The gravity terrain correction - practical considerations

Leaman, D. E.

doi:10.1071/eg998467

Cited by 27 publications

(20 citation statements)

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“…If care has been taken in field station positioning (Leaman 1998) and approaches that incorporate accurate interpolation between DTM points in close proximity to gravity stations are used, 25 metre-cell DTMs are adequate to approximate the full terrain correction beyond 2 metres from the station in most situations and applications. Nevertheless, for maximum accuracy, higher resolution DTMs such as are obtainable from LiDAR data should be employed if available.…”

Section: Discussionmentioning

confidence: 99%

“…Obviously it is desirable, indeed critical in many cases for calculation of the terrain correction to include effects of topographic variation less than 75 metres from the station (Leaman 1998). Equally obviously, this is facilitated by very high resolution terrain models.…”

Section: Inner Zone Terrain Effectsmentioning

confidence: 99%

“…Subsequently terrain corrections have been calculated routinely for all gravity stations acquired in Tasmania, both commercially and by government agencies. This has been performed predominantly by manual methods (Leaman 1998), to a standard radius of 22 km. The topography of Tasmania is such that gravity station corrections well in excess of 10 mGal are not uncommon, while other stations within a few kilometres may be less than 0.5 mGal, underscoring the need for accurate terrain effect characterisation.…”

Section: Introductionmentioning

confidence: 99%

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Revising gravity terrain corrections in Tasmania

Duffett

2016

ASEG Extended Abstracts

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SUMMARYTerrain corrections for determination of the complete Bouguer anomaly are empirically evaluated with respect to a number of different techniques, parameters and digital terrain model data sets, for areas in western and northern Tasmania.For the most part, while terrain corrections calculated from very high resolution terrain models (1.2 metres or better) are presumed to deliver the most accurate results, those computed for the same area using only a Statewide 25 metre-cell digital terrain model to within two metres of gravity stations correspond remarkably well. Internally consistent comprehensive terrain correction of acceptable yet maximal accuracy can therefore be calculated for all Tasmanian gravity stations, even if very high resolution DTMs are unavailable.Fully automatic terrain correction computation from two metres to 167 kilometres from gravity stations will result in significantly improved removal of topographic effects over extant manual corrections, which were limited to 22 kilometres.

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Section: Discussionmentioning

confidence: 99%

Section: Inner Zone Terrain Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Revising gravity terrain corrections in Tasmania

Duffett

2016

ASEG Extended Abstracts

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“…The "innermost-zone" effect (i.e., terrain undulations around the computation point that have a smaller spatial resolution then that of the DEM used) has been neglected in this approach (cf. Leaman, 1998). As such, the spherical terrain corrections omit near-meter effects, as was the case for the planar terrain corrections com-7 puted by Kirby & Featherstone (1999, 2002.…”

Section: [Figure 1]mentioning

confidence: 99%

“…As such, the spherical terrain corrections omit near-meter effects, as was the case for the planar terrain corrections com-7 puted by Kirby & Featherstone (1999, 2002. Leaman (1998) shows that the near-meter effect can reach almost 0.1 mGal in only moderately undulating terrain, thus has to be accounted for in very precise gravity surveys. However, these effects are of less importance for this study as they are practically the same for planar and spherical terrain corrections, thus will cancel when both models are compared to each other (cf.…”

Section: [Figure 1]mentioning

confidence: 99%

Complete spherical Bouguer gravity anomalies over Australia

Kühn

Featherstone

Kirby

2009

Australian Journal of Earth Sciences

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We have computed complete (or refined) spherical Bouguer gravity anomalies for all 1,095,065 land gravity observations in the June 2007 release of the Australian national gravity database. The spherical Bouguer shell contribution was computed using the supplied ground elevations of the gravity observations. The spherical terrain corrections, residual to each Bouguer shell, were computed on a 9 arc-second grid (~250 m by ~250 m spatial resolution) from a global Newtonian integration using heights from version 2.1 of the GEODATA digital elevation model (DEM) over Australia and the GLOBE and JGP95E global DEMs outside Australia. A constant topographic massdensity of 2670 kg/m 3 was used for both the spherical Bouguer shell and spherical terrain correction terms. The difference between the complete spherical and complete planar Bouguer gravity anomaly exhibits an almost constant bias of about -18.7 mGal over areas with moderate elevation changes, thus verifying the planar model as a reasonable 2 approximation in these areas. However, the results suggest that in mountainous areas with large elevation changes, the complete spherical Bouguer gravity anomaly should be selected in preference over the less rigorous complete planar counterpart.

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Insights into the Crustal Structure and Geodynamic Evolution of the Southern Granulite Terrain, India, from Isostatic Considerations

Kumar

Singh

2010

Pure Appl. Geophys.

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The Southern Granulite Terrain of India, formed through an ancient continental collision and uplift of the earth's surface, was accompanied by thickening of the crust. Once the active tectonism ceased, the buoyancy of these deep crustal roots must have supported the Nilgiri and Palani-Cardamom hills. Here, the gravity field has been utilized to provide new constraints on how the force of buoyancy maintains the state of isostasy in the Southern Granulite Terrain. Isostatic calculations show that the seismically derived crustal thickness of 43-44 km in the Southern Granulite Terrain is on average 7-8 km more than that required to isostatically balance the present-day topography. This difference cannot be solely explained applying a constant shift in the mean sea level crustal thickness of 32 km. The isostatic analysis thus indicates that the current topography of the Southern Granulite Terrain is overcompensated, and about 1.0 km of the topographic load must have been eroded from this region without any isostatic readjustment. The observed gravity anomaly, an order of magnitude lower than that expected (-125 mGal), however, shows that there is no such overcompensation. Thermal perturbations up to Pan-African, present-day high mantle heat flow and low Te together negate the possible resistance of the lithosphere to rebound in response to erosional unloading. To isostatically compensate the crustal root, compatible to seismic Moho, a band of high density (2,930 kg m -3 ) in the lower crust and low density (3,210 kg m -3 ) in the lithospheric mantle below the Southern Granulite Terrain is needed. A relatively denser crust due to two distinct episodes of metamorphic phase transitions at 2.5 Ga and 550 Ma and highly mobilized upper mantle during Pan-African thermal perturbation reduced significantly the root buoyancy that kept the crust pulled downward in response to the eroded topography.

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The gravity terrain correction - practical considerations

Cited by 27 publications

References 1 publication

Revising gravity terrain corrections in Tasmania

Revising gravity terrain corrections in Tasmania

Complete spherical Bouguer gravity anomalies over Australia

Insights into the Crustal Structure and Geodynamic Evolution of the Southern Granulite Terrain, India, from Isostatic Considerations

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