Automatic fitting of gravity anomalies using two‐dimensional models

Geophysics ◽  
1984 ◽  
Vol 49 (3) ◽  
pp. 300-302
Author(s):  
Antonio Montalvo
Keyword(s):  
Gravity Anomalies ◽  
Convergence Criterion ◽  
Two Dimensional ◽  
Trial And Error ◽  
Initial Model ◽  
Automatic Construction ◽  
Frequency Domains ◽  
Gravity Measurements ◽  
Automatic Fitting ◽  
The Way

During the last two decades several methods have been reported in the literature (Corbató, 1965; Gerard and Debeglia, 1975; Bhattacharyya, 1978) for the automatic construction of models that fit observed magnetic and gravity measurements by using either space or frequency domains. Whichever approach is employed, the methods proceed as follows. An initial model is proposed and a sequence of corrections is generated in order to improve the fit between the observed and calculated anomalies. These corrections are successively applied to the initial model until a certain convergence criterion is satisfied. The above corresponds to the well‐known trial‐and‐error procedure; the relative advantages of one method over another arise from the way in which the corrections are generated.

GRAVITY ANOMALIES OF TWO‐DIMENSIONAL FAULTS

Geophysics ◽  
1966 ◽  
Vol 31 (2) ◽  
pp. 372-397 ◽  
Author(s):  
L. P. Geldart ◽  
Denis E. Gill ◽  
Bijon Sharma
Keyword(s):  
Fault Plane ◽  
Marked Effect ◽  
Gravity Anomalies ◽  
Two Dimensional ◽  
Gravity Effect ◽  
Fault Density ◽  
Wide Range ◽  
Bed Thickness ◽  
Two Sides ◽  
Simplified Formula

A simplified formula is given for the gravity effect of a horizontal semi‐infinite block truncated by a dipping plane. This formula is used to obtain curves illustrating the gravity anomalies for blocks having different thicknesses and depths truncated by planes dipping at various angles. By combining two blocks, results are obtained for faulted horizontal beds for a wide range of bed thicknesses and depths, fault displacements and dips. These should be useful as guides in interpreting fault anomalies, and in planning gravity programs intended to map faults. The most striking feature of the curves is the marked effect of the dip of the fault plane on the curves for faulted beds. The asymmetry of the fault curves is related mainly to the dip and can be used to determine dips between 30 and 90 degrees. If the dip of the fault, density contrast, and bed thickness are known, the depths to the bed on the two sides of the fault are given by the sizes and positions of the gravity maximum and minimum.

The gravity field over the Ungava Bay region from satellite altimetry and new land-based data: implications for the geology of the area

1999 ◽  
Vol 36 (1) ◽  
pp. 75-89 ◽  
Author(s):  
Hamid Telmat ◽  
Jean-Claude Mareschal ◽  
Clément Gariépy
Keyword(s):  
Satellite Altimetry ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Gravity Models ◽  
Crustal Thickening ◽  
Seismic Line ◽  
Crustal Thinning ◽  
Gravity Measurements ◽  
George River ◽  
Superior Craton

Gravity data were obtained along two transects on the southern coast of Ungava Bay, which provide continuous gravity coverage between Leaf Bay and George River. The transects and the derived gravity profiles extend from the Superior craton to the Rae Province across the New Quebec Orogen (NQO). Interpretation of the transect along the southwestern coast of Ungava Bay suggests crustal thickening beneath the NQO and crustal thinning beneath the Kuujjuaq Terrane, east of the NQO. Two alternative interpretations are proposed for the transect along the southeastern coast of the bay. The first model shows crustal thickening beneath the George River Shear Zone (GRSZ) and two shallow bodies correlated with the northern extensions of the GRSZ and the De Pas batholith. The second model shows constant crustal thickness and bodies more deeply rooted than in the first model. The gravity models are consistent with the easterly dipping reflections imaged along a Lithoprobe seismic line crossing Ungava Bay and suggest westward thrusting of the Rae Province over the NQO. Because no gravity data have been collected in Ungava Bay, satellite altimetry data have been used as a means to fill the gap in data collected at sea. The satellite-derived gravity data and standard Bouguer gravity data were combined in a composite map for the Ungava Bay region. The new land-based gravity measurements were used to verify and calibrate the satellite data and to ensure that offshore gravity anomalies merge with those determined by the land surveys in a reasonable fashion. Three parallel east-west gravity profiles were extracted: across Ungava Bay (59.9°N), on the southern shore of the bay (58.5°N), and onshore ~200 km south of Ungava Bay (57.1°N). The gravity signature of some major structures, such as the GRSZ, can be identified on each profile.

