correlations with gravity and geology have been examined to better understand the nature of the magnetic anomalies. In the area of the Martian dichotomy between 50 and 90 degrees E (here referred to as the Ismenius Area), we find that both the Bouguer and the isostatic gravity anomalies appear to correlate with the magnetic anomalies and a buried fault, and allow for a better constraint on the magnetized crust].

  2. Results from the direct combination of satellite and gravimetric data. [orbit analysis and gravity anomalies

    NASA Technical Reports Server (NTRS)

    Rapp, R. H.

    1974-01-01

    Results have been obtained for the solution of 184 15-deg equal-area blocks directly from the analysis of satellite orbits, and from a combination of the satellite results with terrestrial gravity material. This test computation, made to verify the method, used 17,632 optical observations from ten satellites in 29 arcs averaging in length seven days. Analysis of the satellite results were made by comparing the solved for anomalies with the terrestrial anomaly set, and by developing the solved for anomalies into potential coefficients which were compared to the GEM 3 set of potential coefficients to degree 12. These comparisons indicated improvement in each solution as more arcs were added. The programs used in this solution can easily be used to solve for smaller size blocks and handle additional data types. The only limitation will be computer core availability and computer time.

  3. Gravity and magnetic anomaly modeling and correlation using the SPHERE program and Magsat data

    NASA Technical Reports Server (NTRS)

    Braile, L. W.; Hinze, W. J. (Principal Investigator); Vonfrese, R. R. B.

    1980-01-01

    The spherical Earth inversion, modeling, and contouring software were tested and modified for processing data in the Southern Hemisphere. Preliminary geologic/tectonic maps and selected cross sections for South and Central America and the Caribbean region are being compiled and as well as gravity and magnetic models for the major geological features of the area. A preliminary gravity model of the Andeas Beniff Zone was constructed so that the density columns east and west of the subducted plates are in approximate isostatic equilibrium. The magnetic anomaly for the corresponding magnetic model of the zone is being computed with the SPHERE program. A test tape containing global magnetic measurements was converted to a tape compatible with Purdue's CDC system. NOO data were screened for periods of high diurnal activity and reduced to anomaly form using the IGS-75 model. Magnetic intensity anomaly profiles were plotted on the conterminous U.S. map using the track lines as the anomaly base level. The transcontinental magnetic high seen in POGO and MAGSAT data is also represented in the NOO data.

  4. Spherical Earth analysis and modeling of lithospheric gravity and magnetic anomalies. Ph.D. Thesis - Purdue Univ.

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.

    1980-01-01

    A comprehensive approach to the lithospheric analysis of potential field anomalies in the spherical domain is provided. It has widespread application in the analysis and design of satellite gravity and magnetic surveys for geological investigation.

  5. Chapter 3: Circum-Arctic mapping project: New magnetic and gravity anomaly maps of the Arctic

    USGS Publications Warehouse

    Gaina, C.; Werner, S.C.; Saltus, R.; Maus, S.; Aaro, S.; Damaske, D.; Forsberg, R.; Glebovsky, V.; Johnson, K.; Jonberger, J.; Koren, T.; Korhonen, J.; Litvinova, T.; Oakey, G.; Olesen, O.; Petrov, O.; Pilkington, M.; Rasmussen, T.; Schreckenberger, B.; Smelror, M.

    2011-01-01

    New Circum-Arctic maps of magnetic and gravity anomalies have been produced by merging regional gridded data. Satellite magnetic and gravity data were used for quality control of the long wavelengths of the new compilations. The new Circum-Arctic digital compilations of magnetic, gravity and some of their derivatives have been analyzed together with other freely available regional and global data and models in order to provide a consistent view of the tectonically complex Arctic basins and surrounding continents. Sharp, linear contrasts between deeply buried basement blocks with different magnetic properties and densities that can be identified on these maps can be used, together with other geological and geophysical information, to refine the tectonic boundaries of the Arctic domain. ?? 2011 The Geological Society of London.

  6. Gravity evidence for a shallow intrusion under Medicine Lake volcano, California.

    USGS Publications Warehouse

    Finn, C.; Williams, D.L.

    1982-01-01

    A positive gravity anomaly is associated with Medicine Lake volcano, California. Trials with different Bouguer reduction densities indicate that this positive anomaly cannot be explained by an inappropriate choice of Bouguer reduction density but must be caused by a subvolcanic body. After separating the Medicine Lake gravity high from the regional field, we were able to fit the 27mgal positive residual anomaly with a large, shallow body of high density contrast (+0.41g/cm3) and a thickness of 2.5km. We interpret this body to be an intrusion of dense material emplaced within the several-kilometres-thick older volcanic layer that probably underlies Medicine Lake volcano.-Authors

  7. Principal facts for gravity data collected in the southern Albuquerque Basin area and a regional compilation, central New Mexico

    USGS Publications Warehouse

    Gillespie, Cindy L.; Grauch, V.J.S.; Oshetski, Kim; Keller, Gordon R.

    2000-01-01

    Principal facts for 156 new gravity stations in the southern Albuquerque basin are presented. These data fill a gap in existing data coverage. The compilation of the new data and two existing data sets into a regional data set of 5562 stations that cover the Albuquerque basin and vicinity is also described. Bouguer anomaly and isostatic residual gravity data for this regional compilation are available in digital form from ftp://greenwood.cr.usgs.gov/pub/openfile- reports/ofr-00-490.

  8. Gravity Anomalies of Complex Craters on Earth and the Moon: Insight from Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Collins, G. S.

    2012-12-01

    The impact cratering process alters the density of target rocks and deforms subsurface strata to produce characteristic geophysical anomalies. Principal among these is a broad, circular gravity anomaly concentric to the crater. By accounting for dilatancy--the creation of pore space in a shearing granular material--in numerical models of impact crater formation, the origin of gravity anomalies in complex craters is investigated. A semi-empirical approach is used to account for dilatancy. Shear failure leads to a prescribed increase in distension (porosity), depending on a user-defined function for the dilatancy angle, describing the tendency for the target rock to dilate. Here, the dilatancy angle is defined as a function of porosity, pressure and temperature, based on measurements from soil and rock mechanics experiments. The maximum dilatancy angle occurs at zero porosity, pressure, and temperature and decreases as any of these three variables increase. This approach ensures that, after impact, the increase in distension caused by shear failure is preserved. The final sub-crater porosity distribution can be compared with observations at terrestrial craters and used to make predictions about the gravity anomalies over terrestrial and lunar complex craters. Simulations of terrestrial impacts using the dilatancy model result in porosity and gravity anomalies consistent with observation, provided that the maximum dilatancy angle is only a few degrees. The decrease in dilatancy angle with increasing pressure has three important effects. While a small amount of dilation (bulking) occurs during tensile failure behind the shock wave, in general the high pressures in the shock wave suppress the generation of porosity as it propagates through the target rocks. Moreover, at depths exceeding about 10 km on Earth (60 km on the Moon) the confining pressure is sufficient to suppress porosity generation at any stage during crater formation. As a result, the majority of the

  9. Principal Facts for Gravity Data Collected in Wisconsin: A Web Site and CD-ROM for Distribution of Data

    USGS Publications Warehouse

    Snyder, Stephen L.; Geister, Daniel W.; Daniels, David L.; Ervin, C. Patrick

    2004-01-01

    Principal facts for 40,488 gravity stations covering the entire state of Wisconsin are presented here in digital form. This is a compilation of previously published data collected between 1948 and 1992 from numerous sources, along with over 10,000 new gravity stations collected by the USGS since 1999. Also included are 550 gravity stations from previously unpublished sources. Observed gravity and complete-Bouguer gravity anomaly data for this statewide compilation are included here. Altogether, 14 individual surveys are presented here.

  10. Basement depth estimation from gravity anomalies: two 2.5D approaches coupled with the exponential density contrast model

    NASA Astrophysics Data System (ADS)

    Chakravarthi, V.; Mallesh, K.; Ramamma, B.

    2017-03-01

    We develop two automatic techniques in the spatial domain using the exponential density contrast model (EDCM) to trace the bottom surface of a 2.5D sedimentary basin from the observed gravity anomalies. The interface between the sediments and basement is described with a finite strike polygonal source, whose depth ordinates become the unknown parameters to be estimated. The proposed automatic modeling technique makes use of the forward difference approximation and the inversion solves a system of normal equations using the ridge regression to estimate the unknown parameters. Furthermore, the proposed inversion technique simultaneously estimates the regional gravity background that is associated with the residual gravity anomaly. In either case, forward modeling is realized in the spatial domain through a method that combines both analytical and numerical approaches. The utility of each algorithm was successfully tested on a theoretically produced noisy residual gravity dataset. The validity of the inversion technique is also exemplified with the noisy gravity anomalies attributable to a synthetic structure in the presence of regional gravity background. We demonstrate that the magnitude of gravity anomaly is offset dependent and that it would influence the modeling result. Additionally, some applications with real gravity datasets from the Gediz and Büyük Menderes grabens in western Turkey using the derived EDCMs have produced geologically reasonable results which are in close agreement with those reported previously.

  11. Calculation of gravity and magnetic anomalies along profiles with end corrections and inverse solutions for density and magnetization

    USGS Publications Warehouse

    Cady, John W.

    1977-01-01

    A computer program is presented which performs, for one or more bodies, along a profile perpendicular to strike, both forward calculations for the magnetic and gravity anomaly fields and independent gravity and magnetic inverse calculations for density and susceptibility or remanent magnetization.

  12. Probing the Lunar Polar Crust with GRAIL Gravity

    NASA Astrophysics Data System (ADS)

    Smith, D. E.; Zuber, M. T.; Goossens, S. J.; Rowlands, D. D.; Neumann, G. A.; Mazarico, E.; Genova, A.; Lemoine, F. G.

    2015-12-01

    The lunar polar crust, from latitude ±80° to the pole, exhibits Bouguer gravity anomalies that result from crustal density variations of order ±45 mGal in the south and ±25 mGal in the north, bandpass filtered to wavelengths representing the top 50 km. Evident in the Bouguer gravity at both poles are the signatures of a few large craters and basins. But at both poles, the Bouguer map also displays a large number of small, rather sinuous features, some outlining crater rims and some structures on crater floors, that are distributed more or less uniformly across the region. The root mean square (rms) variation over the 10° radius cap is less than 11 mGals at the south pole and less than 7 mGals in the north. This difference reflects the greater crustal complexity in the south compared to the north, but these magnitudes are approximately 10% of the total field in the polar regions, indicating that substantial density anomalies exist below 50 km depth. Modeling the crustal anomalies in the top 50 km by density contrasts at various depths suggest the rms magnitudes can be explained by small local variations in porosity, or possibly the presence of H2O at concentrations of a few percent. The required concentration increases with depth for a given volume but the possibility that the source of the polar anomalies includes small concentrations of H2O in the crust, however, cannot be ruled out.

  13. Longwavelength gravity anomalies and the deep thermal structure of the Baikal rift

    SciTech Connect

    Diament, M. ); Kogan, M.G. )

    1990-10-01

    The analysis of the gravity field over the Baikal rift area has been carried out in order: (1) to detect the amount of the deep hot material, and (2) to constrain the flexural rigidity of the lithosphere. The authors removed a few first harmonics of the global field and the gravity effects due to the crust from the observed field and found a residual anomaly which is aligned with the rift. This residual, which they attribute to the mantle, shows a minimum of about 15 mgal in amplitude and 900 km width, which is superimposed over a wider minimum with smaller amplitude. A model involving a simple stretching of the lithosphere with diffusion of heat predicts the right order of magnitude for both the amplitude and the wavelength of the 900-km anomaly. Results confirm that the stretching factor is of the order of 1.2 to 1.5. Interpretation of the coherence function computed between gravity and topography shows that the lithosphere in the area has a significant equivalent elastic thickness of about 30 km (i.e. flexural rigidity about 2.3 10{sup 23} N.m.).

  14. Lunar floor-fractured craters as magmatic intrusions: Geometry, modes of emplacement, associated tectonic and volcanic features, and implications for gravity anomalies

    NASA Astrophysics Data System (ADS)

    Jozwiak, Lauren M.; Head, James W.; Wilson, Lionel

    2015-03-01

    , the intrusion concentrates bending primarily at the periphery, resulting in a flat, tabular intrusion. We predict that this process will result in concentric fractures over the region of greatest bending. This location is close to the crater wall in large, flat-floored craters, as observed in the crater Humboldt, and interior to the crater over the domed floor in smaller craters, as observed in the crater Vitello. A variety of volcanic features are predicted to be associated with the solidification and degassing of the intrusion; these include: (1) surface lava flows associated with concentric fractures (e.g., in the crater Humboldt); (2) vents with no associated pyroclastic material, from the deflation of under-pressurized magmatic foam (e.g., the crater Damoiseau); and (3) vents with associated pyroclastic deposits from vulcanian eruptions of highly pressurized magmatic foam (e.g., the crater Alphonsus). The intrusion of basaltic magma beneath the crater is predicted to contribute a positive component to the Bouguer gravity anomaly; we assess the predicted Bouguer anomalies associated with FFCs and outline a process for their future interpretation. We conclude that our proposed mechanism serves as a viable formation process for FFCs and accurately predicts numerous morphologic, morphometric, and geophysical features associated with FFCs. These predictions can be further tested using GRAIL (Gravity Recovery and Interior Laboratory) data.

  15. Gravity survey in the San Luis Valley area, Colorado

    USGS Publications Warehouse

    Gaca, J. Robert; Karig, Daniel E.

    1965-01-01

    During the summers of 1963 and 1964, a regional gravity survey covering 6,000 square miles of the San Luis Valley and surrounding areas was made to determine subsurface basement configurations and to guide future crustal studies. The San Luis Valley, a large intermontane basin, is a segment of the Rio Grande trough, a reef system characterized by volcanism, normal faulting, and tilted fault blocks. The gravity data, accurate to about 0.5 mgal, were reduced to complete-Bouguer anomaly values. The Bouguer-anomaly gravity map delineates a series of en-echelon gravity highs in the central and western San Luis Valley. These gravity highs are interpreted as horsts of Precambrian rock buried by basin fill. A series of en-echelon gravity lows along the eastern edge of the Valley is interpreted as a graben filled with sedimentary and igneous rock estimated to be up to 30,000 ft thick. The relatively high regional gravity over the Sangre de Cristo Mountains suggests that these mountains are locally uncompensated. A subcircular gravity low in the Bonanza area is interpreted as an indication of low-density volcanic rocks within a caldera structure.

  16. Modeling of shallow structures in the Cappadocia region using gravity and aeromagnetic anomalies

    NASA Astrophysics Data System (ADS)

    Kosaroglu, Sinan; Buyuksarac, Aydin; Aydemir, Attila

    2016-07-01

    In this study, shallow structures and bodies creating gravity and magnetic anomalies in the Cappadocia Volcanic Complex region in central Anatolia were investigated in order to determine the tectonic origin and structural setting of young volcanic units. The shallow geological structures in the region are depressions filled with mainly low-density, loose volcano-clastics and ignimbrite sheets associated with the continental Neogene deposits. These units together with other volcanic products are originated from the large Neogene and Quaternary volcanoes of the central Anatolia, particularly in the Cappadocia region. At first, spectral analysis to obtain the cut-off frequencies for the high-pass filter was performed in this investigation. Then, gravity and magnetic data were high-pass filtered to remove the deep and regional effects on anomalies and to unveil only shallow structures' effects. Subsequently, upward and downward continuations were carried out to determine how these shallow structures influence the total anomalies and their contribution in the confining total potential field. In addition, three and two dimensional gravity models (3D and 2D) of the study area were also constructed to obtain the bottom depth of shallow bodies. According to spectral analysis results, shallow structures could be separated into two groups from the power spectrums and bottom depth of deeper structure was commonly determined about 2 km in gravity and magnetic spectrum, both. More shallow structure is at the depth around 0.317 km according to the gravity power spectrum. Obviously, 3D and 2D models are consistent with the spectral analysis results for the deeper unit depth. A circular, large depression (70 × 50 km2) surrounds Mount Melendiz with a 1-2.7 km depth range (2 km in average). Because the depressions around the central volcanoes of Mount Melendiz and Mount Hasan cover very large areas in the basin scale, the shallow and low-density volcanic units can hardly be claimed

  17. Genesis of the largest Amazonian wetland in northern Brazil inferred by morphology and gravity anomalies

    NASA Astrophysics Data System (ADS)

    Rossetti, Dilce de Fátima; Cassola Molina, Eder; Cremon, Édipo Henrique

    2016-08-01

    The Pantanal Setentrional (PS) is the second largest wetland in Brazil, occurring in a region of northern Amazonia previously regarded as part of the intracratonic Solimões Basin. However, while Paleozoic to Neogene strata are recorded in this basin, the PS constitutes a broad region with an expressive record of only Late Pleistocene and Holocene deposits. The hypothesis investigated in the present work is if these younger deposits were formed within a sedimentary basin having a geological history separated from the Solimões Basin. Due to the location in a remote region of low accessibility, the sedimentary fill of the PS wetland remains largely unknown in subsurface. In the present work, we combine geomorphological and gravity data acquired on a global basis by several satellite gravity missions to approach the geological context of this region. The results revealed a wetland characterized in surface by a low-lying terrain with wedge shape and concave-up geometry that is in sharp contact with highland areas of Precambrian rocks of the Guiana Shield. Such contact is defined by a series of mainly NE- or NW-trending straight lineaments that eventually extend into both the Guiana Shield and the PS wetland. Also of relevance is that a great part of the PS wetland sedimentary cover consists of dominantly sandy deposits preserved as residual paleo-landforms with triangular shapes previously related to megafan depositional systems. These are distributed radially at the northern margin of the PS, with axis toward basement rocks and fringes toward the wetland's center, the latter containing the largest megafan landform. The analysis of gravity anomaly data revealed a main NNE-trending chain ∼500 km in length defined by high gravity values (i.e., up to 60 mGal); these are bounded by negative anomalies as low as -90 mGal. The chain with positive gravity anomaly marks the center of a subsiding area having a geological evolution that differs from the adjacent intracratonic

  18. Gravity Survey of the Carson Sink - Data and Maps

    DOE Data Explorer

    Faulds, James E.

    2013-12-31

    A detailed gravity survey was carried out for the entire Carson Sink in western Nevada (Figure 1) through a subcontract to Zonge Engineering, Inc. The Carson Sink is a large composite basin containing three known, blind high‐temperature geothermal systems (Fallon Airbase, Stillwater, and Soda Lake). This area was chosen for a detailed gravity survey in order to characterize the gravity signature of the known geothermal systems and to identify other potential blind systems based on the structural setting indicated by the gravity data. Data: Data were acquired at approximately 400, 800, and 1600 meter intervals for a total of 1,243 stations. The project location and station location points are presented in Figure 14. The station distribution for this survey was designed to complete regional gravity coverage in the Carson Sink area without duplication of available public and private gravity coverage. Gravity data were acquired using a Scintrex CG‐5 gravimeter and a LaCoste and Romberg (L&R) Model‐G gravimeter. The CG‐5 gravity meter has a reading resolution of 0.001 milligals and a typical repeatability of less than 0.005 milligals. The L&R gravity meter has a reading resolution of 0.01 milligals and a typical repeatability of 0.02 milligals. The basic processing of gravimeter readings to calculate through to the Complete Bouguer Anomaly was made using the Gravity and Terrain Correction software version 7.1 for Oasis Montaj by Geosoft LTD. Results: The gravity survey of the Carson Sink yielded the following products. Project location and station location map (Figure 14). Complete Bouguer Anomaly @ 2.67 gm/cc reduction density. Gravity Complete Bouguer Anomaly at 2.50 g/cc Contour Map (Figure 15). Gravity Horizontal Gradient Magnitude Shaded Color Contour Map. Gravity 1st Vertical Derivative Color Contour Map. Interpreted Depth to Mesozoic Basement (Figure 16), incorporating drill‐hole intercept values. Preliminary Interpretation of Results: The Carson Sink

  19. The gravity signature of mantle uplift from impact modeling craters on the Moon

    NASA Astrophysics Data System (ADS)

    Milbury, Colleen; Johnson, Brandon C.; Melosh, H. Jay; Collins, Gareth S.; Blair, David M.; Soderblom, Jason M.; Zuber, Maria T.

    2014-11-01

    NASA’s dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft have globally mapped the lunar gravity field at unprecedented resolution; this has enabled the study of lunar impact craters of all sizes and ages. Soderblom et al. [2014, LPSC abstract #1777] calculated the residual Bouguer anomalies for ~2700 craters 27-184 km in diameter (D). They found that the residual central Bouguer anomaly of craters smaller than 100 km is essentially zero, that there is a transition for 100-150 km, and that craters larger than 184 km have a positive residual Bouguer anomaly that increases with increasing crater size. We use the iSALE shock physics hydrocode to model crater formation, including the effects of porosity and dilatancy (shear bulking). We use strength parameters of gabbroic anorthosite for a 35-km-thick crust, and dunite for the mantle. Our dunite impactors range in size from 6-30 km, which produce craters 86-450 km in diameter. We calculate the Bouguer gravity anomaly due solely to mantle uplift. We eliminate the effects of pressure and temperature on density by setting the output densities from the simulations to 2550 kg/m^3 if they are below the cutoff value of 3000 kg/m^3, and 3220 kg/m^3 if they are above. We compare our modeling results to gravity data from GRAIL. We find that the crater size at which mantle uplift dominates the crater gravity occurs at a crater diameter that is close to the complex crater to peak-ring basin transition. This is in agreement with the observed trend reported by Soderblom et al. [2014, LPSC abstract #1777].

  20. Anomalies.

    ERIC Educational Resources Information Center

    Online-Offline, 1999

    1999-01-01

    This theme issue on anomalies includes Web sites, CD-ROMs and software, videos, books, and additional resources for elementary and junior high school students. Pertinent activities are suggested, and sidebars discuss UFOs, animal anomalies, and anomalies from nature; and resources covering unexplained phenonmenas like crop circles, Easter Island,…

  1. Sedimentary basin analysis using airborne gravity data: a case study from the Bohai Bay Basin, China

    NASA Astrophysics Data System (ADS)

    Li, Wenyong; Liu, Yanxu; Zhou, Jianxin; Zhou, Xihua; Li, Bing

    2016-11-01

    In this paper, we discuss the application of an airborne gravity survey to sedimentary basin analysis. Using high-precision airborne gravity data constrained by drilling and seismic data from the Bohai Bay Basin in eastern China, we interpreted faults, structural elements, sedimentary thickness, structural styles and local structures (belts) in the central area of the Basin by the wavelet transform method. Subsequently, these data were subtracted from the Bouguer gravity to calculate the residual gravity anomalies. On this basis, the faults were interpreted mainly by linear zones of high gravity gradients and contour distortion, while the sedimentary thicknesses were computed by the Euler deconvolution. The structural styles were identified by the combination of gravity anomalies and the local structures interpreted by the first vertical derivative of the residual gravity. The results showed evidence for seven faults, one sag and ten new local structure belts.

  2. Pre-impact crustal porosity and its effect on the gravity signature of lunar craters

    NASA Astrophysics Data System (ADS)

    Milbury, Colleen; Johnson, Brandon C.; Melosh, H. Jay; Collins, Gareth C.; Blair, David M.; Soderblom, Jason M.; Zuber, Maria T.

    2015-04-01

    NASA's dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft have globally mapped the lunar gravity field at unprecedented resolution. Soderblom et al. [2015] made a comprehensive analysis of the residual and central uplift Bouguer gravity anomalies associated with more than 5200 lunar craters. There were two main observations that are related to the work presented here: 1) craters less than ~150 km in diameter (D) have a residual Bouguer anomaly (BA) that is near zero on average (although a negative trend is observed), but have both positive and negative anomalies that vary by approximately ±25 mGal about the mean, and, 2) there is a transition at which the central uplift BA becomes positive and increases with D. Craters that are located in the maria and South Pole-Aitken (SPA) basin were excluded from the analysis because they tend to have more negative signatures than highlands craters. These gravitational signatures contrast with the invariably negative gravity anomalies associated with terrestrial craters. In this study, we investigate pre-impact porosity by modeling crater formation using the iSALE hydrocode, including a new approach to include dilatancy, to determine their effects on the gravity signature of craters. We calculated the BA for the simulations, but due to mantle uplift alone. We find that the magnitude of the BA increases with increasing porosity, and that variable initial porosity of the lunar crust can explain why craters on the Moon exhibit both positive and negative Bouguer anomalies. This can also explain the observed negative residual BA associated with craters formed in the lunar maria and SPA (and associated melt sheet) because they are typically less porous than the highlands crust. Gravity anomalies due to mantle uplift reproduce the observed transition from zero to a positive central uplift BA, which coincides with the morphological transition from complex craters to peak-ring basins.

  3. Disturbance vector in space from surface gravity anomalies using complementary models

    NASA Astrophysics Data System (ADS)

    Cruz, J. Y.

    1985-08-01

    The modeling of the external disturbance vector of the Earth from surface gravity anomaly data is discussed. The low frequency features of the signal are represented in spherical harmonic series. The recovery of the coefficients of the series from the given gravity anomalies is discussed focusing on the use of analytical continuation and ellipsoidal corrections to account for the Earth's topography and ellipticity. The spectrum and data response of the spatial disturbance vector are studied to aid the design of models and experiments. The local models studied to complement the globally valid spherical harmonic model are the residual topographic model (RTM); the classical integral model; three versions of the Dirac approach to collocation; and two versions of the least squares collocation (l.s.c.) approach. Results indicate that the RTM itself should be used to model the high frequency signal variations whenever detailed (e.g., 1km x 1km) height data is available. The residual signal not already modeled by the RTM and spherical harmonic model can in most cases be accurately modeled by the integral model with meantopography accounted for. For high accuracies in mountainous areas, however, a collocation model should be used to account for the full variations of the topography, not just mean topography. Matrix conditioning problems with the l.s.c. approach support preference to the Dirac systems for rigorous treatment of the topography at detailed (5' x 5') resolutions.

  4. Inversion of marine gravity anomalies over southeastern China seas from multi-satellite altimeter vertical deflections

    NASA Astrophysics Data System (ADS)

    Zhang, Shengjun; Sandwell, David T.; Jin, Taoyong; Li, Dawei

    2017-02-01

    The accuracy and resolution of marine gravity field derived from satellite altimetry mainly depends on the range precision and dense spatial distribution. This paper aims at modeling a regional marine gravity field with improved accuracy and higher resolution (1‧ × 1‧) over Southeastern China Seas using additional data from CryoSat-2 as well as new data from AltiKa. Three approaches are used to enhance the precision level of satellite-derived gravity anomalies. Firstly we evaluate a suite of published retracking algorithms and find the two-step retracker is optimal for open ocean waveforms. Secondly, we evaluate the filtering and resampling procedure used to reduce the full 20 or 40 Hz data to a lower rate having lower noise. We adopt a uniform low-pass filter for all altimeter missions and resample at 5 Hz and then perform a second editing based on sea surface slope estimates from previous models. Thirdly, we selected WHU12 model to update the corrections provided in geophysical data record. We finally calculated the 1‧ × 1‧ marine gravity field model by using EGM2008 model as reference field during the remove/restore procedure. The root mean squares of the discrepancies between the new result and DTU10, DTU13, V23.1, EGM2008 are within the range of 1.8- 3.9 mGal, while the verification with respect to shipboard gravity data shows that the accuracy of the new result reached a comparable level with DTU13 and was slightly superior to V23.1, DTU10 and EGM2008 models. Moreover, the new result has a 2 mGal better accuracy over open seas than coastal areas with shallow water depth.

  5. Interpretation of gravity and magnetic anomalies at Lake Rotomahana: Geological and hydrothermal implications

    NASA Astrophysics Data System (ADS)

    Caratori Tontini, F.; de Ronde, C. E. J.; Scott, B. J.; Soengkono, S.; Stagpoole, V.; Timm, C.; Tivey, M.

    2016-03-01

    We investigate the geological and hydrothermal setting at Lake Rotomahana, using recently collected potential-field data, integrated with pre-existing regional gravity and aeromagnetic compilations. The lake is located on the southwest margin of the Okataina Volcanic Center (Haroharo caldera) and had well-known, pre-1886 Tarawera eruption hydrothermal manifestations (the famous Pink and White Terraces). Its present physiography was set by the caldera collapse during the 1886 eruption, together with the appearance of surface activities at the Waimangu Valley. Gravity models suggest that subsidence associated with the Haroharo caldera is wider than the previously mapped extent of the caldera margins. Magnetic anomalies closely correlate with heat-flux data and surface hydrothermal manifestations and indicate that the west and northwestern shore of Lake Rotomahana are characterized by a large, well-developed hydrothermal field. The field extends beyond the lake area with deep connections to the Waimangu area to the south. On the south, the contact between hydrothermally demagnetized and magnetized rocks strikes along a structural lineament with high heat-flux and bubble plumes which suggest hydrothermal activity occurring west of Patiti Island. The absence of a well-defined demagnetization anomaly at this location suggests a very young age for the underlying geothermal system which was likely generated by the 1886 Tarawera eruption. Locally confined intense magnetic anomalies on the north shore of Lake Rotomahana are interpreted as basalt dikes with high magnetization. Some appear to have been emplaced before the 1886 Tarawera eruption. A dike located in proximity of the southwest lake shore may be related to the structural lineament controlling the development of the Patiti geothermal system, and could have been originated from the 1886 Tarawera eruption.

  6. Seismic and gravity anomaly evidence of large-scale compressional deformation off SW Portugal

    NASA Astrophysics Data System (ADS)

    Cunha, T. A.; Watts, A. B.; Pinheiro, L. M.; Myklebust, R.

    2010-04-01

    Multi-channel seismic and gravity anomaly data have been used to determine the extent of compressional deformation along the SW Portugal rifted continental margin and place constraints on the long-term (> 1 M.a.) strength of the lithosphere. The seismic sections suggest that the region of compressional deformation is broad (˜ 100 km) and has been active since the Miocene. Integration with recently compiled high-resolution bathymetric data shows that the main thrust front is located along the base of the continental slope, between north of the Gorringe Bank and the Setúbal Canyon. Gravity data show that the thrust front is associated with a narrow isostatic anomaly 'high' of up to 70 mGal that is flanked on its NW edge by a broad 'low' of up to 20 mGal. This high-low 'couple' can be explained by compressional loading of extended continental lithosphere that increased its flexural strength (or equivalent elastic thickness, Te) since rifting. Based on combined 2-D backstripping and gravity modelling techniques we estimate a Te of ˜ 10 km during the main stretching episode, in the Late Jurassic (maybe earliest Cretaceous?), and of 35-50 km during the Miocene to Recent compression. The existence of a broad region of deformation off SW Portugal together with a strong lithosphere have implications for the rupture models of large earthquakes in the region, such as the 1755 Great Lisbon earthquake, particularly when accounting for a complex, multiple rupture in faults which cut through lithosphere of distinct nature and origin, as appears to be required by modellers to explain the historical observational data.

  7. 3D free-air gravity anomaly modeling for the Southeast Indian Ridge

    NASA Astrophysics Data System (ADS)

    Girolami, Chiara; Heyde, Ingo; Rinaldo Barchi, Massimiliano; Pauselli, Cristina

    2016-04-01

    In this study we analyzed the free-air gravity anomalies measured on the northwestern part of the Southeast Indian Ridge (hereafter SEIR) during the BGR cruise INDEX2012 with RV FUGRO GAUSS. The survey area covered the ridge from the Rodriguez Triple Junction along about 500 km towards the SSE direction. Gravity and magnetic data were measured along 65 profiles with a mean length of 60 km running approximately perpendicular to the ridge axis. The final gravity data were evaluated every 20 seconds along each profile. This results in a sampling interval of about 100 m. The mean spacing of the profiles is about 7 km. Together with the geophysical data also the bathymetry was measured along all profiles with a Kongsberg Simrad EM122 multibeam echosounder system. Previous studies reveal that the part of the ridge covered by the high resolution profiles is characterized by young geologic events (the oldest one dates back to 1 Ma) and that the SEIR is an intermediate spreading ridge. We extended the length of each profile to the area outside the ridge, integrating INDEX2012 high resolution gravity and bathymetric data with low resolution data derived from satellite radar altimeter measurements. The 3D forward gravity modeling made it possible to reconstruct a rough crustal density model for an extended area (about 250000 km2) of the SEIR. We analyzed the gravity signal along those 2D sections which cross particular geological features (uplifted areas, accommodation zones, hydrothermal fields and areas with hints for extensional processes e.g. OCCs) in order to establish a correlation between the gravity anomaly signal and the surface geology. We started with a simple "layer-cake" geologic model consisting of four density bodies which represent the sea, upper oceanic crust, lower oceanic crust and the upper mantle. Considering that in the study area the oceanic crust is young, we did not include the sediment layer. We assumed the density values of these bodies considering

  8. Bayesian signal processing techniques for the detection of highly localised gravity anomalies using quantum interferometry technology

    NASA Astrophysics Data System (ADS)

    Brown, Gareth; Ridley, Kevin; Rodgers, Anthony; de Villiers, Geoffrey

    2016-10-01

    Recent advances in the field of quantum technology offer the exciting possibility of gravimeters and gravity gradiometers capable of performing rapid surveys with unprecedented precision and accuracy. Measurements with sub nano-g (a billionth of the acceleration due to gravity) precision should enable the resolution of underground structures on metre length scales. However, deducing the exact dimensions of the structure producing the measured gravity anomaly is known to be an ill-posed inversion problem. Furthermore, the measurement process will be affected by multiple sources of uncertainty that increase the range of plausible solutions that fit the measured data. Bayesian inference is the natural framework for accommodating these uncertainties and providing a fully probabilistic assessment of possible structures producing inhomogeneities in the gravitational field. Previous work introduced the probability of excavation map as a means to convert the high-dimensional space belonging to the posterior distribution to an easily interpretable map. We now report on the development of the inference model to account for spatial correlations in the gravitational field induced by variations in soil density.

  9. Venus - Global gravity and topography

    NASA Astrophysics Data System (ADS)

    McNamee, J. B.; Borderies, N. J.; Sjogren, W. L.

    1993-05-01

    A new gravity field determination that has been produced combines both the Pioneer Venus Orbiter (PVO) and the Magellan Doppler radio data. Comparisons between this estimate, a spherical harmonic model of degree and order 21, and previous models show that significant improvements have been made. Results are displayed as gravity contours overlaying a topographic map. We also calculate a new spherical harmonic model of topography based on Magellan altimetry, with PVO altimetry included where gaps exist in the Magellan data. This model is also of degree and order 21, so in conjunction with the gravity model, Bouguer and isostatic anomaly maps can be produced. These results are very consistent with previous results, but reveal more spatial resolution in the higher latitudes.

  10. Gravity anomalies, flexure and mantle rheology seaward of circum-Pacific trenches

    NASA Astrophysics Data System (ADS)

    Hunter, J.; Watts, A. B.

    2016-10-01

    We have used ensemble averages of satellite-derived free-air gravity anomaly data, together with inverse modelling techniques, to determine the effective elastic thickness, Te, of circum-Pacific subducting oceanic lithosphere and its relationship to plate age. Synthetic modelling tests show that Te can be recovered best using gravity anomaly, rather than bathymetry, data and profiles that are at least 750 km long. Inverse modelling based on a uniform Te elastic plate suggests that Te increases with age of the subducting oceanic lithosphere and is given approximately by the depth to the 390 ± 10 °C oceanic isotherm based on a cooling plate model. Misfits between the observed and calculated gravity anomalies are significantly improved if a mechanically weak zone is included between the trench axis and the outer rise. This weak zone is coincident with observations of bend-faulting and seismicity. Inverse modelling shows that Te landward of the outer rise is generally 40-65 per cent less than the Te seaward of the outer rise. Both landward and seaward Te increases with age of the lithosphere and are given by the depth to the 342-349 °C and 671-714 °C oceanic isotherm, respectively. A dependence of Te on age is consistent with models for the cooling of oceanic lithosphere as it moves away from a mid-ocean ridge and the temperature-dependent ductile creep of oceanic lithospheric minerals such as olivine. By comparing the observed Te to the predicted Te based on laboratory-derived yield strength envelopes and an assumption of elastic-perfectly plastic deformation, we have attempted to constrain the rheology of oceanic lithosphere. Regardless of the assumed friction coefficient, the dry-olivine low-temperature plasticity flow laws of Goetze, Evans & Goetze, Raterron et al. and Mei et al. all provide quite a good fit to the observed Te at circum-Pacific subduction zones. This result contrasts with the Hawaiian Islands, where these flow laws are generally too strong to

  11. On the possible deep origin of long-wavelength gravity anomalies on the Moon and Mercury

    NASA Astrophysics Data System (ADS)

    Steinberger, B.; Werner, SC

    2012-04-01

    Like on the Earth and Mars, but notably different from Venus, the non-equilibrium equipotential shape of the Moon is dominated by very long wavelengths, in particular spherical harmonic degree two. Preliminary results from the Messenger mission indicate that the same is also the case for Mercury. We extend here a method that we previously applied to the Earth, Venus and Mars to study which part of the gravity anomalies have likely a sublithospheric mantle origin. The method is based on the assumption that density anomalies in both the convecting mantle and the lithosphere of planets and the Moon have the same spectral characteristic as inferred on the Earth from seismic tomography. We then apply a presumed pressure and temperature dependence of viscosity, that is based on mineral physics and consistent with other constraints on viscosity structure for the Earth's mantle to construct radial viscosity profiles. We compute geoid kernels for the planetary bodies, assuming a viscous mantle and an elastic lithosphere. Combining geoid kernels and density spectra, we can predict gravity spectra arising from density anomalies both in the convecting mantle and the lithosphere. By comparison, we infer which part of the observed spectra is likely derived from the convecting mantle. Our previous results had indicated that this is probably the case up to about spherical harmonic degree l=30 for Earth, 40 for Venus and 5 for Mars. Here we conclude that a sublithospheric mantle origin is likely up to l=5 for the Moon, and perhaps l=4 for Mercury. For these degrees, radially averaged mantle density anomalies can be inferred. Similar to the Earth and Mars, the Moon and possibly Mercury can be interpreted to have a dominant degree-two convection pattern. Given large uncertainties, results for Mercury remain tentative. The degree-two non-hydrostatic shape interpreted here as a consequence of mantle convection also includes excess flattening, such that it is not necessary to invoke a

  12. Implications of new gravity data for Baikal Rift zone structure

    NASA Technical Reports Server (NTRS)

    Ruppel, C.; Kogan, M. G.; Mcnutt, M. K.

    1993-01-01

    Newly available, 2D Bouguer gravity anomaly data from the Baikal Rift zone, Siberia, indicate that this discrete, intracontinental rift system is regionally compensated by an elastic plate about 50 km thick. However, spectral and spatial domain analyses and isostatic anomaly calculations show that simple elastic plate theory does not offer an adequate explanation for compensation in the rift zone, probably because of significant lateral variations in plate strength and the presence of subsurface loads. Our results and other geophysical observations support the interpretation that the Baikal Rift zone is colder than either the East African or Rio Grande rift.

  13. Spectral analysis of GEOS-3 altimeter data and frequency domain collocation. [to estimate gravity anomalies

    NASA Technical Reports Server (NTRS)

    Eren, K.

    1980-01-01

    The mathematical background in spectral analysis as applied to geodetic applications is summarized. The resolution (cut-off frequency) of the GEOS 3 altimeter data is examined by determining the shortest wavelength (corresponding to the cut-off frequency) recoverable. The data from some 18 profiles are used. The total power (variance) in the sea surface topography with respect to the reference ellipsoid as well as with respect to the GEM-9 surface is computed. A fast inversion algorithm for matrices of simple and block Toeplitz matrices and its application to least squares collocation is explained. This algorithm yields a considerable gain in computer time and storage in comparison with conventional least squares collocation. Frequency domain least squares collocation techniques are also introduced and applied to estimating gravity anomalies from GEOS 3 altimeter data. These techniques substantially reduce the computer time and requirements in storage associated with the conventional least squares collocation. Numerical examples given demonstrate the efficiency and speed of these techniques.

  14. Preimpact porosity controls the gravity signature of lunar craters

    NASA Astrophysics Data System (ADS)

    Milbury, C.; Johnson, B. C.; Melosh, H. J.; Collins, G. S.; Blair, D. M.; Soderblom, J. M.; Nimmo, F.; Bierson, C. J.; Phillips, R. J.; Zuber, M. T.

    2015-11-01

    We model the formation of lunar complex craters and investigate the effect of preimpact porosity on their gravity signatures. We find that while preimpact target porosities less than ~7% produce negative residual Bouguer anomalies (BAs), porosities greater than ~7% produce positive anomalies whose magnitude is greater for impacted surfaces with higher initial porosity. Negative anomalies result from pore space creation due to fracturing and dilatant bulking, and positive anomalies result from destruction of pore space due to shock wave compression. The central BA of craters larger than ~215 km in diameter, however, are invariably positive because of an underlying central mantle uplift. We conclude that the striking differences between the gravity signatures of craters on the Earth and Moon are the result of the higher average porosity and variable porosity of the lunar crust.

  15. Flexure and gravity anomalies of the oceanic lithosphere beneath the Louisville seamount

    NASA Astrophysics Data System (ADS)

    Hwang, Gyuha; Kim, Seung-Sep

    2016-08-01

    We have calculated the elastic thickness (Te), flexural deflection, and gravity anomaly of the oceanic crust beneath the Louisville seamount (LSC-03), near the Kermadec trench. A regional-residual separation of the bathymetry was performed to remove the effect of other geologic features (e.g., the trench). We used the uniform density and dense core models to approximate the total mass of the seamount, which was defined as the surface load required for flexural deformation. From the flexure modeling results, we found that more flexural depression was predicted by the uniform density model than by the dense core model. However, the uniform density model predicted a significantly smaller gravity anomaly than observed, whereas the dense core model minimized the prediction misfits reasonably. The best flexure model was found with a Te of 16 km for the uniform density model and 6 km for the dense core model. The flexure computed with the dense core model was consistent with the seismically detected Moho. The flexure modeling for LSC-03, thus, indicates that the dense core model better approximates the inner structure of the LSC-03. Based on the crustal age and geochronology of the given seamount, the age of the oceanic crust at the time of seamount formation (Δt) is 20 Ma. If this is the case, however, the Te estimates from both flexure models require some degree of lithospheric reheating by Louisville hotspot activity. Alternatively, considering the tectonic plate motion of the Osbourn Trough, Δt becomes approximately 4 Ma. This younger lithosphere model is more consistent with the observed flexural deformation and the Te estimate from the dense core model. Therefore, the time that the seamount-induced lithospheric deformation occurred may be far earlier than the age-dated volcanism.

  16. Implications of the Utopia Gravity Anomaly for the Resurfacing of the Northern Plains of Mars

    NASA Technical Reports Server (NTRS)

    Banerdt, W. B.

    2004-01-01

    Whereas the surface units of the northern plain of Mars generally exhibit ages ranging from late Hesperian to Amazonian, interpretation of precise topographic measurements indicate that the age of the underlying "basement" is early Noachian, or almost as old as the southern highlands. This suggests that widespread but relatively superficial resurfacing has occurred throughout the northern plains since the end of early heavy bombardment. In this abstract I examine some of the possible implications of the subsurface structure inferred for the Utopia basin from gravity data on the nature of this resurfacing. The large, shallow, circular depression in Utopia Planitia has been identified as a huge impact basin, based on both geological evidence and detailed analysis of MOLA topography. Its diameter (approx. 3000 km) is equivalent to that of the Hellas basin, as is its inferred age (early Noachian). However, whereas Hellas is extremely deep with rough terrain and large slopes, the Utopia basin is a smooth, shallow, almost imperceptible bowl. Conversely, Utopia displays one of the largest (non-Tharsis-related) positive geoid anomalies on Mars, in contrast to a much more subdued negative anomaly over Hellas.

  17. Spatial variability of tidal gravity anomalies and its correlation with the effective elastic thickness of the lithosphere

    NASA Astrophysics Data System (ADS)

    Shukowsky, Wladimir; Mantovani, Marta S. M.

    1999-07-01

    Associations of the Earth tidal gravity response to physical properties of the lithosphere have been attempted at least for the last four decades. Although experimental data suggest this association, rigorous models have not yet been proposed. In this work, statistical tests are performed on the available World Gravity Earth Tides data set. Autocorrelation analysis shows that the M2 tidal gravity anomalies (TGAs) are significantly correlated up to a distance of about 500 km, with an approximately exponential correlation decay. The analysis of the latitudinal dependence of the anomalies shows that the anomaly variance, estimated inside of different latitude bands, follows a cos 4ϕ curve within the ±45° latitude interval and defines the noise level for the M2 gravity anomaly data set. The regression analysis between M2 TGA and the lithosphere effective elastic thickness (EET) estimates shows that these quantities are significantly correlated, with a correlation coefficient of -0.82. The wide range of TGA and EET values, combined with a good global distribution of the data used in the regression analysis, makes the regression equation suitable to be used as a predictor for EET values in areas where M2 TGA data exist and meet the required quality criteria.

  18. The mineralogy of global magnetic anomalies. [rock magnetic signatures and MAGSAT geological, and gravity correlations in West Africa

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E. (Principal Investigator)

    1982-01-01

    Problems with the Curie balance, which severely hindered the acquisition of data, were rectified. Chemical analytical activities are proceeding satisfactorily. The magnetization characteristics of metamorphic suites were analyzed and susceptibility data for a wide range of metamorphic and igneous rocks. These rock magnetic signatures are discussed as well as the relationships between geology, gravity and MAGSAT anomalies of West Africa.

  19. Segmentation of the Himalayas as revealed by arc-parallel gravity anomalies.

    PubMed

    Hetényi, György; Cattin, Rodolphe; Berthet, Théo; Le Moigne, Nicolas; Chophel, Jamyang; Lechmann, Sarah; Hammer, Paul; Drukpa, Dowchu; Sapkota, Soma Nath; Gautier, Stéphanie; Thinley, Kinzang

    2016-09-21

    Lateral variations along the Himalayan arc are suggested by an increasing number of studies and carry important information about the orogen's segmentation. Here we compile the hitherto most complete land gravity dataset in the region which enables the currently highest resolution plausible analysis. To study lateral variations in collisional structure we compute arc-parallel gravity anomalies (APaGA) by subtracting the average arc-perpendicular profile from our dataset; we compute likewise for topography (APaTA). We find no direct correlation between APaGA, APaTA and background seismicity, as suggested in oceanic subduction context. In the Himalayas APaTA mainly reflect relief and erosional effects, whereas APaGA reflect the deep structure of the orogen with clear lateral boundaries. Four segments are outlined and have disparate flexural geometry: NE India, Bhutan, Nepal &India until Dehradun, and NW India. The segment boundaries in the India plate are related to inherited structures, and the boundaries of the Shillong block are highlighted by seismic activity. We find that large earthquakes of the past millennium do not propagate across the segment boundaries defined by APaGA, therefore these seem to set limits for potential rupture of megathrust earthquakes.

  20. Segmentation of the Himalayas as revealed by arc-parallel gravity anomalies

    PubMed Central

    Hetényi, György; Cattin, Rodolphe; Berthet, Théo; Le Moigne, Nicolas; Chophel, Jamyang; Lechmann, Sarah; Hammer, Paul; Drukpa, Dowchu; Sapkota, Soma Nath; Gautier, Stéphanie; Thinley, Kinzang

    2016-01-01

    Lateral variations along the Himalayan arc are suggested by an increasing number of studies and carry important information about the orogen’s segmentation. Here we compile the hitherto most complete land gravity dataset in the region which enables the currently highest resolution plausible analysis. To study lateral variations in collisional structure we compute arc-parallel gravity anomalies (APaGA) by subtracting the average arc-perpendicular profile from our dataset; we compute likewise for topography (APaTA). We find no direct correlation between APaGA, APaTA and background seismicity, as suggested in oceanic subduction context. In the Himalayas APaTA mainly reflect relief and erosional effects, whereas APaGA reflect the deep structure of the orogen with clear lateral boundaries. Four segments are outlined and have disparate flexural geometry: NE India, Bhutan, Nepal & India until Dehradun, and NW India. The segment boundaries in the India plate are related to inherited structures, and the boundaries of the Shillong block are highlighted by seismic activity. We find that large earthquakes of the past millennium do not propagate across the segment boundaries defined by APaGA, therefore these seem to set limits for potential rupture of megathrust earthquakes. PMID:27649782

  1. Segmentation of the Himalayas as revealed by arc-parallel gravity anomalies

    NASA Astrophysics Data System (ADS)

    Hetényi, György; Cattin, Rodolphe; Berthet, Théo; Le Moigne, Nicolas; Chophel, Jamyang; Lechmann, Sarah; Hammer, Paul; Drukpa, Dowchu; Sapkota, Soma Nath; Gautier, Stéphanie; Thinley, Kinzang

    2016-09-01

    Lateral variations along the Himalayan arc are suggested by an increasing number of studies and carry important information about the orogen’s segmentation. Here we compile the hitherto most complete land gravity dataset in the region which enables the currently highest resolution plausible analysis. To study lateral variations in collisional structure we compute arc-parallel gravity anomalies (APaGA) by subtracting the average arc-perpendicular profile from our dataset; we compute likewise for topography (APaTA). We find no direct correlation between APaGA, APaTA and background seismicity, as suggested in oceanic subduction context. In the Himalayas APaTA mainly reflect relief and erosional effects, whereas APaGA reflect the deep structure of the orogen with clear lateral boundaries. Four segments are outlined and have disparate flexural geometry: NE India, Bhutan, Nepal & India until Dehradun, and NW India. The segment boundaries in the India plate are related to inherited structures, and the boundaries of the Shillong block are highlighted by seismic activity. We find that large earthquakes of the past millennium do not propagate across the segment boundaries defined by APaGA, therefore these seem to set limits for potential rupture of megathrust earthquakes.

  2. Modelling the gravity and magnetic field anomalies of the Chicxulub crater

    NASA Technical Reports Server (NTRS)

    Aleman, C. Ortiz; Pilkington, M.; Hildebrand, A. R.; Roest, W. R.; Grieve, R. A. F.; Keating, P.

    1993-01-01

    The approximately 180-km-diameter Chicxulub crater lies buried by approximately 1 km of sediment on the northwestern corner of the Yucatan Peninsula, Mexico. Geophysical, stratigraphic and petrologic evidence support an impact origin for the structure and biostratigraphy suggests that a K/T age is possible for the impact. The crater's location is in agreement with constraints derived from proximal K/T impact-wave and ejecta deposits and its melt-rock is similar in composition to the K/T tektites. Radiometric dating of the melt rock reveals an age identical to that of the K/T tektites. The impact which produced the Chicxulub crater probably produced the K/T extinctions and understanding the now-buried crater will provide constraints on the impact's lethal effects. The outstanding preservation of the crater, the availability of detailed gravity and magnetic data sets, and the two-component target of carbonate/evaporites overlying silicate basement allow application of geophysical modeling techniques to explore the crater under most favorable circumstances. We have found that the main features of the gravity and magnetic field anomalies may be produced by the crater lithologies.

  3. Detailed Gravity and Magnetic Survey of the Taylorsville Triassic Basin

    SciTech Connect

    Ali A. Nowroozi; John Leftwich

    1997-12-31

    Our research to date has involved the Interpretation of the Bouguer Gravity Anomaly Associated with the Richmond and Taylorsville Triassic Basins and its Vicinity. Continental rift basins around the world contain about 5% of the earth's sedimentary layers and produce about 20% of the total hydrocarbon production of the world (Ziegler (1983). Nearly 30 large basins of this type are reported by Manspeizer and Cousminer (1988) in eastern North America and northwestern Africa. There are eleven exposed basins of this type in the state of Virginia, from which nine are totally and two partially within the state's border. The number of unexposed basin's is not known. Exploration and drilling have been hampered largely because surface data are insufficient for even evaluation of those basins which are partly or completely exposed in the Piedmont Province. Generation of data through random exploratory drilling and seismic exploration is much too expensive and, therefore, these methods have not been widely used. In order to remedy this situation, we have used a geophysical method and completed a detailed and dense ground gravity surveys of the Richmond (Nowroozi and Wong, 1989, Daniels and Nowroozi, 1987). In this work we report our progress on collecting existing gravity data in a rectangular area covering the Richmond and Taylorsville Basins and its vicinity. The area covers one degree latitude and one degree longitude, starting at 37 North, 77 West and ending at 38 North, 78 West. Dr. David Daniels of the United State Geological Survey supplied us with more than 4900 Bouguer gravity anomalies in this area. The purpose of this progress report is to present the data in form of several maps and discuss its relation to the geology of the Triassic Basins and its vicinity. Johnson and others (1985) also presented a map of the Bouguer gravity anomaly of this area. However, their map covers a smaller area, and it is based on smaller number of observations.

  4. A FORTRAN program to implement the method of finite elements to compute regional and residual anomalies from gravity data

    NASA Astrophysics Data System (ADS)

    Agarwal, B. N. P.; Srivastava, Shalivahan

    2010-07-01

    In view of the several publications on the application of the Finite Element Method (FEM) to compute regional gravity anomaly involving only 8 nodes on the periphery of a rectangular map, we present an interactive FORTRAN program, FEAODD.FOR, for wider applicability of the technique. A brief description of the theory of FEM is presented for the sake of completeness. The efficacy of the program has been demonstrated by analyzing the gravity anomaly over Salt dome, South Houston, USA using two differently oriented rectangular blocks and over chromite deposits, Camaguey, Cuba. The analyses over two sets of data reveal that the outline of the ore body/structure matches well with the maxima of the residuals. Further, the data analyses over South Houston, USA, have revealed that though the broad regional trend remains the same for both the blocks, the magnitudes of the residual anomalies differ approximately by 25% of the magnitude as obtained from previous studies.

  5. Isostatic gravity map of the Monterey 30 x 60 minute quadrangle and adjacent areas, California

    USGS Publications Warehouse

    Langenheim, V.E.; Stiles, S.R.; Jachens, R.C.

