Production of a residual gravity field map for Tasmania and some implications

Leaman, D. E.; Richardson, R. G.

doi:10.1071/eg989181

Cited by 12 publications

(10 citation statements)

References 1 publication

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“…The observed Bouguer anomalies are not particularly valuable, due to the effects of the continental margin, and these have been removed, using the method of Leaman & Richardson (1989) as updated to crustal model MANTLE91. This model is subject to further revision, and refinement will be possible once a detailed survey of the Tasman Peninsula, now in progress, is complete.…”

Section: Gravity Surveymentioning

confidence: 99%

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Gravity survey and structure of the Forestier Peninsula, Southern Tasmania

Leaman¹

1997

PPRST

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A gravity survey coupled with review of regional mapping has shown that the widespread exposure of Jurassic dolerite across the Foresrier Peninsula is due largely to repetition of a thick sheet by gently ramped Tertiary fault-blocks. Feeders for the sheet appear to be located near the centre of the peninsula and to be related to concealed pre-Permian structures, such as granitoid margins. At least two major fault zones were eroded during the mid Tertiary and these, as well as the peninsula ties to mainland Tasmania and the Tasman Peninsula, now consist of Tertiary materials covered by Recent sands. The western edge of the East Tasmanian batholith extends approximately north south beneath the centre of the peninsula.

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Section: Gravity Surveymentioning

confidence: 99%

“…Neither survey was able to define any local structures or adequately define regional character, al though the Tasmanian data base has depended on such data in this area (e.g. Leaman et al 1980, Leaman & Richardson 1989. The regional data previously available were supplemented by a single detailed traverse near Dunalley (Leaman 1973).…”

Section: Introductionmentioning

confidence: 99%

Gravity survey and structure of the Forestier Peninsula, Southern Tasmania

Leaman¹

1997

PPRST

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“…A shift in the datum may be applied to change the mean of the residual Bouguer anomalies; however, as mentioned by Gupta and Ramani (1980), the choice of a constant datum shift would create distortions (in shape and amplitude) in some part of the map. These preliminary results suggest that the separation of the regional and residual fields is best achieved by applying geological thought to the problem (Gupta and Ramani, 1980;Leaman and Richardson, 1989;Leaman, 1994).…”

Section: Future Researchmentioning

confidence: 83%

Production of a residual gravity anomaly map for Gaspésie (northern Appalachian Mountains), Quebec, by a graphical method

Pinet

Keating

Brouillette

et al. 2006

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The authors present a residual gravity map for Gaspésie based on a separation of the regional and residual fields by a graphical method. This map results from the smoothing of 24 gravity profiles with lengths that far exceed the dimension of the zone of interest. The base value of the regional field has been estimated by taking into account surface data and by calculating the maximum gravity lows associated with relatively low-density Silurian-Devonian rocks. The residual gravity map includes all the gravity features that are clearly associated with shallow sources and shows a minimum distortion of the shape of the anomalies. Current Research 2006-D1 1 N. Pinet et al. Résumé : Nous présentons une carte de l'anomalie de Bouguer résiduelle de la péninsule de la Gaspésie basée sur une méthode graphique de séparation des composantes régionale et résiduelle du champ de gravité. Cette carte résulte du lissage de 24 profils de gravité dont la longueur excède grandement les dimensions de la zone d'intérêt. La valeur de base de la composante régionale a été estimée en prenant en compte les données de surface et en calculant les bas gravimétriques maximums associés aux roches siluriennes et dévoniennes de densité relativement faible. La carte de l'anomalie de Bouguer résiduelle comprend l'ensemble des anomalies clairement associées à des sources peu profondes et montre une distorsion minimale de la forme des anomalies gravimétriques.

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“…Previous regional -residual separations for the Tasmanian gravity field have been produced by Johnson (1974) using grid averaging and Fourier series approximation; Leaman er al., (1980) who used space domain averaging filters and forward modelling; and Leaman and Richardson (1989) who refined the modelling approach to create the MANTLE88 regional field.…”

Section: Figurementioning

confidence: 99%

“…The MANTLE88 model of Leaman and Richardson (1989) (revised as MANTLE91) was used as the starting point for the production of a new crustal model for Tasmania. The main changes include the addition of oceanic crust to the model and an increase in the maximum crustal thickness to 29.5 km in order to match the overall anomaly amplitude (280 mGal).…”

Section: Forward Modellingmentioning

confidence: 99%

A Comparison of Regional - Residual Separation Techniques for Gravity Surveys

Roach

Leaman²,

Richardson

1993

Exploration Geophysics

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Tasmania lies on a triangular extension of the Australian continental crust, surrounded on two sides by deep ocean basins. Strong regional effects from these features obscure much of the short wavelength character in the observed gravity data. Interpretation of the data requires reliable separation of the residual and regional components of the gravity field.Bouguer gravity data covering onshore and offshore Tasmania have been used to test a variety of methods of regionalresidual separation, including trend surfaces, filtering, upward continuation and forward modelling.Forward modelling was used to calculate a regional field from a three-dimensional model for Tasmania consisting of continental crust, oceanic crust, water and the mantle. The main advantage of modelling is that it enables the incorporation of geological and geophysical constraints into the regional field. Automated separation techniques are simple, fast and purely numerical but do not allow the incorporation of geological constraints. Quantitative interpretation of the resultant residual maps is difficult and uncertain. All automated methods tested produce undefined dc shifts which limit the usefulness of the residuals. Of the automated methods, trend surfaces produce residual maps which show the best correlation with known geology.The preferred method of regional -residual separation is forward modelling, although it is both time consuming and subjective. Quantitative interpretation of residuals from modelling can be carried out with a greater degree of confidence since the regional field has a well-defined geological basis.

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Production of a residual gravity field map for Tasmania and some implications

Cited by 12 publications

References 1 publication

Gravity survey and structure of the Forestier Peninsula, Southern Tasmania

Gravity survey and structure of the Forestier Peninsula, Southern Tasmania

Production of a residual gravity anomaly map for Gaspésie (northern Appalachian Mountains), Quebec, by a graphical method

A Comparison of Regional - Residual Separation Techniques for Gravity Surveys

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