A comparison between sea-bottom gravity and satellite altimeter-derived gravity in coastal environments: A case study of the Gulf of Manfredonia (SW Adriatic Sea)

2021 ◽  
Author(s):  
Luigi Sante Zampa ◽  
Emanuele Lodolo ◽  
Nicola Creati ◽  
Martina Busetti ◽  
Gianni Madrussani ◽  
...  
Keyword(s):  
Gravity Field ◽  
Satellite Altimetry ◽  
Adriatic Sea ◽  
Gravity Anomalies ◽  
Satellite Altimeter ◽  
Sea Bottom ◽  
Marine Gravity ◽  
Gravity Measurements ◽  
Near Shore ◽  
Italian Coasts

<p>In this study, we present a comparative analysis between two types of gravity data used in geophysical applications: satellite altimeter-derived gravity and sea-bottom gravity.</p><p>It is largely known that the marine gravity field derived from satellite altimetry in coastal areas is generally biased by signals back-scattered from the nearby land. As a result, the derived gravity anomalies are mostly unreliable for geophysical and geological interpretations of near-shore environments.</p><p>To quantify the errors generated by the land-reflected signals and to verify the goodness of the geologic models inferred from gravity, we compared two different altimetry models with sea-bottom gravity measurements acquired along the Italian coasts from the early 50s to the late 80s.</p><p>We focused on the Gulf of Manfredonia, located in the SE sector of the Adriatic Sea, where: (i) two different sea-bottom gravity surveys have been conducted over the years, (ii) the bathymetry is particularly flat, and (iii) seismic data revealed a prominent carbonate ridge covered by hundreds of meters of Oligocene-Quaternary sediments.</p><p>Gravity field derivatives have been used to enhance both: (i) deep geological contacts, and (ii) coastal noise. The analyses outlined a “ringing-noise effect” which causes the altimeter signal degradation up to 17 km from the coast.</p><p>Differences between the observed gravity and the gravity calculated from a geological model constrained by seismic, showed that all datasets register approximately the same patterns, associated with the Gondola Fault Zone, a major structural discontinuity traversing roughly E-W the investigated area.</p><p>This study highlights the importance of implementing gravity anomalies derived from satellite-altimetry with high-resolution near-shore data, such as the sea-bottom gravity measurements available around the Italian coasts. Such analysis may have significant applications in studying the link between onshore and offshore geological structures in transitional areas.</p>

New Research on Gravity Field in Lithuanian Territory

2017 ◽  
Author(s):  
Petras Petroškevicius ◽  
Romuald Obuchovski ◽  
Rosita Birvydienė ◽  
Ricardas Kolosovskis ◽  
Raimundas Putrimas ◽  
...  
Keyword(s):  
Gravity Field ◽  
Gravity Anomalies ◽  
Satellite Geodesy ◽  
Accuracy Estimation ◽  
Coordinate Determination ◽  
Improve Accuracy ◽  
Gravity Measurements ◽  
Normal Heights ◽  
Rms Error ◽  
New Research

New research of Lithuanian territory gravity field was started in 2016 with aim to improve accuracy of quasigeoid as well as accuracy of normal heights determined by methods of satellite geodesy. Obtained data could be used in the research of geophysics, geodynamics as well as in performing the precise navigation. Quartz automatic gravimeters Scintrex CG-5 are planned to be used for the survey consisting of 30000 points. Method of gravity measurements was worked out. RMS error of gravity determined with this method does not exceed 60 @Gal. Coordinates and heights of measured points are determined with GNSS using LitPOS network and LIT15G quasigeoid model. RMS error of coordinate determination does not exceed 0,20 m, for normal heights – 0,15 m. Method of gravity anomalies determination and their accuracy estimation was prepared.