    2002-01-01

    The digital dataset consists of one file (monterey_100k.iso) containing 2,385 gravity stations. The file, monterey_100k.iso, contains the principal facts of the gravity stations, with one point coded per line. The format of the data is described below. Each gravity station has a station name, location (latitude and longitude, NAD27 projection), elevation, and an observed gravity reading. The data are on the IGSN71 datum and the reference ellipsoid is the Geodetic Reference System 1967 (GRS67). The free-air gravity anomalies were calculated using standard formulas (Telford and others, 1976). The Bouguer, curvature, and terrain corrections were applied to the free-air anomaly at each station to determine the complete Bouguer gravity anomalies at a reduction density of 2.67 g/cc. An isostatic correction was then applied to remove the long-wavelength effect of deep crustal and/or upper mantle masses that isostatically support regional topography.

  6. Estimation of regional mass anomalies from Gravity Recovery and Climate Experiment (GRACE) over Himalayan region

    NASA Astrophysics Data System (ADS)

    Agrawal, R.; Singh, S. K.; Rajawat, A. S.; Ajai

    2014-11-01

    Time-variable gravity changes are caused by a combination of postglacial rebound, redistribution of water and snow/ice on land and as well as in the ocean. The Gravity Recovery and Climate Experiment (GRACE) satellite mission, launched in 2002, provides monthly average of the spherical harmonic co-efficient. These spherical harmonic co-efficient describe earth's gravity field with a resolution of few hundred kilometers. Time-variability of gravity field represents the change in mass over regional level with accuracies in cm in terms of Water Equivalent Height (WEH). The WEH reflects the changes in the integrated vertically store water including snow cover, surface water, ground water and soil moisture at regional scale. GRACE data are also sensitive towards interior strain variation, surface uplift and surface subsidence cover over a large area. GRACE data was extracted over the three major Indian River basins, Indus, Ganga and Brahmaputra, in the Himalayas which are perennial source of fresh water throughout the year in Northern Indian Plain. Time series analysis of the GRACE data was carried out from 2003-2012 over the study area. Trends and amplitudes of the regional mass anomalies in the region were estimated using level 3 GRACE data product with a spatial resolution at 10 by 10 grid provided by Center for Space Research (CSR), University of Texas at Austin. Indus basin has shown a subtle decreasing trend from 2003-2012 however it was observed to be statistically insignificant at 95 % confidence level. Ganga and Brahmaputra basins have shown a clear decreasing trend in WEH which was also observed to be statistically significant. The trend analysis over Ganga and Brahamputra basins have shown an average annual change of -1.28 cm and -1.06 cm in terms of WEH whereas Indus basin has shown a slight annual change of -0.07 cm. This analysis will be helpful to understand the loss of mass in terms of WEH over Indian Himalayas and will be crucial for hydrological and

  7. Marine Gravity Measurements at the Subduction Zone offshore Central Chile

    NASA Astrophysics Data System (ADS)

    Heyde, I.; Kopp, H.; Reichert, C.

    2003-12-01

    Gravity measurements were carried out during RV SONNE cruise SO-161 (SPOC) in late 2001 between 28° S and 44° S offshore Central Chile along a total length of about 17500 km. The mean accuracy of the data measured with the seagravimeter system KSS31M of BGR is better than 1 mGal. Further foreign marine gravity data were not included due to their considerable lower accuracy. Additional marine gravity data derived from satellite altimetry are needed to augment our data from the survey area. The SPOC data set was compared with 3 different satellite gravity data compilations. The data set with the best statistical results for the gravity differences was used for further gravity map compilations. The map of the freeair gravity is dominated by the anomalies of the main topographic features in the survey area. In the W the oceanic crust of the subducting Nazca Plate is characterized by weak positve gravity anomalies. Landward the anomalies decrease rapidly to less than minus 150 mGal in the Chilean trench. Further towards the coast extends a broad zone of alternating positve and negative freeair gravity anomalies. These could be interpreted either in terms of morphology of the continental slope or heterogeneous density distribution in the upper crust. Additionally Bouguer gravity anomalies were calculated. The anomalies on the Nazca Plate are strongly positive with a clear south - north trending increase of values, which reflect the increasing age of the oceanic crust. The effect of isostatic compensation was calculated assuming Vening-Meinesz models with different parameters. The gravity effect of the isostatic compensation root was eliminated from the Bouguer gravity anomalies and serves as a residual field. The interpretation of isostatic residual fields in this complicated tectonic environment leads to the detection of a series of offshore basins. In the N and the centre of the survey area the distribution of the profiles is rather uniform. For these areas 3D

  8. A gravity model for the Coso geothermal area, California

    SciTech Connect

    Feighner, M.A.; Goldstein, N.E.

    1990-08-01

    Two- and three-dimensional gravity modeling was done using gridded Bouguer gravity data covering a 45 {times} 45 km region over the Coso geothermal area in an effort to identify features related to the heat source and to seek possible evidence for an underlying magma chamber. Isostatic and terrain corrected Bouguer gravity data for about 1300 gravity stations were obtained from the US Geological Survey. After the data were checked, the gravity values were gridded at 1 km centers for the area of interest centered on the Coso volcanic field. Most of the gravity variations can be explained by two lithologic units: (1) low density wedges of Quarternary alluvium with interbedded thin basalts (2.4 g/cm{sup 3}) filling the Rose Valley and Coso Basin/Indian Wells Valley, and (2) low density cover of Tertiary volcanic rocks and intercalated Coso Formation (2.49 g/cm{sup 3}). A 3-D iterative approach was used to find the thicknesses of both units. The gravity anomaly remaining after effects from Units 1 and 2 are removed is a broad north-south-trending low whose major peak lies 5 km north of Sugarloaf Mountain, the largest of the less than 0.3 m.y. old rhyolite domes in the Coso Range. Most of this residual anomaly can be accounted for by a deep, low-density (2.47 g/cm{sup 3}) prismatic body extending from 8 to about 30 km below the surface. While some of this anomaly might be associated with fractured Sierran granitic rocks, its close correlation to a low-velocity zone with comparable geometry suggests that the residual anomaly is probably caused a large zone of partial melt underlying the rhyolite domes of the Coso Range. 12 refs., 9 figs.

  9. Middle proterozoic tectonic activity in west Texas and eastern New Mexico and analysis of gravity and magnetic anomalies

    SciTech Connect

    Adams, D.C.; Keller, G.R. )

    1994-03-01

    The Precambrian history of west Texas and eastern New Mexico is complex, consisting of four events: Early Proterozoic orogenic activity (16309-1800 Ma), formation of the western granite-rhyolite province (WGRP) (1340-1410 Ma), Grenville age tectonics (1116-1232 Ma), and middle Proterozoic extension possibly related to mid-continent rifting (1086-1109 Ma). Pre-Grenville tectonics, Grenville tectonics, and mid-continent rifting are represented in this area by the Abilene gravity minimum (AGM) and bimodal igneous rocks, which are probably younger. We have used gravity modeling and the comparison of gravity and magnetic anomalies with rock types reported from wells penetrating Precambrian basement to study the AGM and middle Proterozoic extension in this area. The AGM is an east-northeast-trending, 600 km long, gravity low, which extends from the Texas-Oklahoma border through the central basin platform (CBP) to the Delaware basin. This feature appears to predate formation of the mafic body in the CBP (1163 Ma) and is most likely related to Pre-Grenville tectonics, possibly representing a continental margin arc batholith. Evidence of middle Proterozoic extension is found in the form of igneous bodies in the CBP, the Van Horn uplift, the Franklin Mountains, and the Sacramento Mountains. Analysis of gravity and magnetic anomalies shows that paired gravity and magnetic highs are related to mafic intrusions in the upper crust. Mapping of middle Proterozoic igneous rocks and the paired anomalies outlines a 530 km diameter area of distributed east-west-oriented extension. The Debaca-Swisher terrain of shallow marine and clastic sedimentary rocks is age correlative with middle Proterozoic extension. These rocks may represent the lithology of possible Proterozoic exploration targets. Proterozoic structures were reactivated during the Paleozoic, affecting both the structure and deposition in the Permian basin.

  10. Multifractal singular value decomposition (MSVD) for extraction of marine gravity anomaly

    NASA Astrophysics Data System (ADS)

    LYU, Wenchao; Zhu, Benduo; Qiu, Yan

    2015-04-01

    The concept of singularity is used for characterizing different types of nonlinear natural processes, including volcanic eruptions, faults, cloud formation, landslides, rainfall, hurricanes, flooding, earthquakes, wildfires, oil fields and mineralization. The singularity often results in anomalous amounts of energy release or material accumulation within a narrow spatial-temporal interval.The marine gravitation field has multi-fractal features, which show different scale invariant properties in region and local field. The SVD can be used in geophysical data processing for signal and noise separation, radar processing for enhancing weak signals in vertical seismic profiles (VSP). It has also been used in multi component seismic polarization filters and evaluating the amount of wavy reflections in ground-penetrating radar (GPR) images of base surge deposits. With the SVD, a matrix X can be decomposed to a series of eigenvalues. The eigenvalues conformed fractal or multi-fractal distribution described with the power-law function. The multi-fractal SVD can be used for feature extraction and anomaly identification for marine gravity investigation.This paper aims to analyze the marine gravitation data using the SVD and multifractal methods. This paper will also aim to more clearly define the spatial relationship between marine mineralization and the deep geological structures in the field by extracting the marine gravitation information at a particular frequency to provide valuable in depth evidence for predicting new deposits and deep tectonic.

  11. Determining the COB location along the Iberian margin and Galicia Bank from gravity anomaly inversion, residual depth anomaly and subsidence analysis

    NASA Astrophysics Data System (ADS)

    Cowie, Leanne; Kusznir, Nick; Manatschal, Gianreto

    2015-11-01

    Knowledge and understanding of the ocean-continent transition (OCT) structure, continent-ocean boundary (COB) location and crustal type are of critical importance in evaluating rifted continental margin formation and evolution. OCT structure, COB location and magmatic type also have important implications for the understanding of the geodynamics of continental breakup and in the evaluation of petroleum systems in deep-water frontier oil and gas exploration at rifted continental margins. Mapping the distribution of thinned continental crust and lithosphere, its distal extent and the start of unequivocal oceanic crust and hence determining the OCT structure and COB location at rifted continental margins is therefore a generic global problem. In order to assist in the determination of the OCT structure and COB location, we present methodologies using gravity anomaly inversion, residual depth anomaly (RDA) analysis and subsidence analysis, which we apply to the west Iberian rifted continental margin. The west Iberian margin has one of the most complete data sets available for deep magma-poor rifted margins, so there is abundant data to which the results can be calibrated. Gravity anomaly inversion has been used to determine Moho depth, crustal basement thickness and continental lithosphere thinning; subsidence analysis has been used to determine the distribution of continental lithosphere thinning; and RDAs have been used to investigate the OCT bathymetric anomalies with respect to expected oceanic bathymetries at rifted continental margins. These quantitative analytical techniques have been applied to the west Iberian rifted continental margin along profiles IAM9, Lusigal 12 (with the TGS-extension) and ISE-01. Our predictions of OCT structure, COB location and magmatic type (i.e. the volume of magmatic addition, whether the margin is `normal' magmatic, magma-starved or magma-rich) have been tested and validated using ODP wells (Legs 103, 149 and 173), which provide

  12. Multiple episodes of rifting in Central and East Africa: A re-evaluation of gravity data

    NASA Astrophysics Data System (ADS)

    Ebinger, C. J.; Ibrahim, A.

    1994-12-01

    A compilation of new and existing gravity data, as well as geophysical and geological data, is used to assess the cumulative effects of multiple rifting episodes on crustal and upper mantle density structures beneath the Uganda-Kenya-Ethiopia-Sudan border region. This compilation includes new gravity and geological data collected in 1990 in south-western Ethiopia. Variations in the trends and amplitudes of Bouguer gravity anomalies reveal three overlapping rift systems: Mesozoic, Paleogene and Miocene-Recent. Each of these rift systems is a number of 40 100 km long sedimentary basins, and each system is approximately 1000 km long. The Bouguer anomaly patterns indicate that the Ethiopian and East African plateaux and corresponding gravity anomalies are discrete tectonic features. Models of structural and gravity profiles of two basins (Omo and Chew Bahir basins) suggest that pre-Oligocene (Cretaceous?) strata underlie 3 km or more of Neogene-Recent strata within the northern Kenya rift, and that more than 2 km of Neogene-Recent strata underlie parts of the southern Main Ethiopian rift. The superposition of perhaps three rifting episodes in the Lake Turkana (Omo) region has led to 90% crustal thinning (β ≈ 2).

  13. High-resolution residual geoid and gravity anomaly data of the northern Indian Ocean - An input to geological understanding

    NASA Astrophysics Data System (ADS)

    Sreejith, K. M.; Rajesh, S.; Majumdar, T. J.; Srinivasa Rao, G.; Radhakrishna, M.; Krishna, K. S.; Rajawat, A. S.

    2013-01-01

    Geoid data are more sensitive to density distributions deep within the Earth, thus the data are useful for studying the internal processes of the Earth leading to formation of geological structures. In this paper, we present much improved version of high resolution (1' × 1') geoid anomaly map of the northern Indian Ocean generated from the altimeter data obtained from Geodetic Missions of GEOSAT and ERS-1 along with ERS-2, TOPEX/POSIDEON and JASON satellites. The geoid map of the Indian Ocean is dominated by a significant low of -106 m south of Sri Lanka, named as the Indian Ocean Geoid Low (IOGL), whose origin is not clearly known yet. The residual geoid data are retrieved from the geoid data by removing the long-wavelength core-mantle density effects using recent spherical harmonic coefficients of Earth Gravity Model 2008 (EGM2008) up to degree and order 50 from the observed geoid data. The coefficients are smoothly rolled off between degrees 30-70 in order to avoid artifacts related to the sharp truncation at degree 50. With this process we observed significant improvement in the residual geoid data when compared to the previous low-spatial resolution maps. The previous version was superposed by systematic broad regional highs and lows (like checker board) with amplitude up to ±12 m, though the trends of geoid in general match in both versions. These methodical artifacts in the previous version may have arisen due to the use of old Rapp's geo-potential model coefficients, as well as sharp truncation of reference model at degree and order 50. Geoid anomalies are converted to free-air gravity anomalies and validated with cross-over corrected ship-borne gravity data of the Arabian Sea and Bay of Bengal. The present satellite derived gravity data matches well with the ship-borne data with Root Mean Square Error (RMSE) of 5.1-7.8 mGal, and this is found to be within the error limits when compared with other globally available satellite data. Spectral analysis of

  14. Development of the negative gravity anomaly of the 85°E Ridge, northeastern Indian Ocean - A process oriented modelling approach

    NASA Astrophysics Data System (ADS)

    Sreejith, K. M.; Radhakrishna, M.; Krishna, K. S.; Majumdar, T. J.

    2011-08-01

    The 85°E Ridge extends from the Mahanadi Basin, off northeastern margin of India to the Afanasy Nikitin Seamount in the Central Indian Basin. The ridge is associated with two contrasting gravity anomalies: negative anomaly over the north part (up to 5°N latitude), where the ridge structure is buried under thick Bengal Fan sediments and positive anomaly over the south part, where the structure is intermittently exposed above the seafloor. Ship-borne gravity and seismic reflection data are modelled using process oriented method and this suggest that the 85°E Ridge was emplaced on approximately 10-15 km thick elastic plate ( Te) and in an off-ridge tectonic setting. We simulated gravity anomalies for different crust-sediment structural configurations of the ridge that were existing at three geological ages, such as Late Cretaceous, Early Miocene and Present. The study shows that the gravity anomaly of the ridge in the north has changed through time from its inception to present. During the Late Cretaceous the ridge was associated with a significant positive anomaly with a compensation generated by a broad flexure of the Moho boundary. By Early Miocene the ridge was approximately covered by the post-collision sediments and led to alteration of the initial gravity anomaly to a small positive anomaly. At present, the ridge is buried by approximately 3 km thick Bengal Fan sediments on its crestal region and about 8 km thick pre- and post-collision sediments on the flanks. This geological setting had changed physical properties of the sediments and led to alter the minor positive gravity anomaly of Early Miocene to the distinct negative gravity anomaly.

  15. Gravity and fault structures, Long Valley caldera, California

    SciTech Connect

    Carle, S.F.; Goldstein, N.E.

    1987-07-01

    The main and catastrophic phase of eruption in Long Valley occurred 0.73 m.y. ago with the eruption of over 600 km/sup 3/ of rhyolitic magma. Subsequent collapse of the roof rocks produced a caldera which is now elliptical in shape, 32 km east-west by 17 km north-south. The caldera, like other large Quarternary silicic ash-flow volcanoes that have been studied by various workers, has a nearly coincident Bouguer gravity low. Earlier interpretations of the gravity anomaly have attributed the entire anomaly to lower density rocks filling the collapsed structure. However, on the basis of many additional gravity stations and supporting subsurface data from several new holes, a much more complex and accurate picture has emerged of caldera structure. From a three-dimensional inversion of the residual Bouguer gravity data we can resolve discontinuities that seem to correlate with extensions of pre-caldera faults into the caldera and faults associated with the ring fracture. Some of these faults are believed related to the present-day hydrothermal upflow zone and the zone of youngest volcanic activity within the caldera.

  16. Mantle dynamics models for Venus - comparison of spatial and spectral characteristics of inferred gravity anomalies and topography with observations

    NASA Astrophysics Data System (ADS)

    Steinberger, Bernhard; Werner, Stephanie C.

    2013-04-01

    Venus and Earth have similar size and probably also core radius, such that many results that have been obtained for Earth's mantle could apply to Venus as well. Yet a fundamental difference between the two planets is that Earth features plate tectonics, whereas Venus appears to be in the rigid lid regime. From a variety of constraints, a substantial increase of viscosity with depth in the Earth's mantle, reaching around 10**23 Pas in the lower mantle above D'', can be inferred. Mantle convection models with a sufficiently high temperature as boundary condition at the core-mantle-boundary invariably yield thermal plumes. With a rigid lid as upper boundary and the high lower mantle viscosity, mantle dynamics models typically yield around 10 plumes, which are long-lived (hundreds of Myr lifespan) and slowly moving (typically < 1cm/yr). These modelling results appear to match well with the distribution of volcanism in space and time as inferred from observations. Besides volcanism, topography and gravity anomalies can yield further insights towards the internal dynamics of Venus: If we assume the same spectrum (in terms of spherical harmonic expansion) of thermal density anomalies, as inferred from tomography models on Earth, and a similar radial viscosity structure, except without viscosity jump at the spinel-perovskite transition on Venus, we find that we can match most of both the gravity and topography spectrum on Venus up to about degree 40. This probably implies that - in contrast to Earth - topography on Venus is mostly dynamically supported from within. The main exception is degree two gravity on Venus, which is much less than predicted, implying that the mantle on Venus has much less degree-two structure, and therefore probably no features corresponding to the Earth's Large Low Shear wave Velocity Provinces (LLSVPs). Here we focus on predictions from dynamic models: We compare model predictions of mantle density anomaly spectra for both Earth (where we

  17. Integrating stations from the North America Gravity Database into a local GPS-based land gravity survey

    USGS Publications Warehouse

    Shoberg, Thomas G.; Stoddard, Paul R.

    2013-01-01

    The ability to augment local gravity surveys with additional gravity stations from easily accessible national databases can greatly increase the areal coverage and spatial resolution of a survey. It is, however, necessary to integrate such data seamlessly with the local survey. One challenge to overcome in integrating data from national databases is that these data are typically of unknown quality. This study presents a procedure for the evaluation and seamless integration of gravity data of unknown quality from a national database with data from a local Global Positioning System (GPS)-based survey. The starting components include the latitude, longitude, elevation and observed gravity at each station location. Interpolated surfaces of the complete Bouguer anomaly are used as a means of quality control and comparison. The result is an integrated dataset of varying quality with many stations having GPS accuracy and other reliable stations of unknown origin, yielding a wider coverage and greater spatial resolution than either survey alone.

  18. Regional gravity and magnetic anomalies related to a Proterozoic carbonatite terrane in the eastern Mojave Desert, California

    NASA Astrophysics Data System (ADS)

    Denton, K. M.; Ponce, D. A.; Miller, D. M.; Jernigan, C. T.

    2014-12-01

    One of the world's largest rare earth element carbonatite deposits is located at Mountain Pass in the eastern Mojave Desert, California. The 1.4 Ga carbonatite deposit is hosted by and intruded into 1.7 Ga gneiss and schist that occurs in a narrow north-northwest trending belt along the eastern parts of Clark Mountain Range, Mescal Range, and Ivanpah Mountains. The carbonatite is associated with an ultrapotassic intrusive suite that ranges from shonkinite through syenite and granite. Regional geophysical data reveal that the eastern Mojave carbonatite terrane occurs along the northeast edge of a prominent magnetic high and the western margin of a gravity high along the eastern Clark Mountain Range. To improve our understanding of the geophysical and structural framework of the eastern Mojave carbonatite terrane, we collected over 1900 gravity stations and over 600 physical rock property samples to augment existing geophysical data. Carbonatite intrusions typically have distinct gravity, magnetic, and radiometric signatures because these deposits are relatively dense, contain magnetite, and are enriched in thorium or uranium. However, our results show that the carbonatite is essentially nonmagnetic with an average susceptibility of 0.18 x 10-3 SI (n=31) and the associated ultrapotassic intrusive suite is very weakly magnetic with an average susceptibility of 2.0 x 10-3 SI (n=36). Although the carbonatite body is nonmagnetic, it occurs along a steep gradient of a prominent aeromagnetic anomaly. This anomaly may reflect moderately magnetic mafic intrusive rocks at depth. East of the ultrapotassic intrusive rocks, a prominent north trending magnetic anomaly occurs in the central part of Ivanpah Valley. Based on geologic mapping in the Ivanpah Mountains, this magnetic anomaly may reflect Paleoproterozoic mafic intrusive rocks related to the 1.7 Ga Ivanpah Orogeny. Physical property measurements indicate that exposed amphibolite along the eastern Ivanpah Mountains are

  19. Model parameter estimations from residual gravity anomalies due to simple-shaped sources using Differential Evolution Algorithm

    NASA Astrophysics Data System (ADS)

    Ekinci, Yunus Levent; Balkaya, Çağlayan; Göktürkler, Gökhan; Turan, Seçil

    2016-06-01

    An efficient approach to estimate model parameters from residual gravity data based on differential evolution (DE), a stochastic vector-based metaheuristic algorithm, has been presented. We have showed the applicability and effectiveness of this algorithm on both synthetic and field anomalies. According to our knowledge, this is a first attempt of applying DE for the parameter estimations of residual gravity anomalies due to isolated causative sources embedded in the subsurface. The model parameters dealt with here are the amplitude coefficient (A), the depth and exact origin of causative source (zo and xo, respectively) and the shape factors (q and ƞ). The error energy maps generated for some parameter pairs have successfully revealed the nature of the parameter estimation problem under consideration. Noise-free and noisy synthetic single gravity anomalies have been evaluated with success via DE/best/1/bin, which is a widely used strategy in DE. Additionally some complicated gravity anomalies caused by multiple source bodies have been considered, and the results obtained have showed the efficiency of the algorithm. Then using the strategy applied in synthetic examples some field anomalies observed for various mineral explorations such as a chromite deposit (Camaguey district, Cuba), a manganese deposit (Nagpur, India) and a base metal sulphide deposit (Quebec, Canada) have been considered to estimate the model parameters of the ore bodies. Applications have exhibited that the obtained results such as the depths and shapes of the ore bodies are quite consistent with those published in the literature. Uncertainty in the solutions obtained from DE algorithm has been also investigated by Metropolis-Hastings (M-H) sampling algorithm based on simulated annealing without cooling schedule. Based on the resulting histogram reconstructions of both synthetic and field data examples the algorithm has provided reliable parameter estimations being within the sampling limits of

  20. Lunar impact basins revealed by Gravity Recovery and Interior Laboratory measurements.

    PubMed

    Neumann, Gregory A; Zuber, Maria T; Wieczorek, Mark A; Head, James W; Baker, David M H; Solomon, Sean C; Smith, David E; Lemoine, Frank G; Mazarico, Erwan; Sabaka, Terence J; Goossens, Sander J; Melosh, H Jay; Phillips, Roger J; Asmar, Sami W; Konopliv, Alexander S; Williams, James G; Sori, Michael M; Soderblom, Jason M; Miljković, Katarina; Andrews-Hanna, Jeffrey C; Nimmo, Francis; Kiefer, Walter S

    2015-10-01

    Observations from the Gravity Recovery and Interior Laboratory (GRAIL) mission indicate a marked change in the gravitational signature of lunar impact structures at the morphological transition, with increasing diameter, from complex craters to peak-ring basins. At crater diameters larger than ~200 km, a central positive Bouguer anomaly is seen within the innermost peak ring, and an annular negative Bouguer anomaly extends outward from this ring to the outer topographic rim crest. These observations demonstrate that basin-forming impacts remove crustal materials from within the peak ring and thicken the crust between the peak ring and the outer rim crest. A correlation between the diameter of the central Bouguer gravity high and the outer topographic ring diameter for well-preserved basins enables the identification and characterization of basins for which topographic signatures have been obscured by superposed cratering and volcanism. The GRAIL inventory of lunar basins improves upon earlier lists that differed in their totals by more than a factor of 2. The size-frequency distributions of basins on the nearside and farside hemispheres of the Moon differ substantially; the nearside hosts more basins larger than 350 km in diameter, whereas the farside has more smaller basins. Hemispherical differences in target properties, including temperature and porosity, are likely to have contributed to these different distributions. Better understanding of the factors that control basin size will help to constrain models of the original impactor population.

  1. Lunar impact basins revealed by Gravity Recovery and Interior Laboratory measurements

    PubMed Central

    Neumann, Gregory A.; Zuber, Maria T.; Wieczorek, Mark A.; Head, James W.; Baker, David M. H.; Solomon, Sean C.; Smith, David E.; Lemoine, Frank G.; Mazarico, Erwan; Sabaka, Terence J.; Goossens, Sander J.; Melosh, H. Jay; Phillips, Roger J.; Asmar, Sami W.; Konopliv, Alexander S.; Williams, James G.; Sori, Michael M.; Soderblom, Jason M.; Miljković, Katarina; Andrews-Hanna, Jeffrey C.; Nimmo, Francis; Kiefer, Walter S.

    2015-01-01

    Observations from the Gravity Recovery and Interior Laboratory (GRAIL) mission indicate a marked change in the gravitational signature of lunar impact structures at the morphological transition, with increasing diameter, from complex craters to peak-ring basins. At crater diameters larger than ~200 km, a central positive Bouguer anomaly is seen within the innermost peak ring, and an annular negative Bouguer anomaly extends outward from this ring to the outer topographic rim crest. These observations demonstrate that basin-forming impacts remove crustal materials from within the peak ring and thicken the crust between the peak ring and the outer rim crest. A correlation between the diameter of the central Bouguer gravity high and the outer topographic ring diameter for well-preserved basins enables the identification and characterization of basins for which topographic signatures have been obscured by superposed cratering and volcanism. The GRAIL inventory of lunar basins improves upon earlier lists that differed in their totals by more than a factor of 2. The size-frequency distributions of basins on the nearside and farside hemispheres of the Moon differ substantially; the nearside hosts more basins larger than 350 km in diameter, whereas the farside has more smaller basins. Hemispherical differences in target properties, including temperature and porosity, are likely to have contributed to these different distributions. Better understanding of the factors that control basin size will help to constrain models of the original impactor population. PMID:26601317

  2. Complete Bouguer gravity map of the Medicine Lake Quadrangle, California

    USGS Publications Warehouse

    Finn, C.

    1981-01-01

    A mathematical technique, called kriging, was programmed for a computer to interpolate hydrologic data based on a network of measured values in west-central Kansas. The computer program generated estimated values at the center of each 1-mile section in the Western Kansas Groundwater Management District No. 1 and facilitated contouring of selected values that are needed in the effective management of ground water for irrigation. The kriging technique produced objective and reproducible maps that illustrated hydrologic conditions in the Ogallala aquifer, the principal source of water in west-central Kansas. Maps of the aquifer, which use a 3-year average, included the 1978-80 water-table altitudes, which ranged from about 2,580 to 3,720 feet; the 1978-80 saturated thicknesses, which ranged from about 0 to 250 feet; and the percentage changes in saturated thickness from 1950 to 1978-80, which ranged from about a 50-percent increase to a 100-percent decrease. A map showing errors of estimate also was provided as a measure of reliability for the 1978-80 water-table altitudes. Errors of estimate ranged from 2 to 24 feet. (USGS)

  3. Gravity anomaly and geoid undulation results in local areas from GEOS-3 altimeter data

    NASA Technical Reports Server (NTRS)

    Rapp, R. H.

    1979-01-01

    The adjusted GEOS-3 altimeter data, taken as averages within a data frame, have been used to construct free air anomaly and geoid undulation profiles and maps in areas of geophysical interest. Profiles were constructed across the Philippine Trench (at a latitude of 6 deg) and across the Bonin Trench (at a latitude of 28 deg). In the latter case an anomaly variation of 443 mgals in 143 km was derived from the altimeter data. These variations agreed reasonably with terrestrial estimates, considering the predicted point accuracy was about + or - 27 mgals. An area over the Patton Sea mounts was also investigated with the altimeter anomaly field agreeing well with the terrestrial data except for the point directly over the top of the sea mount. It is concluded that the GEOS-3 altimeter data is valuable not only for determining 5 deg and 1 deg x 1 deg mean anomalies, but also can be used to describe more local anomaly variations.

  4. The determination of gravity anomalies from geoid heights using the inverse Stokes' formula, Fourier transforms, and least squares collocation

    NASA Technical Reports Server (NTRS)

    Rummel, R.; Sjoeberg, L.; Rapp, R. H.

    1978-01-01

    A numerical method for the determination of gravity anomalies from geoid heights is described using the inverse Stokes formula. This discrete form of the inverse Stokes formula applies a numerical integration over the azimuth and an integration over a cubic interpolatory spline function which approximates the step function obtained from the numerical integration. The main disadvantage of the procedure is the lack of a reliable error measure. The method was applied on geoid heights derived from GEOS-3 altimeter measurements in the calibration area of the GEOS-3 satellite.

  5. The Wallula fault and tectonic framework of south-central Washington, as interpreted from magnetic and gravity anomalies

    NASA Astrophysics Data System (ADS)

    Blakely, Richard J.; Sherrod, Brian L.; Weaver, Craig S.; Wells, Ray E.; Rohay, Alan C.

    2014-06-01

    The Yakima fold and thrust belt (YFTB) in central Washington has accommodated regional, mostly north-directed, deformation of the Cascadia backarc since prior to emplacement of Miocene flood basalt of the Columbia River Basalt Group (CRBG). The YFTB consists of two structural domains. Northern folds of the YFTB strike eastward and terminate at the western margin of a 20-mGal negative gravity anomaly, the Pasco gravity low, straddling the North American continental margin. Southern folds of the YFTB strike southeastward, form part of the Olympic-Wallowa lineament (OWL), and pass south of the Pasco gravity low as the Wallula fault zone. An upper crustal model based on gravity and magnetic anomalies suggests that the Pasco gravity low is caused in part by an 8-km-deep Tertiary basin, the Pasco sub-basin, abutting the continental margin and concealed beneath CRBG. The Pasco sub-basin is crossed by north-northwest-striking magnetic anomalies caused by dikes of the 8.5 Ma Ice Harbor Member of the CRBG. At their northern end, dikes connect with the eastern terminus of the Saddle Mountains thrust of the YFTB. At their southern end, dikes are disrupted by the Wallula fault zone. The episode of NE-SW extension that promoted Ice Harbor dike injection apparently involved strike-slip displacement on the Saddle Mountains and Wallula faults. The amount of lateral shear on the OWL impacts the level of seismic hazard in the Cascadia region. Ice Harbor dikes, as mapped with aeromagnetic data, are dextrally offset by the Wallula fault zone a total of 6.9 km. Assuming that dike offsets are tectonic in origin, the Wallula fault zone has experienced an average dextral shear of 0.8 mm/y since dike emplacement 8.5 Ma, consistent with right-lateral stream offsets observed at other locations along the OWL. Southeastward, the Wallula fault transfers strain to the north-striking Hite fault, the possible location of the M 5.7 Milton-Freewater earthquake in 1936.

  6. Analyzing the Broken Ridge area of the Indian Ocean using magnetic and gravity anomaly maps and geoid undulation and bathymetry data

    NASA Technical Reports Server (NTRS)

    Lazarewicz, A. R.; Sailor, R. V. (Principal Investigator)

    1982-01-01

    A higher resolution anomaly map of the Broken Ridge area (2 degree dipole spacing) was produced and reduced to the pole using quiet time data for this area. The map was compared with equally scaled maps of gravity anomaly, geoid undulation, and bathymetry. The ESMAP results were compared with a NASA MAGSAT map derived by averaging data in two-degree bins. A survey simulation was developed to model the accuracy of MAGSAT anomaly maps as a function of satellite altitude, instrument noise level, external noise model, and crustal anomaly field model. A preliminary analysis of the geophysical structure of Broken Ridge is presented and unresolved questions are listed.

  7. New Gravity and Magnetic Maps of the San Juan Volcanic Field, Southwestern Colorado

    NASA Astrophysics Data System (ADS)

    Drenth, B. J.; Keller, G. R.

    2004-12-01

    A very large simple Bouguer anomaly gravity low, about 100 km by 150 km in map view and reaching values less than -350 mGals, lies over the Oligocene San Juan volcanic field in southwestern Colorado. Roughly 15-18 different calderas represent the eruptive sources of the andesitic-rhyolitic rocks of this large volcanic field, and most are located within two swarms: the Silverton-Lake City (western) caldera complex, and the central complex that includes the Creede, Bachelor, and La Garita calderas. The prominent gravity low over the region has been previously interpreted to be due to the presence a low-density granitic batholith that underlies the volcanic field in the upper crust. However, there are complicating issues in this interpretation. First, many of the volcanic rocks are notably less dense than the Bouguer reduction density of 2.67 g/cc used for processing of the gravity data, meaning that those rocks exposed at the surface could account for a significant portion of the gravity low. Second, the extreme topographic relief in the region requires that terrain corrections (always positive algebraically) be applied. To meet these needs, a new complete Bouguer gravity map of the volcanic field has been prepared using the new traditionally terrain corrected U. S. gravity database. Modeling these data show that the caldera fill is a major contributor to the gravity low but that an upper crustal batholith is also required to satisfy the observed data. In addition, a second map is being prepared. It is derived by applying a new complex Bouguer correction that takes geologically reasonable surface densities and digital elevation data into account, and as a result will provide a much clearer picture of the nature of the subsurface batholith. A new aeromagnetic map of the region has also been completed. This represents a significant improvement over previous merging efforts in southwestern Colorado, as numerous and previously under-utilized high-resolution aeromagnetic

  8. Geoid undulations and gravity anomalies over the Aral Sea, the Black Sea and the Caspian Sea from a combined GEOS-3/SEASAT/GEOSAT altimeter data set

    NASA Technical Reports Server (NTRS)

    Au, Andrew Y.; Brown, Richard D.; Welker, Jean E.

    1991-01-01

    Satellite-based altimetric data taken by GOES-3, SEASAT, and GEOSAT over the Aral Sea, the Black Sea, and the Caspian Sea are analyzed and a least squares collocation technique is used to predict the geoid undulations on a 0.25x0.25 deg. grid and to transform these geoid undulations to free air gravity anomalies. Rapp's 180x180 geopotential model is used as the reference surface for the collocation procedure. The result of geoid to gravity transformation is, however, sensitive to the information content of the reference geopotential model used. For example, considerable detailed surface gravity data were incorporated into the reference model over the Black Sea, resulting in a reference model with significant information content at short wavelengths. Thus, estimation of short wavelength gravity anomalies from gridded geoid heights is generally reliable over regions such as the Black Sea, using the conventional collocation technique with local empirical covariance functions. Over regions such as the Caspian Sea, where detailed surface data are generally not incorporated into the reference model, unconventional techniques are needed to obtain reliable gravity anomalies. Based on the predicted gravity anomalies over these inland seas, speculative tectonic structures are identified and geophysical processes are inferred.

  9. Principal facts for gravity stations in Dixie; Fairview, and Stingaree valleys, Churchill and Pershing counties, Nevada

    USGS Publications Warehouse

    Schaefer, D.H.; Thomas, J.M.; Duffrin, B.G.

    1984-01-01

    During March through July 1979, gravity measurements were made at 300 stations in Dixie Valley, Nevada. In December 1981, 45 additional stations were added--7 in Dixie Valley, 23 in Fairview Valley, and 15 in Stingaree Valley. Most altitudes were determined by using altimeters or topographic maps. The gravity observations were made with a Worden temperature-controlled gravimeter with an initial scale factor of 0.0965 milliGal/scale division. Principal facts for each of the 345 stations are tabulated; they consist of latitude, longitude, altitude, observed gravity, free-air anomaly, terrain correction, and Bouguer anomaly values at a bedrock density of 2.67 grams/cu cm. (Lantz-PTT)

  10. Correlation of gravity with the Maquereau Group, southern Gaspe Peninsula, Quebec

    NASA Astrophysics Data System (ADS)

    Seguin, Maurice K.

    1986-06-01

    Gravity observations at 150 locations in the Port-Daniel and Chandler area, southeastern Gaspé, Quebec, delineate an E-W to ENE-WSW trending elliptical positive Bouguer gravity anomaly with an amplitude of 19 mGal and a residual gravity anomaly of circa 22 mGal. This anomaly correlates closely with the Lower Cambrian and/or Hadrynian Maquereau Group, the steep gradients defining it coinciding with the contact between the group and the surrounding Ordovician and Siluro-Devonian sedimentary rocks. On the basis of its similar geological setting, this gravity anomaly may be compared with the positive Bouguer anomalies observed over the Fleur de, Lys zone to the east of the Baie Verte lineament in Newfoundland. Tridimensional modelling of the gravity data is inconsistent with a serpentinite dome as originally proposed and it suggests that the Maquereau Group represents an upthrusted slice of deep-seated volcanosedimentary sequences. These were originally located on the lower segment of the continental slope; they constituted a topographic high during the final process of the mountain building at the Taconic phase (Middle to Upper Ordovician time). The most probable way of emplacement of the Maquereau block is through a tear-fault running E-W to ESE-WNW in the southern Gulf of St. Lawrence west of Cape Breton and resulting from Early Paleozoic continental collision between a Eurafrican continent and a North American continent which had a salient located beneath the site of the modern Gulf. The Maquereau may then have been reactivated with a left-lateral motion accompanied of a rotation about a sub-horizontal axis. The presumed Baie Verte-Brompton line ought to be displaced to the north and the Humber zone is narrowed.

  11. Gravity and magnetic anomalies used to delineate geologic features associated with earthquakes and aftershocks in the central Virginia seismic zone

    NASA Astrophysics Data System (ADS)

    Shah, A. K.; Horton, J.; McNamara, D. E.; Spears, D.; Burton, W. C.

    2013-12-01

    Estimating seismic hazard in intraplate environments can be challenging partly because events are relatively rare and associated data thus limited. Additionally, in areas such as the central Virginia seismic zone, numerous pre-existing faults may or may not be candidates for modern tectonic activity, and other faults may not have been mapped. It is thus important to determine whether or not specific geologic features are associated with seismic events. Geophysical and geologic data collected in response to the Mw5.8 August 23, 2011 central Virginia earthquake provide excellent tools for this purpose. Portable seismographs deployed within days of the main shock showed a series of aftershocks mostly occurring at depths of 3-8 km along a southeast-dipping tabular zone ~10 km long, interpreted as the causative fault or fault zone. These instruments also recorded shallow (< 4 km) aftershocks clustered in several areas at distances of ~2-15 km from the main fault zone. We use new airborne geophysical surveys (gravity, magnetics, radiometrics, and LiDAR) to delineate the distribution of various surface and subsurface geologic features of interest in areas where the earthquake and aftershocks took place. The main (causative fault) aftershock cluster coincides with a linear, NE-trending gravity gradient (~ 2 mgal/km) that extends over 20 km in either direction from the Mw5.8 epicenter. Gravity modeling incorporating seismic estimates of Moho variations suggests the presence of a shallow low-density body overlying the main aftershock cluster, placing it within the upper 2-4 km of the main-fault hanging wall. The gravity, magnetic, and radiometric data also show a bend in generally NE-SW orientation of anomalies close to the Mw5.8 epicenter. Most shallow aftershock clusters occur near weaker short-wavelength gravity gradients of one to several km length. In several cases these gradients correspond to geologic contacts mapped at the surface. Along the gravity gradients, the

  12. Dip distribution of Oita-Kumamoto Tectonic Line located in central Kyushu, Japan, estimated by eigenvectors of gravity gradient tensor

    NASA Astrophysics Data System (ADS)

    Kusumoto, Shigekazu

    2016-09-01

    We estimated the dip distribution of Oita-Kumamoto Tectonic Line located in central Kyushu, Japan, by using the dip of the maximum eigenvector of the gravity gradient tensor. A series of earthquakes in Kumamoto and Oita beginning on 14 April 2016 occurred along this tectonic line, the largest of which was M = 7.3. Because a gravity gradiometry survey has not been conducted in the study area, we calculated the gravity gradient tensor from the Bouguer gravity anomaly and employed it to the analysis. The general dip distribution of the Oita-Kumamoto Tectonic Line was found to be about 65° and tends to be higher towards its eastern end. In addition, we estimated the dip around the largest earthquake to be about 60° from the gravity gradient tensor. This result agrees with the dip of the earthquake source fault obtained by Global Navigation Satellite System data analysis.[Figure not available: see fulltext.

  13. Disturbance Vector in Space from Surface Gravity Anomalies Using Complementary Models.

    DTIC Science & Technology

    1985-08-01

    Lelgemann, D., "Spherical Approximation and the Combination of Gravimetric and Satellite Data," Bolletino di Geodesia e Scienze Affini, vol. 32, No. 4... Geodesia e Scienze Affini, vol. 41, No. 1, pp. 89-103, 1982. Rapp, R.H., "A FORTRAN Program for the Computation of the Normal Gravity and Gravitational

  14. Gravity measurements and terrain corrections using a digital terrain model in the NW Himalaya

    NASA Astrophysics Data System (ADS)

    Banerjee, Paramesh

    1998-12-01

    Areas recently gravity surveyed in the NW Himalaya are characterized by high-elevation and high-amplitude topographic undulations. A new method of applying combined Bouguer and terrain corrections using a digital terrain model is highly accurate and offers advantages over conventional techniques by saving efforts and being more flexible. Partitioning parameters for station-dependent inner-zone compartments and station-independent outer zones can be optimally selected for the desired accuracy requirements. A digital terrain database is used to obtain the outer-zone corrections. In the situation of the NW Himalaya surveys, a 1.2 km inner zone is divided into 112 compartments for each station and a digital terrain database containing nearly 16 000 data points for 30″×30″ compartments was applied using the computer program EFFECT.FOR, to compute combined Bouguer and terrain corrections for a 20 km range. The terrain corrections between 20 and 170 km were computed using National Geophysical Data Centre (NGDC) 5'×5' gridded global elevation database. The magnitude of the terrain correction varies between 3 and 50 mGal. The effects of the 20 km range terrain correction are more pronounced on short-medium wavelength anomalies. The Swarghat gravity high is further enhanced while several high-frequency pseudo-anomalies disappear after applying the terrain corrections. The refined Bouguer anomaly varies from -160 mGal at the southern end of the section, to -310 mGal at the northern end, suggesting a Moho depth variation from 45 to nearly 60 km. The steepness of the northward negative gravity gradient, typical for the Himalaya, is considerably reduced after applying a terrain correction for the 170 km range.

  15. Use of gravity potential field methods for defining a shallow magmatic intrusion: the Mt. Amiata case history (Tuscany, Central Italy)

    NASA Astrophysics Data System (ADS)

    Girolami, Chiara; Rinaldo Barchi, Massimiliano; Pauselli, Cristina; Heyde, Ingo

    2016-04-01

    We analyzed the Bouguer gravity anomaly signal beneath the Mt. Amiata area in order to reconstruct the subsurface setting. The study area is characterized by a pronounced gravity minimum, possibly correlated with the observed anomalous heat flow and hydrothermal activity. Using different approaches, previous authors defined a low density body (generally interpreted as a magmatic intrusion) beneath this area, which could explain the observed gravity anomaly minimum. However the proposed geologic models show different geometries and densities for the batholith. The gravity data used in this study (kindly provided by eni) were acquired from different institutions (eni, OGS, USDMA and Servizio Geologico d'Italia) and collected in a unique dataset, consisting of about 50000 stations, randomly distributed, which cover Central Italy, with a spacing of less than 1 km. For each station the elevation and the Bouguer gravity anomaly data are given. From this dataset, we created two maps of the Bouguer gravity anomaly and the topography, using the Minimum Curvature gridding method considering a grid cell size of 500m x 500m. The Bouguer gravity anomaly has been computed using a density of 2.67 g/cm3. From these maps we extracted a window of about 240 km2 (12x20 km) for the study area, which includes the Mt. Amiata region and the adjacent Radicofani sedimentary basin. The first part of this study was focused on calculating the first order vertical derivative and the power spectra analysis of the Bouguer gravity anomaly to enhance the effect of shallow bodies and estimating the source depth respectively. The second part of this study was focused on constructing a 3D geological density model of the subsurface setting of the studied area, implementing a forward modelling approach. The stratigraphy of the study area's upper crust schematically consists of six litho-mechanical units, whose density was derived from velocity data collected by active seismic surveys. A preliminary

  16. Oregon Magnetic and Gravity Maps and Data: A Web Site for Distribution of Data

    USGS Publications Warehouse

    Roberts, Carter W.; Kucks, Robert P.; Hill, Patricia L.

    2008-01-01

    This web site gives the results of a USGS project to acquire the best available, public-domain, aeromagnetic and gravity data in the United States and merge these data into uniform, composite grids for each State. The results for the State of Oregon are presented here on this site. Files of aeromagnetic and gravity grids and images are available for these States for downloading. In Oregon, 49 magnetic surveys have been knit together to form a single digital grid and map. Also, a complete Bouguer gravity anomaly grid and map was generated from 40,665 gravity station measurements in and adjacent to Oregon. In addition, a map shows the location of the aeromagnetic surveys, color-coded to the survey flight-line spacing. This project was supported by the Mineral Resource Program of the USGS.

  17. Illinois, Indiana, and Ohio Magnetic and Gravity Maps and Data: A Website for Distribution of Data

    USGS Publications Warehouse

    Daniels, David L.; Kucks, Robert P.; Hill, Patricia L.

    2008-01-01

    This web site gives the results of a USGS project to acquire the best available, public-domain, aeromagnetic and gravity data in the United States and merge these data into uniform, composite grids for each state. The results for the three states, Illinois, Indiana, and Ohio are presented here in one site. Files of aeromagnetic and gravity grids and images are available for these states for downloading. In Illinois, Indiana, and Ohio, 19 magnetic surveys have been knit together to form a single digital grid and map. And, a complete Bouguer gravity anomaly grid and map was generated from 128,227 gravity station measurements in and adjacent to Illinois, Indiana, and Ohio. In addition, a map shows the location of the aeromagnetic surveys, color-coded to the survey flight-line spacing. This project was supported by the Mineral Resource Program of the USGS.

  18. First application of airborne gravity to oil exploration in the Shengli oil province, eastern China

    NASA Astrophysics Data System (ADS)

    Li, Wenyong; Zhoud, Jianxin; Liu, Yanxu; Xu, Jianchun

    2015-07-01

    An airborne gravity survey was successfully conducted over the Dongying, Gudao and Gudong oilfields of Shengli oil province, eastern China. These survey areas cover onshore and offshore regions of the south-west Bohai Sea. The data were processed using the potential field transformation approach. The derived Bouguer gravity data correlate well with features such as known faults, swells and sags identified by earlier seismic survey and drilling data. The depth to the Cenozoic basement in the study area, including the Dongying, Gudao, and Gudong oilfields, was calculated by means of gravity inversion constrained by seismic and drilling data. The differences between the depths to the Cenozoic basement calculated from gravity anomaly and those determined by the earlier seismic and drilling data are less than 5%.

  19. Michigan Magnetic and Gravity Maps and Data: A Website for the Distribution of Data

    USGS Publications Warehouse

    Daniels, David L.; Kucks, Robert P.; Hill, Patricia L.; Snyder, Stephen L.

    2009-01-01

    This web site provides the best available, public-domain, aeromagnetic and gravity data in the State of Michigan and merges these data into composite grids that are available for downloading. The magnetic grid is compiled from 25 separate magnetic surveys that have been knit together to form a single composite digital grid and map. The magnetic survey grids have been continued to 305 meters (1,000 feet) above ground and merged together to form the State compilation. A separate map shows the location of the aeromagnetic surveys, color-coded to the survey flight-line spacing. In addition, a complete Bouguer gravity anomaly grid and map were generated from more than 20,000 gravity station measurements from 33 surveys. A table provides the facts about each gravity survey where known.

  20. Detailed gravity and aeromagnetic surveys in the Black Rock Desert Area, Utah. Topical report

    SciTech Connect

    Serpa, L.F.; Cook, K.L.

    1980-01-01

    Aeromagnetic and gravity surveys were conducted during 1978 in the Black Rock Desert, Utah over an area of about 2400 km/sup 2/ between the north-trending Pavant and Cricket Mountains. The surveys assisted in evaluating the geothermal resources in the Meadow-Hatton Known Geothermal Resource Area (KGRA) and vicinity by delineating geophysical characteristics of the subsurface. The gravity measurements from approximately 700 new stations were reduced to complete Bouguer gravity anomaly values with the aid of a computerized terrain-correction program and contoured at an interval of 1 milligal. The aeromagnetic survey was drape flown at an altitude of 305 m (1000 ft) and a total intensity residual aeromagnetic map with a contour interval of 20 gammas was produced. Two gravity and aeromagnetic east-west profiles and one north-south profile were modeled using a simultaneous 2 1/2-dimensional modeling technique to provide a single model satisfying both types of geophysical data.

  1. Spherical-earth gravity and magnetic anomaly modeling by Gauss-Legendre quadrature integration

    NASA Technical Reports Server (NTRS)

    Von Frese, R. R. B.; Hinze, W. J.; Braile, L. W.; Luca, A. J.

    1981-01-01

    Gauss-Legendre quadrature integration is used to calculate the anomalous potential of gravity and magnetic fields and their spatial derivatives on a spherical earth. The procedure involves representation of the anomalous source as a distribution of equivalent point gravity poles or point magnetic dipoles. The distribution of equivalent point sources is determined directly from the volume limits of the anomalous body. The variable limits of integration for an arbitrarily shaped body are obtained from interpolations performed on a set of body points which approximate the body's surface envelope. The versatility of the method is shown by its ability to treat physical property variations within the source volume as well as variable magnetic fields over the source and observation surface. Examples are provided which illustrate the capabilities of the technique, including a preliminary modeling of potential field signatures for the Mississippi embayment crustal structure at 450 km.

  2. Gorringe Ridge gravity and magnetic anomalies are compatible with thrusting at a crustal scale

    NASA Astrophysics Data System (ADS)

    Galindo-Zaldívar, J.; Maldonado, A.; Schreider, A. A.

    2003-06-01

    The main features of the deep structure of the Gorringe Ridge are analysed on the basis of gravity and magnetic measurements, as well as seismic profiles, drill holes, rock dredges, submersible observations and seismicity data. The gravity and magnetic models of the Gettysburg and Ormonde seamounts, which form the Gorringe Ridge, suggest that the Moho is approximately flat and the upper part of the ridge corresponds to a northwestwards vergent fold. This structure is the result of a northwestward vergent thrust that deformed the oceanic crust, with a minimum slip of approximately 20 km. The activity of the thrust probably started 20 Myr, and produced the recent stages of seamount uplift. The seamount is mainly composed of gabbros of the oceanic crust, serpentinized rocks and alkaline basalts. The large antiform, located in the hangingwall of the thrust, is probably deformed by minor faults. This oceanic ridge is a consequence of the oblique convergence between the African Plate and the overlapping Eurasian Plate.

  3. Spherical-earth Gravity and Magnetic Anomaly Modeling by Gauss-legendre Quadrature Integration

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.; Luca, A. J. (Principal Investigator)

    1981-01-01

    The anomalous potential of gravity and magnetic fields and their spatial derivatives on a spherical Earth for an arbitrary body represented by an equivalent point source distribution of gravity poles or magnetic dipoles were calculated. The distribution of equivalent point sources was determined directly from the coordinate limits of the source volume. Variable integration limits for an arbitrarily shaped body are derived from interpolation of points which approximate the body's surface envelope. The versatility of the method is enhanced by the ability to treat physical property variations within the source volume and to consider variable magnetic fields over the source and observation surface. A number of examples verify and illustrate the capabilities of the technique, including preliminary modeling of potential field signatures for Mississippi embayment crustal structure at satellite elevations.

  4. A Study of Terrain Reductions, Density Anomalies and Geophysical Inversion Methods in Gravity Field Modelling

    DTIC Science & Technology

    1984-04-01

    Geodesy and Gravity Branch FOR THE COQONDER DONALD H.* ECKHARDT Director Earth Sciences Division This report has been reviewed by the ESD Public Affairs...report was prepared by Rene Forsberg, Geodetic Institute, Denmark, and Research Associate, Department of Geodetic Science and Surveying, The Ohio...Certain computer funds used in this study were supplied by the Instruction and Research Computer Center through the Department of Geodetic Science and

  5. Accurate and Efficient Regularized Inversion Approach for the Interpretation of Isolated Gravity Anomalies

    NASA Astrophysics Data System (ADS)

    Mehanee, Salah A.

