An interpretation of gravity measurements on the west coast of Canada

1969 ◽  
Vol 6 (3) ◽  
pp. 463-474 ◽  
Author(s):  
R. A. Stacey ◽  
L. E. Stephens
Keyword(s):  
Gravity Field ◽  
Bouguer Anomaly ◽  
Vancouver Island ◽  
Coast Mountains ◽  
Bouguer Anomalies ◽  
Queen Charlotte Islands ◽  
Gravity Measurements ◽  
Terrain Corrections ◽  
Tectonic Belt ◽  
Local Anomalies

The survey area lies close to the continental margin and includes parts of the Insular Tectonic Belt and the Coast Mountains igneous and metamorphic complex, which are part of the Cordilleran (geological) Region. In an endeavor to clarify the structure of the Insular Tectonic Belt and the Coast Mountains complex, gravity measurements have been made using Worden or LaCoste and Romberg meters at 12–15 km intervals throughout the Queen Charlotte Islands, Vancouver Island, and the coastal areas of the British Columbia mainland. Measurements have been made at the same interval using a LaCoste and Romberg underwater gravity meter wherever the depth of water is less than 300 fathoms (< 540 m) along the fiords of the mainland coast and over the continental shelf. The observed gravity values have been reduced to Bouguer anomalies and terrain corrections have been calculated using either Bible's tables or a computer system based on the attraction of the rectangular prismatic block.The major features of gravity field are: (1) a positive Bouguer anomaly along the western edge of the area, which is associated with the change from continental to oceanic crust, and (2) a negative anomaly along the Coast Mountains, which is attributed to the thickening of the continental crust below these mountains. On the eastern side of the Queen Charlotte Islands, Hecate Strait, Queen Charlotte Sound, and Vancouver Island, the average Bouguer anomaly is approximately zero, with local anomalies superimposed on a fairly flat gravity field. Several of these local anomalies are related to density variations in the surface rocks.

scholarly journals Thickness and Basal Configuration of Lower Blue Glacier, Washington, Determined by Gravimetry

1965 ◽  
Vol 5 (41) ◽  
pp. 637-650 ◽  
Author(s):  
Charles E. Corbató
Keyword(s):  
Gravity Field ◽  
Three Dimensional ◽  
Successive Approximations ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Gravity Measurements ◽  
Computational Errors ◽  
Terrain Corrections ◽  
Seismic Reflections ◽  
Regional Gravity

AbstractGravity measurements at 146 stations on lower Blue Glacier were used to determine the subglacial bedrock configuration. The gravity values, station elevations and density contrast were carefully measured, and terrain corrections thoroughly evaluated to insure accuracy of the Bottguer anomalies. A series of successive approximations results in evaluation of the regional gravity field and a three-dimensional model of the glacier whose gravimetric effects fit the range of the observational and computational errors. Comparison with bore holes and seismic reflections indicates no significant errors in the model and accuracies of 5–10 per cent in the calculated thicknesses of the glacier.

scholarly journals Gravity modelling of the lower crust in Sardinia (Italy)

1997 ◽  
Vol 40 (5) ◽  
Author(s):  
M. T. Carrozzo ◽  
R. Balia ◽  
M. Loddo ◽  
D. Luzio ◽  
C. Margiotta ◽  
...  
Keyword(s):  
Lower Crust ◽  
Local Density ◽  
A Priori ◽  
Seismic Refraction ◽  
Bouguer Anomaly ◽  
Bouguer Anomalies ◽  
Velocity Models ◽  
Gravity Measurements ◽  
Low Pass ◽  
Inversion Techniques

In this paper an example is given of an application of statistical techniques to the Bouguer anomalies analysis in order to design a simple crustal model using few a priori assumptions. All gravity measurements carried out in Sardinia have been collected and processed. The Bouguer anomalies have been calculated according to local density estimates. Spectral analysis of the Bouguer anomalies has been carried out along selected profiles in order to estimate the mean depth of the Moho discontinuity and that of an infracrustal discontinuity. The use of this technique inferred the presence of a discontinuity at a mean depth of ~ 28 km, interpreted as Moho and the likely presence of an infracrustal discontinuity at a mean depth of ~18 km, interpreted as the upper-lower crust transition. In order to roughly reconstruct the shape of these interfaces, 2D inversion techniques were applied to the large wavelength components of the Bouguer anomalies, relative to profiles oriented along the E-W direction, extracted from low-pass filtered Bouguer anomaly maps. The density model obtained is compatible with some velocity models achieved from the interpretation of the seismic refraction profiles carried out within the European Geotraverse project.

scholarly journals High-precision local gravity survey along planned motorway tunnel in the Slovak Karst

2019 ◽  
Vol 49 (2) ◽  
pp. 207-227 ◽  
Author(s):  
Pavol Zahorec ◽  
Juraj Papčo ◽  
Peter Vajda ◽  
Stanislav Szabó
Keyword(s):  
Laser Scanning ◽  
Gravity Data ◽  
Digital Terrain Model ◽  
Gravity Survey ◽  
Railway Tunnel ◽  
Bouguer Anomalies ◽  
Terrain Model ◽  
Gravity Measurements ◽  
Terrain Corrections ◽  
The Difference