Painting, aesthetics of

2018 ◽  
Author(s):  
Robert Hopkins
Keyword(s):  
Picture Plane ◽  
Essential Elements ◽  
Two Dimensional ◽  
Art Forms ◽  
The Aesthetic ◽  
Aesthetic Values ◽  
Dimensional Picture ◽  
Do So ◽  
The Way

Why care about painting as an art? Does it offer to engage our aesthetic interest in ways that other art forms do not, or does it merely reproduce the aesthetic satisfactions they provide? Most paintings involve both marks on a surface, and something represented by those marks. Some attempts to say what is distinctive about painting concentrate on the former feature, understanding the art as an exploration of the two-dimensional picture plane. Others concentrate on the representational aspect, seeking to find something special about the things painting can represent, or the way in which it achieves this. The most promising approaches acknowledge both aspects, and do so as essential elements in the experiencewe have of painting. One such approach turns on the idea that the configurational aspect ‘inflects’ the representational, so that what we see in the picture itself somehow involves the marks from which the painting is composed. Another sees painting as offering aesthetic values found elsewhere, but in a distinctive form. Taking seriously the idea of our experience of painting also helps us to say something about a set of paintings we are otherwise in danger of ignoring - abstract works.

Painting, aesthetics of

2018 ◽  
Author(s):  
Robert Hopkins
Keyword(s):  
Picture Plane ◽  
Essential Elements ◽  
Two Dimensional ◽  
Art Forms ◽  
The Aesthetic ◽  
Aesthetic Values ◽  
Dimensional Picture ◽  
The Way

Why care about painting as an art? Does it offer to engage our aesthetic interest in ways that other art forms do not, or does it merely reproduce the aesthetic satisfactions they provide? Most paintings involve both marks on a surface, and something represented by those marks. Some attempts to say what is distinctive about painting concentrate on the former feature, understanding the art as an exploration of the two-dimensional picture plane. Others concentrate on the representational aspect, seeking to find something special about the things painting can represent, or the way in which it achieves this. The most promising approach acknowledges both aspects, and does so as essential elements in the experience we have of painting. If successful, this allows us to see painting as offering aesthetic values found elsewhere, but in a distinctive form. It also helps us to say something about a set of paintings we are otherwise in danger of ignoring – abstract works.

scholarly journals Theoretical Gravity Anomalies of Glaciers Having Parabolic Cross-Sections

1964 ◽  
Vol 5 (38) ◽  
pp. 255-257 ◽  
Author(s):  
Charles E. Corbató
Keyword(s):  
Cross Sections ◽  
Lower Boundary ◽  
Gravity Anomalies ◽  
Vertical Axis ◽  
Two Dimensional ◽  
Axis Of Symmetry ◽  
Upper Boundary

AbstractEquations and a graph are presented for calculating gravity anomalies on a two-dimensional glacier model having a horizontal upper boundary and a lower boundary which is a parabola with a vertical axis of symmetry.

scholarly journals Gravity Measurements on the Athabaska Glacier, Alberta, Canada

1963 ◽  
Vol 4 (35) ◽  
pp. 617-631
Author(s):  
E. R. Kanasewich
Keyword(s):  
Cross Section ◽  
Three Dimensional ◽  
Gravity Anomalies ◽  
Independent Data ◽  
Surface Slope ◽  
Average Shear Stress ◽  
Glacier Valley ◽  
Gravity Measurements ◽  
Average Shear ◽  
Made In

AbstractThe thickness of the Athabaska Glacier has been obtained along eight transverse profiles by an investigation of gravity anomalies. Three-dimensional computations with a low-speed digital computer were made in this study to acquire more precise results than previously obtained. The thickness of the glacier varies front 326 m. on a line below the lower ice fall to 49 m. near the terminus. The accuracy of the results is discussed and compared with independent data from bore holes and a seismic program. The cross-section of the glacier valley was found to approximate a parabola on several lines. From a knowledge of the thickness. shape and surface slope of the glacier, the average shear stress exerted by the bed on the ice was found to be 1.0 bar.

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