    2014-08-01

    A very fast and efficient approach for gravity data inversion based on the regularized conjugate gradient method has been developed. This approach simultaneously inverts for the depth ( z), and the amplitude coefficient ( A) of a buried anomalous body from the gravity data measured along a profile. The developed algorithm fits the observed data by a class of some geometrically simple anomalous bodies, including the semi-infinite vertical cylinder, infinitely long horizontal cylinder, and sphere models using the logarithms of the model parameters [log( z) and log(| A|)] rather than the parameters themselves in its iterative minimization scheme. The presented numerical experiments have shown that the original (non-logarithmed) minimization scheme, which uses the parameters themselves ( z and | A|) instead of their logarithms, encountered a variety of convergence problems. The aforementioned transformation of the objective functional subjected to minimization into the space of logarithms of z and | A| overcomes these convergence problems. The reliability and the applicability of the developed algorithm have been demonstrated on several synthetic data sets with and without noise. It is then successfully and carefully applied to seven real data examples with bodies buried in different complex geologic settings and at various depths inside the earth. The method is shown to be highly applicable for mineral exploration, and for both shallow and deep earth imaging, and is of particular value in cases where the observed gravity data is due to an isolated body embedded in the subsurface.

  6. Structure of the midcontinent basement. Topography, gravity, seismic, and remote sensing

    NASA Technical Reports Server (NTRS)

    Guinness, E. A.; Strebeck, J. W.; Arvidson, R. E.; Scholz, K.; Davies, G. F.

    1981-01-01

    Some 600,000 discrete Bouguer gravity estimates of the continental United States were spatially filtered to produce a continuous tone image. The filtered data were also digitally painted in color coded form onto a shaded relief map. The resultant image is a colored shaded relief map where the hue and saturation of a given image element is controlled by the value of the Bouguer anomaly. Major structural features (e.g., midcontinent gravity high) are readily discernible in these data, as are a number of subtle and previously unrecognized features. A linear gravity low that is approximately 120 to 150 km wide extends from southeastern Nebraska, at a break in the midcontinent gravity high, through the Ozark Plateau, and across the Mississippi embayment. The low is also aligned with the Lewis and Clark lineament (Montana to Washington), forming a linear feature of approximately 2800 km in length. In southeastern Missouri the gravity low has an amplitude of 30 milligals, a value that is too high to be explained by simple valley fill by sedimentary rocks.

  7. Connected magma plumbing system between Cerro Negro and El Hoyo Complex, Nicaragua revealed by gravity survey

    NASA Astrophysics Data System (ADS)

    MacQueen, Patricia; Zurek, Jeffrey; Williams-Jones, Glyn

    2016-11-01

    Cerro Negro, near León, Nicaragua is a young, relatively small basaltic cinder cone volcano that has been unusually active during its short lifespan. Multiple explosive eruptions have deposited significant amounts of ash on León and the surrounding rural communities. While a number of studies investigate the geochemistry and stress regime of the volcano, subsurface structures have only been studied by diffuse soil gas surveys. These studies have raised several questions as to the proper classification of Cerro Negro and its relation to neighboring volcanic features. To address these questions, we collected 119 gravity measurements around Cerro Negro volcano in an attempt to delineate deep structures at the volcano. The resulting complete Bouguer anomaly map revealed local positive gravity anomalies (wavelength 0.5 to 2 km, magnitude +4 mGal) and regional positive (10 km wavelength, magnitudes +10 and +8 mGal) and negative (12 and 6 km wavelength, magnitudes -18 and -13 mGal) Bouguer anomalies. Further analysis of these gravity data through inversion has revealed both local and regional density anomalies that we interpret as intrusive complexes at Cerro Negro and in the Nicaraguan Volcanic Arc. The local density anomalies at Cerro Negro have a density of 2700 kg m-3 (basalt) and are located between -250 and -2000 m above sea level. The distribution of recovered density anomalies suggests that eruptions at Cerro Negro may be tapping an interconnected magma plumbing system beneath El Hoyo, Cerro La Mula, and Cerro Negro, and more than seven other proximal volcanic features, implying that Cerro Negro should be considered the newest cone of a Cerro Negro-El Hoyo volcanic complex.

  8. On Different Techniques for the Calculation of Bougher Gravity Anomalies for Joint Inversion of Geophysical Data in the Rio Grande Rift

    NASA Astrophysics Data System (ADS)

    Zamora, A.; Hussein, M. J.; Velasco, A. A.

    2012-12-01

    Density variations in the Earth result from different material properties, which reflect the tectonic processess attributed to a region. Density variations can be identified through measurable material properties, such as seismic velocities, gravity field, magnetic field, etc. Gravity anomaly inversions are particularly sensitive to density variations but suffer from significant non-uniqueness. However, using inverse models with gravity Bougher anomalies and other geophysical data, we can determine three dimensional structural and geological properties of the given area. We explore different techniques for the calculation of Bougher gravity anomalies for their use in joint inversion of multiple geophysical data sets. Various 2- and 3-Dimensional (3-D) gravity profile forward modeling programs have been developed as variations of existing algorithms; these variations have similarities, differences, and strengths and weaknesses. The purpose of this study is to determine the most effective gravity forward modeling method that can be used to combine the information provided by complementary datasets, such as gravity and seismic information, to improve the accuracy and resolution of Earth models obtained for the underlying structure of the Rio Grande Rift. In an effort to determine the most appropriate method to use in a joint inversion algorithm and a data fusion approach currently in development, we test each approach by using a model of the Rio Grande Rift obtained from seismic surface wave dispersion and receiver functions. We find that there are different uncertainties associated with each methodology that affect the accuracy achieved by including gravity profile forward modeling. Moreover, there exists a bigger margin of error associated to the 2-D methods due to the simplification of calculations that do not take into account the 3-D characteristics of the Earth's structure.

  9. Geophysical investigations on the gravity and aeromagnetic anomalies of the region between Sapanca and Duzce, along the North Anatolian Fault, Turkey

    NASA Astrophysics Data System (ADS)

    Tigli, Cigdem Sendur; Ates, Abdullah; Aydemir, Attila

    2012-12-01

    In this paper, it is aimed to model subsurface structures to the east of the Gulf of Izmit through Duzce by using the gravity and aeromagnetic anomaly data. 1/500.000 scaled gravity anomaly map of the area was taken from the General Directorate of Mineral Research and Exploration (MTA) and it was digitized. The aeromagnetic anomaly data were obtained in the digital form. 3D and 2D models were constructed to reveal the subsurface structure in two different inset regions in the study area including most important negative and positive gravity anomalies. Seismic velocities obtained from the deep seismic recordings were converted to densities. In addition, density information from a previous research was also taken. These densities were used for construction of 3D and 2D gravity models where it was shown that there are narrow and long sedimentary basins and depressions with 0.5-3 km depths. These sedimentary basins with the shape of negative flower structures indicating pull-apart basins are controlled by the active fault segments of the North Anatolian Fault (NAF). Earthquake epicenter data were also correlated with the constructed models from the gravity anomalies. Positive gravity anomalies are also caused by very shallow (about 2 km) masses that are accepted as the crustal origin intrusions into the fractures of the NAF and, ophiolites and gabbro outcropping on the surface of the studied regions. These intrusives and remnants of the Tethys Ocean are located between the fault segments where the fault bifurcates and they also constitute barriers for straight extension of the NAF. Analytic signal method was applied to the aeromagnetic anomaly data to determine the locations and boundaries of the causative bodies. Those bodies are observed around Duzce, and to the E-SE of it, to the NW of Golyaka and a large mass between Adapazari and Sapanca. Shallow settlement of these magmatics was confirmed by the second vertical derivative of the aeromagnetic data. An anti

  10. Preliminary isostatic residual gravity anomaly map of Paso Robles 30 x 60 minute quadrangle, California

    USGS Publications Warehouse

    McPhee, D.K.; Langenheim, V.E.; Watt, J.T.

    2011-01-01

    This isostatic residual gravity map is part of an effort to map the three-dimensional distribution of rocks in the central California Coast Ranges and will serve as a basis for modeling the shape of basins and for determining the location and geometry of faults within the Paso Robles quadrangle. Local spatial variations in the Earth\\'s gravity field, after accounting for variations caused by elevation, terrain, and deep crustal structure reflect the distribution of densities in the mid- to upper crust. Densities often can be related to rock type, and abrupt spatial changes in density commonly mark lithological or structural boundaries. High-density rocks exposed within the central Coast Ranges include Mesozoic granitic rocks (exposed northwest of Paso Robles), Jurassic to Cretaceous marine strata of the Great Valley Sequence (exposed primarily northeast of the San Andreas fault), and Mesozoic sedimentary and volcanic rocks of the Franciscan Complex [exposed in the Santa Lucia Range and northeast of the San Andreas fault (SAF) near Parkfield, California]. Alluvial sediments and Tertiary sedimentary rocks are characterized by low densities; however, with increasing depth of burial and age, the densities of these rocks may become indistinguishable from those of older basement rocks.

  11. Lithosphere mechanical behavior inferred from tidal gravity anomalies: a comparison of Africa and South America

    NASA Astrophysics Data System (ADS)

    Mantovani, Marta S. M.; Shukowsky, Wladimir; de Freitas, Silvio R. C.; Brito Neves, Benjamim B.

    2005-02-01

    Earlier studies have shown that the amplitude difference of the M2 gravity tidal component (TGA) between the measured and calculated response for a viscoelastic Earth is significantly correlated to the effective elastic thickness (Te) of the lithosphere. Using a regression equation obtained from a global distribution, data from TGA were integrated with those obtained by other methods (gravity-topography coherence and thermo-mechanical analysis) providing a spatial coverage sufficient to establish regional Te patterns for South America and Africa. A comparison and association between the Te distributions for both continents indicates that for the African plate, the effective elastic thickness map clearly shows a remarkable dichotomy of the Neoproterozoic rocks and reworked older rocks. But for the case of South American plate that is moving faster than the African plate, lower Te values are observed only for areas where extensive tectonics with intense volcanism has acted, suggesting that a colder mantle underlies this continental plate, while a hotter asthenosphere is observed beneath the African plate. This is in part attributed to its relatively slow motion which prevented dissipating the earlier developed high temperature.

  12. Improved global prediction of 300 nautical mile mean free air anomalies

    NASA Technical Reports Server (NTRS)

    Cruz, J. Y.

    1982-01-01

    Current procedures used for the global prediction of 300nm mean anomalies starting from known values of 1 deg by 1 deg mean anomalies yield unreasonable prediction results when applied to 300nm blocks which have a rapidly varying gravity anomaly field and which contain relatively few observed 60nm blocks. Improvement of overall 300nm anomaly prediction is first achieved by using area-weighted as opposed to unweighted averaging of the 25 generated 60nm mean anomalies inside the 300nm block. Then, improvement of prediction over rough 300nm blocks is realized through the use of fully known 1 deg by 1 deg mean elevations, taking advantage of the correlation that locally exists between 60nm mean anomalies and 60nm mean elevations inside the 300nm block. An improved prediction model which adapts itself to the roughness of the local anomaly field is found to be the model of Least Squares Collocation with systematic parameters, the systematic parameter being the slope b which is a type of Bouguer slope expressing the correlation that locally exists between 60nm mean anomalies and 60nm mean elevations.

  13. Slow-light enhancement of Beer-Lambert-Bouguer absorption

    NASA Astrophysics Data System (ADS)

    Mortensen, Niels Asger; Xiao, Sanshui

    2007-04-01

    The authors theoretically show how slow light in an optofluidic environment facilitates enhanced light-matter interactions, by orders of magnitude. The proposed concept provides strong opportunities for improving existing miniaturized chemical absorbance cells for Beer-Lambert-Bouguer absorption measurements widely employed in analytical chemistry.

  14. Preliminary gravity investigations of the Wahmonie Site, Nevada Test Site, Nye County, Nevada

    SciTech Connect

    Ponce, D.A.

    1981-12-31

    A gravity survey of the southwest corner of the Nevada Test Site was completed during 1979 to 1980 as part of an effort to characterize a possible radioactive waste storage site in granitic rocks. The survey outlined a large, broad, and flat gravity high centered near Wahmonie Site. Combined geophysical data indicate that the anomalous area is underlain by a dense, magnetic, and possibly intrusive body. Gravity data show a +15 milligal Bouguer anomaly coincident with a large positive aeromagnetic anomaly. The data reveal a prominent fault at the west edge of the inferred intrusive. Both gravity and magnetic anomalous highs extend NNE over a horst composed predominantly of rhyodacite of the Tertiary Salyer Formation. Local aeromagnetic highs are closely associated with two granodiorite exposures on the eastern edge of the horst. A local gravity high of about +2 milligal is centered directly over the southern granodiorite exposure and another high is centered over the northern exposure. A steep gravity gradient outlining the gravity high coincides with the outer edge of a zone of hydrothermal alteration which surrounds the horst. The gravity gradient probably marks the approximate limit of an intrusive body.

  15. Isostasy, Stress and Gravitational Potential Energy in the Southern Atlantic - Insights from Satellite Gravity Observations

    NASA Astrophysics Data System (ADS)

    Goetze, H. J.; Klinge, L.; Scheck-Wenderoth, M.; Dressel, I.; Sippel, J.

    2015-12-01

    New satellite gravity fields e.g. EGM2008, GoCo3S and very recently EIGEN-6C4 (Förste et al., 2014) provide high-accuracy and globally uniform information of the Earth's gravity field and partly of its gradients. The main goal of this study is to investigate the impact of this new gravity field and its processed anomalies (Bouguer, Free-air and Vening-Meinesz residual fields) on lithospheric modelling of passive plate margins in the area of the Southern Atlantic. In an area fixed by the latitudes 20° N - 50° S and longitudes 70° W - 20° E we calculated station-complete Bouguer anomalies (bathymetry/topography corrected) both on- and offshore and compared them with the gravity effect of a velocity model which bases on S - waves tomography (Schaeffer and Lebedev, 2013). The corresponding maps provide more insight in the abnormal mass distribution of oceanic lithosphere and the ocean-continent transition zones on both sides of the Atlantic Ocean than Free-air anomalies which are masked by bathymetry. In a next step we calculated isostatic residual fields (Vening-Meinesz isostasy with regard to different lithospheric rigidities) to remove global components (long wavelengths) from the satellite gravity. The Isostatic residual field will be compared with the GPE (gravitational potential energy). GPE variations in the Southern Atlantic, relative to the reference state, were calculated as ΔGPE. Often the oceanic lithosphere is characterized by negative ∆GPE values indicating that the ocean basin is in compression. Differences from this observation will be compared with the state of stress in the area of the passive margins of South America and South Africa and the oceanic lithosphere in between. Schaeffer, A. J. and S. Lebedev, Global shear-speed structure of the upper mantle and transition zone. Geophys. J. Int., 194 (1), 417-449, 2013. doi:10.1093/gji/ggt095

  16. GOCE and Future Gravity Missions for Geothermal Energy Exploitation

    NASA Astrophysics Data System (ADS)

    Pastorutti, Alberto; Braitenberg, Carla; Pivetta, Tommaso; Mariani, Patrizia

    2016-08-01

    Geothermal energy is a valuable renewable energy source the exploitation of which contributes to the worldwide reduction of consumption of fossil fuels oil and gas. The exploitation of geothermal energy is facilitated where the thermal gradient is higher than average leading to increased surface heat flow. Apart from the hydrologic circulation properties which depend on rock fractures and are important due to the heat transportation from the hotter layers to the surface, essential properties that increase the thermal gradient are crustal thinning and radiogenic heat producing rocks. Crustal thickness and rock composition form the link to the exploration with the satellite derived gravity field, because both induce subsurface mass changes that generate observable gravity anomalies. The recognition of gravity as a useful investigation tool for geothermal energy lead to a cooperation with ESA and the International Renewable Energy Agency (IRENA) that included the GOCE derived gravity field in the online geothermal energy investigation tool of the IRENA database. The relation between the gravity field products as the free air gravity anomaly, the Bouguer and isostatic anomalies and the heat flow values is though not straightforward and has not a unique relationship. It is complicated by the fact that it depends on the geodynamical context, on the geologic context and the age of the crustal rocks. Globally the geological context and geodynamical history of an area is known close to everywhere, so that a specific known relationship between gravity and geothermal potential can be applied. In this study we show the results of a systematic analysis of the problem, including some simulations of the key factors. The study relies on the data of GOCE and the resolution and accuracy of this satellite. We also give conclusions on the improved exploration power of a gravity mission with higher spatial resolution and reduced data error, as could be achieved in principle by flying

  17. The alpine Swiss-French airborne gravity survey

    NASA Astrophysics Data System (ADS)

    Verdun, Jérôme; Klingelé, Emile E.; Bayer, Roger; Cocard, Marc; Geiger, Alain; Kahle, Hans-Gert

    2003-01-01

    In February 1998, a regional-scale, airborne gravity survey was carried out over the French Occidental Alps within the framework of the GéoFrance 3-D research program.The survey consisted of 18 NS and 16 EW oriented lines with a spacing of 10 and 20 km respectively, covering the whole of the Western French Alps (total area: 50 000 km2; total distance of lines flown: 10 000 km). The equipment was mounted in a medium-size aircraft (DeHavilland Twin Otter) flowing at a constant altitude of 5100 m a.s.l, and at a mean ground speed of about 280 km h-1. Gravity was measured using a LaCoste & Romberg relative, air/sea gravimeter (type SA) mounted on a laser gyro stabilized platform. Data from 5 GPS antennae located on fuselage and wings and 7 ground-based GPS reference stations were used to determine position and aircraft induced accelerations.The gravimeter passband was derived by comparing the vertical accelerations provided by the gravimeter with those estimated from the GPS positions. This comparison showed that the gravimeter is not sensitive to very short wavelength aircraft accelerations, and therefore a simplified formulation for computing airborne gravity measurements was developed. The intermediate and short wavelength, non-gravitational accelerations were eliminated by means of digital, exponential low-pass filters (cut-off wavelength: 16 km). An important issue in airborne gravimetry is the reliability of the airborne gravity surveys when compared to ground surveys. In our studied area, the differences between the airborne-acquired Bouguer anomaly and the ground upward-continued Bouguer anomaly of the Alps shows a good agreement: the rms of these differences is equal to 7.68 mGal for a spatial resolution of 8 km. However, in some areas with rugged topography, the amplitudes of those differences have a striking correlation with the topography. We then argue that the choice of an appropriate density (reduction by a factor of 10 per cent) for computing the

  18. Seismicity and tectonic relationships of the Nemaha Uplift and Midcontinent geophysical anomaly. Final project summary

    SciTech Connect

    Burchett, R.R.; Luza, K.V.; Van Eck, O.J.; Wilson, F.W.

    1983-02-01

    The geological surveys of Iowa, Nebraska, Kansas, and Oklahoma conducted a 4- to 6-year investigation of the seismicity and tectonic relationships of the Nemaha Uplift and associated geologic features in the Midcontinent. Regional geological, gravity, aeromagnetic, seismological, and topographic information were compiled on 1:1,000,000-scale base maps. The following maps were prepared: (1) relief, (2) earthquake epicenter and station location, (3) lineament, (4) geologic bedrock, (5) structure contour (base of Kansas City Group or older Pennsylvanian rock units), (6) Precambrian configuration, (7) Bouguer gravity anomaly, (8) aeromagnetic, and (9) Precambrian rock type. One correlation between earthquakes and tectonic structures was made. There appears to be recent as well as historical earthquake activity associated with the Humbolt Fault zone, southeastern Nebraska and northeastern Kansas.

  19. Gravity is the Key Experiment to Address the Habitability of the Ocean in Jupiter's Moon Europa

    NASA Astrophysics Data System (ADS)

    Sessa, A. M.; Dombard, A. J.

    2013-12-01

    Life requires three constituents: a liquid solvent (i.e., water), a chemical system that can form large molecules to record genetic information (e.g., carbon based) as well as chemical nutrients (e.g., nitrogen, phosphorous), and a chemical disequilibrium system that can provide metabolic energy. While it is believed that there is a saline water layer located between the rock and ice layers in Jupiter's moon Europa, which would satisfy the first requirement, it is unknown if the other conditions are currently met. The likelihood that Europa is a haven for life in our Solar System skyrockets, however, if there is currently active volcanism at the rock-water interface, much the same that volcanic processes enable the chemosynthetic life that forms the basis of deep sea-vent communities at the bottom of Earth's oceans. Exploring the volcanic activity on this interface is challenging, as direct observation via a submersible or high-resolution indirect observations via a dense global seismic network on the surface is at present technically (and fiscally!) untenable. Thus, gravity studies are the best way to explore currently the structure of this all-important interface. Though mostly a silicate body with only a relatively thin (~100 km) layer of water, Europa is different from the terrestrial planets in that this rock-water interface, and not the surface, represents the largest density contrast across the moon's near-surface layers, and thus topography on this interface could conceivably dominate the gravity. Here, we calculate the potential anomalies that arise from topography on the surface, the water-ice interface (at 20 km depth), and the rock-water interface, finding that the latter dominates the free-air gravity at the longest wavelengths (spherical harmonic degrees < 10) and the Bouguer gravity at intermediate wavelengths (degrees ~10-50), and only for the shortest wavelengths (degrees > 50) does the water-ice interface (and presumably mass-density anomalies

  20. Magnetic investigation and 2½ D gravity profile modelling across the Beattie magnetic anomaly in the southeastern Karoo Basin, South Africa

    NASA Astrophysics Data System (ADS)

    Baiyegunhi, Christopher; Gwavava, Oswald

    2017-02-01

    The southeastern Karoo Basin is considered to be one of the most prospective areas for shale gas exploration in South Africa. An interesting magnetic anomaly, the Beattie magnetic anomaly (BMA), and geologic intrusions are seen on the magnetic map. To date, the source of the BMA and interconnectivity of the igneous intrusions are not well understood. In this study, we investigate the interconnectivity of the igneous intrusions and possible location of the source of the BMA using gravity and magnetic methods. The gravity model results showed that igneous intrusions are interconnected at depth, which probably pose threat by increasing the risk of fracking the Karoo for shale gas exploration. The magnetic results revealed that the BMA becomes stronger with depth. The average depths to the top of the shallow and deep magnetic sources were estimated to be approximately 0.6 and 15 km, respectively.

  1. Gravity anomaly at a Pleistocene lake bed in NW Alaska interpreted by analogy with Greenland's Lake Taserssauq and its floating ice tongue

    USGS Publications Warehouse

    Barnes, D.F.

    1987-01-01

    A possible example of a very deep glacial excavation is provided by a distinctive gravity low located at the front of a valley glacier that once flowed into glacial Lake Aniuk (formerly Lake Noatak) in the western Brooks Range. Geologic and geophysical data suggest that sediments or ice filling a glacially excavated valley are the most probable cause of the 30-50 mGal anomaly. Reasonable choices of geometric models and density contrasts indicate that the former excavation is now filled with a buried-ice thickness of 700 m or sediment thicknesses greater than 1 km. No direct evidence of efficient excavation was observed in Greenland, but efficient glacial erosion behind a floating polar ice tongue could explain the excavation that caused the Alaskan gravity anomaly. -from Author

  2. Gravity survey of marine field: Case study for Silurian reef exploration

    SciTech Connect

    Heigold, P.C.; Whitaker, S.T. )

    1989-08-01

    A gravity survey conducted over and around Marine field in southwestern Illinois has been used as an example to show how measurement of the local gravity field can aid in the search for Silurian reefs in the Illinois basin. Acquisition parameters for gravity surveys over Silurian reefs should be calculated beforehand from simple models of the reef based on estimates of density contrasts, depths, and size. Residual and derivative mapping techniques generally enhance gravity anomalies and enable more accurate portrayals of the structural relief on buried reefs. The second vertical derivative map of the residual Bouguer gravity anomaly surface at Marine field compares very well with the structure of the reef as mapped from subsurface data. This study indicates that similar mapping techniques could be effective on other reefs throughout the Illinois basin. Although gravity mapping methods are potentially powerful exploration tools in themselves, the writers believe that their proper role is as a part of a more comprehensive exploration approach. Gravity surveys can be used effectively as an initial exploration method in reef-prone areas to define smaller, prospect-size areas in which more intensive exploration techniques can subsequently be focused.

  3. MODTOHAFSD — A GUI based JAVA code for gravity analysis of strike limited sedimentary basins by means of growing bodies with exponential density contrast-depth variation: A space domain approach

    NASA Astrophysics Data System (ADS)

    Chakravarthi, V.; Sastry, S. Rajeswara; Ramamma, B.

    2013-07-01

    Based on the principles of modeling and inversion, two interpretation methods are developed in the space domain along with a GUI based JAVA code, MODTOHAFSD, to analyze the gravity anomalies of strike limited sedimentary basins using a prescribed exponential density contrast-depth function. A stack of vertical prisms all having equal widths, but each one possesses its own limited strike length and thickness, describes the structure of a sedimentary basin above the basement complex. The thicknesses of prisms represent the depths to the basement and are the unknown parameters to be estimated from the observed gravity anomalies. Forward modeling is realized in the space domain using a combination of analytical and numerical approaches. The algorithm estimates the initial depths of a sedimentary basin and improves them, iteratively, based on the differences between the observed and modeled gravity anomalies within the specified convergence criteria. The present code, works on Model-View-Controller (MVC) pattern, reads the Bouguer gravity anomalies, constructs/modifies regional gravity background in an interactive approach, estimates residual gravity anomalies and performs automatic modeling or inversion based on user specification for basement topography. Besides generating output in both ASCII and graphical forms, the code displays (i) the changes in the depth structure, (ii) nature of fit between the observed and modeled gravity anomalies, (iii) changes in misfit, and (iv) variation of density contrast with iteration in animated forms. The code is used to analyze both synthetic and real field gravity anomalies. The proposed technique yielded information that is consistent with the assumed parameters in case of synthetic structure and with available drilling depths in case of field example. The advantage of the code is that it can be used to analyze the gravity anomalies of sedimentary basins even when the profile along which the interpretation is intended fails to

  4. Deep structure study of the salt body of Jbel Rheouis (central tunisia) from geological and gravity data

    NASA Astrophysics Data System (ADS)

    Bouzid, Wajih; Abbes, Chedly; Gabtni, Hakim; Hassine, Mouna

    2016-04-01

    Jbel Rheouis situated in south west of Sidi Bouzid, central Tunisia, is a complex structure located at a tectonic node between N-S, NE-SW and NW-SE corridors. It was considered as a diapir containing the most complete series of The Upper Triassic formation in Central Tunisia. The good quality of preserved fossils markers especially at the limestone levels made it possible for Burollet (1952) to propose a lithostratigraphic description of the Rheouis Formation. This stratigraphy was clarified by Soussi and Abbes (2004) basing on new paleontological, palynological and outcrops detailed mapping data. Thus, they assigned the base of this outcrops series to Carnian and its top to Rhaetian. Using these geological and lithostratigraphic data we suspects that the base of the Rheouis formation formed by black limestone can be correlated to the Rehach limestone in the South of Tunisia where this level is laying on a clayey sandstones level identified as the Lower Triassic outcrops. In this concept, this study intend to investigate the Rheouis structure and to identify it's nature basing on the intra salt structures identification and the nature of the Lower Triassic sediments buried beneath the Black limestones, using a combination of geological, lithostratigraphic and geophysical (gravity) data. The gravity data used in this work were obtained from the ONM with a mesh of 1Km /1Km. All the data were merged and reduced using the 1967 International gravity formula. Free air and Bouguer gravity correction were made using sea level as a datum and 2.4 g/cm³ as a reduction density. The Bouguer anomaly map shows a variation in anomaly values range from -12.5 mGal to -4.5 mGal with a contrasted anomaly distribution. This map present 5 gravity maxima and 4 gravity minima where the major direction of those maxima and minima are N-S, NE-SW and NW-SE. The presence of a relative positive anomaly concentrated J.Rheouis can be explained by a mass excess probably due to the uplift of the

  5. OCT structure, COB location and magmatic type of the S Angolan & SE Brazilian margins from integrated quantitative analysis of deep seismic reflection and gravity anomaly data

    NASA Astrophysics Data System (ADS)

    Cowie, Leanne; Kusznir, Nick; Horn, Brian

    2014-05-01

    Integrated quantitative analysis using deep seismic reflection data and gravity inversion have been applied to the S Angolan and SE Brazilian margins to determine OCT structure, COB location and magmatic type. Knowledge of these margin parameters are of critical importance for understanding rifted continental margin formation processes and in evaluating petroleum systems in deep-water frontier oil and gas exploration. The OCT structure, COB location and magmatic type of the S Angolan and SE Brazilian rifted continental margins are much debated; exhumed and serpentinised mantle have been reported at these margins. Gravity anomaly inversion, incorporating a lithosphere thermal gravity anomaly correction, has been used to determine Moho depth, crustal basement thickness and continental lithosphere thinning. Residual Depth Anomaly (RDA) analysis has been used to investigate OCT bathymetric anomalies with respect to expected oceanic bathymetries and subsidence analysis has been used to determine the distribution of continental lithosphere thinning. These techniques have been validated for profiles Lusigal 12 and ISE-01 on the Iberian margin. In addition a joint inversion technique using deep seismic reflection and gravity anomaly data has been applied to the ION-GXT BS1-575 SE Brazil and ION-GXT CS1-2400 S Angola deep seismic reflection lines. The joint inversion method solves for coincident seismic and gravity Moho in the time domain and calculates the lateral variations in crustal basement densities and velocities along the seismic profiles. Gravity inversion, RDA and subsidence analysis along the ION-GXT BS1-575 profile, which crosses the Sao Paulo Plateau and Florianopolis Ridge of the SE Brazilian margin, predict the COB to be located SE of the Florianopolis Ridge. Integrated quantitative analysis shows no evidence for exhumed mantle on this margin profile. The joint inversion technique predicts oceanic crustal thicknesses of between 7 and 8 km thickness with

  6. Gravity field over the Sea of Galilee: Evidence for a composite basin along a transform fault

    USGS Publications Warehouse

    Ben-Avraham, Z.; ten Brink, U.; Bell, R.; Reznikov, M.

    1996-01-01

    The Sea of Galilee (Lake Kinneret) is located at the northern portion of the Kinneret-Bet Shean basin, in the northern Dead Sea transform. Three hundred kilometers of continuous marine gravity data were collected in the lake and integrated with land gravity data to a distance of more than 20 km around the lake. Analyses of the gravity data resulted in a free-air anomaly map, a variable density Bouguer anomaly map, and a horizontal first derivative map of the Bouguer anomaly. These maps, together with gravity models of profiles across the lake and the area south of it, were used to infer the geometry of the basins in this region and the main faults of the transform system. The Sea of Galilee can be divided into two units. The southern half is a pull-apart that extends to the Kinarot Valley, south of the lake, whereas the northern half was formed by rotational opening and transverse normal faults. The deepest part of the basinal area is located well south of the deepest bathymetric depression. This implies that the northeastern part of the lake, where the bathymetry is the deepest, is a young feature that is actively subsiding now. The pull-apart basin is almost symmetrical in the southern part of the lake and in the Kinarot Valley south of the lake. This suggests that the basin here is bounded by strike-slip faults on both sides. The eastern boundary fault extends to the northern part of the lake, while the western fault does not cross the northern part. The main factor controlling the structural complexity of this area is the interaction of the Dead Sea transform with a subperpendicular fault system and rotated blocks.

  7. An analysis of methods for gravity determination and their utilization for the calculation of geopotential numbers in the Slovak national levelling network

    NASA Astrophysics Data System (ADS)

    Majkráková, Miroslava; Papčo, Juraj; Zahorec, Pavol; Droščák, Branislav; Mikuška, Ján; Marušiak, Ivan

    2016-09-01

    The vertical reference system in the Slovak Republic is realized by the National Levelling Network (NLN). The normal heights according to Molodensky have been introduced as reference heights in the NLN in 1957. Since then, the gravity correction, which is necessary to determine the reference heights in the NLN, has been obtained by an interpolation either from the simple or complete Bouguer anomalies. We refer to this method as the "original". Currently, the method based on geopotential numbers is the preferred way to unify the European levelling networks. The core of this article is an analysis of different ways to the gravity determination and their application for the calculation of geopotential numbers at the points of the NLN. The first method is based on the calculation of gravity at levelling points from the interpolated values of the complete Bouguer anomaly using the CBA2G_SK software. The second method is based on the global geopotential model EGM2008 improved by the Residual Terrain Model (RTM) approach. The calculated gravity is used to determine the normal heights according to Molodensky along parts of the levelling lines around the EVRF2007 datum point EH-V. Pitelová (UELN-1905325) and the levelling line of the 2nd order NLN to Kráľova hoľa Mountain (the highest point measured by levelling). The results from our analysis illustrate that the method based on the interpolated value of gravity is a better method for gravity determination when we do not know the measured gravity. It was shown that this method is suitable for the determination of geopotential numbers and reference heights in the Slovak national levelling network at the points in which the gravity is not observed directly. We also demonstrated the necessity of using the precise RTM for the refinement of the results derived solely from the EGM2008.

  8. Gravity fields in eastern Halmahera and the Bonin Arc: Implications for ophiolite origin and emplacement

    NASA Astrophysics Data System (ADS)

    Milsom, John; Hall, Robert; Padmawidjaja, Tatang

    1996-02-01

    Classic ophiolites, as exemplified by the Troodos Massif in Cyprus and the Papuan Ultramafic Belt in eastern New Guinea, are large overthrust masses which are generally associated with large positive gravity anomalies. However, similar rocks occurring in extensive fragmented terranes which have also been described as ophiolitic do not produce large gravity effects. The eastern part of the island of Halmahera, in northeastern Indonesia, is an ophiolite of this latter type. On the two eastern arms of the island, a Mesozoic ophiolitic basement is overlain by, and imbricated with, Upper Cretaceous and Paleogene arc volcanic and sedimentary rocks. Bouguer gravity values are generally in the range +50 to +150 mGal and are characterised by steep local gradients indicative of shallow sources. The Bouguer gravity average suggests that the crust is at least 20 km thick, and it must be even thicker if a significant part of the anomalous gravity field is due to the presence of a cold and therefore dense, lithospheric slab within the asthenosphere, associated with the present-day subduction beneath Halmahera. The absence of any exposures of continental basement rocks or of quartzose sediments in eastern Halmahera suggests that these ophiolites have not been overthrust onto continental crust and that the thickening occurred in an intraoceanic island arc. The Paleogene arc was evidently characterised by volcanism occurring over an unusually wide area. In this it resembles the Izu-Bonin volcanic arc, which, like Halmahera, has been situated at the margin of the Philippine Sea Plate throughout its history. The gravity field of the Halmahera ophiolite is comparable with that of the Bonin volcanic arc, but there is no Halmahera parallel to the very high gravity fields recorded over the Bonin Islands forearc ridge. The equivalents of this part of the Paleogene arc may be represented by the ophiolitic complexes now distributed along the northern margin of the orogenic belt in New

  9. Gravity survey in part of the Snake River Plain, Idaho - a preliminary report

    USGS Publications Warehouse

    Baldwin, Harry L.; Hill, David P.

    1960-01-01

    During the early summer of 1959, a total of 1,187 gravity stations were occupied on the western part of the Snake River plain in Idaho. An area of 2,000 square miles extending from Glenns Ferry, Idaho, to Caldwell, Idaho, was covered with a station density of one station per two square miles. An additional 1,200 square miles of surrounding area, mainly from Caldwell, Idaho, to the Oregon-Idaho state line, was covered with a density of one station per seven square miles. The mean reproducibility of the observed gravities of these stations was 0.05 milligal, with a maximum discrepancy of 0.2 milligal. Gravity data were reduced to simple Bouguer values using a combined free-air and Bouguer correction of 0.06 milligal per foot. The only anomalies found with closure in excess of 10 milligals are two elongated highs, orientated northwest-southeast, with the northwestern high offset to the northeast by 10 miles. The smaller of these highs extends from Meridian, Idaho, to Nyssa, Oregon, and the larger extends from Swan Falls, Idaho, to Glenns Ferry, Idaho. The maximum value recorded is a simple Bouguer value of -66.5 milligals with respect to the International Ellipsoid. Gradients on the sides of these highs are largest on the northeast sides, reaching six milligals per mile in places. Graticule interpretations of a profile across the southeastern high using a density contrast of 0.3 gm per cubic centimeter indicate an accumulation of lava reaching a thickness of at least 28,000 feet. The Snake River investigation was made for the purpose of searching out, defining, and interpreting gravity anomalies present on the western part of the Snake River lava plain in Idaho. In particular, it was desired to further define gradients associated with the gravity high shown by the regional work of Bonini and Lavin (1957). It was not planned to cover any specific area, but rather to let the observed anomalies determine the course of the field work. The study was undertaken as part of a

  10. New fast least-squares algorithm for estimating the best-fitting parameters due to simple geometric-structures from gravity anomalies

    PubMed Central

    Essa, Khalid S.

    2013-01-01

    A new fast least-squares method is developed to estimate the shape factor (q-parameter) of a buried structure using normalized residual anomalies obtained from gravity data. The problem of shape factor estimation is transformed into a problem of finding a solution of a non-linear equation of the form f(q) = 0 by defining the anomaly value at the origin and at different points on the profile (N-value). Procedures are also formulated to estimate the depth (z-parameter) and the amplitude coefficient (A-parameter) of the buried structure. The method is simple and rapid for estimating parameters that produced gravity anomalies. This technique is used for a class of geometrically simple anomalous bodies, including the semi-infinite vertical cylinder, the infinitely long horizontal cylinder, and the sphere. The technique is tested and verified on theoretical models with and without random errors. It is also successfully applied to real data sets from Senegal and India, and the inverted-parameters are in good agreement with the known actual values. PMID:25685472

  11. Evaluation of Gravity and Aeromagnetic Anomalies for the Deep Structure and Possibility of Hydrocarbon Potential of the Region Surrounding Lake Van, Eastern Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Aydemir, Attila; Ates, Abdullah; Bilim, Funda; Buyuksarac, Aydin; Bektas, Ozcan

    2013-11-01

    The North Anatolian Fault (NAF) is not observed on the surface beyond 40 km southeast of Karliova town toward the western shoreline of Lake Van. Various amplitudes of gravity and aeromagnetic anomalies are observed around the lake and surrounding region. In the gravity anomaly map, contour intensity is observed from the north of Mus city center toward Lake Van. There is a possibility that the NAF extends from here to the lake. Because there is no gravity data within the lake, the extension of the NAF is unknown and uncertain in the lake and to the east. Meanwhile, it is observed from the aeromagnetic anomalies that there are several positive and negative amplitude anomalies aligned around a slightly curved line in the east-west direction. The same curvature becomes much clearer in the analytic signal transformation map. The volcanic mountains of Nemrut and Suphan, and magnetic anomalies to the east of the Lake Van are all lined up and extended with this slightly curved line, provoking thoughts that a fault zone that was not previously mapped may exist. The epicenter of the major earthquake event that occurred on October 23, 2011 is located on this fault zone. The fault plane solution of this earthquake indicates a thrust fault in the east-west direction, consistent with the results of this study. Volcanic mountains in this zone are accepted as still being active because of gas seepages from their calderas, and magnetic anomalies are caused by buried causative bodies, probably magmatic intrusions. Because of its magmatic nature, this zone could be a good prospect for geothermal energy exploration. In this study, the basement of the Van Basin was also modelled three-dimensionally (3D) in order to investigate its hydrocarbon potential, because the first oil production in Anatolia was recorded around the Kurzot village in this basin. According to the 3D modelling results, the basin is composed of three different depressions aligned in the N-S direction and many

  12. The Emerson Lake Body: A link between the Landers and Hector Mine earthquakes, southern California, as inferred from gravity and magnetic anomalies

    USGS Publications Warehouse

    Langenheim, V.E.; Jachens, R.C.

    2002-01-01

    Gravity and magnetic data indicate a mafic crustal heterogeneity that lies between the Hector Mine 16 October 1999 (Mw 7.1) and Landers 28 June 1992 (Mw 7.3) epicenters. The aftershocks and ruptures of these two events avoided the interior of the body. Two- and three-dimensional modeling of the potential-field anomalies shows that the source, here named the Emerson Lake body (ELB), extends to a depth of approximately 15 km. The source of the gravity and magnetic anomaly is most likely Jurassic diorite because exposures of these rocks coincide with both gravity and magnetic highs west of Emerson Lake. Seismic tomography also shows higher velocities within the region of the ELB. We propose that the ELB was an important influence on the rupture geometry of the Landers and Hector Mine ruptures and that the ELB may have played a role in transferring of stress from the Landers earthquake to the Hector Mine hypocenter. Seismicity before the Landers earthquake also tended to avoid the ELB, suggesting that the ELB affects how strain is distributed in this part of the Mojave Desert. Thus, faults within the body should have limited rupture sizes and lower seismic hazard than faults bounding or outside this mafic crustal heterogeneity.

  13. GRAIL Gravity Observations of Peak-Ring Basins on the Moon: Implications for Basin Formation

    NASA Astrophysics Data System (ADS)

    Baker, D. M.; Head, J. W.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

    2012-12-01

    Reassessment of the formation of peak-ring basins on the Moon using image and altimetry data from the Lunar Reconnaissance Orbiter has yielded a number of morphometric properties of these basin types that are helping to constrain the processes leading to their formation and the formation of larger multi-ring basins [1,2]. These analyses demonstrate the importance of the volume and depth of impact melting in modifying the interior morphology of large impact craters. At the onset diameter of peak-ring basins, the depth of the basin's melted zone approaches the depth of the transient crater, creating a strengthless interior melt cavity that facilitates gravitational collapse of the transient crater. The melt cavity suppresses central peak formation, and peak rings are formed outward from the melt zone boundary by the interaction of deep-seated rotational faults in the collapsing wall of the transient crater and huge vertical uplifts in the central portions of the basin. The final configuration of the peak-ring basin has a kilometers-thick slab of cooled residual impact melt resting on an uplifted mantle plug with little or no unmelted crustal material. Highly faulted and fractured, dilatant and possibly thickened crust should occur below and outward from the peak ring due to inward and upward translation of collapsed transient crater rim material. As a result of this configuration, the gravity structure should reflect an anomalously high density, uplifted impact melt plus mantle zone spatially confined to within the peak ring. Surrounding this should be a highly fractured, low density zone of possibly thickened crust. Bouguer gravity anomalies derived from Gravity Recovery and Interior Laboratoy (GRAIL) gravity data and Lunar Orbiter Laser Altimeter (LOLA) altimetry data show spatial patterns that are consistent with those predicted by the formation model briefly outlined above. Nearly all 17 peak-ring basins that have been cataloged on the Moon show positive Bouguer

  14. 3-D inversion of gravity data in spherical coordinates with application to the GRAIL data

    NASA Astrophysics Data System (ADS)

    Liang, Qing; Chen, Chao; Li, Yaoguo

    2014-06-01

    Three-dimensional (3-D) inversion of gravity data has been widely used to reconstruct the density distributions of ore bodies, basins, crust, lithosphere, and upper mantle. For global model of 3-D density structures of planetary interior, such as the Earth, the Moon, or Mars, it is necessary to use an inversion algorithm that operates in the spherical coordinates. We develop a 3-D inversion algorithm formulated with specially designed model objective function and radial weighting function in the spherical coordinates. We present regional and global synthetic examples to illustrate the capability of the algorithm. The inverted results show density distribution features consistent with the true models. We also apply the algorithm to a set of lunar Bouguer gravity anomaly derived from the Gravity Recovery and Interior Laboratory (GRAIL) gravity field and obtain a lunar 3-D density distribution. High-density anomalies are clearly identified underlying lunar basins, a wide region of the lateral density heterogeneities that exist beneath the South Pole-Aitken basin are found, and low-density anomalies are distributed beneath the Feldspathic Highlands Terrane on the lunar far-side. The consistency of these results with those obtained independently from other existing methods verifies the newly developed algorithm.

  15. OCT structure, COB location and magmatic type of the SE Brazilian & S Angolan margins from integrated quantitative analysis of deep seismic reflection and gravity anomaly data

    NASA Astrophysics Data System (ADS)

    Cowie, L.; Kusznir, N. J.; Horn, B.

    2013-12-01

    Knowledge of ocean-continent transition (OCT) structure, continent-ocean boundary (COB) location and magmatic type are of critical importance for understanding rifted continental margin formation processes and in evaluating petroleum systems in deep-water frontier oil and gas exploration. The OCT structure, COB location and magmatic type of the SE Brazilian and S Angolan rifted continental margins are much debated; exhumed and serpentinised mantle have been reported at these margins. Integrated quantitative analysis using deep seismic reflection data and gravity inversion have been used to determine OCT structure, COB location and magmatic type for the SE Brazilian and S Angolan margins. Gravity inversion has been used to determine Moho depth, crustal basement thickness and continental lithosphere thinning. Residual Depth Anomaly (RDA) analysis has been used to investigate OCT bathymetric anomalies with respect to expected oceanic bathymetries and subsidence analysis has been used to determine the distribution of continental lithosphere thinning. These techniques have been validated on the Iberian margin for profiles IAM9 and ISE-01. In addition a joint inversion technique using deep seismic reflection and gravity anomaly data has been applied to the ION-GXT BS1-575 SE Brazil and ION-GXT CS1-2400 S Angola. The joint inversion method solves for coincident seismic and gravity Moho in the time domain and calculates the lateral variations in crustal basement densities and velocities along profile. Gravity inversion, RDA and subsidence analysis along the S Angolan ION-GXT CS1-2400 profile has been used to determine OCT structure and COB location. Analysis suggests that exhumed mantle, corresponding to a magma poor margin, is absent beneath the allochthonous salt. The thickness of earliest oceanic crust, derived from gravity and deep seismic reflection data is approximately 7km. The joint inversion predicts crustal basement densities and seismic velocities which are

  16. Gravity anomalies, Quaternary vents, and Quaternary faults in the southern Cascade Range, Oregon and California: Implications for arc and backarc evolution

    USGS Publications Warehouse

    Blakely, R.J.; Christiansen, R.L.; Guffanti, M.; Wells, R.E.; Donnelly-Nolan, J. M.; Muffler, L.J. Patrick; Clynne, M.A.; Smith, James G.

    1997-01-01

    Isostatic residual gravity anomalies in the southern Cascade Range of northern California and southern Oregon are spatially correlated with broad zones of Quaternary magmatism as reflected by the total volume of Quaternary volcanic products, the distribution of Quaternary vents, and the anomalously low teleseismic P wave velocities in the upper 30 km of crust. The orientation of Quaternary faults also appears to be related to gravity anomalies and volcanism in this area, trending generally north-south within the magmatic regions and northwest-southeast as they enter the neighboring amagmatic zones to the north and south. The relationship between gravity anomalies, vent density, and fault orientations may indicate in a broad sense the strength of the middle and upper crust. The southern Cascade Range occupies a transition zone where horizontal stress is transferred from the northwest-southeast dextral shear of the Walker Lane belt to the east-west extension characteristic of the Cascade arc in central Oregon. Faulting along north-south strikes in the volcanically active areas indicates the east-west extensional stresses in thermally weakened crust, whereas northwest faulting between the volcanically active areas reflects the northwest trending, right lateral shear strain of the Walker Lane belt. The segmentation of the arc reflected in Quaternary magmatism may be caused by differential extension behind crustal blocks of the forearc rotating clockwise with respect to North America. In this view the volcanic centers at Mount Shasta, Medicine Lake volcano, and Lassen Peak in northern California are situated along the southern parts of the trailing edges of two distinct segments of the forearc where additional extension is implied by their differential clockwise rotation. U.S. copyright. Published in 1997 by the American Geophysical Union.

  17. Gravity anomalies, Quaternary vents, and Quaternary faults in the southern Cascade Range, Oregon and California: Implications for arc and backarc evolution

    NASA Astrophysics Data System (ADS)

    Blakely, Richard J.; Christiansen, Robert L.; Guffanti, Marianne; Wells, Ray E.; Donnelly-Nolan, Julie M.; Muffler, L. J. Patrick; Clynne, Michael A.; Smith, James G.

    1997-10-01

    Isostatic residual gravity anomalies in the southern Cascade Range of northern California and southern Oregon are spatially correlated with broad zones of Quaternary magmatism as reflected by the total volume of Quaternary volcanic products, the distribution of Quaternary vents, and the anomalously low teleseismic P wave velocities in the upper 30 km of crust. The orientation of Quaternary faults also appears to be related to gravity anomalies and volcanism in this area, trending generally north-south within the magmatic regions and northwest-southeast as they enter the neighboring amagmatic zones to the north and south. The relationship between gravity anomalies, vent density, and fault orientations may indicate in a broad sense the strength of the middle and upper crust. The southern Cascade Range occupies a transition zone where horizontal stress is transferred from the northwest-southeast dextral shear of the Walker Lane belt to the east-west extension characteristic of the Cascade arc in central Oregon. Faulting along north-south strikes in the volcanically active areas indicates the east-west extensional stresses in thermally weakened crust, whereas northwest faulting between the volcanically active areas reflects the northwest trending, right lateral shear strain of the Walker Lane belt. The segmentation of the arc reflected in Quaternary magmatism may be caused by differential extension behind crustal blocks of the forearc rotating clockwise with respect to North America. In this view the volcanic centers at Mount Shasta, Medicine Lake volcano, and Lassen Peak in northern California are situated along the southern parts of the trailing edges of two distinct segments of the forearc where additional extension is implied by their differential clockwise rotation.

  18. Analysis of gravity data in Central Valleys, Oaxaca, southern, Mexico

    NASA Astrophysics Data System (ADS)

    Gonzalez, T.; Ferrusquia, I.

    2015-12-01

    The region known as Central Valleys is located in the state of Oaxaca, southern, Mexico (16.3o- 17.7 o N Lat. and 96 o - 97 o W Long.) In its central portion is settled the capital of the state. There are very few published detailed geological studies.. Geomorphological and geological features, indicates that Central Valleys and surrounding mountains conform a graben structure. Its shape is an inverted Y, centred on Oaxaca City. The study area was covered by a detailed gravity survey with a homogenous distribution of stations. The Bouguer gravity map is dominated by a large gravity low, oriented NW-SE. In order to know the characteristics of anomalies observed gravity, data transformations were used. The use of spectral methods has increased in recent years, especially for the estimation of the depth of the source. Analysis of the gravity data sheds light on the regional depth of the Graben basement and the spatial distribution of the volcanic rocks

  19. Geomodel constructs of the Earth's crust for water continuation of the Korotaikha depression from gravity and magnetic data for revealing promising areas of oil and gas accumulation

    NASA Astrophysics Data System (ADS)

    Litvinova, Tamara; Kudryavtsev, Ivan

    2016-04-01

    The paper considers the results of re-interpretation of geophysical data within the water continuation of the Korotaikha depression. To solve the issue of identifying promising areas of oil and gas accumulation in the region, magnetic and gravity materials were reprocessed: digital maps of potential fields at 1: 500 000 scale were compiled on a frame network of seismic lines (3 lines on land and 3 lines in water area) made by reflection-CDP, density models to a depth of 20 km by solving the direct problem of gravity prospecting in GM-SYS module (Geosoft) in 2D formulation were constructed. Deep reflection-CDP seismic sections specified according to the deep wells were used as starting models. Correctness of the selected density models was controlled by comparing the theoretical curve with the values interpolated on the profile line from the digital model of gravity anomaly (Bouguer, density of the intermediate layer of 2.67 g/cm3). Magnetic modeling was performed using geometry of blocks from the obtained density models to a depth of 20 km and is based on selection of local anomaly sources in the upper section (in the Triassic strata). Blocks of the Precambrian basement were used as sources of regional magnetic anomalies in the considered models. Modeling constructs show the defining role of the topography of terrigenous and carbonate complex boundary within the Paleozoic section as a source of gravity anomalies for the region under study. These findings are confirmed by comparison of gravity and seismic data (maps of local gravity anomalies and structural maps of reflecting horizons) and additionally substantiated by analysis of the nature of local magnetic anomalies distribution. The latter are associated with the Triassic basalt horizons at the top of the terrigenous complex and thus also reflect structures of the sedimentary cover, which are registered independently by gravity data.

  20. Submarine structure of Reunion Island (Indian Ocean) inferred from gravity

    NASA Astrophysics Data System (ADS)

    Gailler, L.; Lénat, J.

    2008-12-01

    La Reunion is a large (diameter: 220 km; height: 7 km), mostly immerged (97%) oceanic volcanic system. New land and marine gravity data are used to study the structure of its submarine part. The gravity models are interpreted jointly with the published geology interpretations and compared with magnetic models. This allows us to derive a new model of the shallow and internal structure of the submarine flanks. Recent cruises have collected high quality gravity, magnetic and multi-beam swath bathymetry data over the submarine flanks of La Réunion and the surrounding oceanic plate. A new Bouguer anomaly map has been computed for a reduction density of 2.67.103 kg m-3. A magnetic anomalies map covering the same area has been also built. Studies based on bathymetric and acoustic data have previously shown the presence of different types of submarine features: a coastal shelf, huge bulges built by debris avalanches and sediment deposits, erosion canyons, volcanic constructions near the coast, isolated seamounts offshore, and elongate volcanic ridges on the Mascarene plate. On the new Bouguer anomaly map, all these features are associated with negative anomalies. They have been modeled using 2 3/4 D modeling techniques. The short wavelength anomalies over the coastal shelf area can be explained by piles of low density layers. This suggests that they are mostly built by hyaloclastites which are generally characterized by lower densities than lava flows. The voluminous debris avalanche deposits which formed the huge Submarine Bulges to the east, north, west, and south of the island have also been modeled as low density formations. Each bulge is modeled with an overall density less than 2.67.103 kg m-3, in order to account for its long wavelength anomaly. Some shorter wavelength features are superimposed on these long wavelength negative anomalies. They probably represent heterogeneities within the bulges. Some shallow ones can be associated with observed surface geological

  1. Importance of the Decompensative Correction of the Gravity Field for Study of the Upper Crust: Application to the Arabian Plate and Surroundings

    NASA Astrophysics Data System (ADS)

    Kaban, Mikhail K.; El Khrepy, Sami; Al-Arifi, Nassir

    2017-01-01

    The isostatic correction represents one of the most useful "geological" reduction methods of the gravity field. With this correction it is possible to remove a significant part of the effect of deep density heterogeneity, which dominates in the Bouguer gravity anomalies. However, even this reduction does not show the full gravity effect of unknown anomalies in the upper crust since their impact is substantially reduced by the isostatic compensation. We analyze a so-called decompensative correction of the isostatic anomalies, which provides a possibility to separate these effects. It was demonstrated that this correction is very significant at the mid-range wavelengths and may exceed 100 m/s2 (mGal), therefore ignoring this effect would lead to wrong conclusions about the upper crust structure. At the same time, the decompensative correction is very sensitive to the compensation depth and effective elastic thickness of the lithosphere. Therefore, these parameters should be properly determined based on other studies. Based on this technique, we estimate the decompensative correction for the Arabian plate and surrounding regions. The amplitude of the decompensative anomalies reaches ±250 m/s2 10-5 (mGal), evidencing for both, large density anomalies of the upper crust (including sediments) and strong isostatic disturbances of the lithosphere. These results improve the knowledge about the crustal structure in the Middle East.