Abstract Results from a detailed gravity survey realized along the planned highway tunnel in the karstic area of Slovak Karst in the eastern Slovakia are presented. Detailed gravity profiles crossed an area of rugged topography, therefore the terrain corrections played a crucial role in the gravity data processing. The airborne laser scanning technique (LiDAR) was used in order to compile a high-resolution digital terrain model (DTM) of the surrounding area and to calculate terrain corrections properly. The difference between the Bouguer anomalies calculated with an available nationwide DTM and those with new LiDAR-based model can be significant in some places as it is presented in the paper. A new method for Bouguer correction density analysis based on surface data is presented. Special underground gravity measurements in the existing nearby railway tunnel were also conducted in order to determine the mean density of the topographic rocks. The Bouguer anomalies were used to interpret lithological contacts and tectonic/karstic discontinuities.

scholarly journals Thickness and Basal Configuration of Lower Blue Glacier, Washington, Determined by Gravimetry

1965 ◽  
Vol 5 (41) ◽  
pp. 637-650 ◽  
Author(s):  
Charles E. Corbató
Keyword(s):  
Gravity Field ◽  
Three Dimensional ◽  
Successive Approximations ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Gravity Measurements ◽  
Computational Errors ◽  
Terrain Corrections ◽  
Seismic Reflections ◽  
Regional Gravity

AbstractGravity measurements at 146 stations on lower Blue Glacier were used to determine the subglacial bedrock configuration. The gravity values, station elevations and density contrast were carefully measured, and terrain corrections thoroughly evaluated to insure accuracy of the Bottguer anomalies. A series of successive approximations results in evaluation of the regional gravity field and a three-dimensional model of the glacier whose gravimetric effects fit the range of the observational and computational errors. Comparison with bore holes and seismic reflections indicates no significant errors in the model and accuracies of 5–10 per cent in the calculated thicknesses of the glacier.

III.—Recent Observations on the Glaciation of British Columbia and Adjacent Regions

1888 ◽  
Vol 5 (8) ◽  
pp. 347-350 ◽  
Author(s):  
Geo. M. Dawson
Keyword(s):  
British Columbia ◽  
Glacial Period ◽  
Coast Range ◽  
Coast Mountains ◽  
One Stage ◽  
Queen Charlotte Islands ◽  
Glacier Ice ◽  
Inland Ice ◽  
Great Valley ◽  
The U.S

Previous observations in British Columbia have shown that at one stage in the Glacial period—that of maximum glaciation—a great confluent ice-mass has occupied the region which may be named the Interior Plateau, between the Coast Mountains and Gold and Eocky Mountain Kanges. From the 55th to the 49th parallel this great glacier has left traces of its general southward or southeastward movement, which are distinct from those of subsequent local glaciers. The southern extensions or terminations of this confluent glacier, in Washington and Idaho Territories, have quite recently been examined by Mr. Bailley Willis and Prof. T. C. Chamberlin, of the U.S. Geological Survey. There is, further, evidence to show that this inland-ice flowed also, by transverse valleys and gaps, across the Coast Range, and that the fiords of the coast were thus deeply filled with glacier-ice which, supplemented by that originating on the Coast Range itself, buried the entire great valley which separates Vancouver Island from the mainland and discharged seaward round both ends of the island. Further north, the glacier extending from the mainland coast touched the northern shores of the Queen Charlotte Islands.

scholarly journals Accuracy Analysis of Gravity Field Changes from Grace RL06 and RL05 Data Compared to in Situ Gravimetric Measurements in the Context of Choosing Optimal Filtering Type

2020 ◽  
Vol 55 (3) ◽  
pp. 100-117
Author(s):  
Viktor Szabó ◽  
Dorota Marjańska
Keyword(s):  
Gravity Field ◽  
Ocean Circulation ◽  
Gravity Data ◽  
The Other ◽  
Subsurface Water ◽  
Satellite Gravity ◽  
Absolute Gravimetry ◽  
The Earth ◽  
Gravity Measurements ◽  
Gravity Recovery

AbstractGlobal satellite gravity measurements provide unique information regarding gravity field distribution and its variability on the Earth. The main cause of gravity changes is the mass transportation within the Earth, appearing as, e.g. dynamic fluctuations in hydrology, glaciology, oceanology, meteorology and the lithosphere. This phenomenon has become more comprehensible thanks to the dedicated gravimetric missions such as Gravity Recovery and Climate Experiment (GRACE), Challenging Minisatellite Payload (CHAMP) and Gravity Field and Steady-State Ocean Circulation Explorer (GOCE). From among these missions, GRACE seems to be the most dominating source of gravity data, sharing a unique set of observations from over 15 years. The results of this experiment are often of interest to geodesists and geophysicists due to its high compatibility with the other methods of gravity measurements, especially absolute gravimetry. Direct validation of gravity field solutions is crucial as it can provide conclusions concerning forecasts of subsurface water changes. The aim of this work is to present the issue of selection of filtration parameters for monthly gravity field solutions in RL06 and RL05 releases and then to compare them to a time series of absolute gravimetric data conducted in quasi-monthly measurements in Astro-Geodetic Observatory in Józefosław (Poland). The other purpose of this study is to estimate the accuracy of GRACE temporal solutions in comparison with absolute terrestrial gravimetry data and making an attempt to indicate the significance of differences between solutions using various types of filtration (DDK, Gaussian) from selected research centres.

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

&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;Gravity field derivatives have been used to enhance both: (i) deep geological contacts, and (ii) coastal noise. The analyses outlined a &amp;#8220;ringing-noise effect&amp;#8221; which causes the altimeter signal degradation up to 17 km from the coast.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;

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.

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