  2. Gravity anomaly across the Yap Trench, Sorol Trough, and southernmost Parece Vela Basin and its implications for the flexural deformation of the lithosphere and regional isostasy

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Lee, S.; Okino, K.; Koizumi, K.

    2005-12-01

    In June 2005, R/V Hakuho-maru (KH05-01-Leg 3) conducted a geological and geophysical survey of the southern tip of the Parece Vela Basin (PVB). The survey also profiled the Yap trench, the Yap arc and back-arc region, and Sorol Trough and collected multibeam bathymetry, gravity and magnetic data. In addition, one multichannel seismic reflection profiling across the Yap trench and two dredge rock samplings in the southwestern PVB were carried out. The shipboard free-air gravity field was measured by ZLS Dynamic Gravity Meter D-004 with calibration ties performed at Ocean Research Institute, University of Tokyo and at Apra Harbor in Guam. The shipboard gravity anomaly data show clear match with those derived from satellite altimetry. Also included in our analysis is the shipboard gravity data previously collected by R/V Onnuri. The Yap trench is unique in that it has a short trench-arc distance (approx. 50 km). This proximity has long been interpreted as feature resulting from a collision of over-thickened Caroline Ridge with the trench. In recent years, however, a new hypothesis has been put forward that such feature can be explained by initiation or rejuvenation of subduction, and that the style of subduction changes between north and south of the Sorol Trough. Our survey also revealed peculiar hook-shaped structures in the southernmost PVB and other evidences for large-scale, complex rotational deformation on the seafloor, whose origin remains unclear at this stage. To better understand the nature of these structures and features across Yap trench, Sorol Trough and in southernmost PVB, we examine the regional isostasy using the recently collected bathymetric and gravity data. The density information is deduced from studies conducted at other subduction systems, including Izu-Bonin Mariana trench, and from our own seismic experiment. Preliminary analysis shows that much of the features may be maintained by the flexural rigidity of the lithosphere, especially near

  3. Imaging of subsurface lineaments in the southwestern part of the Thrace Basin from gravity data

    NASA Astrophysics Data System (ADS)

    Aydogan, D.; Pinar, A.; Elmas, A.; Bal, O. Tarhan; Yuksel, S.

    2013-04-01

    Linear anomalies, as an indicator of the structural features of some geological bodies, are very important for the interpretation of gravity and magnetic data. In this study, an image processing technique known as the Hough transform (HT) algorithm is described for determining invisible boundaries and extensions in gravity anomaly maps. The Hough function implements the Hough transform used to extract straight lines or circles within two-dimensional potential field images. It is defined as image and Hough space. In the Hough domain, this function transforms each nonzero point in the parameter domain to a sinusoid. In the image space, each point in the Hough space is transformed to a straight line or circle. Lineaments are depicted from these straight lines which are transformed in the image domain. An application of the Hough transform to the Bouguer anomaly map of the southwestern part of the Thrace Basin, NW Turkey, shows the effectiveness of the proposed approach. Based on geological data and gravity data, the structural features in the southwestern part of the Thrace Basin are investigated by applying the proposed approach and the Blakely and Simpson method. Lineaments identified by these approaches are generally in good accordance with previously-mapped surface faults.

  4. Structure of the Tucson Basin, Arizona from gravity and aeromagnetic data

    USGS Publications Warehouse

    Rystrom, Victoria Louise

    2003-01-01

    Interpretation of gravity and high-resolution aeromagnetic data reveal the three-dimensional geometry of the Tuscson Basin, Arizona and the lithology of its basement. Limited drill hole and seismic data indicate that the maximum depth to the crystalline basement is approximately 3600 meters and that the sedimentary sequences in the upper ~2000 m of the basin were deposited during the most recent extensional episode that commenced about 13 Ma. The negative density contrasts between these upper Neogene and Quaternary sedimentary sequences and the adjacent country rock produce a Bouguer residual gravity low, whose steep gradients clearly define the lateral extent of the upper ~2000m of the basin. The aeromagnetic maps show large positive anomalies associated with deeply buried, late Cretaceous-early Tertiary and mid-Tertiary igneous rocks at and below the surface of the basin. These magnetic anomalies provide insight into the older (>13 Ma) and deeper structures of the basin. Simultaneous 2.5-dimensional modeling of both gravity and magnetic anomalies constrained by geologic and seismic data delineates the thickness of the basin and the dips of the buried faults that bound the basin. This geologic-based forward modeling approach to using geophysical data is shown to result in more information about the geologic and tectonic history of the basin as well as more accurate depth to basement determinations than using generalized geophysical inversion techniques.

  5. The Wallula fault and tectonic framework of south-central Washington, as interpreted from magnetic and gravity anomalies

    SciTech Connect

    Blakely, Richard J.; Sherrod, Brian; Weaver, Craig; Wells, Ray E.; Rohay, Alan C.

    2013-11-13

    Magnetic and gravity data, collected in south-central Washington near the Yakima Fold and Thrust Belt (YFTB) are used to model upper crustal structure, the extent of the late Columbia River Basalt flow named the Ice Harbor member, the vertical conduits (dikes) that the Ice Harbor erupted from, and whether the dikes are offset or affected by faulting on the Wallula Fault zone.

  6. Integration of magnetic, gravity, and well data in imaging subsurface geology in the Ksar Hirane region (Laghouat, Algeria)

    NASA Astrophysics Data System (ADS)

    Farhi, Walid; Boudella, Ammar; Saibi, Hakim; Bounif, Mohand Ou Abdallah

    2016-12-01

    Gravity and magnetic surveys, comprised of data from 985 gravity stations and 1373 magnetic stations, were recorded in the Ksar Hirane region in Laghouat, Algeria from May-August 2011 to study the poorly understood thickness of the sedimentary rocks and the structure of the basement rocks. The Bouguer anomalies vary from -48 mGal (northwest) to -58 mGal (southeast) and the magnetic intensities from 42,094 nT (northwest) to 42,344 nT (southeast). The constrained two-dimensional (2-D) forward modeling, three-dimensional (3-D) inversion of measured gravity and magnetic datasets helped us highlight the structure of the basement rocks at Ksar Hirane and determine the thickness of the sedimentary cover. Prominent NE-SW-trending geophysical anomalies that affect the study area were revealed by potential field gradient methods and were in agreement with the geological structure trends. The 3-D constrained inversion of magnetic data showed magnetized Precambrian metamorphic basement rock at shallow depths (approximately 3 km) in the southeast region and deeper (>10 km) in the northwestern part of the region, presenting similar results to that of the 2-D forward modeling of gravity and magnetic data. The inverted gravity data explain the structural architecture of the Ksar Hirane area, dissected by NE-SW sub-vertical faults.

  7. Gravity anomalies near the east Pacific rise with wavelengths shorter than 3300 km recovered from GEOS-3/ATS-6 satellite-to-satellite Doppler tracking data

    NASA Technical Reports Server (NTRS)

    Marsh, J. G.; Marsh, B. D.; Conrad, T. D.; Wells, W. T.; Williamson, R. G.

    1977-01-01

    The velocity of the GEOS-3 satellite measured by Doppler as a function of time from the ATS-6 satellite was used to recover gravity anomalies in the region of the East Pacific. The orbit GEOS-3 at an altitude of 840 km was perturbed by spatial changes in Earth's gravitational field. These perturbations were measured via ATS-6 which is in a synchronous orbit at an altitude of about 40,000 km. The range-rate data were reduced using a gravitational field model complete to the 12 degree and order. A simulation of the possible effects causing the remaining range-rate residuals relative to the 12, 12 field shows that in general the dominant effect is the neglect of the higher degree and order coefficients of the gravitational field model.

  8. Main crustal discontinuities of Morocco derived from gravity data

    NASA Astrophysics Data System (ADS)

    Khattach, D.; Houari, M. R.; Corchete, V.; Chourak, M.; El Gout, R.; Ghazala, H.

    2013-08-01

    Sharp linear gradients in maps of potential field data are generally assumed to result from sharp discontinuities or boundaries between rocks having different densities or magnetic susceptibilities and are usually associated with faults or other geological contacts. The computation of the horizontal gradients of the gravity field permits us to localize the limits of such blocks and then the fault locations. The horizontal derivative maxima of the Bouguer anomaly and its upward continuation at several heights show lineaments that could reflect the layout of faults and/or contacts and their dip directions. The application of this method to the Bouguer anomaly map of Morocco (with 19,571 points, using an average crustal density ρ = 2.67 g/cm3) allowed us to perform a multiscale analysis of the gravimetric lineaments of the country. The obtained structural map is consistent with several faults already identified in previous studies, and highlights five new major subsurface faults systems with location and dip: the Saghro fault system; Bou-Arfa Midelt fault system; Sidi Slimane Mezquitem fault; Ksar El Kebir-Chefchaouen fault and the Rifan West Mediterranean fault. In addition, this study suggests a new shape and localization for the Agadir-Oujda trans-Moroccan major fault with a NE-SW direction and 900 km length, subdividing Morocco into two main domains. The results of this study contribute to the improvement of the regional structural map of the north western part of Africa, which is situated within the convergence zone between Africa and Eurasia.

  9. Polyhedral shape model for terrain correction of gravity and gravity gradient data based on an adaptive mesh

    NASA Astrophysics Data System (ADS)

    Guo, Zhikui; Chen, Chao; Tao, Chunhui

    2016-04-01

    Since 2007, there are four China Da yang cruises (CDCs), which have been carried out to investigate polymetallic sulfides in the southwest Indian ridge (SWIR) and have acquired both gravity data and bathymetry data on the corresponding survey lines(Tao et al., 2014). Sandwell et al. (2014) published a new global marine gravity model including the free air gravity data and its first order vertical gradient (Vzz). Gravity data and its gradient can be used to extract unknown density structure information(e.g. crust thickness) under surface of the earth, but they contain all the mass effect under the observation point. Therefore, how to get accurate gravity and its gradient effect of the existing density structure (e.g. terrain) has been a key issue. Using the bathymetry data or ETOPO1 (http://www.ngdc.noaa.gov/mgg/global/global.html) model at a full resolution to calculate the terrain effect could spend too much computation time. We expect to develop an effective method that takes less time but can still yield the desired accuracy. In this study, a constant-density polyhedral model is used to calculate the gravity field and its vertical gradient, which is based on the work of Tsoulis (2012). According to gravity field attenuation with distance and variance of bathymetry, we present an adaptive mesh refinement and coarsening strategies to merge both global topography data and multi-beam bathymetry data. The local coarsening or size of mesh depends on user-defined accuracy and terrain variation (Davis et al., 2011). To depict terrain better, triangular surface element and rectangular surface element are used in fine and coarse mesh respectively. This strategy can also be applied to spherical coordinate in large region and global scale. Finally, we applied this method to calculate Bouguer gravity anomaly (BGA), mantle Bouguer anomaly(MBA) and their vertical gradient in SWIR. Further, we compared the result with previous results in the literature. Both synthetic model

  10. Software Analysis of New Space Gravity Data for Geophysics and Climate Research

    NASA Technical Reports Server (NTRS)

    Deese, Rupert; Ivins, Erik R.; Fielding, Eric J.

    2012-01-01

    Both the Gravity Recovery and Climate Experiment (GRACE) and Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellites are returning rich data for the study of the solid earth, the oceans, and the climate. Current software analysis tools do not provide researchers with the ease and flexibility required to make full use of this data. We evaluate the capabilities and shortcomings of existing software tools including Mathematica, the GOCE User Toolbox, the ICGEM's (International Center for Global Earth Models) web server, and Tesseroids. Using existing tools as necessary, we design and implement software with the capability to produce gridded data and publication quality renderings from raw gravity data. The straight forward software interface marks an improvement over previously existing tools and makes new space gravity data more useful to researchers. Using the software we calculate Bouguer anomalies of the gravity tensor's vertical component in the Gulf of Mexico, Antarctica, and the 2010 Maule earthquake region. These maps identify promising areas of future research.

  11. The Lunar Crustal Thickness from Analysis of the Lunar Prospector Gravity and Clementine Topography Datasets

    NASA Technical Reports Server (NTRS)

    Asmar, S.; Schubert, G.; Konopliv, A.; Moore, W.

    1999-01-01

    The Lunar Prospector spacecraft has mapped the gravity field of the Moon to a level of resolution never achieved before, and a spherical harmonic representation to degree and order 100 is available. When combined with the topography dataset produced by the Clementine mission, the resulting Bouguer anomaly map is interpreted to model the thickness of the lunar crust. Such models are crucial to understanding the lunar thermal history and the formation of geological features such as mascon basins, several more of which have been newly discovered from this dataset. A two-layer planetary model was used to compute the variations of the depth to the lunar Moho. The thickness values ranged from near 0 to 120 km. There is significant agreement with previous work using the Clementine gravitational field data with differences in specific locations such as South Pole-Aitken Basin, for example.

  12. Wisconsin gravity minimum: Solution of a geologic and geophysical puzzle and implications for cratonic evolution

    SciTech Connect

    Allen, D.J.; Hinze, W.J. )

    1992-06-01

    An intense Bouguer gravity anomaly minimum extending across much of Wisconsin cannot be explained by the surface Phanerozoic sedimentary strata, the basement Precambrian geology, or the topography of the region. The most intense ({minus}100 mgal) part of the minimum coincides with the 1.47 Ga anorogenic granitic Wolf River batholith of northeastern Wisconsin. In southern Wisconsin, however, the densities of the Precambrian basement rocks, which are older than the batholith, provide no clue to the origin of the anomaly. The gradients of the minimum indicate that the source of the anomaly is in the upper crust. Furthermore, nearby deep seismic reflection data indicate that lower crustal structures do not significantly contribute to the gravity minimum. Thus, the minimum is appropriately interpreted as originating from the low-density Wolf River batholith that crops out only in northeastern Wisconsin but is buried beneath a veneer of older rocks in the southern and central parts of the state. Gravity modeling suggests that the batholith is at least 10 km thick and encompasses an area of {approximately}50,000 km{sup 2}. This interpretation provides an important clue to the origin of similar negative gravity anomalies of the Phanerozoic strata-covered craton. Also, the presence of this massive granitic body appears to have influenced the evolution of the craton - e.g., by controlling the location of the 1.1 Ga Midcontinent rift system and the Paleozoic Wisconsin arch. The fact that the Wolf River batholith is mostly buried suggests that central Wisconsin has been tectonically stable for the past 1.47 b.y. and that the Precambrian basement has been minimally eroded.

  13. Internal architecture of the Tuxtla volcanic field, Veracruz, Mexico, inferred from gravity and magnetic data

    NASA Astrophysics Data System (ADS)

    Espindola, Juan Manuel; Lopez-Loera, Hector; Mena, Manuel; Zamora-Camacho, Araceli

    2016-09-01

    The Tuxtla Volcanic Field (TVF) is a basaltic volcanic field emerging from the plains of the western margin of the Gulf of Mexico in the Mexican State of Veracruz. Separated by hundreds of kilometers from the Trans-Mexican Volcanic Belt to the NW and the Chiapanecan Volcanic Arc to the SE, it stands detached not only in location but also in the composition of its rocks, which are predominantly alkaline. These characteristics make its origin somewhat puzzling. Furthermore, one of the large volcanoes of the field, San Martin Tuxtla, underwent an eruptive period in historical times (CE 1793). Such volcanic activity conveys particular importance to the study of the TVF from the perspective of volcanology and hazard assessment. Despite the above circumstances, few investigations about its internal structure have been reported. In this work, we present analyses of gravity and aeromagnetic data obtained from different sources. We present the complete Bouguer anomaly of the area and its separation into regional and residual components. The aeromagnetic data were processed to yield the reduction to the pole, the analytic signal, and the upward continuation to complete the interpretation of the gravity analyses. Three-dimensional density models of the regional and residual anomalies were obtained by inversion of the gravity signal adding the response of rectangular prisms at the nodes of a regular grid. We obtained a body with a somewhat flattened top at 16 km below sea level from the inversion of the regional. Three separate slender bodies with tops 6 km deep were obtained from the inversion of the residual. The gravity and magnetic anomalies, as well as the inferred source bodies that produce those geophysical anomalies, lie between the Sontecomapan and Catemaco faults, which are proposed as flower structures associated with an inferred deep-seated fault termed the Veracruz Fault. These fault systems along with magma intrusion at the lower crust are necessary features to

  14. Structure and evolution of the lunar Procellarum region as revealed by GRAIL gravity data.

    PubMed

    Andrews-Hanna, Jeffrey C; Besserer, Jonathan; Head, James W; Howett, Carly J A; Kiefer, Walter S; Lucey, Paul J; McGovern, Patrick J; Melosh, H Jay; Neumann, Gregory A; Phillips, Roger J; Schenk, Paul M; Smith, David E; Solomon, Sean C; Zuber, Maria T

    2014-10-02

    The Procellarum region is a broad area on the nearside of the Moon that is characterized by low elevations, thin crust, and high surface concentrations of the heat-producing elements uranium, thorium, and potassium. The region has been interpreted as an ancient impact basin approximately 3,200 kilometres in diameter, although supporting evidence at the surface would have been largely obscured as a result of the great antiquity and poor preservation of any diagnostic features. Here we use data from the Gravity Recovery and Interior Laboratory (GRAIL) mission to examine the subsurface structure of Procellarum. The Bouguer gravity anomalies and gravity gradients reveal a pattern of narrow linear anomalies that border Procellarum and are interpreted to be the frozen remnants of lava-filled rifts and the underlying feeder dykes that served as the magma plumbing system for much of the nearside mare volcanism. The discontinuous surface structures that were earlier interpreted as remnants of an impact basin rim are shown in GRAIL data to be a part of this continuous set of border structures in a quasi-rectangular pattern with angular intersections, contrary to the expected circular or elliptical shape of an impact basin. The spatial pattern of magmatic-tectonic structures bounding Procellarum is consistent with their formation in response to thermal stresses produced by the differential cooling of the province relative to its surroundings, coupled with magmatic activity driven by the greater-than-average heat flux in the region.

  15. Structure and Evolution of the Lunar Procellarum Region as Revealed by GRAIL Gravity Data

    NASA Technical Reports Server (NTRS)

    Andrews-Hanna, Jeffrey C.; Besserer, Jonathan; Head, James W., III; Howett, Carly J. A.; Kiefer, Walter S.; Lucey, Paul J.; McGovern, Patrick J.; Melosh, H. Jay; Neumann, Gregory A.; Phillips, Roger J.; Schenk, Paul M.; Smith, David E.; Solomon, Sean C.; Zuber, Maria T.

    2014-01-01

    The Procellarum region is a broad area on the nearside of the Moon that is characterized by low elevations, thin crust, and high surface concentrations of the heat-producing elements uranium, thorium, and potassium. The Procellarum region has been interpreted as an ancient impact basin approximately 3200 km in diameter, though supporting evidence at the surface would have been largely obscured as a result of the great antiquity and poor preservation of any diagnostic features. Here we use data from the Gravity Recovery and Interior Laboratory (GRAIL) mission to examine the subsurface structure of Procellarum. The Bouguer gravity anomalies and gravity gradients reveal a pattern of narrow linear anomalies that border the Procellarum region and are interpreted to be the frozen remnants of lava-filled rifts and the underlying feeder dikes that served as the magma plumbing system for much of the nearside mare volcanism. The discontinuous surface structures that were earlier interpreted as remnants of an impact basin rim are shown in GRAIL data to be a part of this continuous set of quasi-rectangular border structures with angular intersections, contrary to the expected circular or elliptical shape of an impact basin. The spatial pattern of magmatic-tectonic structures bounding Procellarum is consistent with their formation in response to thermal stresses produced by the differential cooling of the province relative to its surroundings, coupled with magmatic activity driven by the elevated heat flux in the region.

  16. Magsat equivalent source anomalies over the southeastern United States - Implications for crustal magnetization

    NASA Technical Reports Server (NTRS)

    Ruder, M. E.; Alexander, S. S.

    1986-01-01

    The Magsat crustal anomaly field depicts a previously-unidentified long-wavelength negative anomaly centered over southeastern Georgia. Examination of Magsat ascending and descending passes clearly identifies the anomalous region, despite the high-frequency noise present in the data. Using ancillary seismic, electrical conductivity, Bouguer gravity, and aeromagnetic data, a preliminary model of crustal magnetization for the southern Appalachian region is presented. A lower crust characterized by a pervasive negative magnetization contrast extends from the New York-Alabama lineament southeast to the Fall Line. In southern Georgia and eastern Alabama (coincident with the Brunswick Terrane), the model calls for lower crustal magnetization contrast of -2.4 A/m; northern Georgia and the Carolinas are modeled with contrasts of -1.5 A/m. Large-scale blocks in the upper crust which correspond to the Blue Ridge, Charlotte belt, and Carolina Slate belt, are modeled with magnetization contrasts of -1.2 A/m, 1.2 A/m, and 1.2 A/m respectively. The model accurately reproduces the amplitude of the observed low in the equivalent source Magsat anomaly field calculated at 325 km altitude and is spatially consistent with the 400 km lowpass-filtered aeromagnetic map of the region.

  17. Gravity and thermal models for the twin peaks silicic volcanic center, Southwestern Utah

    SciTech Connect

    Carrier, D.L.; Chapman, D.S.

    1981-11-10

    Gravity, heat flow, and surface geology observations have been used as constraints for a thermal model of a late Tertiary silicic volcanic center at Twin Peaks, Utah. Silicic Volcanism began in the area with the extrusion of the Coyote Hills rhyolite 2.74 +- 0.1 m.y. ago, followed by the Cudahy Mine obsidian, felsite, and volcanoclastics, and finally by a complex sequence of domes and flows that lasted until 2.3 +- 0.1 m.y. ago. Basalt sequence span the time 2.5 to 0.9 m.y. Terrain-corrected Bouguer gravity anomalies at Twin Peaks are shaped by three features of varying characteristic dimensions: (1) a major north-northeast trending --30 mGal gravity trough roughly 40 km wide caused by a thick sequence of Cenozoic sediments in the Black Rock Desert Valley, (2) a local roughly circular -7 mGal gravity low, 26 km across, probably related to an intrusive body in the basement, and (3) a series of narrow positive anomalies up to + 10 mGal produced by the major Twin Peaks volcanic domes. The intrusive bodies have been modeled as three-dimensional vertical cylinders; the total volume of intrusive material is estimated to be about 500 km/sup 3/. Simple models, assuming conductive heat transfer and using geometrical constraints from the gravity results, predict that a negligible thermal anomaly should exist 1 m.y. after emplacement of the intrusion. This prediction is consistent with an average heat flow of 96 mW m/sup -2/ for the area, not significantly different from eastern Basin and Range values elsewhere. Magmatic longevity of this system 2.7 to 2.3 m.y. for silicic volcanism of 2.5 to 0.9 m.y. for basaltic volcanism, does not seem to prolong the cooling of the system substantially beyond that predicted by conductive cooling.

  18. Subsurface structure of the eastern edge of the Zagros basin as inferred from gravity and satellite data

    SciTech Connect

    Bushara, M.N.

    1995-09-01

    A data set of 10,505 points of land gravity measurements from southeast Iran obtained from the Bureau Gravimetrique International, combined with Landsat imagery, was used to investigate crustal and Cenozoic lithospheric structure. Interpretation of the Bouguer anomalies reveals three primary structural features. The Zagros Mountain belt is characterized by a progressive decrease in gravity values from -70 mGal near the Persian Gulf to -160 mGal over the structure zone between the Arabian margin and central Iran crustal blocks. The second feature is marked by a backward-L-shaped pair of anomalies that extends from the eastern peripheries of the Zagros basin and wraps around southern Iranian shores. These 15- to 20-km-deep source anomalies, with amplitudes of as much as 10 mGal, are interpreted as intrabasement intrusions demarcating an ancient rift axis. The shallow (6-8)km east-west-trending anomalies are perhaps interbasement uplifts bordered by reverse faults. The third structure, observed on both gravity and Landsat displays, a north-striking eastward-facing topographic escarpment, has a gravity gradient of 0.85 mGal/km, and is right laterally offset approximately 100 km, and is right laterally offset approximately 100 km by the Zagros main recent fault. A comparison of gravity features with surface structures on Thematic Mapper and Landsat Multi-spectral Scanner imagery indicates that a northeast-trending fault system is the result of post-Miocene pervasive transpressive stress coupled with clockwise rotation of underlying basement blocks following the collision of Arabia and Iran. Accommodation structures such as forced folds and {open_quotes}rabbit-ear{close_quotes} anticlines may develop over and on the flanks of the basement blocks, providing remigration and trapping mechanisms for new oil and gas plays.

  19. Analysis of Marine Gravity Anomalies in the Ulleung Basin (East Sea/Sea of Japan) and Its Implications for the Architecture of Rift-Dominated Backarc Basin

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Mook; Kim, Yoon-Mi

    2016-04-01

    Marginal basins locate between the continent and arc islands often exhibit diverse style of opening, from regions that appear to have formed by well-defined and localized spreading center (manifested by the presence of distinct seafloor magnetic anomaly patterns) to those with less obvious zones of extension and a broad magmatic emplacement most likely in the lower crust. Such difference in the style of back-arc basin formation may lead to marked difference in crustal structure in terms of its overall thickness and spatial variations. The Ulleung Basin, one of three major basins in the East Sea/Sea of Japan, is considered to represent a continental rifting end-member of back-arc opening. Although a great deal of work has been conducted on the sedimentary sections in the last several decades, the deep crustal sections have not been systematically investigated for long time, and thus the structure and characteristics of the crust remain poorly understood. This study examines the marine gravity anomalies of the Ulleung Basin in order to understand the crustal structure using crucial sediment-thickness information. Our analysis shows that the Moho depth in general varies from 16 km at the basin center to 22 km at the margins. However, within the basin center, the inferred thickness of the crust is more or less the same (10-12 km), thus by varying only about 10-20% of the total thickness, contrary to the previous impression. The almost-uniformly-thick crust that is thicker than a normal oceanic crust (~ 7 km) is consistent with previous observations using ocean bottom seismometers and recent deep seismic results from the nearby Yamato Basin. Another important finding is that small residual mantle gravity anomaly highs exist in the northern part of the basin. These highs are aligned in the NNE-SSW direction which correspond to the orientation of the major tectonic structures on the Korean Peninsula, raising the possibility that, though by a small degree, they are a

  20. Gravity Data from the Teboursouk Area ("Diapirs Zone", Northern Tunisia): Characterization of Deep Structures and Updated Tectonic Pattern

    NASA Astrophysics Data System (ADS)

    Hachani, Fatma; Balti, Hadhemi; Kadri, Ali; Gasmi, Mohamed

    2016-04-01

    Located between eastern segments of the Atlas and Tell-Rif oro-genic belts, the "Dome zone" of northern Tunisia is characterized by the juxtaposition of various structures that mainly controlled the long geody-namic history of this part of the south-Tethyan Margin. To better understand the organization and deep extension of these structures, gravity data from the Teboursouk key area are proposed. These data include the plotting of Bouguer anomaly map and related parameters such as vertical and horizontal gradients, upward continuation and Euler solution. Compared to geological and structural maps available, they allow the identification of new deep structures and greater precision regarding the characteristics and organization of known ones; consequently, an updated structural pattern is proposed.

  1. Ice Flow, Isostasy and Gravity Anomaly of the Permanent North Polar H2O Ice Cap of Mars

    NASA Astrophysics Data System (ADS)

    Greve, R.; klemann, V.; Wolf, D.

    2000-08-01

    = rhom = 3380 kg per cubic m, shear modulus of the lithosphere mu1 = 64 GPa, shear modulus of the mantle mum = 145 GPa, viscosity of the mantle 71. = 1021 Pas [3]. The thickness of the lithosphere, HI, which is the most crucial parameter of the lithosphere/mantle system, is varied between 50 and 400 km. The field equations of displacement, stress and gravity are solved in the Hankel-wavenumber, k, and Laplace-frequency, s, domain, where they are simply a system of ordinary differential equations in the remaining vertical coordinate, z, and the results are transformed back to the space-time domain by computing the inverse Laplace and Hankel transformations. Additional information is obtained in the original extended abstract.

  2. Local Lunar Gravity Field Analysis over the South Pole-aitken Basin from SELENE Farside Tracking Data

    NASA Technical Reports Server (NTRS)

    Goossens, Sander Johannes; Ishihara, Yoshiaki; Matsumoto, Koji; Sasaki, Sho

    2012-01-01

    We present a method with which we determined the local lunar gravity field model over the South Pole-Aitken (SPA) basin on the farside of the Moon by estimating adjustments to a global lunar gravity field model using SELENE tracking data. Our adjustments are expressed in localized functions concentrated over the SPA region in a spherical cap with a radius of 45deg centered at (191.1 deg E, 53.2 deg S), and the resolution is equivalent to a 150th degree and order spherical harmonics expansion. The new solution over SPA was used in several applications of geophysical analysis. It shows an increased correlation with high-resolution lunar topography in the frequency band l = 40-70, and admittance values are slightly different and more leveled when compared to other, global gravity field models using the same data. The adjustments expressed in free-air anomalies and differences in Bouguer anomalies between the local solution and the a priori global solution correlate with topographic surface features. The Moho structure beneath the SPA basin is slightly modified in our solution, most notably at the southern rim of the Apollo basin and around the Zeeman crater

  3. Geologic implications of topographic, gravity, and aeromagnetic data in the northern Yukon-Koyukuk province and its borderlands, Alaska

    USGS Publications Warehouse

    Cady, J.W.

    1989-01-01

    The northern Yukon-Koyukuk province is characterized by low elevation and high Bouguer gravity and aeromagnetic anomalies in contrast to the adjacent Brooks Range and Ruby geanticline. Using newly compiled digital topographic, gravity, and aeromagnetic maps, the province is divided into three geophysical domains. The Koyukuk domain, which is nearly equivalent to the Koyukuk lithotectonic terrane, is a horseshoe-shaped area, open to the south, of low topography, high gravity, and high-amplitude magnetic anomalies caused by an intraoceanic magmatic arc. The Angayucham and Kanuti domains are geophysical subdivisions of the Angayucham lithotectonic terrane that occur along the northern and southeastern margins of the Yukon-Koyukuk province, where oceanic rocks have been thrust over continental rocks of the Brooks Range and Ruby geanticline. The modeling supports, but does not prove, the hypothesis that the crust of the Kobuk-Koyukuk basin is 32-35 km thick, consisting of a tectonically thickened section of Cretaceous volcanic and sedimentary rocks and older oceanic crust. -from Author

  4. Complete Bouguer gravity and aeromagnetic maps of the Rattlesnake Roadless Area, Missoula County, Montana

    USGS Publications Warehouse

    Kulik, Dolores M.

    1986-01-01

    The rocks in the study area consist mainly of the Helena Formation and the Missoula Group of the Belt Supergroup (Proterozoic Y).  Rock units of less importance are diabase sills and dikes of probable Proterozoic Z age, Middle Cambrian rocks, and glacial deposits.  Structurally, the study area consists of the Rattlesnake thrust system in the south part and a parautochthonous area broken by vertical faults in the north part.

  5. Improving the terrestial gravity dataset in South-Estonia

    NASA Astrophysics Data System (ADS)

    Oja, T.; Gruno, A.; Bloom, A.; Mäekivi, E.; Ellmann, A.; All, T.; Jürgenson, H.; Michelson, M.

    2009-04-01

    The only available gravity dataset covering the whole of Estonia has been observed from 1949 to 1958. This historic dataset has been used as a main input source for many applications including the geoid determination, the realization of the height system, the geological mapping. However, some recent studies have been indicated remarkable systematic biases in the dataset. For instance, a comparison of modern gravity control points with the historic data revealed unreasonable discrepancies in a large region in South-Estonia. However, the distribution of the gravity control was scarce, which did not allow to fully assess the quality of the historic data in the study area. In 2008 a pilot project was called out as a cooperation between Estonian Land Board, Geological Survey of Estonia, Tallinn University of Technology and Estonian University of Life Sciences to densify the detected problematic area (about 2000 km2) with new and reliable gravity data. Field work was carried out in October and November 2008, whereas GPS RTK and relative Scintrex gravimeter CG5 were used for precise positioning and gravity determinations, respectively. Altogether more than 140 new points were determined along the roads. Despite bad weather conditions and unstable observation base of the gravimeter (mostly on the bank of the road), uncertainty better than ±0.1 mGal (1 mGal = 10-5 m/s2) was estimated from the adjustment of gravimeter's readings. The separate gravity dataset of the Estonian Geological Survey were also incorporated into the gravity database of the project for further analysis. Those data were collected within several geological mapping projects in 1981-2007 and contain the data with uncertainty better than ±0.25 mGal. After the collection of new gravity data, a Kriging with proper variogram modeling was applied to form the Bouguer anomaly grids of the historic and the new datasets. The comparison of the resulting grids revealed biases up to -4 mGal at certain regions

  6. Gravity Data Analysis and Modelling for Basin Sedimen of Eastern Java Blocks

    NASA Astrophysics Data System (ADS)

    Khoirunnia, Luthfia

    2016-11-01

    The study of Eastern Java Basin was conducted by 3D modelling subsurface structure using gravity anomaly. The aims of this research are to describe and 3D modelling basin sedimentary system of Eastern Java Blocks based on gravity anomaly. The modelling construction was performed by inversion technique applying Singular Value Decomposition (SVD) method and Occam optimization. This projection method used equivalent central mass of Dampney with height 5.5 km and error data 1,84 × 10-17. Separation of residual anomaly from the complete Bouguer anomaly on a flat plane was done using the upward continuation. This process uses the principle of low pass filter which passes low frequency. Sedimentary basin appears at a depth of 0.2 km to 1.4 km, is shown by their low anomaly in the area, as well as the visible appearance of basin in 3D modeling shown in figure. The result of inversion with Occam h has an error of 1,2% and the SVD has an error of 11%. Sedimentary basin was dominant in Probolinggo, partially in Besuki and Lumajang. The formation occurs due to tectonic processes where the tectonic evolution of the material without significant lateral shift is called as the otokton models, and accompanied by the formation of the basin that follows the development of the subduction system, which is semi-concentric pattern. Sediments are dominated by volcanic sediment, the result of sedimentation because of volcanism events and types of volcanic sediments pyroclasts generally occur in a process or event explosive volcanic magma degassing

  7. Gravity map of Kalabsha area, northwest of Aswan Lake, and its structural significance

    NASA Astrophysics Data System (ADS)

    Abdelrahman, E. M.; Tealeb, A.; Ahmed, H. A.

    A detailed gravity survey was carried out in one of the seismo-active areas at the northwestern region of the High Dam Lake (Kalabsha area) to study its subsurface structure. In order to understand the seismicity of the area, the establishment of a geodynamic model from geological and geodetic data is of great importance. After a series of adjustments and corrections of the measured gravity data, free-air and Bouguer anomaly maps were constructed for the Kalabsha area, and several interpretation techniques were applied to analyse these anomalies. The results of the analysis indicate that the Kalabsha area is affected by several faults trending mainly E-W and N-S. The active area located west of Gebel Marawa is bounded by a set of faults striking NE-SW, N-S and E-W. The throws of these faults range from 160 to 370 m. The minimum depth to the basement complex is about 200 m and its maximum depth is around 600 m. The thickness of the sedimentary column (Nubia sandstone) in the Kalabsha area decreases due west and increases toward the southern and eastern parts of the area. The results explain the tectonic framework of the area well.

  8. Geologic Interpretation of Gravity Anomalies

    DTIC Science & Technology

    1990-04-19

    called boundary or the Moho surface, on which boundary speed is approximately P km/s. Subcru.,tal layer is named peridotite layer. The names indicated...average density of these layers: granite layer -2.7 g/cm , basalt layer -2.9 g/cm’, peridotite layer -3.3 g/cm’. Seismology shows that in regions of...ultrabasic rocks (serpentinous peridotite , dunite) will lie among the sedimentary or acid igneous rocks and they are usually separated among the latter by low

  9. Relation of Topography to Airborne Gravity in Afghanistan and the Tectonic Implications

    NASA Astrophysics Data System (ADS)

    Jung, W.; Brozena, J. M.; Peters, M. F.

    2012-12-01

    As part of a multi-sensor, multi-disciplinary aerogeophysical survey, the US Naval Research Laboratory collected airborne gravity over most of Afghanistan in 2006 (http://pubs.usgs.gov/of/2008/1089/Afghan_grv.html). The data were measured using a pair of ZLS Corporation air-sea gravimeters 7 km altitude above mean sea level aboard an NP-3D Orion aircraft operated by the US Navy's Scientific Development Squadron One (VXS-1). Aircraft positions were determined from kinematic GPS measurements in the aircraft relative to five base stations using differential interferometric techniques. Track spacing was set to 4 km over much of Afghanistan, but was increased to 8 km in the northern block of the survey area. Aircraft ground speed averaged between 300 and 380 knots, faster than ideal for high resolution gravity, but enabled approximately 113,000-km of data tracks to be flown in 220 flight hours, covering more than 330000 km2. In this presentation, we investigate the implications of the airborne gravity data for the tectonic development history of Afghanistan. Afghanistan is described as comprising three different platforms (Wheeler et al., 2005): 1) the north Afghanistan platform north of the Hari-Rud fault (HRF), a part of the Eurasian plate for 250-350 my; 2) the accreted terranes south of the HRF including low flats, formed as island arcs and fragments of continental and oceanic crust collided with the Eurasian plate during the closure of the Tethys Ocean in the past 250 my; and 3) the transpressional plate in the east, formed as the Indian plate moves northward since Cretaceous. The Bouguer anomaly map reveals elongated negative values along the east-west striking HRF, which seems to manifest different tectonic developmental histories across the boundary. Over the southern flats in the accreted terranes platform, the Bouguer anomaly map appears to show a continuation of alternating southwest-northeast trending highs and lows like those over the northern high

  10. Gravity analyses for the crustal structure and subglacial geology of West Antarctica, particularly beneath Thwaites Glacier

    NASA Astrophysics Data System (ADS)

    Diehl, Theresa Marie

    The West Antarctic Ice Sheet (WAIS) is mostly grounded in broad, deep basins (down to 2.5 km below sea level) that are stretched between five crustal blocks. The geometry of the bedrock, being mostly below sea level, induces a fundamental instability in the WAIS through the possibility of runaway grounding line retreat. The crustal environment of the WAIS further influences the ice sheet's fast flow through conditions at the ice-bedrock boundary. This study focuses on understanding the WAIS by examining the subglacial geology (such as volcanoes and sedimentary basins) at the ice-bedrock boundary and the continent's deeper crustal structure- primarily using airborne gravity anomalies. The keystone of this study is a 2004-2005 aerogeophysical survey over one of the most negative mass balance glaciers on the continent: Thwaites Glacier (TG). The gravity anomalies derived from this dataset- as well as gravity-based modeling and spectral crustal boundary depth estimates- reveal a heterogeneous crustal environment beneath the glacier. The widespread Mesozoic rifting observed in the Ross Sea Embayment (RSE) of West Antarctica extends beneath TG, where the crust is ˜27 km thick and cool. Adjacent to TG, spectrally-derived shallow Moho depths for the Marie Byrd Land (MBL) crustal block can be explained by thermal support from warm mantle. I assemble here new compilations of free-air and Bouguer gravity anomalies across West Antarctica (from both airborne and satellite datasets) and re-interpret the extents of West Antarctic crustal block and their boundaries with the rift system. Airy isostatic gravity anomalies reveal that TG is relatively sediment starved, in contrast to the sediment-rich RSE. TG's fast flow velocities could be sustained in this sediment poor environment if higher heat flux in MBL was providing an ample source of subglacial melt water to the glacier. The isostatic anomalies also indicate that TG's outlet rests on a bedrock sill that will impede future

  11. Lunar Crustal Properties: Insights from the GRAIL Gravity Signatures of Lunar Impact Craters

    NASA Astrophysics Data System (ADS)

    Soderblom, J. M.; Andrews-Hanna, J. C.; Evans, A. J.; Johnson, B. C.; Melosh, J., IV; Milbury, C.; Miljkovic, K.; Nimmo, F.; Phillips, R. J.; Smith, D. E.; Solomon, S. C.; Wieczorek, M. A.; Zuber, M. T.

    2014-12-01

    Impact cratering is a violent process, shattering and melting rock and excavating deep-seated material. The resulting scars are apparent on every planetary surface across our Solar System. Subsurface density variations associated with the resulting impact structures contain clues to aid in unlocking the details of this process. High-resolution gravity fields, such as those derived from the Gravity Recovery and Interior Laboratory (GRAIL) mission, are ideal for investigating these density variations. With gravity measurements from GRAIL and topography from the Lunar Orbiter Laser Altimeter (LOLA), we derived high-resolution Bouguer gravity fields (i.e., the gravity field after the contribution from topography is removed) that we correlated with craters mapped from LOLA data. We found that the mass deficit beneath lunar impact craters relates directly to crater size, up to diameter ~130 km, whereas craters larger than this diameter display no further systematic change. This observation, coupled with the greater depth of impact damage expected beneath larger craters, indicates that some process is affecting the production and/or preservation of porosity at depth or otherwise altering the mean density beneath the larger craters (note, measurable mantle uplift is observed for craters larger than ~184-km diameter). The observed crater gravity anomalies, however, exhibit considerable variation about these mean trends, suggesting that other factors are also important in determining the bulk density of impact crater structures. Milbury et al. (this conference) have demonstrated that pre-impact crustal porosity strongly influences the resulting density contrast between the impact damage zone beneath a crater and its surroundings. Herein, we extend these studies using the same GRAIL- and LOLA-derived maps to further investigate the effects that crustal properties have on the bulk density of the rock beneath lunar impact features. We focus, in particular, on the processes that

  12. A 3D synoptic model of Central America inferred from gravity data interpretation

    NASA Astrophysics Data System (ADS)

    Alvarado, G.; Fairhead, D.; Goetze, H.-J.; Lahrmann, B.; Leandro, G.; Luecke, O.; Schmidt, S.

    2007-12-01

    Large portions of the Central American Isthmus have served as key areas for the collaborative research program (SFB 574) and its goal to understand orogenic processes at convergent margins, such as the volatile and fluid cycle and the relationships between tectonics and magmatism. Gravity data from both on- and offshore has been gathered from various institutions and has been combined in a homogeneous data set. Due to difficult access to the high mountains the coverage by gravity observations remains rather incomplete mainly in the area of southern Costa Rica and eastern Nicaragua. Station complete Bouguer anomalies, Free Air anomalies and isostatic residual anomalies maps were compiled as a result of the homogenization of gravity field data. First analyses of the gravity field using curvature methods helps to separate density provinces in the crust. A comparison with the geological map shows a good correlation with tectonical units in most of the region and provides possibilities for crustal segmentation. Sources of gravity anomalies were investigated by Euler deconvolution and source point clusters in depths of 10 km and 30 km were obtained. For the first time a 3D density model up to the Central American lithosphere has been compiled by combining the results of curvature and Euler analysis with constraining data e.g. geological maps, seismic profiles, earthquake hypocenters and new results from tomographic modeling and receiver function analysis of the seismological task group of the SFB 574. The in-house software package IGMAS was used for modeling visualization of the model structures and gravity effects (e.g. serpentinization of the oceanic lithosphere at the Pacific side); it helps to identify borders between tectonic blocks e.g. the Chortis block in the north or the Chorotega block in the south of the research area. At a more local scale our 3D modeling works hand in hand with a small scale 3D modeling by Lücke and Alvarado and provides insight into the

  13. Generation of a High Resolution Grid of Gravity Anomalies by Inversion of Altimetric Data from GEOSAT, TOPEX/POSEIDON, ERS1/2 and JASON-1 Satellites in the Azores Region

    NASA Astrophysics Data System (ADS)

    Calvão, J.

    2006-07-01

    Stacked data from Geosat, Topex/Poseidon, ERS-1/2 and Jason-1 satellites is used to define a precise reference frame of satellite tracks where data with dense coverage from geodetic missions of Geosat (18 months) and ERS-1 (10 months) is adjusted, allowing a detailed recovery of the marine gravity field. A remove-restore procedure is used to obtain residual sea surface heights by removing the low and high frequencies (the global geopotential model EGM96 is used as reference field and the effects of the topography/bathymetry are computed using the RTM correction with the local accurate bathymetric model AZDTM98 and the global model JGP95E. A validation procedure is applied using least squares collocation, followed by a grid generation of residual geoid undulations, that is inverted using an efficient method based on Fast Fourier Transform to obtain residual gravity anomalies. After adding the contributions to the gravity field from the global model and from the topography/bathymetry, the results are compared with adjusted gravity data obtained from gravimetric surveys.

  14. Incipient mantle delamination, active tectonics and crustal thickening in Northern Morocco: Insights from gravity data and numerical modeling

    NASA Astrophysics Data System (ADS)

    Baratin, Laura-May; Mazzotti, Stéphane; Chéry, Jean; Vernant, Philippe; Tahayt, Abdelilah; Mourabit, Taoufik

    2016-11-01

    The Betic-Rif orocline surrounding the Alboran Sea, the westernmost tip of the Mediterranean Sea, accommodates the NW-SE convergence between the Nubia and Eurasia plates. Recent GPS observations indicate a ∼4 mm/yr SW motion of the Rif Mountains, relative to stable Nubia, incompatible with a simple two-plate model. New gravity data acquired in this study define a pronounced negative Bouguer anomaly south of the Rif, interpreted as a ∼40 km-thick crust in a state of non-isostatic equilibrium. We study the correlation between these present-day kinematic and geodynamic processes using a finite-element code to model in 2-D the first-order behavior of a lithosphere affected by a downward normal traction (representing the pull of a high-density body in the upper mantle). We show that intermediate viscosities for the lower crust and uppermost mantle (1021-1022Pas) allow an efficient coupling between the mantle and the base of the brittle crust, thus enabling (1) the conversion of vertical movement, resulting from the downward traction, to horizontal movement and (2) shortening in the brittle upper crust. Our results show that incipient delamination of the Nubian continental lithosphere, linked to slab pull, can explain the present-day abnormal tectonics, contribute to the gravity anomaly observed in northern Morocco, and give insight into recent tectonics in the Western Mediterranean region.

  15. Gravity and Magnetic Survey of the Oaxaca-Juarez Terrane Boundary (Oaxaca Fault), Southern Mexico: Evidence for three Half Grabens

    NASA Astrophysics Data System (ADS)

    Campos-Enriquez, J. O.; Belmonte-Jimenez, S. I.; Ortega-Gutierrez, F.; Keppie-Moorhouse, J. D.; Martinez-Silva, J.; Martinez-Serrano, R.

    2007-05-01

    A geophysical survey of the Oaxaca Fault boundary between the Oaxaca (Oaxaquia) (Zapoteco) and Juarez (Cuicateco) terranes along the Etla and Zaachila valleys area, southern Mexico shows a series of NW-SE Bouguer and magnetic anomalies with stronger gradients towards the east. The basement from the Oaxaca terrane has a high density (2.8 gr/cm3 ) and magnetic susceptibility of up to 0.0051 cgs units, which contrast with the Juarez basement that has a lower density (2.67 gr/cm3) and a higher magnetic susceptibility (values ranging between 0.0025 to 0.0045 cgs units). The magnetic susceptibility is similar south of the Donaji fault. Interpretation of six combined gravity and magnetic NE-SW profiles perpendicular to the valleys indicates the presence of a composite depression comprising three N-S sub-basins with the Etla and Zachila sub-basins located at the northern and southern portions, respectively, separated by a third sub-basin relatively displaced westwards. They are bounded on the east by the steeply W-dipping Oaxaca master fault, and on the west by the gently E-dipping Huitzo-Zimatlan fault. Two interpretations are suggested for the southward continuation of the Oaxaca Fault: 1) it continues southwards at depth with the same strike. Together the Bouguer and total field magnetic anomalies suggest that the Oaxaca fault is continuous from Etla via Oaxaca City and Ocotlán de Morelos probably to Miahuatlán de Porfirio Díaz, and 2) it continues with the same strike but is displaced eastwards ~20 km along a sinistral transfer fault, which forms the northern boundary of the Zaachila sub-basin.

  16. Analysis of gravity and topography in the GLIMPSE study region: Isostatic compensation and uplift of the Sojourn and Hotu Matua Ridge systems

    USGS Publications Warehouse

    Harmon, N.; Forsyth, D.W.; Scheirer, D.S.

    2006-01-01

    The Gravity Lieations Intraplate Melting Petrologic and Seismic Expedition (GLIMPSE) Experiment investigated the formation of a series of non-hot spot, intraplate volcanic ridges in the South Pacific and their relationship to cross-grain gravity lineaments detected by satellite altimetry. Using shipboard gravity measurements and a simple model of surface loading of a thin elastic plate, we estimate effective elastic thicknesses ranging from ???2 km beneath the Sojourn Ridge to a maximum of 10 km beneath the Southern Cross Seamount. These elastic thicknesses are lower than predicted for the 3-9 Ma seafloor on which the volcanoes lie, perhaps due to reheating and thinning of the plate during emplacement. Anomalously low apparent densities estimated for the Matua and Southern Cross seamounts 2050 and 2250 kg m-3, respectively, probably are artifacts caused by the assumption of only surface loading, ignoring the presence of subsurface loading in the form of underplated crust and/or low-density mantle. Using satellite free-air gravity and shipboard bathymetry, we calculate the age-detrended, residual mantle Bouguer anomaly (rMBA). The rMBA corrects the free-air anomaly for the direct effects of topography, including the thickening of the crust beneath the seamounts and volcanic ridges due to surface loading of the volcanic edifices. There are broad, negative rMBA anomalies along the Sojourn and Brown ridges and the Hotu Matua seamount chain that extend nearly to the East Pacific Rise. These negative rMBA anomalies connect to negative free-air anomalies in the western part of the study area that have been recognized previously as the beginnings of the cross-grain gravity lineaments. Subtracting the topographic effects of surface loading by the ridges and seamounts from the observed topography reveals that the ridges are built on broad bands of anomalously elevated seafloor. This swell topography and the negative rMBA anomalies contradict the predictions of lithospheric

  17. 3D Gravity Field Modelling of the Lithosphere along the Dead Sea Transform (DESERT 2002)

    NASA Astrophysics Data System (ADS)

    Götze, H.-J.; Ebbing, J.; Schmidt, S.; Rykakov, M.; Hassouneh, M.; Hrahsha, M.; El-Kelani, R.; Desert Group

    2003-04-01

    From March to May 2002 a gravity field campaign has to be conducted in the area of Dead Sea Rift/Dead Sea Transform with regard to the isostatic state, the crustal density structure of the transform and the lithospheric rigidity in the Central Arava Valley (Jordan). Our multi-national and interdisciplinary gravity group with participants from the Geophysical Institute of Israel, the Natural Resources Authority (Jordan), and the An-Najah National University (Palestine), takes part in the interdisciplinary and international DESERT program which is coordinated by the GeoForschungsZentrum (GFZ, Potsdam, Germany). The study area is located about 100 km away from both the basin of the Dead Sea and the Gulf of Elat/Aqaba basin, respectively. Between March and May 2002 some 800 new gravity observations were recorded at a local scale in the Arava valley and at regional scale along the DESERT seismic line. Station spacing in the area of the Arava valley was 100 - 300 m and in the nearest neighbourhood of the fault 50 m only. The survey of detailed observations covered an area of 10 by 10 km and was completed by a likewise dense survey at the western side of the valley in Israel. All gravity data were tied to the IGSN -71 gravity datum and are terrain-corrected as well. The station complete Bouguer gravity field, Free air anomaly and residual isostatic anomalies (based on both Airy and Vening-Meinesz models) were merged with the existing regional gravity data bases of the region. Constraining information for the 3D density models came from recent geophysical field data acquisition and consist of seismic, seismological, electromagnetic studies, and geological mapping which represent the integrated part of the interdisciplinary research program. Novel methods e.g. curvature techniques, and Euler deconvolution of the gravity fields shed new insight into the structure of upper and lower crust and the causing density domains. In particular the "dip-curvature" reveal a clear course

  18. Gravity Field Analysis and 3D Density Modeling of the Lithosphere Along the Dead Sea Transform

    NASA Astrophysics Data System (ADS)

    Goetze, H.; Ebbing, J.; Hese, F.; Kollersberger, T.; Schmidt, S.; Rybakov, M.; Hassouneh, M.; Hrahsha, M.; El Kelani, R.

    2002-12-01

    The gravity field of Dead Sea Rift / Dead Sea Transform was investigated with regard to the isostatic state, the crustal density structure of the orogeny and the rigidity of the lithosphere in the Central Arava Valley. Our multi-national and interdisciplinary gravity group with participants from the Geophysical Institute of Israel, the Natural Resources Authority (Jordan), and the An-Najah National University (Palestine), is aiming to study the crustal density structure, the isostatic state of the lithosphere and mechanical properties of the Dead Sea Rift system under the framework of the international DESERT program which is coordinated by the GeoForschungsZentrum (GFZ, Potsdam, Germany). The study area is located about 100 km away from both the basin of the Dead Sea and the Gulf of Elat/Aqaba basin, respectively. Between March and May 2002 some 800 new gravity observations were recorded at a local (Arava valley) and regional scale (along the DESERT seismic line). Station spacing in the Arava valley was 100 - 300 m and in the nearest neighborhood of the fault 50 m only. The survey of detailed observations covered an area of 10 by 10 km and was completed by a likewise dense survey at the western side of the valley in Israel. All gravity data were tied to the IGSN -71 gravity datum and are terrain-corrected as well. The station complete Bouguer gravity field, Free air anomaly and residual isostatic anomalies (based on both Airy and Vening-Meinesz models) were merged with the existing regional gravity data bases of the region. Constraining information for the 3D density models at regional and local came from recent geophysical field data acquisition and consist of seismic, seismological, electromagnetic, and geologic studies which represent the integrated part of the interdisciplinary research program. Novel methods e.g. curvature techniques, and Euler deconvolution of the gravity fields shed new insight into the structure of upper and lower crust and the causing

  19. Structure of the Hat Creek graben region: Implications for the structure of the Hat Creek graben and transfer of right-lateral shear from the Walker Lane north of Lassen Peak, northern California, from gravity and magnetic anomalies

    USGS Publications Warehouse

    Langenheim, Victoria; Jachens, Robert C.; Clynne, Michael A.; Muffler, L. J. Patrick

    2016-01-01

    Interpretation of magnetic and new gravity data provides constraints on the geometry of the Hat Creek Fault, the amount of right-lateral offset in the area between Mt. Shasta and Lassen Peak, and confirmation of the influence of pre-existing structure on Quaternary faulting. Neogene volcanic rocks coincide with short-wavelength magnetic anomalies of both normal and reversed polarity, whereas a markedly smoother magnetic field occurs over the Klamath Mountains and its Paleogene cover. Although the magnetic field over the Neogene volcanic rocks is complex, the Hat Creek Fault, which is one of the most prominent normal faults in the region and forms the eastern margin of the Hat Creek Valley, is marked by the eastern edge of a north-trending magnetic and gravity high 20-30 km long. Modeling of these anomalies indicates that the fault is a steeply dipping (~75-85°) structure. The spatial relationship of the fault as modeled by the potential-field data, the youngest strand of the fault, and relocated seismicity suggests that deformation continues to step westward across the valley, consistent with a component of right-lateral slip in an extensional environment. Filtered aeromagnetic data highlight a concealed magnetic body of Mesozoic or older age north of Hat Creek Valley. The body’s northwest margin strikes northeast and is linear over a distance of ~40 km. Within the resolution of the aeromagnetic data (1-2 km), we discern no right-lateral offset of this body. Furthermore, Quaternary faults change strike or appear to end, as if to avoid this concealed magnetic body and to pass along its southeast edge, suggesting that pre-existing crustal structure influenced younger faulting, as previously proposed based on gravity data.

  20. Investigating subglacial landscapes and crustal structure of the Gamburtsev Province in East Antarctica with the aid of new airborne gravity data

    NASA Astrophysics Data System (ADS)

    Jordan, T. A.; Ferraccioli, F.; Studinger, M.; Bell, R. E.; Damaske, D.; Elieff, S.; Finn, C.; Braaten, D. A.; Corr, H.

    2009-12-01

    The AGAP project was undertaken as part of the 2008\\09 field season and explored the Gamburtsev Subglacial Mountains (GSM) province in East Antarctica. AGAP collected >120, 000 line km of new airborne radar, aerogravity and aeromagnetic data. Here we focus on the airborne gravity part of the survey. The airborne gravity data were collected from two Twin Otters operating from remote field camps either side of Dome A. A high-resolution Sander Geophysics AIRGrav system was used for the first time in Antarctica and was mounted in the US plane. A more traditional L&R airborne gravity meter modified by ZLS was installed on the British Antarctic Survey aircraft. The AIRGrav system was flown in draped mode, which proved ideal for the simultaneous acquisition of radar and magnetic data, while the L&R system required flying along constant elevation survey blocks. The processed free-air gravity anomalies exhibit low cross-over errors of 1 mGal over the southern sector of the GSM, where the AIRGrav system was primarily used, and a spatial resolution of 3.5 km. Larger cross-over errors of 3.5 mGal and a coarser spatial resolution of 8 km characterise the northern part of the GSM and the adjacent Lambert Glacier, where the L&R meter was mainly flown. The merged free-air gravity anomaly grid primarily reflects the subglacial topography of the GSM province. The contrast between the Pensacola-Pole and Lambert Glacier basins and the rugged alpine-type relief of the GSM is clearly imaged. A dentritic system of subglacial valleys is mapped in the GSM, in good agreement with independent radar data. Inversion of the free-air gravity data assists in tracing the bedrock under several km-thick and fast-flowing crevassed ice of the Lambert Glacier. Using the ice thickness and bedrock topography data derived from airborne radar we compiled a new Bouguer anomaly map for the GSM province. The new gravity anomaly data can be used to estimate crustal thickness variations under the GSM and

  1. High-Precise Gravity Observations at Archaeological Sites: How We Can Improve the Interpretation Effectiveness and Reliability?

    NASA Astrophysics Data System (ADS)

    Eppelbaum, Lev

    2015-04-01

    the Lesser Caucasus (western Azerbaijan) under conditions of rugged relief and complex geology. This deposit is well investigated by mining and drilling operations and therefore was used as a reference field polygon for testing this approach. A special scheme for obtaining the Bouguer anomalies has been employed to suppress the terrain relief effects dampening the anomaly effects from the objects of prospecting. The scheme is based on calculating the difference between the free-air anomaly and the gravity field determined from a 3D model of a uniform medium with a real topography. 3-D terrain relief model with an interval of its description of 80 km (the investigated 6 profiles of 800 m length are in the center of this interval) was employed to compute (by the use of GSFC software (Khesin et al., 1996)) the gravitational effect of the medium (σ = 2670 kg/m3). With applying such a scheme the Bouguer anomalies were obtained with accuracy in two times higher than that of TC received by the conventional methods. As a result, on the basis of the improved Bouguer gravity with the precise TC data, the geological structure of the deposit was defined (Khesin et al., 1996). Second approach Second approach was employed at the complex Katekh pyrite-polymetallic deposit, which is located at the southern slope of the Greater Caucasus (northern Azerbaijan). The main peculiarities of this area are very rugged topography of SW-NE trend, complex geology and severe tectonics. Despite the availability of conventional ΔgB (TC far zones were computed up to 200 km), for the enhanced calculation of surrounding terrain topography a digital terrain relief model was created (Eppelbaum and Khesin, 2004). The SW-NE regional topography trend in the area of the Katekh deposit occurrence was computed as a rectangular digital terrain relief model (DTRM) of 20 km long and 600 m wide (our interpretation profile with a length of 800 m was located in the geometrical center of the DTRM). As a whole

  2. Optimal Estimation of a High Degree Gravity Field from a Global Set of 1 deg x 1 deg Anomalies to Degree and Order 250.

    DTIC Science & Technology

    1984-08-01

    anomaly blocks was based on empirical relation derived from a Montecarlo approach (Colombo, 1981, p. 78, (3.10): [Ens [N10 (((-16.19570 (-E) + 30.34506) (-E...40.29588) *) 2(2.41) The Montecarlo experiments are described in Colombo (1981, Sec. 3.1) and the sampling error computations were performed as

  3. Basin-fill Aquifer Modeling with Terrestrial Gravity: Assessing Static Offsets in Bulk Datasets using MATLAB; Case Study of Bridgeport, CA

    NASA Astrophysics Data System (ADS)

    Mlawsky, E. T.; Louie, J. N.; Pohll, G.; Carlson, C. W.; Blakely, R. J.

    2015-12-01

    Understanding the potential availability of water resources in Eastern California aquifers is of critical importance to making water management policy decisions and determining best-use practices for California, as well as for downstream use in Nevada. Hydrologic well log data can provide valuable information on aquifer capacity, but is often proprietarily inaccessible or economically unfeasible to obtain in sufficient quantity. In the case of basin-fill aquifers, it is possible to make estimates of aquifer geometry and volume using geophysical surveys of gravity, constrained by additional geophysical and geological observations. We use terrestrial gravity data to model depth-to-basement about the Bridgeport, CA basin for application in preserving the Walker Lake biome. In constructing the model, we assess several hundred gravity observations, existing and newly collected. We regard these datasets as "bulk," as the data are compiled from multiple sources. Inconsistencies among datasets can result in "static offsets," or artificial bull's-eye contours, within the gradient. Amending suspect offsets requires the attention of the modeler; picking these offsets by hand can be a time-consuming process when modeling large-scale basin features. We develop a MATLAB script for interpolating the residual Bouguer anomaly about the basin using sparse observation points, and leveling offset points with a user-defined sensitivity. The script is also capable of plotting gravity profiles between any two endpoints within the map extent. The resulting anomaly map provides an efficient means of locating and removing static offsets in the data, while also providing a fast visual representation of a bulk dataset. Additionally, we obtain gridded basin gravity models with an open-source alternative to proprietary modeling tools.

  4. Bouguer images of the North American craton and its structural evolution

    NASA Technical Reports Server (NTRS)

    Arvidson, R. E.; Bowring, S.; Eddy, M.; Guinness, E.; Leff, C.; Bindschadler, D.

    1984-01-01

    Digital image processing techniques have been used to generate Bouguer images of the North American craton that diplay more of the granularity inherent in the data as compared with existing contour maps. A dominant NW-SE linear trend of highs and lows can be seen extending from South Dakota, through Nebraska, and into Missouri. The structural trend cuts across the major Precambrian boundary in Missouri, separating younger granites and rhyolites from older sheared granites and gneisses. This trend is probably related to features created during an early and perhaps initial episode of crustal assembly by collisional processes. The younger granitic materials are probably a thin cover over an older crust.

  5. Effective photons in weakly absorptive dielectric media and the Beer-Lambert-Bouguer law

    NASA Astrophysics Data System (ADS)

    Judge, A. C.; Brownless, J. S.; Bhat, N. A. R.; Sipe, J. E.; Steel, M. J.; de Sterke, C. Martijn

    2014-04-01

    We derive effective photon modes that facilitate an intuitive and convenient picture of photon dynamics in a structured Kramers-Kronig dielectric in the limit of weak absorption. Each mode is associated with a mode field distribution that includes the effects of both material and structural dispersion, and an effective line-width that determines the temporal decay rate of the photon. These results are then applied to obtain an expression for the Beer-Lambert-Bouguer law absorption coefficient for unidirectional propagation in structured media consisting of dispersive, weakly absorptive dielectric materials.

  6. Gravity data inversion for the lithospheric density structure beneath North China Craton from EGM 2008 model

    NASA Astrophysics Data System (ADS)

    Li, Yuanyuan; Yang, Yushan

    2011-11-01

    The density structures of the crust and upper mantle beneath the North China Craton (NCC) are reconstructed in this paper by using the Bouguer gravity anomaly derived from EGM08 model. The Occam's inversion method and preconditioned conjugate gradient (PCG) are adopted in our paper for solving the 3D density inversion problems. Then the depth weighted function is incorporated into model parameters to avoid the skin effects in inversion. In our study, the Bouguer gravity anomaly derived from EGM08 model is used to study the crust and upper mantle structures beneath the NCC. For reducing the non-uniqueness of our inversion problem, we use the inverted density distribution from 0.5° × 0.5° P-wave tomographic results as our initial model. Finally, the high-resolution 3D density model is established down to 250 km depth for the first time in this region. The density images at eight representative layers (10, 25, 40, 60, 80, 120, 160, 200 km) and eight vertical cross-sections (linear profiles along latitude 35°, 36°, 37°, 38°, 39°, 40°, longitude 108°, 119°) are displayed and compared with the P-wave velocity tomographic images. The 3D-dimensional density model indicates that lateral heterogeneities are widely distributed in different units within the NCC, while their density patterns and depth extensions are significantly different for three main units of NCC, suggesting different tectonic mechanisms that have dominated the evolution of these regions in the Phanerozoic. In particular, our inverted density images demonstrate that the Phanerozoic lithospheric reactivation and thinning may not have influenced the central and western NCC to the same extent as the eastern NCC, most of which preserves relatively thick cratonic lithosphere today. However, localized lithospheric thinning may exist in the circular-Ordos rift systems, whose ancient tectonic belts around the Ordos plateau may have been affected by multi-phase tectonic events in its long evolution

  7. Interpretation of gravity data in a complex volcano-tectonic setting, southwestern Nevada

    NASA Astrophysics Data System (ADS)

    Snyder, David B.; Carr, W. J.

    1984-11-01

    This regional gravity study, based on an irregular 2-km data grid, was conducted during the past few years at Yucca Mountain, southern Nye County, Nevada, as part of a program to locate a suitable repository for high-level nuclear waste. About 100 surface rock samples, three borehole gamma-gamma logs, and one borehole gravity study provide excellent density control. A nearly linear increase in density of 0.26 g/cm3 per kilometer of depth is indicated in the thick tuff sequences that underlie the mountain. Isostatic and 2.0-g/cm3 Bouguer corrections were applied to the observed gravity values to remove regional gradients and topographic effects, respectively. The Bare Mountain gravity high, with an isostatic anomaly maximum of 48 mGal, is connected with a greater gravity high over the Funeral Mountains, to the southwest; together, these highs result from a continuous block of dense, metamorphosed Precambrian and Paleozoic rocks that stretches across much of the Walker Lane from the east edge of Death Valley to Bare Mountain. The Calico Hills gravity high appears more likely to originate from a northeast trending buried ridge of Paleozoic rocks that extends southwestward beneath Busted Butte, 5 km southeast of the proposed repository, where two- and three-dimensional modeling indicates that the pre-Cenozoic rocks lie less than 1000 m beneath the surface. Tuff, at least 4000 m thick, fills a large steep-sided depression in the pretuff rocks beneath Yucca Mountain and Crater Flat. The gravity low and the thick tuff section lie within a large collapse area that includes the Crater Flat-Timber Mountain-Silent Canyon caldera complexes. Gravity lows in Crater Flat itself are interpreted to coincide with the source areas of the Prow Pass Member, the Bullfrog Member, and the Tram Member of the Crater Flat Tuff; these source areas add nearly 350 km2 to the previously recognized extent of the local caldera complexes. Southward extension of the broad gravity low associated with

  8. On the link between particle size and deviations from the Beer-Lambert-Bouguer law for direct transmission

    NASA Astrophysics Data System (ADS)

    Larsen, Michael L.; Clark, Aaron S.

    2014-01-01

    Ballistic photon models of radiative transfer in discrete absorbing random media have demonstrated deviations from the Beer-Lambert-Bouguer law of exponential attenuation. A number of theoretical constructs to quantify the deviation from the Beer-Lambert-Bouguer law have appeared in the literature, several of which rely principally on a statistical measure related to the statistics of the absorber spatial positions alone. Here, we utilize a simple computational model to explore the interplay between the geometric size of the absorbing obstacles and the statistics governing the placement of the absorbers in the volume. We find that a description of the volume that depends on particle size and the spatial statistics of absorbers is not sufficient to fully characterize deviations from the Beer-Lambert-Bouguer law. Implications for future further theoretical and computational explorations of the problem are explored.

  9. Three-dimensional crustal structure of the southern Sierra Nevada from seismic fan profiles and gravity modeling

    USGS Publications Warehouse

    Fliedner, M.M.; Ruppert, S.; Malin, P.E.; Park, S.K.; Jiracek, G.; Phinney, R.A.; Saleeby, J.B.; Wernicke, B.; Clayton, R.; Keller, Rebecca Hylton; Miller, K.; Jones, C.; Luetgert, J.H.; Mooney, W.D.; Oliver, H.; Klemperer, S.L.; Thompson, G.A.

    1996-01-01

    Traveltime data from the 1993 Southern Sierra Nevada Continental Dynamics seismic refraction experiment reveal low crustal velocities in the southern Sierra Nevada and Basin and Range province of California (6.0 to 6.6 km/s), as well as low upper mantle velocities (7.6 to 7.8 km/s). The crust thickens from southeast to northwest along the axis of the Sierra Nevada from 27 km in the Mojave Desert to 43 km near Fresno, California. A crustal welt is present beneath the Sierra Nevada, but the deepest Moho is found under the western slopes, not beneath the highest topography. A density model directly derived from the crustal velocity model but with constant mantle density satisfies the pronounced negative Bouguer anomaly associated with the Sierra Nevada, but shows large discrepancies of >50 mgal in the Great Valley and in the Basin and Range province. Matching the observed gravity with anomalies in the crust alone is not possible with geologically reasonable densities; we require a contribution from the upper mantle, either by lateral density variations or by a thinning of the lithosphere under the Sierra Nevada and the Basin and Range province. Such a model is consistent with the interpretation that the uplift of the present Sierra Nevada is caused and dynamically supported by asthenospheric upwelling or lithospheric thinning under the Basin and Range province and eastern Sierra Nevada.

  10. Three-dimensional crustal structure of the southern Sierra Nevada from seismic fan profiles and gravity modeling

    SciTech Connect

    Fliedner, M.M.; Ruppert, S.; Park, S.K.; and others.

    1996-04-01

    Traveltime data from the 1993 Southern Sierra Nevada Continental Dynamics seismic refraction experiment reveal low velocities in the southern Sierra Nevada and Basin and Range province of California (6.0 to 6.6 km/s), as well as low upper mantle velocities (7.6 to 7.8 km/s). The crust thickens from southeast to northwest along the axis of the Sierra Nevada from 27 km in the Mojave Desert to 43 km near Fresno, California. A crustal welt is present beneath the Sierra Nevada, but the deepest Moho is found under the western slopes, not beneath the highest topography. A density model directly derived from the crustal velocity model but with constant mantle density satisfies the pronounced negative Bouguer anomaly associated with the Sierra Nevada, but shows large discrepancies of >50 mgal in the Great Valley and in the Basin and Range province. Matching the observed gravity with anomalies in the crust alone is not possible with geologically reasonable densities; we require a contribution from the upper mantle, either by lateral density variations or by a thinning of the lithosphere under the Sierra Nevada and the Basin and Range province. Such a model is consistent with the interpretation that the uplift of the present Sierra Nevada is caused and dynamically supported by asthenospheric upwelling or lithospheric thinning under the Basin and Range province and eastern Sierra Nevada. 20 refs., 4 figs.

  11. (abstract) Venus Gravity Field

    NASA Technical Reports Server (NTRS)

    Konopliv, A. S.; Sjogren, W. L.

    1995-01-01

    A global gravity field model of Venus to degree and order 75 (5772 spherical harmonic coefficients) has been estimated from Doppler radio tracking of the orbiting spacecraft Pioneer Venus Orbiter (1979-1992) and Magellan (1990-1994). After the successful aerobraking of Magellan, a near circular polar orbit was attained and relatively uniform gravity field resolution (approximately 200 km) was obtained with formal uncertainties of a few milligals. Detailed gravity for several highland features are displayed as gravity contours overlaying colored topography. The positive correlation of typography with gravity is very high being unlike that of the Earth, Moon, and Mars. The amplitudes are Earth-like, but have significantly different gravity-topography ratios for different features. Global gravity, geoid, and isostatic anomaly maps as well as the admittance function are displayed.

  12. Ocean gravity and geoid determination

    NASA Technical Reports Server (NTRS)

    Kahn, W. D.; Siry, J. W.; Brown, R. D.; Wells, W. T.

    1977-01-01

    Gravity anomalies have been recovered in the North Atlantic and the Indian Ocean regions. Comparisons of 63 2 deg x 2 deg mean free air gravity anomalies recovered in the North Atlantic area and 24 5 deg x 5 deg mean free air gravity anomalies in the Indian Ocean area with surface gravimetric measurements have shown agreement to + or - 8 mgals for both solutions. Geoids derived from the altimeter solutions are consistent with altimetric sea surface height data to within the precision of the data, about + or - 2 meters.

  13. A 3-D gravity model for a volcanic crater in Terceira Island (Azores)

    NASA Astrophysics Data System (ADS)

    Montesinos, F. G.; Camacho, A. G.; Nunes, J. C.; Oliveira, C. S.; Vieira, R.

    2003-08-01

    The seismic response of the São Sebastião volcanic crater, located at the SE end of Terceira Island (Azores), is characterized by an amplification of ground movements inside the crater with respect to the surrounding area. This variability of ground motion is also observed inside the volcanic depression itself. To gain insight into this phenomenon, a gravimetric survey with dense coverage of the region where the depression is located was carried out. Data corrections, including the calculation of terrain density by the Nettleton method and filtering of non-correlated anomalies (noise) by least-squares prediction, led to a Bouguer anomaly map with a standard deviation of 0.213 mGal. The analysis of this map and its interpretation is carried out by means of a stabilized non-linear inversion methodology resulting in a 3-D model of density contrasts, which identifies the geometry of the causative sources in the area. The gravity inversion outlines a correlation between the presence of scoria cones eruptive centres and the zones of negative density contrast in the calculated model. At São Sebastião village, another important structure with negative density contrast is located in places where a more destructive and strong anomalous behaviour has been observed during several seismic events. Furthermore, the gravity inversion seems to confirm a collapse model for São Sebastião crater and to indicate the presence of a deep conduit system compatible with the fissural nature of the volcanism in this area.

  14. Holonomy anomalies

    SciTech Connect

    Bagger, J.; Nemeschansky, D.; Yankielowicz, S.

    1985-05-01

    A new type of anomaly is discussed that afflicts certain non-linear sigma models with fermions. This anomaly is similar to the ordinary gauge and gravitational anomalies since it reflects a topological obstruction to the reparametrization invariance of the quantum effective action. Nonlinear sigma models are constructed based on homogeneous spaces G/H. Anomalies arising when the fermions are chiral are shown to be cancelled sometimes by Chern-Simons terms. Nonlinear sigma models are considered based on general Riemannian manifolds. 9 refs. (LEW)

  15. Correction to the Beer-Lambert-Bouguer law for optical absorption.

    PubMed

    Abitan, Haim; Bohr, Henrik; Buchhave, Preben

    2008-10-10

    The Beer-Lambert-Bouguer absorption law, known as Beer's law for absorption in an optical medium, is precise only at power densities lower than a few kW. At higher power densities this law fails because it neglects the processes of stimulated emission and spontaneous emission. In previous models that considered those processes, an analytical expression for the absorption law could not be obtained. We show here that by utilizing the Lambert W-function, the two-level energy rate equation model is solved analytically, and this leads into a general absorption law that is exact because it accounts for absorption as well as stimulated and spontaneous emission. The general absorption law reduces to Beer's law at low power densities. A criterion for its application is given along with experimental examples.

  16. The Bouguer-Lambert-Beer Absorption Law and Non-Planar Geometries

    NASA Astrophysics Data System (ADS)

    Sinko, John E.; Oh, Benjamin I.

    2011-11-01

    The familiar Bouguer-Lambert-Beer absorption law, often called Beer's law, is an essential component of many laser ablation propulsion models. However, its treatment in non-planar conditions requires a consideration of irradiation geometry. Forms of the absorption law are derived for cylindrical and spherical normal incidence geometries, and for conical nozzles with flat and cylindrical targets. The results indicate that use of a concentrating nozzle optic with a transparent target could provide increased impulse generation for laser propulsion. This improvement would be accomplished using a combination of chosen optics and a transparent target material to generate highly confined ablation in-volume. The surface fluence and ablation depth on a cylindrical target in a parabolic optical nozzle is also derived, and the results are compared to literature raytracing model results and profilometry data, respectively.

  17. Preliminary appraisal of gravity and magnetic data of Syncline Ridge, western Yucca Flat, Nevada Test Site, Nye County, Nevada

    USGS Publications Warehouse

    Ponce, David A.; Hanna, William F.

    1982-01-01

    A gravity and magnetic study of the Syncline Ridge area was conducted as part of an investigation of argillite rocks of the Eleana Formation under consideration as a medium for the possible storage of high-level radioactive waste. Bouguer gravity anomaly data, viewed in light of densities obtained by gamma-gamma logs and previous work of D. L. Healey (1968), delineate two regions of steep negative gradient where Cenozoic rocks and sediments are inferred to abruptly thicken: (1) the western third of the study area where Tertiary volcanic rocks are extensively exposed and (2) the northeast corner of the area where Quaternary alluvium is exposed and where volcanic rocks are inferred to occur at depth. In the remainder of the area, a region extending contiguously from Mine Mountain northwestward through Syncline Ridge to the Eleana Range, the gravity data indicate that the Eleana Formation, where not exposed, is buried at depths of less than about 200 m, except in a limited area of exposed older Paleozoic rocks on Mine Mountain. Quaternary alluvium and Tertiary volcanic rocks are inferred to occur in this region as veneers or shallow dishes of deposit on Tippipah Limestone or Eleana Formation. Low-level aeromagnetic anomaly data, covering the western two-thirds of the study area, delineate relatively magnetic tuff units within the Tertiary volcanic rocks and provide a very attractive means for distinguishing units of normal polarization from units of reversed polarization. If used in conjunction with results of previous magnetization studies of G. D. Bath (1968), the low-level survey may prove to be an effective tool for mapping specific tuff members in the volcanic terrane. The important question of the feasibility of discriminating high-quartz argillite from low-quartz argillite of the Eleana Formation using surface gravity data remains unresolved. If the more highly competent, denser, high-quartz phase should occur as stratigraphic units many tens of meters thick

  18. Bangui Anomaly

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.

    2004-01-01

    Bangui anomaly is the name given to one of the Earth s largest crustal magnetic anomalies and the largest over the African continent. It covers two-thirds of the Central African Republic and therefore the name derives from the capitol city-Bangui that is also near the center of this feature. From surface magnetic survey data Godivier and Le Donche (1962) were the first to describe this anomaly. Subsequently high-altitude world magnetic surveying by the U.S. Naval Oceanographic Office (Project Magnet) recorded a greater than 1000 nT dipolar, peak-to-trough anomaly with the major portion being negative (figure 1). Satellite observations (Cosmos 49) were first reported in 1964, these revealed a 40nT anomaly at 350 km altitude. Subsequently the higher altitude (417-499km) POGO (Polar Orbiting Geomagnetic Observatory) satellite data recorded peak-to-trough anomalies of 20 nT these data were added to Cosmos 49 measurements by Regan et al. (1975) for a regional satellite altitude map. In October 1979, with the launch of Magsat, a satellite designed to measure crustal magnetic anomalies, a more uniform satellite altitude magnetic map was obtained. These data, computed at 375 km altitude recorded a -22 nT anomaly (figure 2). This elliptically shaped anomaly is approximately 760 by 1000 km and is centered at 6%, 18%. The Bangui anomaly is composed of three segments; there are two positive anomalies lobes north and south of a large central negative field. This displays the classic pattern of a magnetic anomalous body being magnetized by induction in a zero inclination field. This is not surprising since the magnetic equator passes near the center of this body.

  19. Reliability of CHAMP Anomaly Continuations

    NASA Technical Reports Server (NTRS)

    vonFrese, Ralph R. B.; Kim, Hyung Rae; Taylor, Patrick T.; Asgharzadeh, Mohammad F.

    2003-01-01

    CHAMP is recording state-of-the-art magnetic and gravity field observations at altitudes ranging over roughly 300 - 550 km. However, anomaly continuation is severely limited by the non-uniqueness of the process and satellite anomaly errors. Indeed, our numerical anomaly simulations from satellite to airborne altitudes show that effective downward continuations of the CHAMP data are restricted to within approximately 50 km of the observation altitudes while upward continuations can be effective over a somewhat larger altitude range. The great unreliability of downward continuation requires that the satellite geopotential observations must be analyzed at satellite altitudes if the anomaly details are to be exploited most fully. Given current anomaly error levels, joint inversion of satellite and near- surface anomalies is the best approach for implementing satellite geopotential observations for subsurface studies. We demonstrate the power of this approach using a crustal model constrained by joint inversions of near-surface and satellite magnetic and gravity observations for Maude Rise, Antarctica, in the southwestern Indian Ocean. Our modeling suggests that the dominant satellite altitude magnetic anomalies are produced by crustal thickness variations and remanent magnetization of the normal polarity Cretaceous Quiet Zone.

  20. Gravity survey and regional geology of the Prince William Sound epicentral region, Alaska: Chapter C in The Alaska earthquake, March 27, 1964: regional effects

    USGS Publications Warehouse

    Case, J.E.; Barnes, D.F.; Plafker, George; Robbins, S.L.

    1966-01-01

    Sedimentary and volcanic rocks of Mesozoic and early Tertiary age form a roughly arcuate pattern in and around Prince William Sound, the epicentral region of the Alaska earthquake of 1964. These rocks include the Valdez Group, a predominantly slate and graywacke sequence of Jurassic and Cretaceous age, and the Orca Group, a younger sequence of early Tertiary age. The Orca consists of a lower unit of dense-average 2.87 g per cm3 (grams per cubic centimeter) pillow basalt and greenstone intercalated with sedimentary rocks and an upper unit of lithologically variable sandstone interbedded with siltstone or argillite. Densities of the clastic rocks in both the Valdez and Orca Groups average about 2.69 g per cm3. Granitic rocks of relatively low density (2.62 g per cm3) cut the Valdez and Orca Groups at several localities. Both the Valdez and the Orca Groups were complexly folded and extensively faulted during at least three major episodes of deformation: an early period of Cretaceous or early Tertiary orogeny, a second orogeny that probably culminated in late Eocene or early Oligocene time and was accompanied or closely followed by emplacement of granitic batholiths, and a third episode of deformation that began in late Cenozoic time and continued intermittently to the present. About 500 gravity stations were established in the Prince William Sound region in conjunction with postearthquake geologic investigations. Simple Bouguer anomaly contours trend approximately parallel to the arcuate geologic structure around the sound. Bouguer anomalies decrease northward from +40 mgal (milligals) at the southwestern end of Montague Island to -70 mgal at College and Harriman Fiords. Most of this change may be interpreted as a regional gradient caused by thickening of the continental crust. Superimposed on the gradient is a prominent gravity high of as much as 65 mgal that extends from Elrington Island on the southwest, across Knight and Glacier Islands to the Ellamar Peninsula

  1. Gravity Data Analysis and Forward Modelling Along the Chilean Margin at 36-42\\deg S

    NASA Astrophysics Data System (ADS)

    Tasarova, Z.; Goetze, H.; Schmidt, S.

    2004-12-01

    The Chilean margin between 36 and 42\\deg S is the subject of new geological and geophysical research. The information about this area come from comprehensive gravity database, field geological observations, seismic reflection profiles (amphibious wide-angle seismic experiment across the subduction zone) at 36-38\\deg S, and the integrated active and passive seismological experiment ISSA 2000 at 36-39\\deg S, including also the receiver function study and the local earthquake tomography model. Based on these constraining data, the 3D density model has been developed within the framework of the German Collaborative Research Center 267 "Deformation Processes in the Andes" (SFB 267, task group F4). The convergent Andean margin, which is subject to some of the earth largest earthquakes, shows pronounced along-strike changes in the tectonic setting, deformation history and its morphological expression. The study area is characterized by much lower (on average less than 2000 meters) and narrower Main Cordillera than in the Central Andes (15-33\\deg S), as well as by a thinner crust. The central part of the study region is the site of the large 1960 Valdivia earthquake, which occurred onshore the transition between the oceanic lithosphere generated at two different spreading centers. This region shows no gravity high, whereas a positive Bouguer gravity anomaly is an omnipresent feature along most of the coastline south of 10\\deg S. The gravity data, combined under agreements from the oil industry data and other sources, as well as the own measurements, were reprocessed and show clearly a local scale segmentation of the region under study. The results of the forward density modelling show that the position of the Nazca plate and changes in its geometry controls the gravity field. Shallower oceanic plate below the forearc region at 36-39\\deg S vs. deeper slab south of 39\\deg S might also have its impact on the plate coupling between the subducting and overriding plates

  2. Gravity Fields of the Moon Derived from GRAIL Primary and Extended Mission Data (Invited)

    NASA Astrophysics Data System (ADS)

    Lemoine, F. G.; Goossens, S. J.; Sabaka, T. J.; Nicholas, J. B.; Mazarico, E.; Rowlands, D. D.; Loomis, B.; Chinn, D. S.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

    2013-12-01

    The Gravity Recovery and Interior Laboratory (GRAIL) spacecraft conducted the mapping of the gravity field of the Moon from March 1, 2012 to May 29, 2012, for the primary mission and from August 30, 2012 to December 14, 2012 for the extended mission and endgame. During both mission phases, the twin spacecraft acquired highly precise Ka-band range-rate (KBRR) intersatellite ranging data and Deep Space Network (DSN) data from altitudes of 2.3 to 98.2 km above the lunar surface. We have processed the GRAIL data using the NASA GSFC GEODYN orbit determination and geodetic parameter estimation program and used the supercomputers of the NASA Center for Climate Simulation (NCCS) at NASA GSFC to accumulate the SRIF arrays and derive the geopotential solutions. During the extended mission, the spacecraft orbits were maintained at a mean altitude of ~23 km, compared to ~50 km during the primary mission. In addition, from December 7 to December 14, 2012, data were acquired from a mean altitude of 11.5 km. With these data, we have derived solutions in spherical harmonics to degree 900. The new gravity solutions show improved correlations with LOLA-derived topography to very high degree and order and resolve many lunar features in the geopotential with a resolution of less than 15 km. We discuss the methods we used for the processing of the GRAIL data, and evaluate these solutions with respect to the derived power spectra, Bouguer anomalies, and fits with independent data (such as from the low-altitude phase of the Lunar Prospector mission).

  3. Geophysical Investigation of Australian-Antarctic Ridge Using High-Resolution Gravity and Bathymetry

    NASA Astrophysics Data System (ADS)

    Kim, S. S.; Lin, J.; Park, S. H.; Choi, H.

    2015-12-01

    Much of the Australian-Antarctic Ridge (AAR) has been remained uncharted until 2011 because of its remoteness and harsh weather conditions. From 2011, the multidisciplinary ridge program initiated by the Korea Polar Research Institute (KOPRI) surveyed the little-explored eastern ends of the AAR to characterize the tectonics, geochemistry, and hydrothermal activity of this intermediate spreading system. In this study, we present a detailed analysis of a 300-km-long supersegment of the AAR to quantify the spatial variations in ridge morphology and axial and off-axis volcanisms as constrained by high-resolution shipboard bathymetry and gravity. The ridge axis morphology alternates between rift valleys and axial highs within relatively short ridge segments. To obtain a geological proxy for regional variations in magma supply, we calculated residual mantle Bouguer gravity anomalies (RMBA), gravity-derived crustal thickness, and residual topography for neighboring seven sub-segments. The results of the analyses revealed that the southern flank of the AAR is associated with shallower seafloor, more negative RMBA, thicker crust, and/or less dense mantle in comparison to the conjugate northern flank. Furthermore, this north-south asymmetry becomes more prominent toward the KR1 supersegment of the AAR. The axial topography of the KR1 supersegment exhibits a sharp transition from axial highs at the western end to rift valleys at the eastern end, with regions of axial highs being associated with more robust magma supply as indicated by more negative RMBA. We also compare and contrast the characteristics of the AAR supersegment with that of other ridges of intermediate spreading rates, including the Juan de Fuca Ridge, Galápagos Spreading Center, and Southeast Indian Ridge west of the Australian-Antarctic Discordance, to investigate the influence of ridge-hotspot interaction on ridge magma supply and tectonics.

  4. High-resolution Gravity Field Models of the Moon Using GRAIL mission Data

    NASA Astrophysics Data System (ADS)

    Lemoine, Frank G.; Goossens, Sander; Sabaka, Terrence J.; Nicholas, Joseph B.; Mazarico, Erwan; Rowlands, David D.; Loomis, Bryant D.; Chinn, Douglas S.; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.

    2015-04-01

    The Gravity Recovery and Interior Laboratory (GRAIL) mission was designed to map the structure of the lunar interior from crust to core and to advance the understanding of the Moon's thermal evolution by producing a high-quality, high-resolution map of the gravitational field of the Moon. GRAIL consisted of two spacecraft, with Ka-band tracking between the two satellites as the single science instrument, with the addition of Earth-based tracking using the Deep Space Network. The science mission was divided into two phases: a primary mission from March 1, 2012 to May 29, 2012, and an extended mission from August 30, 2012 to December 14, 2012. The altitude varied from 3 km to 94 km above the lunar surface during both mission phases. Both the primary and the extended mission data have been processed into global models of the lunar gravity field at NASA/GSFC using the GEODYN software up to 1080 x 1080 in spherical harmonics. In addition to the high-resolution global models, local models have also been developed. Due to varying spacecraft altitude and ground track spacing, the actual resolution of the global models varies geographically. Information beyond the current resolution is still present in the data, as indicated by relatively higher fits in the last part of the extended mission, where the satellites achieved their lowest altitude above lunar surface. Local models of the lunar gravitational field at high resolution were thus estimated to accommodate this signal. Here, we present the current status of GRAIL gravity modeling at NASA/GSFC, for both global and local models. We discuss the methods we used for the processing of the GRAIL data, and evaluate these solutions with respect to the derived power spectra, Bouguer anomalies, and fits with independent data (such as from the low-altitude phase of the Lunar Prospector mission). We also evaluate the prospects for extending the resolution of our current models

  5. Space-Wise approach for airborne gravity data modelling

    NASA Astrophysics Data System (ADS)

    Sampietro, D.; Capponi, M.; Mansi, A. H.; Gatti, A.; Marchetti, P.; Sansò, F.

    2016-12-01

    Regional gravity field modelling by means of remove-compute-restore procedure is nowadays widely applied in different contexts: it is the most used technique for regional gravimetric geoid determination, and it is also used in exploration geophysics to predict grids of gravity anomalies (Bouguer, free-air, isostatic, etc.), which are useful to understand and map geological structures in a specific region. Considering this last application, due to the required accuracy and resolution, airborne gravity observations are usually adopted. However, due to the relatively high acquisition velocity, presence of atmospheric turbulence, aircraft vibration, instrumental drift, etc., airborne data are usually contaminated by a very high observation error. For this reason, a proper procedure to filter the raw observations in both the low and high frequencies should be applied to recover valuable information. In this work, a software to filter and grid raw airborne observations is presented: the proposed solution consists in a combination of an along-track Wiener filter and a classical Least Squares Collocation technique. Basically, the proposed procedure is an adaptation to airborne gravimetry of the Space-Wise approach, developed by Politecnico di Milano to process data coming from the ESA satellite mission GOCE. Among the main differences with respect to the satellite application of this approach, there is the fact that, while in processing GOCE data the stochastic characteristics of the observation error can be considered a-priori well known, in airborne gravimetry, due to the complex environment in which the observations are acquired, these characteristics are unknown and should be retrieved from the dataset itself. The presented solution is suited for airborne data analysis in order to be able to quickly filter and grid gravity observations in an easy way. Some innovative theoretical aspects focusing in particular on the theoretical covariance modelling are presented too

  6. Spectral analysis of topography and gravity in the Basin and Range Province

    USGS Publications Warehouse

    Ricard, Y.; Froidevaux, C.; Simpson, R.

    1987-01-01

    A two-dimensional spectral analysis has been carried out for the topography and the Bouguer gravity anomaly of the Basin and Range Province in western North America. The aim was to investigate the possible presence of dominant wavelengths in the deformation pattern at the surface and at the depth of compensation. The results suggest that a 200-km wavelength in the deep compensating mass distribution has been inherited from an early tectonic phase of extension at an azimuth N65??E. The corresponding surface topography exhibits prominent overtones at wavelength of 100, 75, and possibly 45 km. It is argued that these characterize the non-linear rheology of the upper crust. The short wavelengths in the topography reflect the present phase of deformation, mixed with the results of the older deformations. These results point to a need to extend the physical models of lithospheric stretching beyond the presently available one-phase scenario. However, they show that the boudinage instability concept is consistent with the data. ?? 1987.

  7. Curie Point Depth, Geothermal Gradient and Heat-Flow Estimation and Geothermal Anomaly Exploration from Integrated Analysis of Aeromagnetic and Gravity Data on the Sabalan Area, NW Iran

    NASA Astrophysics Data System (ADS)

    Afshar, A.; Norouzi, G. H.; Moradzadeh, A.; Riahi, M. A.; Porkhial, S.

    2017-03-01

    Prospecting the geothermal resources in northwest of Iran, conducted in 1975, revealed several promising areas and introduced the Sabalan geothermal field as a priority for further studies. The Sabalan Mt., representing the Sabalan geothermal field, is a large stratovolcano which consists of an extensive central edifice built on a probable tectonic horst of underlying intrusive and effusive volcanic rocks. In this study, Curie point depth (CPD), geothermal gradient and heat-flow map were constituted from spectral analysis of the aeromagnetic data for the NW of Iran. The top of the geothermal resource (i.e., the thickness of the overburden) was evaluated by applying the Euler deconvolution method on the residual gravity data. The thickness of the geothermal resource was calculated by subtracting the Euler depths obtained from the CPDs in the geothermal anomalous region. The geothermal anomalous region was defined by the heat-flow value greater than 150 mW/m2. CPDs in the investigated area are found between 8.8 km in the Sabalan geothermal field and 14.1 in the northeast. The results showed that the geothermal gradient is higher than 62 °C/km and the heat-flow is higher than 152 mW/m2 for the geothermal manifestation region; the thickness of the geothermal resource was also estimated to vary between 5.4 and 9.1 km. These results are consistent with the drilling and other geological information. Findings indicate that the CDPs agree with earthquake distribution and the type of thermal spring is related to the depth of the top of the geothermal resource.

  8. Curie Point Depth, Geothermal Gradient and Heat-Flow Estimation and Geothermal Anomaly Exploration from Integrated Analysis of Aeromagnetic and Gravity Data on the Sabalan Area, NW Iran

    NASA Astrophysics Data System (ADS)

    Afshar, A.; Norouzi, G. H.; Moradzadeh, A.; Riahi, M. A.; Porkhial, S.

    2016-12-01

    Prospecting the geothermal resources in northwest of Iran, conducted in 1975, revealed several promising areas and introduced the Sabalan geothermal field as a priority for further studies. The Sabalan Mt., representing the Sabalan geothermal field, is a large stratovolcano which consists of an extensive central edifice built on a probable tectonic horst of underlying intrusive and effusive volcanic rocks. In this study, Curie point depth (CPD), geothermal gradient and heat-flow map were constituted from spectral analysis of the aeromagnetic data for the NW of Iran. The top of the geothermal resource (i.e., the thickness of the overburden) was evaluated by applying the Euler deconvolution method on the residual gravity data. The thickness of the geothermal resource was calculated by subtracting the Euler depths obtained from the CPDs in the geothermal anomalous region. The geothermal anomalous region was defined by the heat-flow value greater than 150 mW/m2. CPDs in the investigated area are found between 8.8 km in the Sabalan geothermal field and 14.1 in the northeast. The results showed that the geothermal gradient is higher than 62 °C/km and the heat-flow is higher than 152 mW/m2 for the geothermal manifestation region; the thickness of the geothermal resource was also estimated to vary between 5.4 and 9.1 km. These results are consistent with the drilling and other geological information. Findings indicate that the CDPs agree with earthquake distribution and the type of thermal spring is related to the depth of the top of the geothermal resource.

  9. Point stability at shallow depths: experience from tilt measurements in the Lower Rhine Embayment, Germany, and implications for high-resolution GPS and gravity recordings

    NASA Astrophysics Data System (ADS)

    Kümpel, H.-J.; Lehmann, K.; Fabian, M.; Mentes, Gy.

    2001-09-01

    From 1996 to 1999, we have studied ground tilts at depths of between 2m and 5m at three sites in the Lower Rhine Embayment (LRE), western Germany. The LRE is a tectonically active extensional sedimentary basin roughly 50km×100km. The purpose of the tilt measurements was (a) to provide insight into the magnitude, nature and variability of background tilts and (b) to assess possible limitations of high-resolution GPS campaigns and microgravity surveys due to natural ground deformation. The tilt readings, sensed by biaxial borehole tiltmeters of baselength 0.85m, cover a frequency range from 10-8Hz to 10-2Hz (periods from minutes to years). Assuming that the tilt signals represent ground displacements on a scale typically not larger than several times the tiltmeters' baselength, and that tilt signals at shallow depth could in a simple geometric way be related to changes in surface elevation and gravity, we try to estimate the magnitude level of point movements and corresponding Bouguer gravity effects that is generally not surpassed. The largest tilt signals observed were some +/-50µradyr-1. If they were observable over a ground section of extension, e.g. 10m, the converted rates may correspond to about +/-0.5mm per 10myr-1 in vertical ground displacement, and +/-0.1µgalyr-1 in Bouguer gravity effect, respectively. Large signals are mostly related to seasonal effects, probably linked to thermomechanical strain. Other causes of ground deformation identified include seepage effects after rainfalls (order of +/-10µrad) and diurnal strains due to thermal heating and/or fluctuations in the water consumption of nearby trees (order of +/-1µrad). Episodic step-like tilt anomalies with amplitudes up to 22µrad at one of the observation sites might reflect creep events associated to a nearby active fault. Except for short-term ground deformation caused by the passage of seismic waves from distant earthquakes, amplitudes of non-identified tilt signals in the studied

  10. Gradients from GOCE reveal gravity changes before Pisagua Mw = 8.2 and Iquique Mw = 7.7 large megathrust earthquakes

    NASA Astrophysics Data System (ADS)

    Álvarez, Orlando; Nacif, Silvina; Spagnotto, Silvana; Folguera, Andres; Gimenez, Mario; Chlieh, Mohamed; Braitenberg, Carla

    2015-12-01

    Considerable improvements in the measurement of the Earth gravity field from GOCE satellite mission have provided global gravity field models with homogeneous coverage, high precision and good spatial resolution. In particular, the vertical gravity gradient (Tzz), in comparison to the classic Bouguer anomaly, defines more accurately superficial mass heterogeneities. Moreover, the correction of these satellite-derived data from the effect of Earth topographic masses by means of new techniques taking into account the Earth curvature, improves results in regional analyses. In a recent work we found a correlation between Tzz and slip distribution for the 2010 Maule Mw = 8.8 earthquake. In the present work, we derive the vertical gravity gradient from the last GOCE only model, corrected by the topographic effect and also by the sediments on depocenters of the offshore region at the Peru-Chile margin, in order to study a spatial relationship between different lobes of the gravity derived signal and the seismic sources of large megathrust earthquakes. In particular, we analyze this relation for the slip models of the 1996 Mw = 7.7 Nazca, 2001 Mw = 8.4 Arequipa, 2007 Mw = 8.0 Pisco events and for the slip models of the 2014 Mw = 8.2 Pisagua and Mw = 7.7 Iquique earthquakes from Schurr et al. (2014), including the previously analyzed 2010 Mw = 8.8 Maule event. Then we find a good correlation between vertical gravity gradients and main rupture zones, correlation that becomes even stronger as the event magnitude increases. Besides this, a gravity fall in the gravity gradient was noticed over the area of the main slip patches at least for the two years before 2014 Mw = 8.2 Pisagua and Mw = 7.7 Iquique earthquakes. Additionally, we found temporal variations of the gravity field after 2010 Mw = 8.8 Maule event, related to the main patches of the slip distribution, and coseismic deformation. Therefore, we analyzed vertical gravity gradient field variations as an indirect measure

  11. Principal facts for about 16,000 gravity stations in the Nevada test site and vicinity

    NASA Astrophysics Data System (ADS)

    Harris, R. N.; Ponce, D. A.; Oliver, H. W.; Healey, D. L.

    The Nevada Test Site (NTS) and vicinity includes portions of the Goldfield, Caliente, Death Valley, and Las Vegas. This report documents and consolidates previously published and recently compiled gravity data to establish a gravity data base of about 16,000 stations for the NTS and vicinity. While compiling data sets, redundant stations and stations having doubtful locations or gravity values were excluded. Details of compiling the gravity data sets are discussed in later sections. Where feasible, an accuracy code has been assigned to each station so that the accuracy or reliability of each station can be evaluated. This data base was used in preparing complete Bouguer and isostatic gravity maps of the NTS and vicinity. Since publication of the complete Bouguer gravity map, additional data were incorporated into the isostatic gravity map. Gravity data were compiled from five sources: 14,183 stations from the U.S. Geological Survey (USGS), 326 stations from Exploration Data Consultants (EDCON) of Denver, Colorado, 906 stations from the Los Alamos National Laboratory (LANL), 212 stations from the University of Texas at Dallas (UTD), and 48 stations from the Defense Mapping Agency (DMA). This investigation is an effort to study several areas for potential storage of high-level radioactive waste. Gravity stations established under YMP are shown. The objective of this gravity survey was to explore for the presence of plutons.

  12. Crustal Accretion and Mantle Geodynamics at Microplates: Constraints from Gravity Analysis

    NASA Astrophysics Data System (ADS)

    Ames, K.; Georgen, J. E.; Dordevic, M. M.

    2013-12-01

    Oceanic crustal accretion occurs in a variety of locations, including mid-ocean ridges and back-arc spreading centers, and in unique settings within these systems, such as plate boundary triple junctions, intra-transform spreading centers, and microplates. This study focuses on crustal accretion and mantle geodynamics at microplates. The Easter and Juan Fernandez microplates are located in the South Pacific along the Pacific, Nazca and Antarctic plate boundaries. Both microplates formed 3-5 Ma and they are currently rotating clockwise at 15 deg/Ma and 9 deg/Ma respectively (e.g., Searle et al. J. Geol. Soc. Lond. 1993). The study area also encompasses the Easter/Sala y Gomez mantle plume and the Foundation seamount chain, both of which are located close to spreading centers. We calculate mantle Bouguer anomaly (MBA) from satellite gravity measurements and shipboard soundings in order to gain a better understanding of the thermal structure of these two oceanic microplates and to quantify the effect that melting anomalies may have on their boundaries. We assume a crustal thickness of 6.0 km, a 1.7 g/cm^3 density difference at the water/crust interface, and a 0.6 g/cm^3 density difference at the crust/mantle interface. The west rift of the Easter microplate has an MBA low ranging from approximately -50 to -100 mGal, while the east rift has slightly higher MBA values ranging from roughly 10 to -50 mGal. The west rift of the Juan Fernandez microplate has a maximum MBA low of about -100 mGal with a sharp increase to -20 mGal at -35 deg S. The east rift of the Juan Fernandez microplate is characterized by more variable MBA, ranging from 0 to -140 mGal. The MBA low associated with the Easter/Sala y Gomez mantle plume has a maximum amplitude about 150 mGal. Likewise, the Foundation seamounts show a gravity low of -140 to -150 mGal. These spatial variations in gravity, as well as published isotopic data and exploratory numerical models, are used to constrain upper mantle

  13. Convergence of the Bouguer-Beer law for radiation extinction in particulate media

    NASA Astrophysics Data System (ADS)

    Frankel, A.; Iaccarino, G.; Mani, A.

    2016-10-01

    Radiation transport in particulate media is a common physical phenomenon in natural and industrial processes. Developing predictive models of these processes requires a detailed model of the interaction between the radiation and the particles. Resolving the interaction between the radiation and the individual particles in a very large system is impractical, whereas continuum-based representations of the particle field lend themselves to efficient numerical techniques based on the solution of the radiative transfer equation. We investigate radiation transport through discrete and continuum-based representations of a particle field. Exact solutions for radiation extinction are developed using a Monte Carlo model in different particle distributions. The particle distributions are then projected onto a concentration field with varying grid sizes, and the Bouguer-Beer law is applied by marching across the grid. We show that the continuum-based solution approaches the Monte Carlo solution under grid refinement, but quickly diverges as the grid size approaches the particle diameter. This divergence is attributed to the homogenization error of an individual particle across a whole grid cell. We remark that the concentration energy spectrum of a point-particle field does not approach zero, and thus the concentration variance must also diverge under infinite grid refinement, meaning that no grid-converged solution of the radiation transport is possible.

  14. The effect of remnant magnetization in the Eastern Galicia Magnetic Anomaly: constraints on the source of the remanence and implications for the geological model

    NASA Astrophysics Data System (ADS)

    Ayarza, P.; Martínez Catalán, J. R.; Alvarez Lobato, F.; Villalaín, J. J.; Reguilón, R.

    2009-04-01

    The Eastern Galicia Magnetic Anomaly (EGMA) spans over an area of ~10000 km2 and with a maximum of 190 nT, is one of the highest amplitude magnetic anomalies of the Iberian Peninsula. From a geological point of view, it occupies the centre of the Lugo-Sanabria Gneiss Dome, an antiformal structure developed during the Late Carboniferous extension that affected the Variscan fold and thrust belt of NW Iberia. The EGMA reaches its maximum values along the Viveiro Fault, a normal fault located at the western boundary of the Lugo-Sanabria Dome, coinciding with a relative low of the Bouguer gravity anomaly. Magnetite-bearing migmatites and inhomogeneous granites outcropping in the northern part of the gneiss dome seem to be the main source of the anomaly. Magnetite grains are heterogeneously distributed, can reach up to 1 cm, and may appear also in the metamorphic country rocks, paragneisses and quartzites, adjacent to the granitoids. These findings led Ayarza and Martínez Catalán (2007) to conclude that the EGMA is caused by the products of partial melting formed during the late Variscan extensional collapse. 2D gravity and magnetic modelling allowed them to interpret the EGMA as the magnetic response of a N-S to NW-SE elongated body, 200 km long and roughly 90 km wide, lens-shaped in cross section and up to 10 km thick, formed by migmatites, inhomogeneous granites and their country rocks, and located at depths between 0 and 20 km. The size of the magnetite grains suggested that magnetic remanence was unlikely and modelling was carried out assuming that the magnetic response of this lens-shaped body was mostly induced by the present-day magnetic field. However, recent NRM and demagnetization studies on a variety of samples have shown that remanence is common and even might get to be important, with Königsberger ratios (Qn) normally below 0.5 but exceptionally exceeding 1. Remanence is mostly produced by high coercitivity minerals (>120 mT) and seem to be post

  15. 2.5-D gravity model of the NiCuPGM mineralized Mount Ayliff Intrusion (Insizwa Complex), South Africa

    NASA Astrophysics Data System (ADS)

    Sander, B. K.; Cawthorn, R. G.

    1996-08-01

    The Mount Ayliff Intrusion is the largest and thickest Karoo-aged sill in South Africa. It contains a small NiCu-platinum-group metal (PGM) sulphide deposit, Waterfall Gorge, at the base of its largest lobe called Insizwa. The deposit was once mined for its Cu. In September 1990, a 900-m-deep, vertical diamond drill exploration borehole was drilled through a thick, central portion of the intrusion. This new geological control confirms an earlier gravity survey-based hypothesis that the intrusion has a thick, hidden keel of ultramafic rock with finite depth extent below the centre of the Insizwa lobe. Along with other new geological evidence, the borehole log affords a unique opportunity to further constrain models for three regional gravity profiles and to arrive at a new, 3-dimensional model for the Insizwa lobe. The background residual terrain-corrected Bouguer gravity anomaly of the Mount Ayliff Intrusion reaches up to +9 mgal. This results from an igneous slab of 0-150 m of picrite overlain by about 600 m of gabbronorite. Superimposed on this anomaly over the central and northwestern Insizwa lobe is a 10-km-wide gravity anomaly with an amplitude of +8 to + 17 mgal and having steep edges. This is interpreted to represent thickening of picrite to 400-800 m in a major, hidden basin bordered by two NW-striking fault lineaments that are believed to mark a hidden graben structure with major geological transgressions at the base of the Insizwa lobe. At least three discrete, thinner picrite basins are interpreted to extend above and beyond both flanks of the graben. Picrite in these basins is modelled to be less than 200 m in thickness. The basins are separated either by the major NW-striking geological transgressions, or by domes in the footwall of the Insizwa lobe, above which no picrite has developed. Locations of several hidden, narrow, discontinuous feeder dykes below the Mount Ayliff Intrusion are postulated. The role of ponding of picrite at the mostly hidden

  16. Gravity and crustal structure

    NASA Technical Reports Server (NTRS)

    Bowin, C. O.

    1976-01-01

    Lunar gravitational properties were analyzed along with the development of flat moon and curved moon computer models. Gravity anomalies and mascons were given particular attention. Geophysical and geological considerations were included, and comparisons were made between the gravitional fields of the Earth, Mars, and the Moon.

  17. Satellite Gravity Drilling the Earth

    NASA Technical Reports Server (NTRS)

    vonFrese, R. R. B.; Potts, L. V.; Leftwich, T. E.; Kim, H. R.; Han, S.-H.; Taylor, P. T.; Ashgharzadeh, M. F.

    2005-01-01

    Analysis of satellite-measured gravity and topography can provide crust-to-core mass variation models for new insi@t on the geologic evolution of the Earth. The internal structure of the Earth is mostly constrained by seismic observations and geochemical considerations. We suggest that these constraints may be augmented by gravity drilling that interprets satellite altitude free-air gravity observations for boundary undulations of the internal density layers related to mass flow. The approach involves separating the free-air anomalies into terrain-correlated and -decorrelated components based on the correlation spectrum between the anomalies and the gravity effects of the terrain. The terrain-decorrelated gravity anomalies are largely devoid of the long wavelength interfering effects of the terrain gravity and thus provide enhanced constraints for modeling mass variations of the mantle and core. For the Earth, subcrustal interpretations of the terrain-decorrelated anomalies are constrained by radially stratified densities inferred from seismic observations. These anomalies, with frequencies that clearly decrease as the density contrasts deepen, facilitate mapping mass flow patterns related to the thermodynamic state and evolution of the Earth's interior.

  18. The Effect of Pre-Impact Porosity and Vertical Density Gradients on the Gravity Signature of Lunar Craters as Seen by GRAIL

    NASA Astrophysics Data System (ADS)

    Milbury, C.; Johnson, B. C.; Melosh, H. J.; Collins, G. S.; Blair, D. M.; Soderblom, J. M.; Nimmo, F.; Phillips, R. J.; Bierson, C. J.; Zuber, M. T.

    2015-09-01

    We use iSALE to model complex crater formation on the Moon. We vary initial target porosity and model vertical density/porosity gradients in the crust. We calculate the Bouguer anomaly associated with the craters and match them to GRAIL observations.

  19. Mars Gravity and Topography Interpretations

    NASA Technical Reports Server (NTRS)

    Zuber, Maria T.; Smith, David E.; Solomon, Sean C.; Phillips, Roger J.

    1999-01-01

    New models of the topography of Mars and its gravity field from the Mars Global Surveyor mission are shedding new light on the structure of the planet and the state of isostatic compensation. Gravity field observations over the flat northern hemisphere plains show a number of anomalies at the 100 to 200 mGal level that have no apparent manifestation in the surface topography. We believe that these anomalies are probably the result of ancient impacts and represent regions of denser material buried beneath the outer depositional crust. Similar anomalies are also found in the region of the north polar ice cap even though a gravity anomaly resulting from the 3 km high icecap has not been uniquely identified. This leads us to speculate that the ice cap is largely compensated and is older than the timescale of isostatic compensation, about 10(exp 15) years.

  20. A gravity survey of parts of quadrangles 26E, 26F, 27E, and 27F, northeastern Arabian Shield, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Miller, C.H.; Showail, A.A.; Kane, M.F.; Khoja, I.A.; Al Ghandi, S. A.

    1989-01-01

    The greatest complete Bouguer anomaly is associated with basaltic lava flows located in the northeastern part of the survey area. The thickness of the basalt in outcrop does not account for the anomalies with the highest amplitudes, but the latter may be due to the presence of a basalt-filled vent. Those anomalies that are present do not define the basalt flows well, but the largest free-air anomaly occurs over the southwestern margin of the Salma Caldera, located about 15 km from the basalt flows. The source of the free-air anomaly is unknown, but it may be related to another hidden basaltic vent.

  1. 3-D density modeling of Mt. Paekdu (N Korea/China) stratovolcano and its evolution by a combination of EGM2008/terrestrial gravity field

    NASA Astrophysics Data System (ADS)

    Götze, Hans-Jürgen; Choi, Sungchan

    2015-04-01

    We combined the global gravity dataset EGM2008 and a local terrestrial gravity data survey to conduct constrained 3-D crustal density modeling of a strato-volcanic complex and the surrounding area located close to the border of North Korea and China. The independent geophysical (seismic, seismology, geochemistry) and petrological constraints will be presented together with the preprocessing of data base by curvature analysis and Euler deconvolution. The multiple data base is used to assist a general interpretation of the investigated area, and the 3D density model (modelled by the in-house IGMAS+ software). Mt. Paekdu is characterized by a low of Bouguer anomaly of some -110 × 10-5 m/s2, which is caused by the combined gravity effects of (1) Moho depth of about 40 km, (2) a zone with both lower P-wave velocity and density than the surrounding, (3) low density volcanic rocks at the surface, and (4) the presence of a magma chamber that has not previously been identified. The terrestrial gravity field measured along the seismic profile shows a remarkable anomaly descending from the southern- to the northern flank of the Mt. Paekdu volcano, which should be a typical anomaly pattern generally observed over the active volcanic area in the world (e.g. the Yellow Stone volcano). The trend is interpreted to be caused by a prominent density difference between a serious of high density mid crustal sill beneath the southern flank and a predicted partial melted zone locating in the northern flank. With the help of several geoscientific observations (seismic, electromagnetic, gravity and geochemistry) and the 3D density model we conclude that a high density sill was formed in Pliocene and early Pleistocene after pre-shield plateau-forming eruption. Since the Pliocene, volcanic activity in the Mt. Paekdu region might be migrated from the southeastern of North Korea to the northwest, following the path of NW-SE-trending faults. Recently observed seismic tremors can be explained

  2. 3-D Density Modeling of the Combined EGM2008/Terrestrial Gravity Field over the Mt. Paekdu (N Korea/China) Stratovolcano and Its Evolution

    NASA Astrophysics Data System (ADS)

    Goetze, H. J.; Choi, S.

    2014-12-01

    In the presentation we get use of the global gravity dataset EGM2008 and a local terrestrial gravity data survey for a constrained 3-D crustal density modeling of a stratovolcano and its surrounding area located close to the border of North Korea and China. The independent geophysical (seismic, seismology, geochemistry) and petrological constraints will be presented together with the preprocessing of data base by curvature analysis and Euler deconvolution. The multiple data base is used to assist a general interpretation of the investigated area in time, and the 3D density model (modelled by the inhouse IGMAS+ software). Mt. Paekdu is characterized by a low of Bouguer anomaly of some -110 ´ 10-5 m/s2, which is caused by the combined gravity effects of (1) Moho depth of about 40 km, (2) a zone with both lower P-wave velocity and density than the surrounding, (3) low density volcanic rocks at the surface, and (4) the presence of a magma chamber that has not previously been identified. The terrestrial gravity field measured along the seismic profile shows a remarkable anomaly descending from the southern- to the northern flank of the Mt. Paekdu volcano, which should be a typical anomaly pattern generally obsered over the active volcanic area in the world (e.g. the Yellow Stone volcano). The trend is interpreted to be caused by a prominent density difference between a serious of high density mid crustal sill beneath the southern flank and a predicted partial melted zone locating in the northern flank. With the help of several geoscientific observations (seismic, electromagnetic, gravity and geochemistry) and the 3D density model we conclude that a high density sill was formed in Pliocene and early Pleistocene after pre-shield plateau-forming eruption. Since the Pliocene, volcanic activity in the Mt. Paekdu region might be migrated from the southeastern of North Korea to the northwest, following the path of NW-SE-trending faults. Recently observed seismic tremors can

  3. Subsurface structures of large volcanic complexes on the nearside of the Moon: A view from GRAIL gravity

    NASA Astrophysics Data System (ADS)

    Huang, Qian; Xiao, Zhiyong; Xiao, Long

    2014-11-01

    The lunar nearside large volcanic complexes, such as the Rümker Hills, Aristarchus Plateau, and Marius Hills are likely sites of intense and sustained magmatic activity. These volcanic complexes, recently proposed to be shield volcanoes, are generally located at regionally high elevations and some feature relatively well-localized positive gravity anomalies. Applying localized spectral analyses on high-resolution gravity data obtained from the Gravity Recovery and Interior Laboratory (GRAIL) mission and topography data returned from the Lunar Reconnaissance Orbiter (LRO) spacecraft, we study the subsurface structures of these volcanic complexes. The gravity signal is predicted using a thin elastic lithospheric model that considers both surface and subsurface loads. Best-fit crustal and load densities show that the topographic highs of Rümker Hills, Marius Hills, Gardner and Kepler are mainly composed of material that has a density of more than 2850 kg m-3, which is consistent with that of emplaced igneous rocks. Both the Aristarchus Plateau and Hortensius have relatively lower crustal and surface load densities, with mean values around 2550 kg m-3, which are well consistent with the average bulk density of the lunar highland crust. These results, together with evidence of multiple volcanic edifices on the surface, suggest that the shallow crusts of the Rümker Hills, Marius Hills, Gardner and Kepler are mainly composed of dense intrusive/extrusive magmatic units, and those of the Aristarchus Plateau and Hortensius are mainly composed of low density materials with only small amounts of superimposed volcanic material. To further constrain the subsurface structures beneath these volcanic complexes, we analyze the Bouguer gravity anomalies for these regions. Results show that dense materials that might be solidified intrusions exist beneath Rümker Hills, Marius Hills, Gardner and Prinz, but no substantial dense materials have been detected beneath the Aristarchus

  4. Understanding Conspicuous Gravity Low Over the Koyna-Warna Seismogenic Region (Maharashtra, India) and Earthquake Nucleation: A Paradigm Shift

    NASA Astrophysics Data System (ADS)

    Vasanthi, A.; Satish Kumar, K.

    2016-06-01

    The continued seismicity in Koyna-Warna region of the western part of Maharastra (India) and its relationship with subsurface structures, concealed below thick volcanic sequences, are studied in detail using gravity field along with newly available deep scientific drilling results. This seismically active zone is marked by a large conspicuous negative gravity anomaly, the causes of which are yet to be fully understood. Recent findings from the boreholes drilled in the Koyna (G upta et al. in Int J Earth Sci 104:1511-1522, 2015) and Killari seismic zones, both of which penetrated the thick Deccan volcanic cover and the underlying Archean crystalline basement, have motivated us to revisit the Bouguer gravity field over this region, using a newly developed finite element method of regional-residual separation. Our study reveals the presence of two thick low-density/low-velocity crustal zones below the Koyna-Warna region, the shallower one between 5 and 13 km depth and the deeper one between 35 and 43 km depth just above the Moho. Both of these zones appear to contain mantle-metasomatised and fractionated magmatic material, respectively. Interestingly, the hypocenters of all M ≥ 5 Koyna earthquakes occur within the upper low-velocity/low-density zone. We also suggest high-order crustal exhumation below this region, which led to the removal of the entire sedimentary and granitic upper crustal column. This process has brought denser mid-crustal lithological facies close to the surface. Quaternary uplifting and movement of fault blocks along the old as well as newly created fault planes seem to be still continuing. A paleo-rift may have existed beneath this region below which Moho temperatures (~600 °C) and mantle heat flow (~31 mW/m2) are still high.

  5. DOWN'S ANOMALY.

    ERIC Educational Resources Information Center

    PENROSE, L.S.; SMITH, G.F.

    BOTH CLINICAL AND PATHOLOGICAL ASPECTS AND MATHEMATICAL ELABORATIONS OF DOWN'S ANOMALY, KNOWN ALSO AS MONGOLISM, ARE PRESENTED IN THIS REFERENCE MANUAL FOR PROFESSIONAL PERSONNEL. INFORMATION PROVIDED CONCERNS (1) HISTORICAL STUDIES, (2) PHYSICAL SIGNS, (3) BONES AND MUSCLES, (4) MENTAL DEVELOPMENT, (5) DERMATOGLYPHS, (6) HEMATOLOGY, (7)…

  6. Mapping of Basement Faults with Gravity and Magnetic Data at NE Mexico

    NASA Astrophysics Data System (ADS)

    Yutsis, V.; Krivosheya, K.; Tamez Ponce, A.

    2012-04-01

    Northeast Mexico is essentially the juncture of two distinctly different tectono-stratigraphic provinces, the eastern Gulf of Mexico (Coastal Plane, Sierra Madre Oriental) province and the western Pacific Mexico (Rivera plate, Meso-American trench, Sierra Madre Occidental) province (Goldhammer & Johnson, 2001). Tectonic evolution in northeast Mexico is dominated by divergent-margin development associated with the opening of the Gulf of Mexico and overprinted by non-igneous Laramide orogenic effects (Pindell et al., 1988). The structural grain of northeast Mexico consists of Triassic to Liassic fault-controlled basement blocks, the development of which reflects in part late Paleozoic orogenic patterns of metamorphism and igneous intrusion (Wilson, 1990). There are different tectonic provinces which are recognized interpreting the basement and sediment cover of this area: Coahuila block, La Popa sub-basin, Sabinas basin, Burgos basin, Sierra Madre Oriental (Monterrey trough), and Parras basin. Mojave-Sonora megashear and San Marcos fault (Chavez-Cabello et al., 2007) are two principal fault zones crossing the northeast Mexico in NW-SE direction. This paper is presented the integral analysis of the gravity and magnetic data in the northeast Mexico. Complementing with a Digital Model of Elevations (DME) that combined with the review of previous geological studies it serves to compare the surface structures and blocks of basement in this area. Also the separation of the most important tectonic blocks was done, and 2.5D geological-geophysical model was finally developed. This model represents in a general way the principal structural characteristics of northeast Mexico. Gravity and magnetic data analysis was used with purpose to study the structure of the substrata in order to allow modeling of the basement structure and its relation with the sedimentary cover features. The Bouguer gravity and the total field aeromagnetic data were supplied by Geological Survey of Mexico

  7. Gravity constraints on lithosphere flexure and the structure of the late Paleozoic Ouachita orogen in Arkansas and Oklahoma, south central North America

    NASA Astrophysics Data System (ADS)

    Harry, Dennis L.; Mickus, Kevin L.

    1998-04-01

    Spectral analysis of Bouguer gravity anomalies in western central Arkansas and eastern Oklahoma indicates that the thickness of the crust in the Ouachita fold and thrust belt increases from 38 km in the western Ouachitas to 44 km in the eastern Ouachitas. The change in crustal thickness occurs near the western end of the Broken Bow uplift and coincides with an abrupt decrease in the flexural rigidity of the lithosphere from 1.8×1024 N m in the western Ouachitas to 5.0×1023 N m in the eastern Ouachitas. The flexural rigidity in the western Ouachitas is similar to values determined in the Appalachian fold and thrust belt and coincides with the depth of the 450°C isotherm predicted by conductive cooling models for the thermal evolution of the early Paleozoic southern Laurentian rifted continental margin. The thick crust in the eastern Ouachitas results in lithosphere that is anomalously weak for rifted continental crust of this age. The thicker crust is attributed to an eastward transition from a rift segment to a transform segment of the Paleozoic continental margin. A layered density model derived from the gravity data shows that strata interpreted to be deformed Ouachita facies rocks are thickest in the eastern Ouachitas and are consistent with a greater amount of shortening in the central thrust belt in Arkansas as compared to Oklahoma. The opposite relationship is observed in the frontal Ouachita province, where shortening appears greater in Oklahoma. The cross-strike changes in the locus of shortening, crustal thickness, flexural rigidity, and the inferred transition from rift to transform segments of the early Paleozoic continental margin all coincide with the location of a previously hypothesized zone of diffuse rightlateral shear located at the western end of the Benton uplift. Flexural modeling indicates that the load required to produce the observed Bouguer gravity low in the Arkoma foreland basin trends parallel to the Benton and Broken Bow uplifts but

  8. Continental and oceanic magnetic anomalies: Enhancement through GRM

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.

    1985-01-01

    In contrast to the POGO and MAGSAT satellites, the Geopotential Research Mission (GRM) satellite system will orbit at a minimum elevation to provide significantly better resolved lithospheric magnetic anomalies for more detailed and improved geologic analysis. In addition, GRM will measure corresponding gravity anomalies to enhance our understanding of the gravity field for vast regions of the Earth which are largely inaccessible to more conventional surface mapping. Crustal studies will greatly benefit from the dual data sets as modeling has shown that lithospheric sources of long wavelength magnetic anomalies frequently involve density variations which may produce detectable gravity anomalies at satellite elevations. Furthermore, GRM will provide an important replication of lithospheric magnetic anomalies as an aid to identifying and extracting these anomalies from satellite magnetic measurements. The potential benefits to the study of the origin and characterization of the continents and oceans, that may result from the increased GRM resolution are examined.

  9. Observational Constraints on the Identification of Shallow Lunar Magmatism: Insights from Floor-Fractured Craters

    NASA Technical Reports Server (NTRS)

    Jozwiak, L. M.; Head, J. W., III; Neumann, G. A.; Wilson, L.

    2016-01-01

    Floor-fractured craters are a class of lunar crater hypothesized to form in response to the emplacement of a shallow magmatic intrusion beneath the crater floor. The emplacement of a shallow magmatic body should result in a positive Bouguer anomaly relative to unaltered complex craters, a signal which is observed for the average Bouguer anomaly interior to the crater walls. We observe the Bouguer anomaly of floor-fractured craters on an individual basis using the unfiltered Bouguer gravity solution from GRAIL and also a degree 100-600 band-filtered Bouguer gravity solution. The low-magnitude of anomalies arising from shallow magmatic intrusions makes identification using unfiltered Bouguer gravity solutions inconclusive. The observed anomalies in the degree 100-600 Bouguer gravity solution are spatially heterogeneous, although there is spatial correlation between volcanic surface morphologies and positive Bouguer anomalies. We interpret these observations to mean that the spatial heterogeneity observed in the Bouguer signal is the result of variable degrees of magmatic degassing within the intrusions.

  10. Observational constraints on the identification of shallow lunar magmatism: Insights from floor-fractured craters

    NASA Astrophysics Data System (ADS)

    Jozwiak, L. M.; Head, J. W., III; Neumann, G. A.; Wilson, L.

    2017-02-01

    Floor-fractured craters are a class of lunar crater hypothesized to form in response to the emplacement of a shallow magmatic intrusion beneath the crater floor. The emplacement of a shallow magmatic body should result in a positive Bouguer anomaly relative to unaltered complex craters, a signal which is observed for the average Bouguer anomaly interior to the crater walls. We observe the Bouguer anomaly of floor-fractured craters on an individual basis using the unfiltered Bouguer gravity solution from GRAIL and also a degree 100-600 band-filtered Bouguer gravity solution. The low-magnitude of anomalies arising from shallow magmatic intrusions makes identification using unfiltered Bouguer gravity solutions inconclusive. The observed anomalies in the degree 100-600 Bouguer gravity solution are spatially heterogeneous, although there is spatial correlation between volcanic surface morphologies and positive Bouguer anomalies. We interpret these observations to mean that the spatial heterogeneity observed in the Bouguer signal is the result of variable degrees of magmatic degassing within the intrusions.

  11. Quantum gravity and the large scale anomaly

    SciTech Connect

    Kamenshchik, Alexander Y.; Tronconi, Alessandro; Venturi, Giovanni E-mail: Alessandro.Tronconi@bo.infn.it

    2015-04-01

    The spectrum of primordial perturbations obtained by calculating the quantum gravitational corrections to the dynamics of scalar perturbations is compared with Planck 2013 and BICEP2/Keck Array public data. The quantum gravitational effects are calculated in the context of a Wheeler-De Witt approach and have quite distinctive features. We constrain the free parameters of the theory by comparison with observations.

  12. Regional Geothermal Characterisation of East Anatolia from Aeromagnetic, Heat Flow and Gravity Data

    NASA Astrophysics Data System (ADS)

    Bektaş, Özcan; Ravat, Dhananjay; Büyüksaraç, Aydin; Bilim, Funda; Ateş, Abdullah

    2007-05-01

    East Anatolia is a region of high topography made up of a 2-km high plateau and Neogene and Quaternary volcanics overlying the subduction-accretion complex formed by the process of collision. The aeromagnetic and gravity data surveyed by the Mineral Research and Exploration (MTA) of Turkey have been used to interpret qualitatively the characteristics of the near-surface geology of the region. The residual aeromagnetic data were low-pass filtered and analyzed to produce the estimates of magnetic bottom using the centroid method and by forward modelling of spectra to evaluate the uncertainties in such estimates. The magnetic bottom estimates can be indicative of temperatures in the crust because magnetic minerals lose their spontaneous magnetization at the Curie temperature of the dominant magnetic minerals in the rocks and, thus, also are called Curie point depths (CPDs). The Curie point depths over the region of Eastern Anatolia vary from 12.9 to 22.6 km. Depths computed from forward modelling of spectra with 200 600 km window sizes suggest that the bottom depths from East Anatolia from the magnetic data may have errors exceeding 5 km; however, most of the obtained depths appear to lie in the above range and indicate that the lower crust is either demagnetized or non-magnetic. In the interpretation of the magnetic map, we also used reduction-to-pole (RTP) and amplitude of total gradient of high-pass filtered anomalies, which reduced dipolar orientation effects of induced aeromagnetic anomalies. However, the features of the RTP and the total gradient of the high-pass filtered aeromagnetic anomalies are not highly correlated to the hot spring water locations. On the other hand, many high-amplitude features seen on the total gradient map can be correlated with the ophiolitic rocks observed on the surface. This interpretation is supported by Bouguer gravity data. In this paper, we recommend that the sources of the widespread thermal activity seen in East Anatolia must

  13. On the tectonic problems of the southern East China Sea and adjacent regions: Evidence from gravity and magnetic data

    NASA Astrophysics Data System (ADS)

    Shang, Luning; Zhang, Xunhua; Han, Bo; Du, Runlin

    2016-02-01

    In this paper, two sets of gravity and magnetic data were used to study the tectonics of the southern East China Sea and Ryukyu trench-arc system: one data set was from the `Geological-geophysical map series of China Seas and adjacent areas' database and the other was newly collected by R/V Kexue III in 2011. Magnetic and gravity data were reorganized and processed using the software MMDP, MGDP and RGIS. In addition to the description of the anomaly patterns in different areas, deep and shallow structure studies were performed by using several kinds of calculation, including a spectrum analysis, upward-continuation of the Bouguer anomaly and horizontal derivatives of the total-field magnetic anomaly. The depth of the Moho and magnetic basement were calculated. Based on the above work, several controversial tectonic problems were discussed. Compared to the shelf area and Ryukyu Arc, the Okinawa Trough has an obviously thinned crust, with the thinnest area having thickness less than 14 km in the southern part. The Taiwan-Sinzi belt, which terminates to the south by the NW-SE trending Miyako fault belt, contains the relic volcanic arc formed by the splitting of the paleo Ryukyu volcanic arc as a result of the opening of the Okinawa Trough. As an important tectonic boundary, the strike-slip type Miyako fault belt extends northwestward into the shelf area and consists of several discontinuous segments. A forearc terrace composed of an exotic terrane collided with the Ryukyu Arc following the subduction of the Philippine Sea Plate. Mesozoic strata of varying thicknesses exist beneath the Cenozoic strata in the shelf basin and significantly influence the magnetic pattern of this area. The gravity and magnetic data support the existence of a Great East China Sea, which suggests that the entire southern East China Sea shelf area was a basin in the Mesozoic without alternatively arranged uplifts and depressions, and might have extended southwestward and connected with the

  14. Crustal structure of Chuan-Dian region derived from gravity data and its tectonic implications

    NASA Astrophysics Data System (ADS)

    Jiang, Wenliang; Zhang, Jingfa; Tian, Tian; Wang, Xin

    2012-12-01

    In this paper, Bouguer gravity data were used to invert crustal structure of the Chuan-Dian region of China. Both multi-scale wavelet analysis and density interface inversive methods were adopted. Three gravity models transverse to major blocks were constructed. Our research indicates that great differences exist in crustal structures between the Eastern Basin and the Western plate, and crustal structures of Chuan-Dian region are closely correlated with tectonic activities of the Eastern Tibetan Plateau. The Western Sichuan platform experienced strong deformation due to eastward extrusion of the Tibetan Plateau. This led to heaving of the upper crust and thickening of the lower crust. The low-density crusts of Western Blocks were deformed by many high-angle faults, and most of these faults cut through to the middle crust. Density structures of upper and middle crusts are restricted by the regional tectonic stress fields and fault zones. The lower crust was deformed by folding, inducing high- and low-density anomalies alternatively. Rocks beneath the Longmenshan sub-block and the Northwestern sub-block of Sichuan were severely broken. For strong eastward extrusion of the plateau, large areas of low-density anomaly were observed in the lower crust. Adjusted by gravity isostasy, the lower crusts of the Chuan-Dian block and the Songpan-Garze block have thickened intensely. Density structures present highly inhomogeneous manner in lateral direction throughout the Western Block. Crustal densities of the Sichuan Basin are much more homogeneous, and the whole lithosphere is denser than that of Western Block. In transitional area between the South China Block and the Chuan-Dian Block, with the decreasing of crustal density, crustal stability is also depressed. In addition, we obtained a detailed map of Moho using variable density model. The Moho topography undulates greatly beneath the Chuan-Dian region. The maximum crustal thickness difference of the Chuan-Dian region is

  15. Phenomenological Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Kimberly, Dagny; Magueijo, Joa~O.

    2005-08-01

    These notes summarize a set of lectures on phenomenological quantum gravity which one of us delivered and the other attended with great diligence. They cover an assortment of topics on the border between theoretical quantum gravity and observational anomalies. Specifically, we review non-linear relativity in its relation to loop quantum gravity and high energy cosmic rays. Although we follow a pedagogic approach we include an open section on unsolved problems, presented as exercises for the student. We also review varying constant models: the Brans-Dicke theory, the Bekenstein varying α model, and several more radical ideas. We show how they make contact with strange high-redshift data, and perhaps other cosmological puzzles. We conclude with a few remaining observational puzzles which have failed to make contact with quantum gravity, but who knows... We would like to thank Mario Novello for organizing an excellent school in Mangaratiba, in direct competition with a very fine beach indeed.

  16. Gravity and magnetic signatures of volcanic plugs related to Deccan volcanism in Saurashtra, India and their physical and geochemical properties

    NASA Astrophysics Data System (ADS)

    Chandrasekhar, D. V.; Mishra, D. C.; Poornachandra Rao, G. V. S.; Mallikharjuna Rao, J.

    2002-07-01

    The Bouguer anomaly and the total intensity magnetic maps of Saurashtra have delineated six circular gravity highs and magnetic anomalies of 40-60 mGal (10 -5m/s 2) and 800-1000 nT, respectively. Three of them in western Saurashtra coincide with known volcanic plugs associated with Deccan Volcanic Province (DVP), while the other three in SE Saurashtra coincide with rather concealed plugs exposed partially. The DVP represents different phases of eruption during 65.5±2.5 Ma from the Reunion plume. The geochemical data of the exposed rock samples from these plugs exhibit a wide variation in source composition, which varies from ultramafic/mafic to felsic composition of volcanic plugs in western Saurashtra and an alkaline composition for those in SE Saurashtra. Detailed studies of granophyres and alkaline rocks from these volcanic plugs reveal a calc-alkaline differentiation trend and a continental tectonic setting of emplacement. The alkaline plugs of SE Saurashtra are associated with NE-SW oriented structural trends, related to the Gulf of Cambay and the Cambay rift basin along the track of the Reunion plume. This indicates a deeper source for these plugs compared to those in the western part and may represent the primary source magma. The Junagadh plug with well differentiated ring complexes in western Saurashtra shows well defined centers of magnetic anomaly while the magnetic anomalies due to other plugs are diffused though of the same amplitude. This implies that other plugs are also associated with mafic/ultramafic components, which may not be differentiated and may be present at subsurface levels. Paleomagnetic measurements on surface rock samples from DVP in Saurashtra suggest a susceptibility of 5.5×10 -2 SI units with an average Koenigsberger ratio ( Qn) of almost one and average direction of remanent magnetization of D=147.4° and I=+56.1°. The virtual geomagnetic pole (VGP) position computed from the mean direction of magnetization for the volcanic

  17. Congenital anomalies

    PubMed Central

    Kunisaki, Shaun M.

    2012-01-01

    Over the past decade, amniotic fluid-derived stem cells have emerged as a novel, experimental approach for the treatment of a wide variety of congenital anomalies diagnosed either in utero or postnatally. There are a number of unique properties of amniotic fluid stem cells that have allowed it to become a major research focus. These include the relative ease of accessing amniotic fluid cells in a minimally invasive fashion by amniocentesis as well as the relatively rich population of progenitor cells obtained from a small aliquot of fluid. Mesenchymal stem cells, c-kit positive stem cells, as well as induced pluripotent stem cells have all been derived from human amniotic fluid in recent years. This article gives a pediatric surgeon’s perspective on amniotic fluid stem cell therapy for the management of congenital anomalies. The current status in the use of amniotic fluid-derived stem cells, particularly as they relate as substrates in tissue engineering-based applications, is described in various animal models. A roadmap for further study and eventual clinical application is also proposed. PMID:22986340

  18. New standards for reducing gravity data: The North American gravity database

    USGS Publications Warehouse

    Hinze, W. J.; Aiken, C.; Brozena, J.; Coakley, B.; Dater, D.; Flanagan, G.; Forsberg, R.; Hildenbrand, T.; Keller, Gordon R.; Kellogg, J.; Kucks, R.; Li, X.; Mainville, A.; Morin, R.; Pilkington, M.; Plouff, D.; Ravat, D.; Roman, D.; Urrutia-Fucugauchi, J.; Veronneau, M.; Webring, M.; Winester, D.

    2005-01-01

    The North American gravity database as well as databases from Canada, Mexico, and the United States are being revised to improve their coverage, versatility, and accuracy. An important part of this effort is revising procedures for calculating gravity anomalies, taking into account our enhanced computational power, improved terrain databases and datums, and increased interest in more accurately defining long-wavelength anomaly components. Users of the databases may note minor differences between previous and revised database values as a result of these procedures. Generally, the differences do not impact the interpretation of local anomalies but do improve regional anomaly studies. The most striking revision is the use of the internationally accepted terrestrial ellipsoid for the height datum of gravity stations rather than the conventionally used geoid or sea level. Principal facts of gravity observations and anomalies based on both revised and previous procedures together with germane metadata will be available on an interactive Web-based data system as well as from national agencies and data centers. The use of the revised procedures is encouraged for gravity data reduction because of the widespread use of the global positioning system in gravity fieldwork and the need for increased accuracy and precision of anomalies and consistency with North American and national databases. Anomalies based on the revised standards should be preceded by the adjective "ellipsoidal" to differentiate anomalies calculated using heights with respect to the ellipsoid from those based on conventional elevations referenced to the geoid. ?? 2005 Society of Exploration Geophysicists. All rights reserved.

  19. The deep crustal structure of the mafic-ultramafic Seiland Igneous Province of Norway from 3-D gravity modelling and geological implications

    NASA Astrophysics Data System (ADS)

    Pastore, Zeudia; Fichler, Christine; McEnroe, Suzanne A.

    2016-12-01

    The Seiland Igneous Province (SIP) is the largest complex of mafic and ultramafic intrusions in northern Fennoscandia intruded at ca. 580-560 Ma. The depth extent and the deep structure of the SIP are mainly unknown apart from three profiles modelled by gravity and refraction seismic data. Utilizing 3-D gravity modelling, a complex model of the deep subsurface structure of the SIP has been developed. The structure is presented in a multiprofile model ranging from the surface to the Moho. The mafic/ultramafic rocks of the SIP are modelled with densities of 3100 and 3300 kg m-3, the surrounding rocks by densities of 2700 and 2900 kg m-3 for upper and lower crust, respectively. This density model explains the pronounced positive Bouguer gravity anomaly of up to 100 mGal above background. Its minimum volume is estimated from the subsurface model to 17 000 km3 and as such we revise downwards the earlier estimations of 25 000 km3. The new subsurface model suggests that most of the SIP has a thickness between 2 and 4 km. An area with roots in an annular pattern is found and two deep-reaching roots have been identified located below the islands of Seiland and Sørøy. The depth of these roots is estimated to approximatively 9 km. The SIP is presently interpreted to be in the Caledonian Kalak Nappe Complex and the roots depth constrains its minimum thickness which is larger than earlier estimated. Furthermore, the rather undisturbed shape of the annular root pattern indicates that the SIP has not been subjected to strong tectonic reworking during the Caledonian orogeny.

  20. New insight on the recent tectonic evolution and uplift of the southern Ecuadorian Andes from gravity and structural analysis of the Neogene-Quaternary intramontane basins

    NASA Astrophysics Data System (ADS)

    Tamay, J.; Galindo-Zaldívar, J.; Ruano, P.; Soto, J.; Lamas, F.; Azañón, J. M.

    2016-10-01

    The sedimentary basins of Loja, Malacatos-Vilcabamba and Catamayo belong to the Neogene-Quaternary synorogenic intramontane basins of South Ecuador. They were formed during uplift of the Andes since Middle-Late Miocene as a result of the Nazca plate subduction beneath the South American continental margin. This E-W compressional tectonic event allowed for the development of NNE-SSW oriented folds and faults, determining the pattern and thickness of sedimentary infill. New gravity measurements in the sedimentary basins indicate negative Bouguer anomalies reaching up to -292 mGal related to thick continental crust and sedimentary infill. 2D gravity models along profiles orthogonal to N-S elongated basins determine their deep structure. Loja Basin is asymmetrical, with a thickness of sedimentary infill reaching more than 1200 m in the eastern part, which coincides with a zone of most intense compressive deformation. The tectonic structures include N-S, NW-SE and NE-SW oriented folds and associated east-facing reverse faults. The presence of liquefaction structures strongly suggests the occurrence of large earthquakes just after the sedimentation. The basin of Malacatos-Vilcabamba has some folds with N-S orientation. However, both Catamayo and Malacatos-Vilcabamba basins are essentially dominated by N-S to NW-SE normal faults, producing a strong asymmetry in the Catamayo Basin area. The initial stages of compression developed folds, reverse faults and the relief uplift determining the high altitude of the Loja Basin. As a consequence of the crustal thickening and in association with the dismantling of the top of the Andes Cordillera, extensional events favored the development of normal faults that mainly affect the basins of Catamayo and Malacatos-Vilcabamba. Gravity research helps to constrain the geometry of the Neogene-Quaternary sedimentary infill, shedding some light on its relationship with tectonic events and geodynamic processes during intramontane basin

  1. Environmental applications of gravity surveying

    SciTech Connect

    Barrows, L.J. ); Nesbit, L.C. ); Khan, W.A. )

    1994-04-01

    The Allis Park Sanitary Landfill Company developed a new landfill near Onway, Michigan in an area which has glacial alluvium and glacial till overlying limestone. There are several solution karst features in the region and some critics had maintained that a new karst collapse could rupture the liner system and allow escape of leachate into the groundwater. The gravity survey was conducted to determine the extent of any karst development at the site. The first portion of the survey was two profiles over some karst features located about five miles southeast of the proposed landfill. These showed negative gravity anomalies. The survey of the proposed landfill site resulted in a 50 microGal contour map of the area and also showed a negative anomaly. This could be due to either elevation variations on the till to limestone bedrock surface or to karst development within the limestone. Because there was no evidence of historic development of new karst features in the region, the gravity anomaly was not further investigated. In another gravity survey, a large retail department store had been remodeled and extended over an area previously occupied by an auto service center. The removal of a waste oil storage tank (UST) had not been documented and the environmental consultant (KEMRON, Inc.) proposed that a gravity survey be used to find the tank location. This proposal was based on calculations of the gravity effects of a UST. The survey resulted in a four-microGal contour map which showed a couple of anomalies which could be due to a tank or a backfilled tank excavation. During the survey, a store employee identified the previous location of the tank and explained that she had personally witnessed its removal. Based on the employee's eye-witness account of the tank removal and the coincidence of her indicated tank location with one of the gravity anomalies the authors recommended the site be granted clean closure.

  2. Combined magnetic and gravity analysis

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Braile, L. W.; Chandler, V. W.; Mazella, F. E.

    1975-01-01

    Efforts are made to identify methods of decreasing magnetic interpretation ambiguity by combined gravity and magnetic analysis, to evaluate these techniques in a preliminary manner, to consider the geologic and geophysical implications of correlation, and to recommend a course of action to evaluate methods of correlating gravity and magnetic anomalies. The major thrust of the study was a search and review of the literature. The literature of geophysics, geology, geography, and statistics was searched for articles dealing with spatial correlation of independent variables. An annotated bibliography referencing the Germane articles and books is presented. The methods of combined gravity and magnetic analysis techniques are identified and reviewed. A more comprehensive evaluation of two types of techniques is presented. Internal correspondence of anomaly amplitudes is examined and a combined analysis is done utilizing Poisson's theorem. The geologic and geophysical implications of gravity and magnetic correlation based on both theoretical and empirical relationships are discussed.

  3. Regional magnetic anomaly constraints on continental rifting

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

  4. The mineralogy of global magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E. (Principal Investigator)

    1982-01-01

    The Curie Balance was brought to operational stage and is producing data of a preliminary nature. Substantial problems experienced in the assembly and initial operation of the instrument were, for the most part, rectified, but certain problems still exist. Relationships between the geology and the gravity and MAGSAT anomalies of West Africa are reexamined in the context of a partial reconstruction of Gondwanaland.

  5. Farside lunar gravity from a mass point model

    NASA Technical Reports Server (NTRS)

    Ananda, M.

    1975-01-01

    A mass point representation of the lunar gravity field was determined from the long-period orbital variations of the Apollo 15 and 16 subsatellites and Lunar Orbiter V. A radial acceleration contour map, evaluated at 100 km altitude from the lunar surface, shows that the nearside is in close agreement with the result derived from the line of sight method by Muller and Sjogren. The farside map shows the highland regions as broad positive gravity anomaly areas and the basins such as Korolev, Hertzsprung, Moscoviense, Mendeleev, and Tsiolkovsky as localized, negative gravity anomaly regions. The farside map has a first-order agreement with the result derived from the harmonic field method by Ferrari. The mass points analysis indicates that the nearside is almost all negative gravity anomaly regions except for the known positive mass anomaly basins (mascons) and the farside is almost all positive gravity anomaly regions except for some localized negative areas near the basins.

  6. Geoid anomalies over Gorringe Ridge, North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Souriau, A.

    1984-04-01

    The geoid anomalies over Gorringe Ridge, a very prominent high in the topography north of the Azores-Gibraltar plate boundary, have been deduced from Seasat alimetric data, and an interpretation of these anomalies together with the gravity anomalies is attempted. The geoid anomalies generated by the topographic high alone with the serpentinite density nearly fit the observed geoid anomalies, so that the structure must be either out of isostatic equilibrium or compensated at great depth. It is shown that a model in isostatic equilibrium with a small negative density contrast extending to 60 km depth or more explains both the gravity and geoid anomalies and is compatible with the deep seismicity north of Gorringe Ridge. Previous nonisostatic models, one involving an uplift of the upper mantle beneath the ridge, one describing a nascent subduction zone, and another involving flexure of the elastic part of the lithosphere due to the ridge loading, are discussed.

  7. Geopotential field anomalies and regional tectonic features

    NASA Astrophysics Data System (ADS)

    Mandea, Mioara; Korte, Monika

    2016-07-01

    Maps of both gravity and magnetic field anomalies offer crucial information about physical properties of the Earth's crust and upper mantle, required in understanding geological settings and tectonic structures. Density and magnetization represent independent rock properties and thus provide complementary information on compositional and structural changes. Two regions are considered: southern Africa (encompassing South Africa, Namibia and Botswana) and Germany. This twofold choice is motivated firstly by the fact that these regions represent rather diverse geological and geophysical conditions (old Archean crust with strong magnetic anomalies in southern Africa, and much younger, weakly magnetized crust in central Europe) and secondly by our intimate knowledge of the magnetic vector ground data from these two regions. We take also advantage of the recently developed satellite potential field models and compare magnetic and gravity gradient anomalies of some 200 km resolution. Comparing short and long wavelength anomalies and the correlation of rather large scale magnetic and gravity anomalies, and relating them to known lithospheric structures, we generally find a better agreement over the southern African region than the German territory. This probably indicates a stronger concordance between near-surface and deeper structures in the former area, which can be perceived to agree with a thicker lithosphere.

  8. Gauge anomalies, gravitational anomalies, and superstrings

    SciTech Connect

    Bardeen, W.A.

    1985-08-01

    The structure of gauge and gravitational anomalies will be reviewed. The impact of these anomalies on the construction, consistency, and application of the new superstring theories will be discussed. 25 refs.

  9. New Insights into the Tectonics of the Midcontintent of U.S.A. from EarthScope USArray Seismic, Gravity, Magnetic and Heat Flow Datasets

    NASA Astrophysics Data System (ADS)

    Ravat, D.; Zhang, H.; Newman, L. C. C.; Lowry, A. R.

    2015-12-01

    We examine crustal and upper mantle structure and physical parameters from EarthScope USArray receiver functions, seismic tomography, gravity, and magnetic anomaly data to understand the tectonic framework of the midcontinent of the U.S. (New Madrid Seismic Zone/Rift Complex, Illinois Basin, Tennessee-Illinois-Kentucky Lineament (TIKL), and Grenville Front). The neodymium (Nd) crustal formation boundary seen in geochemical and the long-wavelength magnetic anomaly data is not apparent in the crustal or mantle seismic parameters or density. This is not completely surprising since the Nd systematics and magnetization is controlled by accessory minerals rather than bulk physical parameters. The USArray station spacing is not sufficient to capture the density and corresponding magnetic variations associated with mafic plutons except where stations are located over the plutons themselves (e.g., the Bloomfield Pluton). With the standard Moho density contrasts, Vp/Vs based crustal densities, and mantle velocity-density relationships, significant long-wavelength residuals (misfit) between observed and modeled Bouguer gravity anomalies remain over the Illinois Basin, the TIKL, and the Grenville Front in Ohio, extending north into Lake Erie and New York. Jointly inverted USArray receiver functions and gravity based Vp/Vs and the crustal thickness suggest that the Moho in the western Illinois basin and the Grenville Front in Ohio are thicker than previously known (about 50 km). The bottom of the strong crustal magnetization layer is unusually thin (15-20 km) in the New Madrid Seismic Zone, which extends northward from there into Illinois, northern Missouri and Indiana. In the Rough Creek Graben, the magnetic layer thickness is about 40 km, which is consistent with the non-magmatic nature of that branch of the rift. These observation may also imply that the rift related basal crustal layer in the New Madrid Seismic Zone is non-magnetic or very weakly magnetic. The thinner

  10. The Mystery of the Mars North Polar Gravity-Topography Correlation(Or Lack Thereof)

    NASA Technical Reports Server (NTRS)

    Phillips, R. J.; Sjogren, W. L.; Johnson, C. L.

    1999-01-01

    Maps of moderately high resolution gravity data obtained from the Mars Global Surveyor (MGS) gravity calibration orbit campaign and high precision topography obtained from the Mars Orbiter Laser Altimeter (MOLA) experiment reveal relationships between gravity and topography in high northern latitudes of Mars. Figure 1 shows the results of a JPL spherical harmonic gravity model bandpass filtered between degrees 6 and 50 contoured over a MOLA topographic image. A positive gravity anomaly exists over the main North Polar cap, but there are at least six additional positive gravity anomalies, as well as a number of smaller negative anomalies, with no obvious correlation to topography. Additional information is contained in the original extended abstract.

  11. The elliptic anomaly

    NASA Technical Reports Server (NTRS)

    Janin, G.; Bond, V. R.

    1980-01-01

    An independent variable different from the time for elliptic orbit integration is used. Such a time transformation provides an analytical step-size regulation along the orbit. An intermediate anomaly (an anomaly intermediate between the eccentric and the true anomaly) is suggested for optimum performances. A particular case of an intermediate anomaly (the elliptic anomaly) is defined, and its relation with the other anomalies is developed.

  12. Subsurface structural mapping of Northern Nasser Lake region, Aswan, Egypt, using Bouguer data

    NASA Astrophysics Data System (ADS)

    Saleh, Salah

    2011-01-01

    In this study, we attempt to delineate the subsurface structures for the tectonic active region of Northern Nasser Lake using integrated interpretation techniques of gravity data with seismicity. The depths to the gravity sources, and the locations of the contacts of density contrast were estimated. Two methods were used for estimating source depths and contact locations: horizontal gradient (HG) and Euler deconvolution methods. Moreover, power spectral analysis, bandpass and upward continuation techniques were applied to evaluate the shallow and deep seated structures. Shallow depth structures were ranging between 0.30 km and 0.80 km. However, two average levels (interfaces) at depth 3.1 km and 7.2 km below the measuring level were revealed for the intermediate and deep seated structures respectively. Results of Euler deconvolution method suggested that, in the eastern part of the area, the basement could be observed on the ground and has become deeper in the central part. The interpreted structural map reveals that the area is affected by a set of faults trending mainly in the NW, E-W, N-S and NE-SW directions. Actually, this map has confirmed the idea that the intersections between the N-S and E-W striking faults along Nasser Lake area have generated seismic pulses. Moreover, three seismic zones (Z1, Z2 and Z3) are well correlated with the fault trends of the subsurface structures as derived from the horizontal gradient map. The present results suggest that there exist seismically-active fault east of High Dam, passing throughout Aswan reservoir from north to south. This fault is occupying region of high stress values which may generate large earthquakes in future, as it has long extension over several kilometers. Furthermore, the evaluated intruded volcanic bodies are found almost at the intersections between the E-W and NW oriented faults. Finally, the area is dissected by basement uplifts and troughs controlled mainly by the NW-SE faults.

  13. Global variations in gravity-derived oceanic crustal thickness: Implications on oceanic crustal accretion and hotspot-lithosphere interactions

    NASA Astrophysics Data System (ADS)

    Lin, J.; Zhu, J.

    2012-12-01

    We present a new global model of oceanic crustal thickness based on inversion of global oceanic gravity anomaly with constrains from seismic crustal thickness profiles. We first removed from the observed marine free-air gravity anomaly all gravitational effects that can be estimated and removed using independent constraints, including the effects of seafloor topography, marine sediment thickness, and the age-dependent thermal structure of the oceanic lithosphere. We then calculated models of gravity-derived crustal thickness through inversion of the residual mantle Bouguer anomaly using best-fitting gravity-modeling parameters obtained from comparison with seismically determined crustal thickness profiles. Modeling results show that about 5% of the global crustal volume (or 9% of the global oceanic surface area) is associated with model crustal thickness <5.2 km (designated as "thin" crust), while 56% of the crustal volume (or 65% of the surface area) is associated with crustal thickness of 5.2-8.6 km thick (designated as "normal" crust). The remaining 39% of the crustal volume (or 26% of the surface area) is associated with crustal thickness >8.6 km and is interpreted to have been affected by excess magmatism. The percentage of oceanic crustal volume that is associated with thick crustal thickness (>8.6 km) varies greatly among tectonic plates: Pacific (33%), Africa (50%), Antarctic (33%), Australia (30%), South America (34%), Nazca (23%), North America (47%), India (74%), Eurasia (68%), Cocos (20%), Philippine (26%), Scotia (41%), Caribbean (89%), Arabian (82%), and Juan de Fuca (21%). We also found that distribution of thickened oceanic crust (>8.6 km) seems to depend on spreading rate and lithospheric age: (1) On ocean basins younger than 5 Ma, regions of thickened crust are predominantly associated with slow and ultraslow spreading ridges. The relatively strong lithospheric plate at slow and ultraslow ridges might facilitate the loading of large magmatic

  14. Inversion for sources of crustal deformation and gravity change at the Yellowstone caldera

    SciTech Connect

    Vasco, D.W.; Taylor, C.L. ); Smith, R.B. )

    1990-11-10

    The Yellowstone caldera was formed in the latest of three explosive eruptions of rhyolites and ash flow tuffs totaling 3,700 km{sup 3} at 2, 1.2, and 0.6 m.y. before present. Its youthful volcanic history, widespread hydrothermal activity, intense seismicity, and extremely high heat flow, in excess of 30 times the continental average, marks the Yellowstone volcanic system as a giant caldera at unrest. Orthometric height increases of the caldera of up to 76 cm, measured from precise leveling surveys from 1923 to 1975-1977, were inverted to determine volume expansion source models for the caldera-wide deformation. For the 1923 to 1977 uplift episode, two regions of expansion were found: (1) in the northern part of the caldera near the Sour Creek resurgent dome of {approximately}0.37 km{sub 3}, and (2) in the southern part of the caldera, near the Mallard Lake resurgent dome of {approximately}0.41 km{sub 3}. Both bodies occur in the upper crust from near-surface depths to 6.0 km, but the largest volume expansions were found in the 3.0-6.0 km depth range. The southern caldera source volume, near the Mallard Lake dome, may extend down to 9.0 km. From 1976 to 1987, nearly simultaneous measurements of elevation and gravity changes were made on a profile across the northern caldera during a period of net uplift. Models of the temporal gravity variation infer that the volume increase for the northern caldera source must lie above 9.0 km and involved a density perturbation greater than +0.002 g/cm{sup 3}. The modeled volumetric sources are in the same general locations as bodies of low P wave velocities, high seismic attenuation, and large negative Bouguer gravity anomalies. It is likely that the modeled volumetric increases were caused by migration of magmas and/or the introduction of large volumes of hydrothermal fluids into the upper crust.

  15. The Effect of Pre-Impact Porosity and Vertical Density Gradients on the Gravity Signature of Lunar Craters

    NASA Astrophysics Data System (ADS)

    Milbury, Colleen; Johnson, Brandon C.; Melosh, H. Jay; Collins, Gareth S.; Blair, David M.; Soderblom, Jason M.; Nimmo, Francis; Phillips, Roger J.; Bierson, Carver J.; Zuber, Maria T.

    2015-11-01

    As a result of NASA’s dual spacecraft Gravity Recovery And Interior Laboratory (GRAIL) mission [Zuber et al., 2013; doi:10.1126/science.1231507], we now know that the lunar crust is highly porous and that the porosity varies laterally [Wieczorek et al., 2013; doi:10.1126/science.1231530] and vertically [Besserer et al., 2014; doi:10.1002/2014GL060240]. Analysis of complex craters located within the lunar highlands reveals that: 1) craters larger than diameter D~210 have positive Bouguer Anomalies (BAs), 2) craters with D ≲ 100 km have both positive and negative BAs that vary about the (near 0) mean by approximately ± 25 mGal, and, 3) D and BA are anticorrelated for craters with D ≲ 100 km [Soderblom et al., 2015; doi:10.1002/2015GL065022]. Numerical modeling by Milbury et al. [2015, LPSC] shows that pre-impact porosity is the dominant influence on the gravity signature of complex craters with D ≲ 100 km, and mantle uplift dominates the gravity for those with D > 140 km. Phillips et al. [2015, LPSC] showed that complex craters located in the South Pole-Aitken (SPA) basin tend to have more-negative BAs than similar craters in the highlands. We use the iSALE hydrocode including pore space compaction [Wünnemann et al., 2006; doi:10.1016/j.icarus.2005.10.013] and dilatant bulking [Collins, 2014; doi:10.1002/2014JE004708] to understand how the gravity signature of impact craters develop. In this study we vary crustal porosity with depth. We find that simulations that have constant porosity with depth have a lower BA for a given crater diameter than those with the same mean porosity, but that vary with depth. We used two different mean porosities (7% and 14%) and found that the BA increases with increasing porosity, similar to simulations with constant porosity. We reproduce the observed anticorrelation between BA and D for D ≲ 100 km only for simulations where the pre-impact porosity is zero or low. Our results support the observation that SPA has lower

  16. 3D gravity inversion and Euler deconvolution to delineate the hydro-tectonic regime in El-Arish area, northern Sinai Peninsula

    NASA Astrophysics Data System (ADS)

    Khalil, Mohamed A.; Santos, Fernando M.; Farzamian, Mohammad

    2014-04-01

    Sinai Peninsula occupies a part of the arid zone belt of northern Africa and southwestern Asia. The largest ephemeral stream in the Sinai Peninsula is called Wadi El-Arish, which winds down northward to the Mediterranean Sea. The delta of Wadi El-Arish has been built by the heavy floods of the Wadi. The Quaternary aquifer is the main water supply of the delta of Wadi El-Arish and its vicinities. The combined action of aridity and extensive pumping from the Quaternary aquifer led to a noticeable increase in groundwater salinity. The hydrochemistry and isotope hydrology confirm that the Quaternary aquifer is recharged by an old saline groundwater from the Pre-Quaternary. A hydrogeological connection between Quaternary and Pre-Quaternary aquifers in the form of fault(s) should exist to explain the hydro-tectonic regime of this area. The Bouguer gravity map shows the high gravity anomaly of the doubly plunging anticline of Risan Aniza Mountain to the south of El-Arish area, which is a part of the Syrian Arc System of northern Sinai Peninsula. A 3D density contrast model, 3D Euler deconvolution, horizontal derivative and least square separation have been performed. The findings showed that (1) two deep regional faults extending NE-SW, surround the Risan Aniza anticline, and (2) two deep local N-S faults are in the area of Delta Wadi El-Arish. These deep faults are proposed to bring the deep Cretaceous aquifer into contact with the shallow Quaternary aquifer and work as a hydrogeological connection between both aquifers. The present hypothesis has some geological evidences from the subsurface lithology of the nearby wells.

  17. Chiral anomalies and differential geometry

    SciTech Connect

    Zumino, B.

    1983-10-01

    Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)

  18. Gravity Waves

    Atmospheric Science Data Center

    2013-04-19

    article title:  Gravity Waves Ripple over Marine Stratocumulus Clouds ... Imaging SpectroRadiometer (MISR), a fingerprint-like gravity wave feature occurs over a deck of marine stratocumulus clouds. Similar ... that occur when a pebble is thrown into a still pond, such "gravity waves" sometimes appear when the relatively stable and stratified air ...

  19. A wavelet transformation approach for multi-source gravity fusion: Applications and uncertainty tests

    NASA Astrophysics Data System (ADS)

    Bai, Yongliang; Dong, Dongdong; Wu, Shiguo; Liu, Zhan; Zhang, Guangxu; Xu, Kaijun

    2016-05-01

    Gravity anomalies detected by different measurement platforms have different characteristics and advantages. There are different kinds of gravity data fusion methods for generating single gravity anomaly map with a rich and accurate spectral content. Former studies using wavelet based gravity fusion method which is a newly developed approach did not pay more attention to the fusion uncertainties. In this paper, we firstly introduce the wavelet based gravity fusion method, and then apply this method to one synthetic model and also to the northern margin of the South China Sea. Wavelet type and the decomposition level are two input parameters for this fusion method, and the uncertainty tests show that fusion results are more sensitive to wavelet type than the decomposition level. The optimal application result of the fusion methodology on the synthetic model is closer to the true anomaly field than either of the simulated shipborne anomaly and altimetry-based anomaly grid. The best fusion result on the northern margin of the South China Sea is based on the 'rbio1.3' wavelet and four-level decomposition. The fusion result contains more accurate short-wavelength anomalies than the altimetry-based gravity anomalies along ship tracks, and it also has more accurate long wavelength characteristics than the shipborne gravity anomalies between ship tracks. The real application case shows that the fusion result has better correspondences to the seafloor topography variations and sub-surface structures than each of the two input gravity anomaly maps (shipborne based gravity anomaly map and altimetry based gravity anomaly map). Therefore, it is possible to map and detect more precise seafloor topography and geologic structures by the new gravity anomaly map.

  20. Three-dimensional gravity ideal body studies in rough terrain

    SciTech Connect

    Ander, M.E.; Huestis, S.P.

    1985-01-01

    An approach to the interpretation of potential field anomaly data is to maximize or minimize some non-linear scalar property of solutions fitting the data. As an example, a comparison of 2-D and 3-D gravity ideal body results from the Lucero Uplift, a westward-tilted fault block located on the western flank of the Rio Grande rift, is discussed. The anomaly was analyzed to obtain bounds on the density contrast, depth of burial, and minimum thickness of its sources. Based on a synthesis of the gravity data with structural analysis and geomorphology, a shallow mafic intrusion is proposed to account for the positive gravity anomaly. 12 refs. (ACR)

  1. Processing Marine Gravity Data Around Korea

    NASA Astrophysics Data System (ADS)

    Lee, Y.; Choi, K.; Kim, Y.; Ahn, Y.; Chang, M.

    2008-12-01

    In Korea currently 4 research ships are under operating in Korea, after the first research vessel equipped shipborne gravity meter was introduced in 1990s. These are Onnuri(launch 1991) of KORDI(Korea Ocean Research & Development Institute), Haeyang2000(launch 1996), Badaro1(launch 2002) of NORI(National Oceanographic Research Institute) and Tamhae2(launch 1997) of KIGAM(Korea Institute of Geoscience and Mineral Resources). Those of research vessel, Haeyang2000 have observed marine gravity data over 150,000 points each year from year 1996 to year 2003. Haeyang2000, about 2,500 tons, is unable to operate onshore so NORI has constructed another 600 tons research ship Badaro1 that has observed marine gravity data onshore since year 2002. Haeyang2000 finished observing marine gravity data offshore within Korean territorial waters until year 2003. Currently Badaro1 is observing marine gravity data onshore. These shipborne gravity data will be very useful and important on geodesy and geophysics research also those data can make a contribution to developing these studies. In this study NORI's shipbrne gravity data from 1996 to 2007 has been processed for fundamental data to compute Korean precise geoid. Marine gravity processing steps as followed. 1. Check the time sequence, latitude and longitude position, etc. of shipborne gravity data 2. Arrangement of the tide level below the pier and meter drift correction of each cruise. 3. Elimination of turning points. 4. The time lag correction. 5. Computation of RV's velocities, Heading angles and the Eötvös correction. 6. Kalman filtering of GPS navigation data using cross-over points. 7. Cross-over correction using least square adjustment. About 2,058,000 points have been processed with NORI's marine gravity data from 1996 to 2007 in this study. The distribution of free-air anomalies was -41.0 mgal to 136.0 mgal(mean 8.90mgal) within Korean territorial waters. The free-air anomalies processed with the marine gravity data are

  2. 2006 Compilation of Alaska Gravity Data and Historical Reports

    USGS Publications Warehouse

    Saltus, Richard W.; Brown, Philip J.; Morin, Robert L.; Hill, Patricia L.

    2008-01-01

    Gravity anomalies provide fundamental geophysical information about Earth structure and dynamics. To increase geologic and geodynamic understanding of Alaska, the U.S. Geological Survey (USGS) has collected and processed Alaska gravity data for the past 50 years. This report introduces and describes an integrated, State-wide gravity database and provides accompanying gravity calculation tools to assist in its application. Additional information includes gravity base station descriptions and digital scans of historical USGS reports. The gravity calculation tools enable the user to reduce new gravity data in a consistent manner for combination with the existing database. This database has sufficient resolution to define the regional gravity anomalies of Alaska. Interpretation of regional gravity anomalies in parts of the State are hampered by the lack of local isostatic compensation in both southern and northern Alaska. However, when filtered appropriately, the Alaska gravity data show regional features having geologic significance. These features include gravity lows caused by low-density rocks of Cenozoic basins, flysch belts, and felsic intrusions, as well as many gravity highs associated with high-density mafic and ultramafic complexes.

  3. Potential causes of absolute gravity changes in Taiwan over 2004-2014

    NASA Astrophysics Data System (ADS)

    Kao, R.; Hwang, C.; Kim, J. W.; Masson, F.; Mouyen, M.

    2015-12-01

    We use absolute gravimeter (AG) and GPS observations collected from 2004 to 2014 in Taiwan to identify mass changes in connection to Moho deepening, volcanism, subsidence, earthquake and plate collision. The gravity observations are measured at sites of different geological settings under the AGTO and NGDS projects. The resulting gravity changes cannot be fully explained by vertical motions derived from GPS. Unlike previous AG gravity studies in Taiwan, we apply hydrology-induced gravity changes to raw gravity measurements using a simple model that estimates the Bouguer gravity effect due to rainfalls. Typhoon Morakot, occurring on August 8, 2009, results in torrential rainfalls and large debris flows in southern Taiwan. Morakot causes a gravity increase of 51.22 μGal near an AG site along the southern cross-island highway. The M7.0 Hengchun earthquake on December 26, 2006 causes a gravity rise of 2.32 μGal at the KDNG AG site near its epicenter. A Moho thickening rate (-0.81 μGal/yr) in central Taiwan and a deep-fault slip rate (-0.94 μGal/yr) in eastern Taiwan are postulated from the gravity changes. Other distinct gravity changes are potentially associated with the subsidence in Yunlin County (-2.73 μGal/yr), the magma coolings in Tatun Volcano Group (0.12 μGal/yr), Green Island (-2.95 μGal/yr) and Orchid Island (-0.97μGal/yr).

  4. Lymphatic Anomalies Registry

    ClinicalTrials.gov

    2016-07-26

    Lymphatic Malformation; Generalized Lymphatic Anomaly (GLA); Central Conducting Lymphatic Anomaly; CLOVES Syndrome; Gorham-Stout Disease ("Disappearing Bone Disease"); Blue Rubber Bleb Nevus Syndrome; Kaposiform Lymphangiomatosis; Kaposiform Hemangioendothelioma/Tufted Angioma; Klippel-Trenaunay Syndrome; Lymphangiomatosis

  5. Antarctic marine gravity field from high-density satellite altimetry

    NASA Technical Reports Server (NTRS)

    Sandwell, David T.

    1992-01-01

    High-density (about 2-km profile spacing) Geosat/GM altimetry profiles were obtained for Antarctic waters (6-deg S to 72 deg S) and converted to vertical gravity gradient, using Laplace's equation to directly calculate gravity gradient from vertical deflection grids and Fourier analysis to construct gravity anomalies from two vertical deflection grids. The resultant gravity grids have resolution and accuracy comparable to shipboard gravity profiles. The obtained gravity maps display many interesting and previously uncharted features, such as a propagating rift wake and a large 'leaky transform' along the Pacific-Antarctic Rise.

  6. Ebstein anomaly: a review.

    PubMed

    Galea, Joseph; Ellul, Sarah; Schembri, Aaron; Schembri-Wismayer, Pierre; Calleja-Agius, Jean

    2014-01-01

    Cardiac congenital abnormalities are a leading cause in neonatal mortality occurring in up to 1 in 200 of live births. Ebstein anomaly, also known as Kassamali anomaly, accounts for 1 percent of all congenital cardiac anomalies. This congenital abnormality involves malformation of the tricuspid valve and of the right ventricle. In this review, the causes of the anomaly are outlined and the pathophysiology is discussed, with a focus on the symptoms, management, and treatments available to date.

  7. Venus gravity

    NASA Technical Reports Server (NTRS)

    Reasenberg, Robert D.

    1993-01-01

    The anomalous gravity field of Venus shows high correlation with surface features revealed by radar. We extract gravity models from the Doppler tracking data from the Pioneer Venus Orbiter (PVO) by means of a two-step process. In the first step, we solve the nonlinear spacecraft state estimation problem using a Kalman filter-smoother. The Kalman filter was evaluated through simulations. This evaluation and some unusual features of the filter are discussed. In the second step, we perform a geophysical inversion using a linear Bayesian estimator. To allow an unbiased comparison between gravity and topography, we use a simulation technique to smooth and distort the radar topographic data so as to yield maps having the same characteristics as our gravity maps. The maps presented cover 2/3 of the surface of Venus and display the strong topography-gravity correlation previously reported. The topography-gravity scatter plots show two distinct trends.

  8. Mars gravity field via the short data arcs

    NASA Technical Reports Server (NTRS)

    Sjogren, W. L.; Lorell, J.; Reinbold, S. J.; Wimberly, R. N.

    1973-01-01

    Short arc reduction of satellite Mars tracking data shows that: (1) There is one large gravity high covering the region of Nix Olympica and the three peaks to the east (about 110 deg longitude). It has an amplitude of 50 milligals at 2200-km altitude and implies a surface mass anomaly times greater than any on earth; (2) there are no large negative gravity anomalies comparable to the positive; and (3) the large 3000-km canyon seems to originate in a gravity high and end in a gravity low.

  9. Spacecraft Environmental Anomalies Handbook

    DTIC Science & Technology

    1989-08-01

    engineering solutions for mitigating the effects of environmental anomalies have been developed. Among the causes o, spacecraft anomalies are surface...have been discovered after years of investig!:tion, and engineering solutions for mitigating the effccts of environmental anomalies have been developed...23 * 6.4.3 Fauth Tolerant Solutions .............................................................................. 23 6.4.4. Methods

  10. South Atlantic Anomaly

    Atmospheric Science Data Center

    2013-04-19

    article title:  The South Atlantic Anomaly     View larger GIF image The South Atlantic Anomaly (SAA) . Even before the cover opened, the Multi-angle Imaging ... Atlantic Anomaly location:  Atlantic Ocean Global Images First Light Images region:  Before the ...

  11. Constraining the rheology of the lithosphere through joint geodynamic and gravity inversion

    NASA Astrophysics Data System (ADS)

    Kaus, Boris; Baumann, Tobias; Popov, Anton

    2014-05-01

    Understanding the physics of lithospheric deformation requires good constraints on lithospheric rheology and in particular on the effective viscosity. Typically, rheology is determined from laboratory experiments on small rock samples, which are extrapolated to geological conditions - an extrapolation over 10 orders of magnitude in deformation rates. Ideally, we thus need a new independent method that allows constraining the effective rheology of the lithosphere directly from geophysical data, which is the aim of this work. Our method uses the fact that the geodynamically controlling parameters of lithospheric deformation are its effective viscosity and density structure. By appropriately parametrising the rheological structure of the lithosphere we perform instantaneous forward simulations of present-day lithospheric deformation scenarios with a finite element method to compute the gravity field as well as surface velocities. The forward modelling results can be compared with observations such as Bouguer anomalies and GPS-derived surface velocities. More precisely, we automatise the forward modelling procedure with a Markov-Chain Monte Carlo method, and in fact solve a joint geodynamic and gravity inverse problem. The resulting misfit can be illustrated as a function of rheological model parameters and a more detailed analysis allows constraining probabilistic parameter ranges. Yet, the lithosphere has non-linear rheologies that can be plastic or temperature-dependent powerlaw creep depending on stresses. As the thermal structure of the lithosphere is in general poorly constrained, and only affects the dynamics of the lithosphere in an indirect manner, we developed a parameterised rheology that excludes a direct temperature dependency. To test the accuracy of this approximation we perform lithospheric-scale collision forward models that incorporate a temperature-dependent visco-plastic rheology to create synthetic surface observations. In a second step, we deploy

  12. A combined magnetometry and gravity study across Zagros orogeny in Iran

    NASA Astrophysics Data System (ADS)

    Abedi, Maysam; Oskooi, Behrooz

    2015-11-01

    the Urumieh-Dokhtar Magmatic Assemblage (UDMA). The UDMA zone increases the magnetic and the Bouguer anomalies by intruding into the CD zone as well.

  13. Gravity Effects of Solar Eclipse and Inducted Gravitational Field

    NASA Astrophysics Data System (ADS)

    Tang, K.; Wang, Q.; Zhang, H.; Hua, C.; Peng, F.; Hu, K.

    2003-12-01

    During solar eclipses in recent decades, gravity anomalies were observed and difficult to be explained by Newton's gravitational theory. During the solar eclipse of 1995, India scientists Mishra et al. recorded a gravity valley in amplitude of 12 μ Gal; they interpreted that qualitatively as atmospheric effects. During the total solar eclipse of March 1997, we conducted a comprehensive geophysical observation at Mohe geophysical observatory of China (with latitude of 53.490 N and longitude of 122.340 E. From the data we recorded, we found two valleys about 5 to 7 μ Gal. Unnikrishnan et al. inferred this gravity anomaly was caused by the environment changes. We know that the observation had been conducting in a room inside a small building with a stable coal heating system; the temperature variation inside the experimental room was less 10C during the eclipse. Moreover, the measured atmospheric pressure change was less 1hPa during the eclipse. It is reasonable to believe that surrounding environment of the observatory excluded the significant gravity variations caused by temperature, pressure variation and local moving of persons and vehicles. To further study the gravity effects related to solar eclipses, our scientific team took more observations during Zambia total solar eclipse of June 2001 and Australia total solar eclipse of December 2002. After data corrections, we found respectively two gravity anomalies, with 3 to 4μ Gal for Zambia eclipse and 1.5μ Gal for Australia eclipse. As many scientists have pointed out that pressure-gravity factor is lower than 0.3μ Gal/hPa, it means that any gravity anomaly great than 0.5μ Gal could not be inferred as the results of atmospheric pressure change. The two more gravity anomalies recorded during the solar eclipses provided us strong evidences that some gravity anomalies could not simply be inferred as atmospheric pressure change. We have tried to explain those anomalies by the induced gravitational field.

  14. Detailed petrophysical characterization enhances geological mapping of a buried substratum using aeromagnetic and gravity data; application to the southwestern Paris basin

    NASA Astrophysics Data System (ADS)

    Baptiste, Julien; Martelet, Guillaume; Faure, Michel; Beccaletto, Laurent; Chen, Yan; Reninger, Pierre-Alexandre

    2016-04-01

    Mapping the geometries (structure and lithology) of a buried basement is a key for targeting resources and for improving the regional geological knowledge. The Paris basin is a Mesozoic to Cenozoic intraplate basin set up on a Variscan substratum, which crops out in the surrounding massifs. We focus our study on the southwestern part of the Paris basin at its junction with the Aquitaine basin. This Mezo-Cenozoic cover separates the Armorican Massif and the Massif Central which compose of several litho-tectonic units bounded by crustal-scale shear zones. In spite of several lithological and structural correlations between various domains of the two massifs, their geological connection, hidden below the Paris basin sedimentary cover, is still largely debated. Potential field geophysics have proven effective for mapping buried basin/basement interfaces. In order to enhance the cartographic interpretation of these data, we have set up a detailed petrophysical library (field magnetic susceptibility data and density measurements on rock samples) of the Paleozoic rocks outcropping in the Variscan massifs. The combination of aeromagnetic and gravity data supported by the petrophysical signatures and field/borehole geological information, is carried out to propose a new map of the architecture of the Variscan substratum. The new synthetic map of geophysical signature of the Paris basin basement combines: i) the magnetic anomaly reduced to the pole, ii) the vertical gradient of the Bouguer anomaly and iii) the tilt derivative of the magnetic anomaly reduced to the pole. Based on this information, the Eastern extension of the major shear zones below the sedimentary cover is assessed. The petrophysical signatures were classified in three classes of magnetic susceptibility and density: low, intermediate and high. Basic rocks have high magnetization and density values whereas granite, migmatite and orthogneiss show low magnetization and density values, Proterozoic and Paleozoic

  15. Analysis of spacecraft anomalies

    NASA Technical Reports Server (NTRS)

    Bloomquist, C. E.; Graham, W. C.

    1976-01-01

    The anomalies from 316 spacecraft covering the entire U.S. space program were analyzed to determine if there were any experimental or technological programs which could be implemented to remove the anomalies from future space activity. Thirty specific categories of anomalies were found to cover nearly 85 percent of all observed anomalies. Thirteen experiments were defined to deal with 17 of these categories; nine additional experiments were identified to deal with other classes of observed and anticipated anomalies. Preliminary analyses indicate that all 22 experimental programs are both technically feasible and economically viable.

  16. The mineralogy of global magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E. (Principal Investigator)

    1984-01-01

    Experimental and analytical data on magnetic mineralogy was provided as an aid to the interpretation of magnetic anomaly maps. An integrated program, ranging from the chemistry of materials from 100 or more km depth within the Earth, to an examination of the MAGSAT anomaly maps at about 400 km above the Earth's surface, was undertaken. Within this framework, a detailed picture of the pertinent mineralogical and magnetic relationships for the region of West Africa was provided. Efforts were directed toward: (1) examining the geochemistry, mineralogy, magnetic properties, and phases relations of magnetic oxides and metal alloys in rocks demonstrated to have originated in the lower crust of upper mantle, (2) examining the assumption that these rocks portray the nature of their source regions; and (3) examining the regional geology, tectonics, gravity field and the MAGSAT anomaly maps for West Africa.

  17. The "parity" anomaly on an unorientable manifold

    NASA Astrophysics Data System (ADS)

    Witten, Edward

    2016-11-01

    The "parity" anomaly—more accurately described as an anomaly in time-reversal or reflection symmetry—arises in certain theories of fermions coupled to gauge fields and/or gravity in a spacetime of odd dimension. This anomaly has traditionally been studied on orientable manifolds only, but recent developments involving topological superconductors have made it clear that one can get more information by asking what happens on an unorientable manifold. In this paper, we give a full description of the "parity" anomaly for fermions coupled to gauge fields and gravity in 2 +1 dimensions on a possibly unorientable spacetime. We consider an application to topological superconductors and another application to M theory. The application to topological superconductors involves using knowledge of the "parity" anomaly as an ingredient in constructing gapped boundary states of these systems and in particular in gapping the boundary of a ν =16 system in a topologically trivial fashion. The application to M theory involves showing the consistency of the path integral of an M theory membrane on a possibly unorientable worldvolume. In the past, this has been done only in the orientable case.

  18. The Effect of Pre-Impact Porosity and Vertical Density Gradients on the Gravity Signature of Lunar Craters as Seen by GRAIL

    NASA Astrophysics Data System (ADS)

    Milbury, C.; Johnson, B. C.; Melosh, H., IV; Collins, G. S.; Blair, D. M.; Soderblom, J. M.; Nimmo, F.; Bierson, C. J.; Phillips, R. J.; Zuber, M. T.

    2015-12-01

    As a result of NASA's dual spacecraft Gravity Recovery And Interior Laboratory (GRAIL) mission [Zuber et al., 2013; doi:10.1126/science.1231507], we now know that the lunar crust is highly porous and that the porosity varies laterally [Wieczorek et al., 2013; doi:10.1126/science.1231530] and vertically [Besserer et al., 2014; doi:10.1002/2014GL060240]. Analysis of complex craters located within the lunar highlands reveals that: 1) craters larger than diameter D~210 have positive Bouguer Anomalies (BAs), 2) craters with D ≲ 100 km have both positive and negative BAs that vary about the (near 0) mean by approximately ± 25 mGal, and, 3) D and BA are anticorrelated for craters with D ≲ 100 km [Soderblom et al., 2015; submitted]. Numerical modeling by Milbury et al. [2015, LPSC] shows that pre-impact porosity is the dominant influence on the gravity signature of complex craters with D ≲ 100 km, and mantle uplift dominates the gravity for those with D > 140 km. Phillips et al. [2015, LPSC] showed that complex craters located in the South Pole-Aitken (SPA) basin tend to have more-negative BAs than similar craters in the highlands. By including (pre-impact) vertical porosity/density gradients in our impact simulations, we reproduce the observed anticorrelation between BA and D for D ≲ 100 km, and the observed difference between the BAs of SPA and highland craters. We use the iSALE hydrocode including pore space compaction [Wünnemann et al., 2006; doi:10.1016/j.icarus.2005.10.013] and dilatant bulking [Collins, 2014; doi:10.1002/2014JE004708] to understand how the gravity signature of impact craters develop. In this study we vary density/porosity with depth. We find that simulations that have constant porosity with depth have a lower BA for a given crater diameter than those with varying porosity. We used two different mean porosities (7% and 14%) and found that the BA increases with increasing porosity, similar to simulations with constant porosity. Larger

  19. Quantum gravity.

    NASA Astrophysics Data System (ADS)

    Maślanka, K.

    A model of reality based on quantum fields, but with a classical treatment of gravity, is inconsistent. Finding a solution has proved extremely difficult, possibly due to the beauty and conceptual simplicity of general relativity. There is a variety of approaches to a consistent theory of quntum gravity. At present, it seems that superstring theory is the most promising candidate.

  20. Gravity investigations

    SciTech Connect

    Healey, D.L.

    1983-12-31

    A large density contrast exists between the Paleozoic rocks (including the rocks of Climax stock) and less dense, Tertiary volcanic rocks and alluvium. This density contrast ranges widely, and herein for interpretive purposes, is assumed to average 0.85 Mg/m{sup 3} (megagrams per cubic meter). The large density contrast makes the gravity method a useful tool with which to study the interface between these rock types. However, little or no density contrast is discernible between the sedimentary Paleozoic rocks that surround the Climax stock and the intrusive rocks of the stock itself. Therefore the gravity method can not be used to define the configuration of the stock. Gravity highs coincide with outcrops of the dense Paleozoic rocks, and gravity lows overlie less-dense Tertiary volcanic rocks and Quaternary alluvium. The positions of three major faults (Boundary, Yucca, and Butte faults) are defined by steep gravity gradients. West of the Climax stock, the Tippinip fault has juxtaposed Paleozoic rocks of similar density, and consequently, has no expression in the gravity data in that area. The gravity station spacing, across Oak Spring Butte, is not sufficient to adequately define any gravity expression of the Tippinip fault. 18 refs., 5 figs.

  1. Contributions of satellite-determined gravity results in geodesy

    NASA Technical Reports Server (NTRS)

    Khan, M. A.

    1974-01-01

    Different forms of the theoretical gravity formula are summarized and methods of standardization of gravity anomalies obtained from satellite gravity and terrestrial gravity data are discussed in the context of three most commonly used reference figures, e.g., International Reference Ellipsoid, Reference Ellipsoid 1967, and Equilibrium Reference Ellipsoid. These methods are important in the comparison and combination of satellite gravity and gravimetric data as well as the integration of surface gravity data, collected with different objectives, in a single reference system. For ready reference, tables for such reductions are computed. Nature of the satellite gravity anomalies is examined to aid the geophysical and geodetic interpretation of these anomalies in terms of the tectonic features of the earth and the structure of the earth's crust and mantle. Computation of the Potsdam correction from satellite-determined geopotential is reviewed. The contribution of the satellite gravity results in decomposing the total observed gravity anomaly into components of geophysical interest is discussed. Recent work on the possible temporal variations in the geogravity field is briefly reviewed.

  2. Gravity model studies of Newberry Volcano, Oregon

    USGS Publications Warehouse

    Gettings, M.E.; Griscom, A.

    1988-01-01

    Newberry Volcano, a large Quaternary volcano located about 60 km east of the axis of the High Cascades volcanoes in central Oregon, has a coincident positive residual gravity anomaly of about 12 mGals. Model calculations of the gravity anomaly field suggest that the volcano is underlain by an intrusive complex of mafic composition of about 20-km diameter and 2-km thickness, at depths above 4 km below sea level. However, uplifted basement in a northwest trending ridge may form part of the underlying excess mass, thus reducing the volume of the subvolcanic intrusive. A ring dike of mafic composition is inferred to intrude to near-surface levels along the caldera ring fractures, and low-density fill of the caldera floor probably has a thickness of 0.7-0.9 km. The gravity anomaly attributable to the volcano is reduced to the east across a north-northwest trending gravity anomaly gradient through Newberry caldera and suggests that normal, perhaps extensional, faulting has occurred subsequent to caldera formation and may have controlled the location of some late-stage basaltic and rhyolitic eruptions. Significant amounts of felsic intrusive material may exist above the mafic intrusive zone but cannot be resolved by the gravity data. -Authors

  3. Gravity model studies of Newberry Volcano, Oregon

    SciTech Connect

    Gettings, M.E.; Griscom, A.

    1988-09-10

    Newberry, Volcano, a large Quaternary volcano located about 60 km east of the axis of the High Cascades volcanoes in central Oregon, has a coincident positive residual gravity anomaly of about 12 mGals. Model calculations of the gravity anomaly field suggest that the volcano is underlain by an intrusive complex of mafic composition of about 20-km diameter and 2-km thickness, at depths above 4 km below sea level. However, uplifted basement in a northwest trending ridge may form part of the underlying excess mass, thus reducing the volume of the subvolcanic intrusive. A ring dike of mafic composition is inferred to intrude to near-surface levels along the caldera ring fractures, and low-density fill of the caldera floor probably has a thickness of 0.7--0.9 km. The gravity anomaly attributable to the volcano is reduced to the east across a north-northwest trending gravity anomaly gradient through Newberry caldera and suggests that normal, perhaps extensional, faulting has occurred subsequent to caldera formation and may have controlled the location of some late-stage basaltic and rhyolitic eruptions. Significant amounts of felsic intrusive material may exist above the mafic intrusive zone but cannot be resolved by the gravity data.

  4. Noncommutative topological theories of gravity

    NASA Astrophysics Data System (ADS)

    García-Compeán, H.; Obregón, O.; Ramírez, C.; Sabido, M.

    2003-08-01

    The possibility of noncommutative topological gravity arising in the same manner as Yang-Mills theory is explored. We use the Seiberg-Witten map to construct such a theory based on a SL(2,C) complex connection, from which the Euler characteristic and the signature invariant are obtained. Finally, we speculate on the description of noncommutative gravitational instantons, as well as noncommutative local gravitational anomalies.

  5. Constraining the rheology of the lithosphere through joint geodynamic and gravity inversion

    NASA Astrophysics Data System (ADS)

    Baumann, T.; Kaus, B.; Popov, A.

    2013-12-01

    Understanding the physics of lithospheric deformation and continental collision requires good constraints on lithospheric rheology. Typically, rheology is determined from laboratory experiments on small rock samples, which are extrapolated to geological conditions - an extrapolation over 10 orders of magnitude in deformation rates. These laboratory experiments generally show that small changes in the composition of the rocks, such as adding a bit of water, can dramatically change its viscosity. Moreover, it is unclear which rock type gives the best mechanical description of, for example, the upper crust and whether a small sample is even appropriate to describe the large scale mechanical behavior of the crust. So the viscosity of the lithosphere is probably the least constrained parameter in geodynamics. Ideally, we thus need a new independent method that allows constraining the effective rheology of the lithosphere directly from geophysical data, which is the aim of this work. Our method uses the fact that the geodynamically controlling parameters of lithospheric deformation are its effective viscosity and density structure. By appropriately parameterising the rheological structure of the lithosphere we perform instantaneous forward simulations of present-day lithospheric deformation scenarios with a finite element method to compute the gravity field and surface velocities. The forward modelling results can be compared with observations such as Bouguer anomalies and GPS-derived surface velocities. More precisely, we automatize the forward modelling procedure with a Monte Carlo method, and in fact solve a joint geodynamic and gravity inverse problem. The resulting misfit can be illustrated as a function of rheological model parameters and a more detailed analysis allows constraining probabilistic parameter ranges. For a simplified setup with linear viscous rheologies we can demonstrate mathematically that a joint geodynamic-gravity inversion approach results in a

  6. Taussig-Bing Anomaly

    PubMed Central

    Konstantinov, Igor E.

    2009-01-01

    Taussig-Bing anomaly is a rare congenital heart malformation that was first described in 1949 by Helen B. Taussig (1898–1986) and Richard J. Bing (1909–). Although substantial improvement has since been achieved in surgical results of the repair of the anomaly, management of the Taussig-Bing anomaly remains challenging. A history of the original description of the anomaly, the life stories of the individuals who first described it, and the current outcomes of its surgical management are reviewed herein. PMID:20069085

  7. Hyperbolic Orbits and the Planetary Flylby Anomaly

    NASA Technical Reports Server (NTRS)

    Wilson, T.L.; Blome, H.J.

    2009-01-01

    Space probes in the Solar System have experienced unexpected changes in velocity known as the flyby anomaly [1], as well as shifts in acceleration referred to as the Pioneer anomaly [2-4]. In the case of Earth flybys, ESA s Rosetta spacecraft experienced the flyby effect and NASA s Galileo and NEAR satellites did the same, although MESSENGER did not possibly due to a latitudinal property of gravity assists. Measurements indicate that both anomalies exist, and explanations have varied from the unconventional to suggestions that new physics in the form of dark matter might be the cause of both [5]. Although dark matter has been studied for over 30 years, there is as yet no strong experimental evidence supporting it [6]. The existence of dark matter will certainly have a significant impact upon ideas regarding the origin of the Solar System. Hence, the subject is very relevant to planetary science. We will point out here that one of the fundamental problems in science, including planetary physics, is consistency. Using the well-known virial theorem in astrophysics, it will be shown that present-day concepts of orbital mechanics and cosmology are not consistent for reasons having to do with the flyby anomaly. Therefore, the basic solution regarding the anomalies should begin with addressing the inconsistencies first before introducing new physics.

  8. Algebraic Classification of Weyl Anomalies in Arbitrary Dimensions

    SciTech Connect

    Boulanger, Nicolas

    2007-06-29

    Conformally invariant systems involving only dimensionless parameters are known to describe particle physics at very high energy. In the presence of an external gravitational field, the conformal symmetry may generalize to the Weyl invariance of classical massless field systems in interaction with gravity. In the quantum theory, the latter symmetry no longer survives: A Weyl anomaly appears. Anomalies are a cornerstone of quantum field theory, and, for the first time, a general, purely algebraic understanding of the universal structure of the Weyl anomalies is obtained, in arbitrary dimensions and independently of any regularization scheme.

  9. Gravity brake

    DOEpatents

    Lujan, Richard E.

    2001-01-01

    A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.

  10. Geophysical investigations of a geothermal anomaly at Wadi Ghadir, eastern Egypt

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.; Basta, N. Z.; Melek, Y. S.

    1984-01-01

    During regional heat flow studies a geothermal anomaly was discovered approximately 2 km from the Red Sea coast at Wadi Ghadir, in the Red Sea Hills of Eastern Egypt. A temperature gradient of 55 C/km was measured in a 150 m drillhole at this location, indicating a heat flow of approximately 175 mw/sqm, approximately four times the regional background heat flow for Egypt. Gravity and magnetic data were collected along Wadi Ghadir, and combined with offshore gravity data, to investigate the source of the thermal anomaly. Magnetic anomalies in the profile do not coincide with the thermal anomaly, but were observed to correlate with outcrops of basic rocks. Other regional heat flow and gravity data indicate that the transition from continental to oceanic type lithosphere occurs close to the Red Sea margin, and that the regional thermal anomaly is possibly related to the formation of the Red Sea.

  11. Gravity waves

    NASA Technical Reports Server (NTRS)

    Fritts, David

    1987-01-01

    Gravity waves contributed to the establishment of the thermal structure, small scale (80 to 100 km) fluctuations in velocity (50 to 80 m/sec) and density (20 to 30%, 0 to peak). Dominant gravity wave spectrum in the middle atmosphere: x-scale, less than 100 km; z-scale, greater than 10 km; t-scale, less than 2 hr. Theorists are beginning to understand middle atmosphere motions. There are two classes: Planetary waves and equatorial motions, gravity waves and tidal motions. The former give rise to variability at large scales, which may alter apparent mean structure. Effects include density and velocity fluctuations, induced mean motions, and stratospheric warmings which lead to the breakup of the polar vortex and cooling of the mesosphere. On this scale are also equatorial quasi-biennial and semi-annual oscillations. Gravity wave and tidal motions produce large rms fluctuations in density and velocity. The magnitude of the density fluctuations compared to the mean density is of the order of the vertical wavelength, which grows with height. Relative density fluctuations are less than, or of the order of 30% below the mesopause. Such motions may cause significant and variable convection, and wind shear. There is a strong seasonal variation in gravity wave amplitude. Additional observations are needed to address and quantify mean and fluctuation statistics of both density and mean velocity, variability of the mean and fluctuations, and to identify dominant gravity wave scales and sources as well as causes of variability, both temporal and geographic.

  12. Magnetic Anomalies in the Enderby Basin, the Southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Nogi, Y.; Sato, T.; Hanyu, T.

    2013-12-01

    Magnetic anomalies in the Southern indian Ocean are vital to understanding initial breakup process of Gondwana. However, seafloor age estimated from magnetic anomalies still remain less well-defined because of the sparse observations in this area. To understand the seafloor spreading history related to the initial breakup process of Gondwana, vector magnetic anomaly data as well as total intensity magnetic anomaly data obtained by the R/V Hakuho-maru and the icebreaker Shirase in the Enderby Basin, Southern Indian Ocean, are used. The strikes of magnetic structures are deduced from the vector magnetic anomalies. Magnetic anomaly signals, most likely indicating Mesozoic magnetic anomaly sequence, are obtained almost parallel to the west of WNW-ESE trending lineaments just to the south of Conrad Rise inferred from satellite gravity anomalies. Most of the strikes of magnetic structures indicate NNE-SSW trends, and are almost perpendicular to the WNW-ESE trending lineaments. Mesozoic sequence magnetic anomalies with mostly WNW-ESE strikes are also observed along the NNE-SSW trending lineaments between the south of the Conrad Rise and Gunnerus Ridge. Magnetic anomalies originated from Cretaceous normal polarity superchron are found in these profiles, although magnetic anomaly C34 has been identified just to the north of the Conrad Rise. However Mesozoic sequence magnetic anomalies are only observed in the west side of the WNW-ESE trending lineaments just to the south of Conrad Rise and not detected to the east of Cretaceous normal superchron signals. These results show that counter part of Mesozoic sequence magnetic anomalies in the south of Conrad Rise would be found in the East Enderby Basin, off East Antarctica. NNE-SSW trending magnetic structures, which are similar to those obtained just to the south of Conrad Rise, are found off East Antarctica in the East Enderby Basin. However, some of the strikes show almost E-W orientations. These suggest complicated ridge

  13. Competing Orders and Anomalies

    PubMed Central

    Moon, Eun-Gook

    2016-01-01

    A conservation law is one of the most fundamental properties in nature, but a certain class of conservation “laws” could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the ’t Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed. PMID:27499184

  14. Competing Orders and Anomalies

    NASA Astrophysics Data System (ADS)

    Moon, Eun-Gook

    2016-08-01

    A conservation law is one of the most fundamental properties in nature, but a certain class of conservation “laws” could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the ’t Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed.

  15. Competing Orders and Anomalies.

    PubMed

    Moon, Eun-Gook

    2016-08-08

    A conservation law is one of the most fundamental properties in nature, but a certain class of conservation "laws" could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the 't Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed.

  16. 3D Gravity Inversion using Tikhonov Regularization

    NASA Astrophysics Data System (ADS)

    Toushmalani, Reza; Saibi, Hakim

    2015-08-01

    Subsalt exploration for oil and gas is attractive in regions where 3D seismic depth-migration to recover the geometry of a salt base is difficult. Additional information to reduce the ambiguity in seismic images would be beneficial. Gravity data often serve these purposes in the petroleum industry. In this paper, the authors present an algorithm for a gravity inversion based on Tikhonov regularization and an automatically regularized solution process. They examined the 3D Euler deconvolution to extract the best anomaly source depth as a priori information to invert the gravity data and provided a synthetic example. Finally, they applied the gravity inversion to recently obtained gravity data from the Bandar Charak (Hormozgan, Iran) to identify its subsurface density structure. Their model showed the 3D shape of salt dome in this region.

  17. Evaluation of recent Earth's global gravity field models with terrestrial gravity data

    NASA Astrophysics Data System (ADS)

    Karpik, Alexander P.; Kanushin, Vadim F.; Ganagina, Irina G.; Goldobin, Denis N.; Kosarev, Nikolay S.; Kosareva, Alexandra M.

    2016-03-01

    In the context of the rapid development of environmental research technologies and techniques to solve scientific and practical problems in different fields of knowledge including geosciences, the study of Earth's gravity field models is still important today. The results of gravity anomaly modelling calculated by the current geopotential models data were compared with the independent terrestrial gravity data for the two territories located in West Siberia and Kazakhstan. Statistical characteristics of comparison results for the models under study were obtained. The results of investigations show that about 70% of the differences between the gravity anomaly values calculated by recent global geopotential models and those observed at the points in flat areas are within ±10 mGal, in mountainous areas are within ±20 mGal.

  18. Geological Features and Crustal Structure of the Cretaceous Middle Benue Trough, Nigeria: Insights from Detailed Analysis and Modelling of Magnetic and Gravity Data

    NASA Astrophysics Data System (ADS)

    Anudu, G. K.; Stephenson, R.; Macdonald, D.

    2015-12-01

    The middle Benue Trough is the middle (central) segment of the Nigerian Benue Trough, an intra-continental rift that developed during the second phase of rifting of the Gondwana supercontinent that resulted in the opening of the South Atlantic Ocean, Gulf of Guinea and separation of South America from Africa in the Late Jurassic to Early Cretaceous. Airborne magnetic and terrestrial gravity data from the area have been analysed and modelled in detail. Results obtained using a variety of edge enhancement (derivative) methods applied to high-resolution, airborne magnetic data reveal widespread magmatic intrusions (mainly volcanic/sub-volcanic rocks, with an areal extent greater than 12000 km2) and numerous geological structures. Rose (azimuth frequency) plots show that the geological structural trends are predominantly NE - SW, NW - SE and ESE - WNW with minor ENE -WSW/N - S trends and thus suggest that the area has undergone several phases of tectonic deformation at different geological times. Integrated two-dimensional (2-D) gravity and magnetic modelling along five profiles constrained by 2-D magnetic depth-to-source estimates and available seismological velocity models indicates the presence of a number of distinct crustal bodies and thin crust. Moho depth varies from ca. 21 - 29 km, while the crustal thickness ranges between ca. 19 and 29 km. Shallower Moho and thinner crust are observed along the trough axis. Results from the study also reveal that the amount of crustal thinning and crustal stretching factor (β) across the area varies from 3.3 - 14.5 km and 1.11 - 1.78, respectively. Broad positive to near positive Bouguer gravity anomalies in the region of the trough axis are due to the combined effects of dense (intermediate to basic) magmatic intrusions (both intra-sedimentary and intra-basement/crustal ones), shallow basement horsts (basement uplift zones) and thin crust replaced by dense abnormal upper mantle bodies. Reactivated intra-basement structures

  19. Analogue Gravity.

    PubMed

    Barceló, Carlos; Liberati, Stefano; Visser, Matt

    2011-01-01

    Analogue gravity is a research programme which investigates analogues of general relativistic gravitational fields within other physical systems, typically but not exclusively condensed matter systems, with the aim of gaining new insights into their corresponding problems. Analogue models of (and for) gravity have a long and distinguished history dating back to the earliest years of general relativity. In this review article we will discuss the history, aims, results, and future prospects for the various analogue models. We start the discussion by presenting a particularly simple example of an analogue model, before exploring the rich history and complex tapestry of models discussed in the literature. The last decade in particular has seen a remarkable and sustained development of analogue gravity ideas, leading to some hundreds of published articles, a workshop, two books, and this review article. Future prospects for the analogue gravity programme also look promising, both on the experimental front (where technology is rapidly advancing) and on the theoretical front (where variants of analogue models can be used as a springboard for radical attacks on the problem of quantum gravity).

  20. Vascular anomalies in children.

    PubMed

    Weibel, L

    2011-11-01

    Vascular anomalies are divided in two major categories: tumours (such as infantile hemangiomas) and malformations. Hemangiomas are common benign neoplasms that undergo a proliferative phase followed by stabilization and eventual spontaneous involution, whereas vascular malformations are rare structural anomalies representing morphogenetic errors of developing blood vessels and lymphatics. It is important to properly diagnose vascular anomalies early in childhood because of their distinct differences in morbidity, prognosis and need for a multidisciplinary management. We discuss a number of characteristic clinical features as clues for early diagnosis and identification of associated syndromes.

  1. Antarctic Crustal Thickness from Gravity Inversion

    NASA Astrophysics Data System (ADS)

    Vaughan, A. P.; Kusznir, N. J.; Ferraccioli, F.; Jordan, T. A.

    2013-12-01

    Using gravity anomaly inversion, we have produced the first comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/β) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction. The continental lithosphere thinning distribution, used to define the initial thermal model temperature perturbation is derived from the gravity inversion and uses no a priori isochron information; as a consequence the gravity inversion method provides a prediction of ocean-continent transition location, which is independent of ocean isochron information. The gravity anomaly contribution from ice thickness is included in the gravity inversion, as is the contribution from sediments which assumes a compaction controlled sediment density increase with depth. Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the most recent Bedmap2 ice thickness and bedrock topography compilation south of 60 degrees south (Fretwell et al., 2013) and relatively sparse constraints on sediment thickness. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica penetrated by narrow continental rifts that feature relatively thinner crust. The East Antarctic Rift System (EARS) is a major Permian to Cretaceous age rift system that appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km. This is comparable in scale to the well-studied East African rift system. Intermediate crustal thickness with an inferred linear rift fabric is predicted under Coates Land. An extensive region of either thick oceanic crust or highly thinned continental crust is predicted offshore Oates Land and north Victoria Land, and also off West Antarctica

  2. Dual diaphragmatic anomalies

    PubMed Central

    Padmanabhan, Arjun; Thomas, Abin Varghese

    2016-01-01

    Although diaphragmatic anomalies such as an eventration and hiatus hernia are commonly encountered in incidental chest X-ray imaging, the presence of concomitant multiple anomalies is extremely rare. This is all the more true in adults. Herein, we present the case of a 75-year-old female, while undergoing a routine chest X-ray imaging, was found to have eventration of right hemidiaphragm along with a hiatus hernia as well. PMID:27625457

  3. Simulating Gravity

    ERIC Educational Resources Information Center

    Pipinos, Savas

    2010-01-01

    This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…

  4. Gravity settling

    DOEpatents

    Davis, Hyman R.; Long, R. H.; Simone, A. A.

    1979-01-01

    Solids are separated from a liquid in a gravity settler provided with inclined solid intercepting surfaces to intercept the solid settling path to coalesce the solids and increase the settling rate. The intercepting surfaces are inverted V-shaped plates, each formed from first and second downwardly inclined upwardly curved intersecting conical sections having their apices at the vessel wall.

  5. Gravity and magnetic evidence for a granitic intrusion near Wahmonie Site, Nevada Test Site, Nevada

    SciTech Connect

    Ponce, D.A.

    1984-10-10

    Gravity and magnetic data outline a broad anomaly near Wahmonie Site, Nye County, Nevada. A positive 15-mGal gravity anomaly with a steep western gradient and a broad magnetic anomaly coincident with the gravity high characterize the area. Two-dimensional computer models of the gravity data were made using magnetic, seismic, and electric data as independent constraints. The models indicate the presence of a shallow, relatively high density body of 2.65 kg m{sup -3} buried near Wahmonie Site. Aeromagnetic and ground magnetic data also indicate the presence of a large, shallow body. Two smaller local magnetic highs that occur along a magnetic prominence extending northward from the broad anomaly directly correlate to granodiorite outcrops. This indicates that the main anomaly is produced by a large shallow intrusion.

  6. Global gravity field recovery from the ARISTOTELES satellite mission

    NASA Astrophysics Data System (ADS)

    Visser, P. N. A. M.; Wakker, K. F.; Ambrosius, B. A. C.

    1994-02-01

    One of the primary objectives of the future ARISTOTELES satellite mission is to map Earth's gravity field with high resolution and accuracy. In order to achieve this objective, the ARISTOTELES satellite will be equipped with a gravity gradiometer and a Global Positioning System (GPS) receiver. Global gravity field error analyses have been performed for several combinations of gradiometer and GPS observations. These analyses indicated that the bandwidth limitation of the gradiometer prevents a stable high-accuracy, high-resolution gravity solution if no additional information is available. However, with the addition of high-accuracy GPS observations, a stable gravity field solution can be obtained. A combination of the measurements acquired by the high-quality GPS receiver and the bandwidth-limited gradiometer on board ARISTOTELES will yield a global gravity field model with a resolution of less than 100 km and with an accuracy of better than 5 mGal for gravity anomalies and 10 cm for geoid undulations.

  7. The south-central United States magnetic anomaly

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Braile, L. W. (Principal Investigator); Starich, P. J.

    1984-01-01

    The South-Central United States Magnetic Anomaly is the most prominent positive feature in the MAGSAT scalar magnetic field over North America. The anomaly correlates with increased crustal thickness, above average crustal velocity, negative free air gravity anomalies and an extensive zone of Middle Proterozoic anorogenic felsic basement rocks. Spherical dipole source inversion of the MAGSAT scalar data and subsequent calculation of reduced to pole and derivative maps provide constraints for a crustal magnetic model which corresponds geographically to the extensive Middle Proterozoic felsic rocks trending northeasterly across the United States. These felsic rocks contain insufficient magnetization or volume to produce the anomaly, but are rather indicative of a crustal zone which was disturbed during a Middle Proterozoic thermal event which enriched magnetic material deep in the crust.

  8. Global detailed gravimetric geoid. [based on gravity model derived from satellite tracking and surface gravity data

    NASA Technical Reports Server (NTRS)

    Vincent, S.; Marsh, J. G.

    1973-01-01

    A global detailed gravimetric geoid has been computed by combining the Goddard Space Flight Center GEM-4 gravity model derived from satellite and surface gravity data and surface 1 deg-by-1 deg mean free air gravity anomaly data. The accuracy of the geoid is + or - 2 meters on continents, 5 to 7 meters in areas where surface gravity data are sparse, and 10 to 15 meters in areas where no surface gravity data are available. Comparisons have been made with the astrogeodetic data provided by Rice (United States), Bomford (Europe), and Mather (Australia). Comparisons have also been carried out with geoid heights derived from satellite solutions for geocentric station coordinates in North America, the Caribbean, Europe, and Australia.

  9. Astrometric solar system anomalies

    SciTech Connect

    Nieto, Michael Martin; Anderson, John D

    2009-01-01

    There are at least four unexplained anomalies connected with astrometric data. perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it often experiences a change in total orbital energy per unit mass. next, a secular change in the astronomical unit AU is definitely a concern. It is increasing by about 15 cm yr{sup -1}. The other two anomalies are perhaps less disturbing because of known sources of nongravitational acceleration. The first is an apparent slowing of the two Pioneer spacecraft as they exit the solar system in opposite directions. Some astronomers and physicists are convinced this effect is of concern, but many others are convinced it is produced by a nearly identical thermal emission from both spacecraft, in a direction away from the Sun, thereby producing acceleration toward the Sun. The fourth anomaly is a measured increase in the eccentricity of the Moon's orbit. Here again, an increase is expected from tidal friction in both the Earth and Moon. However, there is a reported unexplained increase that is significant at the three-sigma level. It is produent to suspect that all four anomalies have mundane explanations, or that one or more anomalies are a result of systematic error. Yet they might eventually be explained by new physics. For example, a slightly modified theory of gravitation is not ruled out, perhaps analogous to Einstein's 1916 explanation for the excess precession of Mercury's perihelion.

  10. Stochastic gravity

    NASA Astrophysics Data System (ADS)

    Ross, D. K.; Moreau, William

    1995-08-01

    We investigate stochastic gravity as a potentially fruitful avenue for studying quantum effects in gravity. Following the approach of stochastic electrodynamics ( sed), as a representation of the quantum gravity vacuum we construct a classical state of isotropic random gravitational radiation, expressed as a spin-2 field,h µυ (x), composed of plane waves of random phase on a flat spacetime manifold. Requiring Lorentz invariance leads to the result that the spectral composition function of the gravitational radiation,h(ω), must be proportional to 1/ω 2. The proportionality constant is determined by the Planck condition that the energy density consist ofħω/2 per normal mode, and this condition sets the amplitude scale of the random gravitational radiation at the order of the Planck length, giving a spectral composition functionh(ω) =√16πc 2Lp/ω2. As an application of stochastic gravity, we investigate the Davies-Unruh effect. We calculate the two-point correlation function (R iojo(Oτ-δτ/2)R kolo(O,τ+δτ/2)) of the measureable geodesic deviation tensor field,R iojo, for two situations: (i) at a point detector uniformly accelerating through the random gravitational radiation, and (ii) at an inertial detector in a heat bath of the random radiation at a finite temperature. We find that the two correlation functions agree to first order inaδτ/c provided that the temperature and acceleration satisfy the relationkT=ħa/2πc.

  11. The Interpretation of Enceladus Gravity (Invited)

    NASA Astrophysics Data System (ADS)

    Stevenson, D. J.; Iess, L.; Parisi, M.; Ducci, M.; Asmar, S. W.

    2013-12-01

    The determination of the gravity field by Cassini is challenging because of the small mass and short duration of the gravitational interaction, even with data from three encounters. E19 data have been successfully integrated into the multiarc analysis, providing a stable and consistent gravity field. This required inclusion of the effect of atmospheric drag due to Enceladus' plumes. This presentation will deal only with the interpretation of these data. The dominant features of the non-central gravity are large values for the harmonic coefficients J2 and C22 and a much smaller but statistically significant negative J3. The value of J2/C22=3.55×0.05 is moderately in excess of the value of 10/3 that applies to a synchronously rotating body with no lateral variation in material properties. Given the obvious latitudinal variation of Enceladus' physical characteristics, primarily expressed by the activity centered on the South Pole, it is plausible that the deviation from 10/3 arises primarily because of a positive anomaly in J2 rather than any anomaly in C22. However, applying Radau-Darwin to the value of C22/q (where q is the usual dimensionless measure of the centrifugal effect on gravity) implies that the moment of inertia is about 0.34MR^2. The high heat output and indirect inference for liquid water suggests a fully differentiated Enceladus. For the known mean density and any plausible mantle density, this would require an unreasonably low core density of 2.5 g/cc or less. A more realistic interpretation is that both J2 and C22 are modestly non-hydrostatic, but that J2 is affected more because of a negative mass anomaly in the Southern hemisphere, consistent with the observed negative J3. One non-unique way to reconcile the observed gravity with a realistic MOI of 0.32 to 0.33MR^2 is to assume that the rocky core of Enceladus has retained some memory of a previous faster rotational state. Even if the ice shell is perfectly relaxed, this reconciles the data for a

  12. Mariana Arc structure inferred from gravity and seismic data

    NASA Astrophysics Data System (ADS)

    Sager, W. W.

    1980-10-01

    A two-dimensional gravity model of the lithosphere was constructed along a seismic refraction line near 18°N latitude. Included in the model are crustal layers constrained by seismic refraction results, an estimate of the gravity anomaly caused by the subducting slab, and a model of the low-density mantle beneath the Mariana Trough. With a reasonable anomaly assumed for the slab it is shown that the gravity anomaly caused by the low-density mantle is greatest over the axial bathymetric high and tapers off to the sides. With the bottom of the low-density mantle set at 200 km the density contrast is -0.033 g/cm3. Other depths and densities are tried as well. Several notable anomalies are found on the crustal layers. East of the trench, the crust has been thinned slightly to account for an outer gravity high. Behind the landward wall of the trench, a small, low-density body is modeled to explain a slight offset of the minimum of the free air anomaly from the trench axis. A 50-mGal jump on the observed gravity over the volcanic line is explained by an unusual configuration of the frontal arc Moho.

  13. Magnetic anomalies. [Magsat studies

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A.

    1983-01-01

    The implications and accuracy of anomaly maps produced using Magsat data on the scalar and vector magnetic field of the earth are discussed. Comparisons have been made between the satellite maps and aeromagnetic survey maps, showing smoother data from the satellite maps and larger anomalies in the aircraft data. The maps are being applied to characterize the structure and tectonics of the underlying regions. Investigations are still needed regarding the directions of magnetization within the crust and to generate further correlations between anomaly features and large scale geological structures. Furthermore, an increased data base is recommended for the Pacific Ocean basin in order to develop a better starting model for Pacific tectonic movements. The Pacific basin was large farther backwards in time and subduction zones surround the basin, thereby causing difficulties for describing the complex break-up scenario for Gondwanaland.

  14. Cosmological hints of modified gravity?

    NASA Astrophysics Data System (ADS)

    Di Valentino, Eleonora; Melchiorri, Alessandro; Silk, Joseph

    2016-01-01

    The recent measurements of cosmic microwave background (CMB) temperature and polarization anisotropies made by the Planck satellite have provided impressive confirmation of the Λ CDM cosmological model. However interesting hints of slight deviations from Λ CDM have been found, including a 95% C.L. preference for a "modified gravity" (MG) structure formation scenario. In this paper we confirm the preference for a modified gravity scenario from Planck 2015 data, find that modified gravity solves the so-called Alens anomaly in the CMB angular spectrum, and constrains the amplitude of matter density fluctuations to σ8=0.81 5-0.048+0.032 , in better agreement with weak lensing constraints. Moreover, we find a lower value for the reionization optical depth of τ =0.059 ±0.020 (to be compared with the value of τ =0.079 ±0.017 obtained in the standard scenario), more consistent with recent optical and UV data. We check the stability of this result by considering possible degeneracies with other parameters, including the neutrino effective number, the running of the spectral index and the amount of primordial helium. The indication for modified gravity is still present at about 95% C.L., and could become more significant if lower values of τ were to be further confirmed by future cosmological and astrophysical data. When the CMB lensing likelihood is included in the analysis the statistical significance for MG simply vanishes, indicating also the possibility of a systematic effect for this MG signal.

  15. Gravity field fine structure estimation techniques for a spaceborne gravity gradiometer

    NASA Technical Reports Server (NTRS)

    Kahn, W. D.; Englar, T. S., Jr.

    1987-01-01

    Use of standard estimation techniques to recover geopotential fine structure from gradiometer data requires the adjustment of small subsets of parameters while constraining others to their a priori values in order to minimize the computational load. Here, gravitational anomalies are selected as a parametrization of the gravity field which permits such an approach. Techniques coupled with numerical results for a spaceborne gravity gradiometer mission simulation are described which demonstrate that if a satellite is in a polar/circular orbit at an altitude of 160 km, 1 deg mean free air gravity anomalies can be recovered to an accuracy of 0.4 mgal, where 1 mgal = 0.001 cm/sq s.

  16. Looking beneath Snake River Plain using gravity and magnetic methods Murari Khatiwada and G. Randy Keller, ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, OK 73069

    NASA Astrophysics Data System (ADS)

    Khatiwada, M.; Keller, G.

    2010-12-01

    Tectonic evolution and structural complexities of the Snake River Plain (SRP), the role of extension in its formation, and the effects of the YellowStone (YS) hotspot track have been a topic of scientific discussion for decades. In this research, we are addressing some of these issues by focusing on the Western Snake River Plain (WRSP) using a pre-existing gravity and magnetic database compiled through a community effort. These data are available at the Pan American Center for Environmental studies (http://research.utep.edu/paces). In the regional context of the SRP, the Complete Bouguer Anomaly (CBA) ranges by about 210 mGal with the highest value in the vicinity of the WRSP. We used upward continuation filters, bandpass filters, and directional derivative filters to delineate features by wavelength and trend. Total Magnetic Intensity (TMI) was also analyzed. The magnetic intensity ranges over 600 nT with much more complex and erratic magnetic signatures that arise from the shallow basalt and rhyolite deposits within the region. We used pseudogravity and tilt derivative filters for further processing of the magnetic data. We are able to identify the major structural components in the area using gravity and magnetic data and their processing. The bounding normal faults of the WSRP are well observed. We constructed an axial gravity profile along the SRP starting at Walla Walla, Washington and extending through Yellowstone to Reygate, Montana. CBA values along this profile show that the western and central sections of the SPR have higher gravity anomaly values than the eastern sections and the YS area. We used forward gravity modeling of the subsurface structures across the WSRP starting from the Basin and Range province on the southwest to the Atlanta Lobe of the Idaho Batholith on the northeast. From the model, we observed that the Moho depth increases northeastward and varies between 30 and 46 km along the profile. These results match with receiver function Moho

  17. Identification of Baribis fault - West Java using second vertical derivative method of gravity

    NASA Astrophysics Data System (ADS)

    Sari, Endah Puspita; Subakti, Hendri

    2015-04-01

    Baribis fault is one of West Java fault zones which is an active fault. In modern era, the existence of fault zone can be observed by gravity anomaly. Baribis fault zone has not yet been measured by gravity directly. Based on this reason, satellite data supported this research. Data used on this research are GPS satellite data downloaded from TOPEX. The purpose of this research is to determine the type and strike of Baribis fault. The scope of this research is Baribis fault zone which lies on 6.50o - 7.50o S and 107.50o - 108.80o E. It consists of 5146 points which one point to another is separated by 1 minute meridian. The method used in this research is the Second Vertical Derivative (SVD) of gravity anomaly. The Second Vertical Derivative of gravity anomaly show as the amplitude of gravity anomaly caused by fault structure which appears as residual anomaly. The zero value of residual gravity anomaly indicates that the contact boundary of fault plane. Second Vertical Derivative method of gravity was applied for identifying Baribis fault. The result of this research shows that Baribis fault has a thrust mechanism. It has a lineament strike varies from 107o to 127o. This result agrees with focal mechanism data of earthquakes occurring on this region based on Global CMT catalogue.

  18. An Atlas of Earth Gravity Model 2008

    NASA Astrophysics Data System (ADS)

    Melvin, P. J.

    2009-12-01

    The Earth Gravity Model 2008 (Pavlis, et al.) is a 2190th order and degree spherical harmonic model. Software developed by the author in the 1980s and currently used for orbit determination is employed to evaluate and map 10 different fields on the ellipsoid: the undulation of the geoid, radial (free air) gravity anomaly, East-West and North-South deflections of the vertical and radial-radial, radial-longitude, radial-latitude, longitude-longitude, longitude-latitude and latitude-latitude gravity gradient components. Although of less detail than other surface level data sets (e.g., Sandwell: global gravity for Google earth), these evaluations have the advantage of being global and in stunning (10 arc minute) detail, and could be used to provide insights in studies of, say, isostasy, plate tectonics, or orogeny especially with lineations highlighted by the derivative fields. A variety of projections are used: plate carre, transverse Mercator, spherical and animated spherical. The gray scale of the images is optimized by use of histograms. Undulation of the Geoid Radial Gravity Anomaly

  19. Towards 3D multi-scale teleseismic and gravity data inversion using hybrid DSM/SPECFEM technique : application to the Pyrenees

    NASA Astrophysics Data System (ADS)

    Martin, Roland; Monteiller, Vadim; Chevrot, Sébastien; Wang, Yi; Komatitsch, Dimitri; Dufréchou, Grégory

    2015-04-01

    . The idea is to constrain the densities and the wave speeds simultaneously by a joint inversion of seismic waveforms and gravity data. The novelty of the approach is to improve tomographic images by using a full waveform inversion which provides finely resolved images of lithospheric structures, including the geometry of the main seismic interfaces such as the Moho. We take the spectral finite element SPECFEM3D package to model the wave propagation at the regional scale and we use MPI-based PRACE parallel platforms. This new tomographic approach has been applied to the Pyrenees, which thanks to the PYROPE and IBERARRAY experiments, has been densely covered by seismological probes. The gravimetric data come from the BGI. In this region, strong Bouguer gravity anomalies and strong constrasts in first P wave arrival time delays are observed. We have been able to identify, through reverse-time migration and also some first full waveform inversions using the adjoint theory, that strong Moho jumps from 25 down 60 kms depths can be detected at different locations around the France-Spain border.

  20. Recovery of Gravity Anomalies from Gridded Geoid Height Data.

    DTIC Science & Technology

    1976-07-01

    contributors from the Weapon Systems Support Branch Mess rs Melvin E Shultz, Robert M Pen man, Joel B Starkey , James M Barth, Daniel J. Browning, and...near the - - I boundary. These errors of localization affect the parameter vector S - S x and the coefficient matri x A so that the erro rs carry over...which is best solved by means of spectral representation [9]. The Fourier transform of equation (A30 ) is EpQ (o)) = SpQ (w) - Ilp~(w

  1. Weyl anomaly and initial singularity crossing

    NASA Astrophysics Data System (ADS)

    Awad, Adel

    2016-04-01

    We consider the role of quantum effects, mainly, Weyl anomaly in modifying Friedmann-Lemaitre-Robertson-Walker (FLRW) model singular behavior at early times. Weyl anomaly corrections to FLRW models have been considered in the past, here we reconsider this model and show the following: The singularity of this model is weak according to Tipler and Krolak, therefore, the spacetime might admit a geodesic extension. Weyl anomaly corrections change the nature of the initial singularity from a big bang singularity to a sudden singularity. The two branches of solutions consistent with the semiclassical treatment form a disconnected manifold. Joining these two parts at the singularity provides us with a C1 extension to nonspacelike geodesics and leaves the spacetime geodesically complete. Using Gauss-Codazzi equations one can derive generalized junction conditions for this higher-derivative gravity. The extended spacetime obeys Friedmann and Raychaudhuri equations and the junction conditions. The junction does not generate Dirac delta functions in matter sources which keeps the equation of state unchanged.

  2. CHAMP Magnetic Anomalies of the Antarctic Crust

    NASA Technical Reports Server (NTRS)

    Kim, Hyung Rae; Gaya-Pique, Luis R.; vonFrese, Ralph R. B.; Taylor, Patrick T.; Kim, Jeong Woo

    2003-01-01

    Regional magnetic signals of the crust are strongly masked by the core field and its secular variations components and hence difficult to isolate in the satellite measurements. In particular, the un-modeled effects of the strong auroral external fields and the complicated- behavior of the core field near the geomagnetic poles conspire to greatly reduce the crustal magnetic signal-to-noise ratio in the polar regions relative to the rest of the Earth. We can, however, use spectral correlation theory to filter the static lithospheric and core field components from the dynamic external field effects. To help isolate regional lithospheric from core field components, the correlations between CHAMP magnetic anomalies and the pseudo magnetic effects inferred from gravity-derived crustal thickness variations can also be exploited.. Employing these procedures, we processed the CHAMP magnetic observations for an improved magnetic anomaly map of the Antarctic crust. Relative to the much higher altitude Orsted and noisier Magsat observations, the CHAMP magnetic anomalies at 400 km altitude reveal new details on the effects of intracrustal magnetic features and crustal thickness variations of the Antarctic.

  3. Predicting gravity and sediment thickness in Afghanistan

    NASA Astrophysics Data System (ADS)

    Jung, W.; Brozena, J.; Peters, M.

    2013-02-01

    The US Naval Research Laboratory conducted comprehensive high-altitude (7 km above mean sea level) aero-geophysical surveys over Afghanistan in 2006 (Rampant Lion I). The surveys were done in collaboration with the US Geological Survey and upon the request of Islamic Republic of Afghanistan Ministry of Mines. In this study, we show that a best fitting admittance between topography and airborne gravity in western Afghanistan can be used to predict airborne gravity for the no-data area of eastern Afghanistan where the mountains are too high to conduct airborne surveys, due to the threat of ground fire. The differences between the airborne and the predicted gravity along a tie-track through the no-data area were found to be within ±12 mGal range with rms difference 7.3 mGal, while those between the predicted gravity from a simple Airy model (with compensation depth of 32 km and crustal density of 2.67 g cm-3) and the airborne gravity were within ±22 mGal range with rms difference 10.3 mGal. A combined airborne free-air anomaly has been constructed by merging the predicted gravity with the airborne data. We also demonstrate that sediment thickness can be estimated for basin areas where surface topography and airborne free-air anomaly profiles do not show a correlation presumably because of thick sediments. In order to estimate sediment thickness, we first determine a simple linear relationship from a scatter plot of the airborne gravity points and the interpolated Shuttle Radar Topography Mission (SRTM) topography along the Rampant Lion I tracks, and computed corresponding quasi-topography tracks by multiplying the linear relationship with the airborne free-air anomalies. We then take the differences between the SRTM and quasi-topography as a first-order estimate of sediment thickness. A global gravity model (GOCO02S), upward continued to the same altitude (7 km above mean sea level) as the data collection, was compared with the low-pass filtered (with cutoff

  4. The Voyager Anomaly and the GEM Theory

    NASA Astrophysics Data System (ADS)

    Brandenburg, J. E.

    For over a decade, the Pioneer Anomaly (PA) was an object of study and remains unresolved. Basically it is a sunward constant acceleration of the spacecraft that appeared unambiguously after the satellites passage beyond Saturn. It now appears possible the PA acceleration is the appearance of second, string-like, solution to the Einstein Equations first discussed in the context of charged finite mass charged particle potentials as part of the GEM theory. The exact solution to the metric equations is similar in form to the Schwartzchild Solution but with a positive sign: grr = (1 + rG/r)-1 where rG is a characteristic radius corresponding to the Schwartzchild radius. Adopting the approximation that for weak fields the metric becomes a Newtonian gravity potential: grr ≅-2ϕ, a string potential form is obtained in the limit grr ≅1-2ϕ, for r < < rG, grr≅r/rG (1-r/rG…). For the choice rG = cTH, this produces an effective gravity acceleration a ≅ c/TH = 8 x 10-10 m/sec2 in agreement with observations. The "turn on" for this potential apparently occurs with the encounter with Jupiter, which raised the spacecraft to above escape velocity. The possible physical meaning of this second metric appearance is found to be a gravitational form of Lenz's law, where objects departing from gravity potentials experience a resistance that keeps them bound at long distances.

  5. Gravity and Magnetic Surveys Over the Santa Rita Fault System, Southeastern Arizona

    USGS Publications Warehouse

    Hegmann, Mary

    2001-01-01

    Gravity and magnetic surveys were performed in the northeast portion of the Santa Rita Experimental Range, in southeastern Arizona, to identify faults and gain a better understanding of the subsurface geology. A total of 234 gravity stations were established, and numerous magnetic data were collected with portable and truck-mounted proton precession magnetometers. In addition, one line of very low frequency electromagnetic data was collected together with magnetic data. Gravity anomalies are used to identify two normal faults that project northward toward a previously identified fault. The gravity data also confirm the location of a second previously interpreted normal fault. Interpretation of magnetic anomaly data indicates the presence of a higher-susceptibility sedimentary unit located beneath lowersusceptibility surficial sediments. Magnetic anomaly data identify a 1-km-wide negative anomaly east of these faults caused by an unknown source and reveal the high variability of susceptibility in the Tertiary intrusive rocks in the area.

  6. Hawking radiation and covariant anomalies

    SciTech Connect

    Banerjee, Rabin; Kulkarni, Shailesh

    2008-01-15

    Generalizing the method of Wilczek and collaborators we provide a derivation of Hawking radiation from charged black holes using only covariant gauge and gravitational anomalies. The reliability and universality of the anomaly cancellation approach to Hawking radiation is also discussed.

  7. XYY chromosome anomaly and schizophrenia.

    PubMed

    Rajagopalan, M; MacBeth, R; Varma, S L

    1998-02-07

    Sex chromosome anomalies have been associated with psychoses, and most of the evidence is linked to the presence of an additional X chromosome. We report a patient with XYY chromosome anomaly who developed schizophrenia.

  8. Subduction dynamics: Constraints from gravity field observations

    NASA Technical Reports Server (NTRS)

    Mcadoo, D. C.

    1985-01-01

    Satellite systems do the best job of resolving the long wavelength components of the Earth's gravity field. Over the oceans, satellite-borne radar altimeters such as SEASAT provide the best resolution observations of the intermediate wavelength components. Satellite observations of gravity contributed to the understanding of the dynamics of subduction. Large, long wavelength geoidal highs generally occur over subduction zones. These highs are attributed to the superposition of two effects of subduction: (1) the positive mass anomalies of subducting slabs themselves; and (2) the surface deformations such as the trenches convectively inducted by these slabs as they sink into the mantle. Models of this subduction process suggest that the mantle behaves as a nonNewtonian fluid, its effective viscosity increases significantly with depth, and that large positive mass anomalies may occur beneath the seismically defined Benioff zones.

  9. Digital Isostatic Gravity Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California

    USGS Publications Warehouse

    Ponce, David A.; Mankinen, E.A.; Davidson, J.G.; Morin, R.L.; Blakely, R.J.

    2000-01-01

    An isostatic gravity map of the Nevada Test Site area was prepared from publicly available gravity data (Ponce, 1997) and from gravity data recently collected by the U.S. Geological Survey (Mankinen and others, 1999; Morin and Blakely, 1999). Gravity data were processed using standard gravity data reduction techniques. Southwest Nevada is characterized by gravity anomalies that reflect the distribution of pre-Cenozoic carbonate rocks, thick sequences of volcanic rocks, and thick alluvial basins. In addition, regional gravity data reveal the presence of linear features that reflect large-scale faults whereas detailed gravity data can indicate the presence of smaller-scale faults.

  10. Creating chiral anomalies

    NASA Astrophysics Data System (ADS)

    Bradlyn, Barry; Cano, Jennifer; Wang, Zhijun; Hirschberger, Max; Ong, N. Phuan; Bernevig, B. Andrei

    Materials with intrinsic Weyl points should present exotic magnetotransport phenomena due to spectral flow between Weyl nodes of opposite chirality - the so-called ``chiral anomaly''. However, to date, the most definitive transport data showing the presence of a chiral anomaly comes from Dirac (not Weyl) materials. These semimetals develop Weyl fermions only in the presence of an externally applied magnetic field, when the four-fold degeneracy is lifted. In this talk we examine Berry phase effects on transport due to the emergence of these field-induced Weyl point and (in some cases) line nodes. We pay particular attention to the differences between intrinsic and field-induced Weyl fermions, from the point of view of kinetic theory. Finally, we apply our analysis to a particular material relevant to current experiments performed at Princeton.

  11. Ebstein Anomaly in Pregnancy.

    PubMed

    Rusdi, Lusiani; Azizi, Syahrir; Suwita, Christopher; Karina, Astrid; Nasution, Sally A

    2016-10-01

    A 27-year-old primiparous woman with 28 weeks gestational age was admitted to our hospital with worsening shortness of breath. She was diagnosed with Ebstein's anomaly three years ago, but preferred to be left untreated. The patient was not cyanotic and her vital signs were stable. Her ECG showed incomplete RBBB and prolonged PR-interval. Blood tests revealed mild anemia. Observation of two-dimensional echo with color flow Doppler study showed Ebstein's anomaly with PFO as additional defects, EF of 57%, LV and LA dilatation, RV atrialization, severe TR, and moderate PH with RVSP of 44.3 mmHg. The patient then underwent elective sectio caesaria at 30 weeks of gestational age; both the mother and her baby were alive and were in good conditions.

  12. Mars gravity - High-resolution results from Viking Orbiter 2

    NASA Technical Reports Server (NTRS)

    Sjogren, W. L.

    1979-01-01

    Doppler radio-tracking data have provided detailed measurements for a Martian gravity map extending from 30 deg S to 65 deg N in latitude and through 360 deg of longitude. The feature resolution is approximately 500 km, revealing a huge anomaly associated with Olympus Mons, a mascon in Isidis Planitia, and other anomalies correlated with volcanic structure. Olympus Mons has been modeled with a 600 km surface disk having a mass of 8.7 times 10 to the 21st grams.

  13. Principal facts for gravity stations in the vicinity of San Bernardino, Southern California

    USGS Publications Warehouse

    Anderson, Megan L.; Roberts, Carter W.; Jachens, Robert C.

    2000-01-01

    New gravity measurements in the vicinity of San Bernardino, California were collected to help define the characteristics of the Rialto-Colton fault. The data were processed using standard reduction formulas and parameters. Rock properties such as lithology, magnetic susceptibility and density also were measured at several locations. Rock property measurements will be helpful for future modeling and density inversion calculations from the gravity data. On both the Bouguer and isostatic gravity maps, a prominent, 13-km long (8 mi), approximately 1-km (0.62 mi) wide gradient with an amplitude of 7 mGal, down to the northeast, is interpreted as the gravity expression of the Rialto-Colton fault. The gravity gradient strikes in a northwest direction and runs from the San Jacinto fault zone at its south end to San Sevine Canyon at the foot of the San Gabriel mountains at its north end. The Rialto-Colton fault has experienced both right-lateral strike-slip and normal fault motion that has offset basement rocks; therefore it is interpreted as a major, through-going fault.

  14. Waste Isolation Pilot Plant (WIPP) site gravity survey and interpretation

    SciTech Connect

    Barrows, L.J.; Fett, J.D.

    1983-04-01

    A portion of the WIPP site has been extensively surveyed with high-precision gravity. The main survey (in T22S, R31E) covered a rectangular area 2 by 4-1/3 mi encompassing all of WIPP site Zone II and part of the disturbed zone to the north of the site. Stations were at 293-ft intervals along 13 north-south lines 880 ft apart. The data are considered accurate to within a few hundredths of a milligal. Long-wavelength gravity anomalies correlate well with seismic time structures on horizons below the Castile Formation. Both the gravity anomalies and the seismic time structures are interpreted as resulting from related density and velocity variations within the Ochoan Series. Shorter wavelength negative gravity anomalies are interpreted as resulting from bulk density alteration in the vicinity of karst conduits. The WIPP gravity survey was unable to resolve low-amplitude, long-wavelength anomalies that should result from the geologic structures within the disturbed zone. It did indicate the degree and character of karst development within the surveyed area.

  15. Network gravity

    NASA Astrophysics Data System (ADS)

    Lombard, John

    2017-01-01

    We introduce the construction of a new framework for probing discrete emergent geometry and boundary-boundary observables based on a fundamentally a-dimensional underlying network structure. Using a gravitationally motivated action with Forman weighted combinatorial curvatures and simplicial volumes relying on a decomposition of an abstract simplicial complex into realized embeddings of proper skeletons, we demonstrate properties such as a minimal volume-scale cutoff, the necessity of a term playing the role of a positive definite cosmological constant as a regulator for nondegenerate geometries, and naturally emergent simplicial structures from Metropolis network evolution simulations with no restrictions on attachment rules or regular building blocks. We see emergent properties which echo results from both the spinfoam formalism and causal dynamical triangulations in quantum gravity, and provide analytical and numerical results to support the analogy. We conclude with a summary of open questions and intent for future work in developing the program.

  16. Pathogenesis of Vascular Anomalies

    PubMed Central

    Boon, Laurence M.; Ballieux, Fanny; Vikkula, Miikka

    2010-01-01

    Vascular anomalies are localized defects of vascular development. Most of them occur sporadically, i.e. there is no familial history of lesions, yet in a few cases clear inheritance is observed. These inherited forms are often characterized by multifocal lesions that are mainly small in size and increase in number with patient’s age. On the basis of these inherited forms, molecular genetic studies have unraveled a number of inherited mutations giving direct insight into the pathophysiological cause and the molecular pathways that are implicated. Genetic defects have been identified for hereditary haemorrhagic telangiectasia (HHT), inherited cutaneomucosal venous malformation (VMCM), glomuvenous malformation (GVM), capillary malformation - arteriovenous malformation (CM-AVM), cerebral cavernous malformation (CCM) and some isolated and syndromic forms of primary lymphedema. We focus on these disorders, the implicated mutated genes and the underlying pathogenic mechanisms. We also call attention to the concept of Knudson’s double-hit mechanism to explain incomplete penetrance and the large clinical variation in expressivity of inherited vascular anomalies. This variability renders the making of correct diagnosis of the rare inherited forms difficult. Yet, the identification of the pathophysiological causes and pathways involved in them has had an unprecedented impact on our thinking of their etiopathogenesis, and has opened the doors towards a more refined classification of vascular anomalies. It has also made it possible to develop animal models that can be tested for specific molecular therapies, aimed at alleviating the dysfunctions caused by the aberrant genes and proteins. PMID:21095468

  17. Could the Pioneer anomaly have a gravitational origin?

    SciTech Connect

    Tangen, Kjell

    2007-08-15

    If the Pioneer anomaly has a gravitational origin, it would, according to the equivalence principle, distort the motions of the planets in the Solar System. Since no anomalous motion of the planets has been detected, it is generally believed that the Pioneer anomaly can not originate from a gravitational source in the Solar System. However, this conclusion becomes less obvious when considering models that either imply modifications to gravity over long distances or gravitational sources localized to the outer Solar System, given the uncertainty in the orbital parameters of the outer planets. Following the general assumption that the Pioneer spacecraft move geodesically in a spherically symmetric space-time metric, we derive the metric disturbance that is needed in order to account for the Pioneer anomaly. We then analyze the residual effects on the astronomical observables of the three outer planets that would arise from this metric disturbance, given an arbitrary metric theory of gravity. Providing a method for comparing the computed residuals with actual residuals, our results imply that the presence of a perturbation to the gravitational field necessary to induce the Pioneer anomaly is in conflict with available data for the planets Uranus and Pluto, but not for Neptune. We therefore conclude that the motion of the Pioneer spacecraft must be nongeodesic. Since our results are model-independent within the class of metric theories of gravity, they can be applied to rule out any model of the Pioneer anomaly that implies that the Pioneer spacecraft move geodesically in a perturbed space-time metric, regardless of the origin of this metric disturbance.

  18. The south-central United States magnetic anomaly

    NASA Technical Reports Server (NTRS)

    Starich, P. J.; Hinze, W. J.; Braile, L. W.

    1985-01-01

    A positive magnetic anomaly, which dominates the MAGSAT scalar field over the south-central United States, results from the superposition of magnetic effects from several geologic sources and tectonic structures in the crust. The highly magnetic basement rocks of this region show good correlation with increased crustal thickness, above average crustal velocity and predominantly negative free-air gravity anomalies, all of which are useful constraints for modeling the magnetic sources. The positive anomaly is composed of two primary elements. The western-most segment is related to middle Proterozoic granite intrusions, rhyolite flows and interspersed metamorphic basement rocks in the Texas panhandle and eastern New Mexico. The anomaly and the magnetic crust are bounded to the west by the north-south striking Rio Grande Rift. The anomaly extends eastward over the Grenville age basement rocks of central Texas, and is terminated to the south and east by the buried extension of the Ouachita System. The northern segment of the anomaly extends eastward across Oklahoma and Arkansas to the Mississippi Embayment. It corresponds to a general positive magnetic region associated with the Wichita Mountains igneous complex in south-central Oklahoma and 1.2 to 1.5 Ga. felsic terrane to the north.

  19. Sourceof The Jarraf Gravity and Magnetic Anomaliesoffshore Libya.

    NASA Astrophysics Data System (ADS)

    Reeh, G.

    The Jarrafa anomaly is one of several high wavenumber feature in the NW Libyan offshore region. The interpretation of Jarrafa anomaly suggest that it may be caused by body of high density and magnetization.The analysis of the power spectrum of the anomalies indicates that it results from two groups of source; the shallower group at maximum depth of 5 km is interpreted as the depth to the top of causative body of the anomalies and a deeper group at depth of 11km probably refer to the depth of local basement. The boundary analysis derived from applied horizontal gradient to gravity and magnetic data reveal lineaments many of which can related to geologi- cal structures and tectonic elements. The poor correlation between the pseudograv- ity fields for induced magnetization with the observed gravity fields strongly suggests that the causative structure have remanent magnetization. Three-dimensional interpre- tation techniques indicate that the magnetic source of the Jarrafa magnetic anomaly has induced magnetization intensity of 0.43 A/m. The magnetic model shows that it has a base level at 15 km. The analysis and interpretation of the gravity and magnetic data suggests that the source of the Jarrafa anomaly is a basic igneous rock and it may have formed during Jurassic extensional phase.

  20. Gravity effect of sediment compaction: examples from the North Sea and the Rhine Graben

    NASA Astrophysics Data System (ADS)

    Cowie, Patience A.; Karner, Garry D.

    1990-07-01

    A Fourier domain expression for calculating the gravity effect of a continuously varying density structure is used to investigate the way in which sediment compaction modifies the shape of the gravity anomaly across a sedimentary basin. In general, sediment density increases with depth in a basin as the overburden thickness increases. The effect of the increase in sediment density is to reduce the gravity contribution from the density contrasts in the deeper parts of the basin relative to near surface contributions. For a theoretical uncompensated basin, the gravity effect of the sediments is calculated for a density-depth variation described by: (1) a simple exponential increase in sediment density with depth, and (2) an exponential modified to include a local density inversion representative of sediment overpressuring. It is shown that for both cases, the calculated gravity does not necessarily reflect the morphology of the sediment-basement interface. The gravity effect is most sensitive to the distribution of the youngest stratigraphic units within the basin. Results of modeling observed gravity anomalies across the Viking and Rhine Graben show that the small peak-to-trough amplitude of the gravity anomalies across these basins can be attributed to the increase in sediment density with depth rather than the compensation of the basin. For the Rhine Graben, it is further shown that the wavelength of the gravity anomaly is strongly controlled by the flexural strength of the lithosphere. Together these results suggest that while the amplitude of gravity anomalies across extensional basins may be primarily reflecting compaction of the sediment infill, the anomaly wavelength is more sensitive to the compensation mechanism.

  1. Geopotential field anomalies and regional tectonic features - two case studies: southern Africa and Germany

    NASA Astrophysics Data System (ADS)

    Korte, Monika; Mandea, Mioara

    2016-05-01

    Maps of magnetic and gravity field anomalies provide information about physical properties of the Earth's crust and upper mantle, helpful in understanding geological conditions and tectonic structures. Depending on data availability, whether from the ground, airborne, or from satellites, potential field anomaly maps contain information on different ranges of spatial wavelengths, roughly corresponding to sources at different depths. Focussing on magnetic data, we compare amplitudes and characteristics of anomalies from maps based on various available data and as measured at geomagnetic repeat stations. Two cases are investigated: southern Africa, characterized by geologically old cratons and strong magnetic anomalies, and the smaller region of Germany with much younger crust and weaker anomalies. Estimating lithospheric magnetic anomaly values from the ground stations' time series (repeat station crustal biases) reveals magnetospheric field contributions causing time-varying offsets of several nT in the results. Similar influences might be one source of discrepancy when merging anomaly maps from different epochs. Moreover, we take advantage of recently developed satellite potential field models and compare magnetic and gravity gradient anomalies of ˜ 200 km resolution. Density and magnetization represent independent rock properties and thus provide complementary information on compositional and structural changes. Comparing short- and long-wavelength anomalies and the correlation of rather large-scale magnetic and gravity anomalies, and relating them to known lithospheric structures, we generally find a better agreement in the southern African region than the German region. This probably indicates stronger concordance between near-surface (down to at most a few km) and deeper (several kilometres down to Curie depth) structures in the former area, which can be seen to agree with a thicker lithosphere and a lower heat flux reported in the literature for the southern

  2. Induced gravity II: grand unification

    NASA Astrophysics Data System (ADS)

    Einhorn, Martin B.; Jones, D. R. Timothy

    2016-05-01

    As an illustration of a renormalizable, asymptotically-free model of induced gravity, we consider an SO(10) gauge theory interacting with a real scalar multiplet in the adjoint representation. We show that dimensional transmutation can occur, spontaneously breaking SO(10) to SU(5)⊗U(1), while inducing the Planck mass and a positive cosmological constant, all proportional to the same scale v. All mass ratios are functions of the values of coupling constants at that scale. Below this scale (at which the Big Bang may occur), the model takes the usual form of Einstein-Hilbert gravity in de Sitter space plus calculable corrections. We show that there exist regions of parameter space in which the breaking results in a local minimum of the effective action giving a positive dilaton (mass)2 from two-loop corrections associated with the conformal anomaly. Furthermore, unlike the singlet case we considered previously, some minima lie within the basin of attraction of the ultraviolet fixed point. Moreover, the asymptotic behavior of the coupling constants also lie within the range of convergence of the Euclidean path integral, so there is hope that there will be candidates for sensible vacua. Although open questions remain concerning unitarity of all such renormalizable models of gravity, it is not obvious that, in curved backgrounds such as those considered here, unitarity is violated. In any case, any violation that may remain will be suppressed by inverse powers of the reduced Planck mass.

  3. Approaches to Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Oriti, Daniele

    2009-03-01

    Preface; Part I. Fundamental Ideas and General Formalisms: 1. Unfinished revolution C. Rovelli; 2. The fundamental nature of space and time G. 't Hooft; 3. Does locality fail at intermediate length scales R. Sorkin; 4. Prolegomena to any future quantum gravity J. Stachel; 5. Spacetime symmetries in histories canonical gravity N. Savvidou; 6. Categorical geometry and the mathematical foundations of quantum gravity L. Crane; 7. Emergent relativity O. Dreyer; 8. Asymptotic safety R. Percacci; 9. New directions in background independent quantum gravity F. Markopoulou; Questions and answers; Part II: 10. Gauge/gravity duality G. Horowitz and J. Polchinski; 11. String theory, holography and quantum gravity T. Banks; 12. String field theory W. Taylor; Questions and answers; Part III: 13. Loop Quantum Gravity T. Thiemann; 14. Covariant loop quantum gravity? E. LIvine; 15. The spin foam representation of loop quantum gravity A. Perez; 16. 3-dimensional spin foam quantum gravity L. Freidel; 17. The group field theory approach to quantum gravity D. Oriti; Questions and answers; Part IV. Discrete Quantum Gravity: 18. Quantum gravity: the art of building spacetime J. Ambjørn, J. Jurkiewicz and R. Loll; 19. Quantum Regge calculations R. Williams; 20. Consistent discretizations as a road to quantum gravity R. Gambini and J. Pullin; 21. The causal set approach to quantum gravity J. Henson; Questions and answers; Part V. Effective Models and Quantum Gravity Phenomenology: 22. Quantum gravity phenomenology G. Amelino-Camelia; 23. Quantum gravity and precision tests C. Burgess; 24. Algebraic approach to quantum gravity II: non-commutative spacetime F. Girelli; 25. Doubly special relativity J. Kowalski-Glikman; 26. From quantum reference frames to deformed special relativity F. Girelli; 27. Lorentz invariance violation and its role in quantum gravity phenomenology J. Collins, A. Perez and D. Sudarsky; 28. Generic predictions of quantum theories of gravity L. Smolin; Questions and

  4. Physicochemical isotope anomalies

    SciTech Connect

    Esat, T.M.

    1988-06-01

    Isotopic composition of refractory elements can be modified, by physical processes such as distillation and sputtering, in unexpected patterns. Distillation enriches the heavy isotopes in the residue and the light isotopes in the vapor. However, current models appear to be inadequate to describe the detailed mass dependence, in particular for large fractionations. Coarse- and fine-grained inclusions from the Allende meteorite exhibit correlated isotope effects in Mg both as mass-dependent fractionation and residual anomalies. This isotope pattern can be duplicated by high temperature distillation in the laboratory. A ubiquitous property of meteoritic inclusions for Mg as well as for most of the other elements, where measurements exist, is mass-dependent fractionation. In contrast, terrestrial materials such as microtektites, tektite buttons as well as lunar orange and green glass spheres have normal Mg isotopic composition. A subset of interplanetary dust particles labelled as chondritic aggregates exhibit excesses in {sup 26}Mg and deuterium anomalies. Sputtering is expected to be a dominant mechanism in the destruction of grains within interstellar dust clouds. An active proto-sun as well as the present solar-wind and solar-flare flux are of sufficient intensity to sputter significant amounts of material. Laboratory experiments in Mg show widespread isotope effects including residual {sup 26}Mg excesses and mass dependent fractionation. It is possible that the {sup 26}Mg excesses in interplanetary dust is related to sputtering by energetic solar-wind particles. The implication if the laboratory distillation and sputtering effects are discussed and contrasted with the anomalies in meteoritic inclusions the other extraterrestrial materials the authors have access to.

  5. Gravity Waves

    NASA Technical Reports Server (NTRS)

    Vanzandt, T. E.

    1985-01-01

    Atmospheric parameters fluctuate on all scales. In the mesoscale these fluctuations are occasionally sinusoidal so that they can be interpreted as gravity waves. Usually, however, the fluctuations are noise like, so that their cause is not immediately evident. Results of mesoscale observations in the 20 to 120 m altitude range that are suitable for incorporation into a model atmosphere are very limited. In the stratosphere and lower mesosphere observations are sparse and very little data has been summarized into appropriate form. There is much more data in the upper mesosphere and lower thermosphere, but again very little of it has been summarized. The available mesoscale spectra of horizontal wind u versus vertical wave number m in the 20 to 120 km altitude range are shown together with a spectrum from the lower atmosphere for comparison. Further information about these spectra is given. In spite of the large range of altitudes and latitudes, the spectra from the lower atmosphere (NASA, 1971 and DEWAN, 1984) are remarkably similar in both shape and amplitude. The mean slopes of -2.38 for the NASA spectrum and -2.7 for the Dewan spectra are supported by the mean slope of -2.75 found by ROSENBERG et al. (1974). The mesospheric spectrum is too short to establish a shape. Its amplitude is about an order of magnitude larger than the NASA spectrum in the same wave number range. The NASA and Dewan spectra suggest that the mesoscale spectra in the lower atmosphere are insensitive to meteorological conditions.

  6. Detecting Patterns of Anomalies

    DTIC Science & Technology

    2009-03-01

    ct)P (bt|ct) , where A,B and C are mutually exclusive subsets of attributes with at most k elements . This ratio is similar to the previous formula , but...AND SUBTITLE Detecting Patterns of Anomalies 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e...to be dependent if, µ(A,B) ≥ βµ (2.1) where, βµ is a threshold parameter, set to a low value of 0.1 ( empirically ) in our experi- ments. Thus, for a

  7. Satellite magnetic anomalies over subduction zones - The Aleutian Arc anomaly

    NASA Technical Reports Server (NTRS)

    Clark, S. C.; Frey, H.; Thomas, H. H.

    1985-01-01

    Positive magnetic anomalies seen in MAGSAT average scalar anomaly data overlying some subduction zones can be explained in terms of the magnetization contrast between the cold subducted oceanic slab and the surrounding hotter, nonmagnetic mantle. Three-dimensional modeling studies show that peak anomaly amplitude and location depend on slab length and dip. A model for the Aleutian Arc anomaly matches the general trend of the observed MAGSAT anomaly if a slab thickness of 7 km and a relatively high (induced plus viscous) magnetization contrast of 4 A/m are used. A second source body along the present day continental margin is required to match the observed anomaly in detail, and may be modeled as a relic slab from subduction prior to 60 m.y. ago.

  8. Gravity and tectonic patterns of Mercury

    NASA Astrophysics Data System (ADS)

    Matsuyama, I.; Nimmo, F.

    2008-12-01

    We consider the effect of tidal deformation, spin-orbit resonance, non-zero eccentricity, despinning, and reorientation on the global-scale gravity, shape, and tectonic patterns of planetary bodies. Large variations of the gravity and shape coefficients from the synchronous rotation and zero eccentricity values, J2/C22=10/3 and (b-c)/(a-c)=1/4, arise due to non-synchronous rotation and non-zero eccentricity even in the absence of reorientation or despinning. Reorientation or despinning induce additional variations. As an illustration of this theory, we consider the specific example of Mercury. The large gravity coefficients estimated from the Mariner 10 flybys cannot be attributed to the Caloris basin alone since the required mass excess in this case would have caused Caloris to migrate to one of Mercury's hot poles. Similarly, a large remnant bulge due to a smaller semimajor axis and spin-orbit resonance can be dismissed since the required semimajor axis is unphysically small (< 0.1 AU). Reorientation of a large remnant bulge recording an epoch of faster rotation (without significant semimajor axis variations) can explain the large gravity coefficients. This requires initial rotation rates > 20 times the present value and a positive gravity anomaly associated with Caloris capable of driving 10-45° equatorward reorientation. The required gravity anomaly can be explained by infilling of the basin with material of thicknesses > 7 km, or an annulus of volcanic plains emplaced around the basin with annulus width ~ 1200 km and fill thicknesses > 2 km. The predicted tectonic pattern due to these despinning and reorientation scenarios and radial contraction is in good agreement with the observed lobate scarp pattern.

  9. Estimation of local planetary gravity fields using line of sight gravity data and an integral operator

    NASA Technical Reports Server (NTRS)

    Barriot, J. P.; Balmino, G.

    1992-01-01

    A novel method is presented for mapping line-of-sight gravity data (LOSGD) joining planetary probes and observers during Doppler tracking operations, with a view to geodetic and geophysical applications. LOSGD are in this case mapped as gravity anomalies along a radial direction, at constant altitude, using an inversion procedure in conjunction with a Tikhonov-Arsenine regularization method. The application of different regularization-parameter choices to a synthetic case is followed by application to the real case of Pioneer-Venus orbiter data for Venus' Gula Mons.

  10. Estimation of local planetary gravity fields using line of sight gravity data and an integral operator

    NASA Astrophysics Data System (ADS)

    Barriot, J. P.; Balmino, G.

    1992-09-01

    A novel method is presented for mapping line-of-sight gravity data (LOSGD) joining planetary probes and observers during Doppler tracking operations, with a view to geodetic and geophysical applications. LOSGD are in this case mapped as gravity anomalies along a radial direction, at constant altitude, using an inversion procedure in conjunction with a Tikhonov-Arsenine regularization method. The application of different regularization-parameter choices to a synthetic case is followed by application to the real case of Pioneer-Venus orbiter data for Venus' Gula Mons.

  11. Broadscale Postseismic Gravity Change Following the 2011 Tohoku-Oki Earthquake and Implication for Deformation by Viscoelastic Relaxation and Afterslip

    NASA Technical Reports Server (NTRS)

    Han, Shin-Chan; Sauber, Jeanne; Pollitz, Fred

    2014-01-01

    The analysis of GRACE gravity data revealed post-seismic gravity increase by 6 micro-Gal over a 500 km scale within a couple of years after the 2011 Tohoku-Oki earthquake, which is nearly 40-50% of the co-seismic gravity change. It originates mostly from changes in the isotropic component corresponding to the M(sub rr) moment tensor element. The exponential decay with rapid change in a year and gradual change afterward is a characteristic temporal pattern. Both viscoelastic relaxation and afterslip models produce reasonable agreement with the GRACE free-air gravity observation, while their Bouguer gravity patterns and seafloor vertical deformations are distinctly different. The post-seismic gravity variation is best modeled by the bi-viscous relaxation with a transient and steady state viscosity of 10(exp 18) and 10(exp 19) Pa s, respectively, for the asthenosphere. Our calculated higher-resolution viscoelastic relaxation model, underlying the partially ruptured elastic lithosphere, yields the localized post-seismic subsidence above the hypocenter reported from the GPS-acoustic seafloor surveying.

  12. Gravity Fields and Interiors of the Saturnian Satellites

    NASA Technical Reports Server (NTRS)

    Rappaport, N. J.; Armstrong, J. W.; Asmar, Sami W.; Iess, L.; Tortora, P.; Somenzi, L.; Zingoni, F.

    2006-01-01

    This viewgraph presentation reviews the Gravity Science Objectives and accomplishments of the Cassini Radio Science Team: (1) Mass and density of icy satellites (2) Quadrupole field of Titan and Rhea (3) Dynamic Love number of Titan (4) Moment of inertia of Titan (in collaboration with the Radar Team) (5) Gravity field of Saturn. The proposed measurements for the extended tour are: (1) Quadrupole field of Enceladus (2) More accurate measurement of Titan k2 (3) Local gravity/topography correlations for Iapetus (4) Verification/disproof of "Pioneer anomaly".

  13. Einstein, Entropy and Anomalies

    NASA Astrophysics Data System (ADS)

    Sirtes, Daniel; Oberheim, Eric

    2006-11-01

    This paper strengthens and defends the pluralistic implications of Einstein's successful, quantitative predictions of Brownian motion for a philosophical dispute about the nature of scientific advance that began between two prominent philosophers of science in the second half of the twentieth century (Thomas Kuhn and Paul Feyerabend). Kuhn promoted a monistic phase-model of scientific advance, according to which a paradigm driven `normal science' gives rise to its own anomalies, which then lead to a crisis and eventually a scientific revolution. Feyerabend stressed the importance of pluralism for scientific progress. He rejected Kuhn's model arguing that it fails to recognize the role that alternative theories can play in identifying exactly which phenomena are anomalous in the first place. On Feyerabend's account, Einstein's predictions allow for a crucial experiment between two incommensurable theories, and are an example of an anomaly that could refute the reigning paradigm only after the development of a competitor. Using Kuhn's specification of a disciplinary matrix to illustrate the incommensurability between the two paradigms, we examine the different research strategies available in this peculiar case. On the basis of our reconstruction, we conclude by rebutting some critics of Feyerabend's argument.

  14. The XXXXY Chromosome Anomaly

    PubMed Central

    Zaleski, Witold A.; Houston, C. Stuart; Pozsonyi, J.; Ying, K. L.

    1966-01-01

    The majority of abnormal sex chromosome complexes in the male have been considered to be variants of Klinefelter's syndrome but an exception should probably be made in the case of the XXXXY individual who has distinctive phenotypic features. Clinical, radiological and cytological data on three new cases of XXXXY syndrome are presented and 30 cases from the literature are reviewed. In many cases the published clinical and radiological data were supplemented and re-evaluated. Mental retardation, usually severe, was present in all cases. Typical facies was observed in many; clinodactyly of the fifth finger was seen in nearly all. Radiological examination revealed abnormalities in the elbows and wrists in all the 19 personally evaluated cases, and other skeletal anomalies were very frequent. Cryptorchism is very common and absence of Leydig's cells may differentiate the XXXXY chromosome anomaly from polysomic variants of Klinefelter's syndrome. The relationship of this syndrome to Klinefelter's syndrome and to Down's syndrome is discussed. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11Fig. 12Fig. 13Fig. 14Fig. 15 PMID:4222822

  15. Results of Gravity Fieldwork Conducted in March 2008 in the Moapa Valley Region of Clark County, Nevada

    USGS Publications Warehouse

    Scheirer, Daniel S.; Andreasen, Arne Dossing

    2008-01-01

    In March 2008, we collected gravity data along 12 traverses across newly-mapped faults in the Moapa Valley region of Clark County, Nevada. In areas crossed by these faults, the traverses provide better definition of the gravity field and, thus, the density structure, than prior gravity observations. Access problems prohibited complete gravity coverage along all of the planned gravity traverses, and we added and adjusted the locations of traverses to maximize our data collection. Most of the traverses exhibit isostatic gravity anomalies that have gradients characteristic of exposed or buried faults, including several of the newly-mapped faults.

  16. Gravity and geoid model for South America

    NASA Astrophysics Data System (ADS)

    Blitzkow, Denizar; Oliveira Cancoro de Matos, Ana Cristina; do Nascimento Guimarães, Gabriel; Pacino, María Cristina; Andrés Lauría, Eduardo; Nunes, Marcelo; Castro Junior, Carlos Alberto Correia e.; Flores, Fredy; Orihuela Guevara, Nuris; Alvarez, Ruber; Napoleon Hernandez, José

    2016-04-01

    In the last 20 years, South America Gravity Studies (SAGS) project has undertaken an ongoing effort in establishing the fundamental gravity network (FGN); terrestrial, river and airborne relative gravity densifications; absolute gravity surveys and geoid (quasi-geoid) model computation for South America. The old FGN is being replaced progressively by new absolute measurements in different countries. In recent years, Argentina, Bolivia, Brazil, Ecuador, Paraguay and Venezuela organizations participated with relative gravity surveys. Taking advantage of the large amount of data available, GEOID2015 model was developed for 15°N and 57°S latitude and 30 ° W and 95°W longitude based on EIGEN-6C4 until degree and order 200 as a reference field. The ocean area was completed with mean free air gravity anomalies derived from DTU10 model. The short wavelength component was estimated using FFT. The global gravity field models EIGEN-6C4, DIR_R5 were used for comparison with the new model. The new geoid model has been evaluated against 1,319 GPS/BM, in which 592 are located in Brazil and the reminder in other countries. The preliminary RMS difference between GPS/BM and GEOID2015 throughout South America and in Brazil is 46 cm and 17 cm, respectively. New activities are carrying out with the support of the IGC (Geographic and Cartographic Institute) under the coordination of EPUSP/LTG and CENEGEO (Centro de Estudos de Geodesia). The new project aims to establish new gravity points with the A-10 absolute gravimeter in South America. Recent such surveys occurred in São Paulo state, Argentina and Venezuela.

  17. Improving compact gravity inversion based on new weighting functions

    NASA Astrophysics Data System (ADS)

    Ghalehnoee, Mohammad Hossein; Ansari, Abdolhamid; Ghorbani, Ahmad

    2016-11-01

    We have developed a method to estimate the geometry, location and densities of anomalies coming from two-dimensional gravity data based on compact gravity inversion technique. Compact gravity inversion is simple, fast and user friendly but severely depends on the number of model parameters, i.e. by increasing the model parameters, the anomalies tend to concentrate near the surface. To overcome this ambiguity new weighting functions based on density contrast, depth, and compactness models have been introduced. Variable compactness factors have been defined here to get either a sharp or a smooth model based on the depth of the source or existence of prior information. Depth weighting derived from one station of gravity data whereas the effect of gravity data is two- and three-dimensional. To compensate this limitation an innovating weighting function namely kernel function has been introduced which multiplies with weight and compactness matrixes to yield a general model weighting function. The method is tested using three different sets of synthetic examples: a body at various depths (20, 40, 80 and 140 m), two bodies at the same depth but various distances to estimate lateral resolution and three bodies with negative and positive density contrast in different depths. The method is also applied to three real gravity data of Woodlawn massive sulfide body, sulfides mineralization of British Colombia and iron ore body of Missouri. The method produces solutions consistent with the known geologic attributes of the gravity sources, illustrating its potential practicality.

  18. Improving compact gravity inversion using new weighting functions

    NASA Astrophysics Data System (ADS)

    Ghalehnoee, Mohammad Hossein; Ansari, Abdolhamid; Ghorbani, Ahmad

    2017-01-01

    We have developed a method to estimate the geometry, location and densities of anomalies coming from 2-D gravity data based on compact gravity inversion technique. Compact gravity inversion is simple, fast and user friendly but severely depends on the number of model parameters, that is, by increasing the model parameters, the anomalies tend to concentrate near the surface. To overcome this ambiguity new weighting functions based on density contrast, depth, and compactness models have been introduced. Variable compactness factors have been defined here to get either a sharp or a smooth model based on the depth of the source or existence of prior information. Depth weighting derived from one station of gravity data whereas the effect of gravity data is 2-D and 3-D. To compensate this limitation an innovating weighting function namely kernel function has been introduced which multiplies with weight and compactness matrixes to yield a general model weighting function. The method is tested using three different sets of synthetic examples: a body at various depths (20, 40, 80 and 140 m), two bodies at the same depth but various distances to estimate lateral resolution and three bodies with negative and positive density contrast in different depths. The method is also applied to three real gravity data of Woodlawn massive sulphide body, sulphides mineralization of British Colombia and iron ore body of Missouri. The method produces solutions consistent with the known geologic attributes of the gravity sources, illustrating its potential practicality.

  19. Magnetic Anomalies in the South of Corad Rise, the Southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Nogi, Y.; Ikehara, M.; Nakamura, Y.; Kameo, K.; Katsuki, K.; Kawamura, S.; Kita, S.

    2008-12-01

    Seafloor age estimated from magnetic anomalies in the Southern Indian Ocean are vital to understanding the fragmentation process of the Gondwana, but the seafloor age still remain less well-defined because of the sparse observations in this area. To understand the seafloor spreading history related to the Gondwana breakup, total intensity and vector geomagnetic field measurements as well as swath bathymetry mapping were conducted during the R/V Hakuho-maru cruise KH-07-4 Leg3 in the Southern Indian Ocean between Cape Town, South Africa, and off Lützow-Holm Bay, Antarctica. Magnetic anomaly data have been collected along WNW-ESE trending structures of unknown origin inferred from satellite gravity anomalies just to the south of Conrad Rise. We have also collected magnetic anomaly data along NNE-SSW trending lineaments from satellite gravity anomaly data between the south of the Conrad Rise and off Lützow-Holm Bay. Magnetic anomalies with amplitude of about 500 nT, originating from normal and reversed magnetization of oceanic crust, are detected along the WNW-ESE trending structures just to the south of Conrad Rise. These magnetic anomalies possibly belong to Mesozoic magnetic anomaly sequence and this shows the part of the oceanic crust just to the south of the Conrad Rise formed before the long Cretaceous normal polarity superchron although magnetic anomaly C34 has been identified just to the north of the Conrad Rise. Magnetic anomalies with amplitude of about 300 nT are also observed along the NNE-SSW trending lineaments between the south of the Conrad Rise and off Lützow-Holm Bay, and most likely indicate Mesozoic magnetic anomaly sequence. These suggest the extinct spreading axes in the south of Conrad Rise and complicated seafloor spreading history in this area.

  20. The gravity field of topography buried by sediments

    NASA Technical Reports Server (NTRS)

    Sandwell, D. T.; Liu, C. S.

    1985-01-01

    The gravity field over topography in the northern Indian Ocean that was completely buried by sediments of the Bengal Fan was investigated to understand the effect of sedimentation on the continental gravity field. An isopach map made from the seismic reflection and refraction in the Bay of Bengal shows two prominent N-S trending features in the basement topography. The northernmost portion of the Ninetyeast Ridge is totally buried by sediments north of 10 deg N. The other buried ridge trends roughly N-S for 1400 km at 85 deg E to the latitude of Sri Lanka and then curves toward the west. It has basement relief up to 6 km. Two free air gravity anomaly profiles across the region show a strong gravity low over the 85 deg E ridge, while the Ninetyeast Ridge shows a gravity high.

  1. Fluid/gravity correspondence for massive gravity

    NASA Astrophysics Data System (ADS)

    Pan, Wen-Jian; Huang, Yong-Chang

    2016-11-01

    In this paper, we investigate the fluid/gravity correspondence in the framework of mas