Gravimetric determination of an intrusive complex under the Island of Faial (Azores): some methodological improvements

Camacho, A. G.; Nunes, João Carlos; Martínez, Esther Ortiz; França, Zilda; Vieira, Ricardo

doi:10.1111/j.1365-246x.2007.03539.x

Cited by 34 publications

(31 citation statements)

References 31 publications

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“…Next, using f , g 0 , g x , g y , we can evaluate the suitability of that cell (filled with a prescribed density value) by the misfit value given by (5). Then, the j th prism producing a minimum misfit value is selected to be definitively filled and aggregated to the growing body (see Camach o et al [2007] for details). For each successive step, the adjusted scale value f decreases and the additional parameters g 0 , g x , g y reach nearly stable values.…”

Section: Methodsmentioning

confidence: 99%

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A new gravity inversion method for multiple subhorizontal discontinuity interfaces and shallow basins

Camacho¹,

Fernández²,

Gottsmann³

2011

J. Geophys. Res.

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[1] We present a method for 3-D gravity inversion designed to obtain density contrast models described by subhorizontal layers limited by irregular discontinuity interfaces and models constituted by shallow basins with light infill. It is based on a previously published inversion method that provides, in a nearly automatic approach, the 3-D geometry of isolated anomalous bodies. The basic adjustment constraints are model fitness (fitting the anomaly data) and model smoothness (minimizing the total anomalous mass). For models corresponding to subhorizontal layers, we consider an additional minimization condition: the proximity to prescribed horizontal interfaces. This condition is arranged by including an additional weighting (inverse proportional to the distance to the interface) in the covariance matrix for model parameters. The approach works, according a growth process that increases, step by step, the volume of the adjusted anomalous bodies. Some advantages of the method are simultaneous adjustment of a (linear) regional gravity trend, possibility of including simultaneously positive and negative anomalous structures in the model, and unified inversion approach for isolated bodies, basins, and subhorizontal interface structures. We include several simulation examples and an application case (layered model for the volcanic island of Tenerife).Citation: Camacho, A. G., J. Fernández, and J. Gottsmann (2011), A new gravity inversion method for multiple subhorizontal discontinuity interfaces and shallow basins,

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Section: Methodsmentioning

confidence: 99%

“…The inversion approach allows us to deal with noisy data by selecting a suitable factor λ for balance between fitness and smoothness of the model. The optimal value is selected to produce uncorrelated residual noise [see Camacho et al , 2007]. The resulting fit level now is ±10 μ Gal.…”

Section: Synthetic Simulation Testsmentioning

confidence: 99%

A new gravity inversion method for multiple subhorizontal discontinuity interfaces and shallow basins

Camacho¹,

Fernández²,

Gottsmann³

2011

J. Geophys. Res.

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“…This local value for average density was determined from the gravity data by looking for a minimum correlation between elevation and gravity anomaly for the shortest wavelength components of topography. It is attained just by means of the further inversion process, according to an improvement developed by Camacho et al (2007), which allows to modify the initial assumed terrain density. .…”

Section: Datamentioning

confidence: 99%

Structure of Alluvial Valleys from 3-D Gravity Inversion: The Low Andarax Valley (Almería, Spain) Test Case

Camacho

Carmona

García‐Jerez

et al. 2014

Pure Appl. Geophys.

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This paper presents a gravimetric study ( We interpret several low density alignments as corresponding to SE faults striking about N 140-145ºE. Some detected basement elevations (as one, previously known by boreholes, in Viator village) are apparently connected with the fault pattern. The outcomes of this work are:(1) new gravimetric data, (2) new methodological options, and (3) resulting structural conclusions.3

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“…Relative gravity data were acquired in 1965 by Coelho (1968), in 1977 by Mendes-Victor and Ribeiro (1978), and in the period 1998-2002 by Camacho et al (2007). To determine possible biases between surveys and to evaluate the accuracy of the former ones, repeated surveys were analyzed for S.…”

Section: Gravity Data Merging and Griddingmentioning

confidence: 99%

Sensitivity analysis of the gravity geoid estimation: A case study on the Azores plateau

Catalão¹,

Bos²

2008

Physics of the Earth and Planetary Interiors

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A numerical investigation into the effects of high-resolution heterogeneous data on the estimation of the geoid is presented for the area of the Azores plateau. Gravity data were complemented with highresolution digital terrain models, mass density models from geophysical information, and the most recent geopotential model from the CHAMP mission (GGM02) to derive a high-precision gravity model. Gravity data were reduced from the residual terrain model effects and the GGM02C model, and a grid with 1.5' spatial resolution was generated by least squares collocation. The gravimetric geoid model was computed by the direct evaluation of Stokes' integral with a spherical cap radius of 0.8 degree, with gravity data reduced by Helmert's second condensation method. The geoid model was evaluated over sea by comparison with six years of Topex/Poseidon altimeter data and an absolute agreement of 14 cm RMS was achieved after removing the bias. Over land, the geoid was compared with a total of 223 GPS/levelling points corresponding to five different vertical datums. Locally adjusted solutions were determined for each island with a four-parameter model, and a maximum RMS of 12 cm (on Pico) and a minimum of 2.1 cm (on Faial) were determined. As a result of persistent volcanic and tectonic activity on most of the Azores islands, this geoid residual standard deviation must not be viewed as purely geoid error but containing, in addition, levelling and GPS position errors and vertical displacement. The effect on geoid accuracy of the digital terrain model resolution, of the spatial density of gravity data, and of the mass density was evaluated and two important conclusions were derived. First, the digital terrain model resolution has a clear effect on the geoid accuracy, with a maximum RMS of 3.4 cm on S. Miguel. Second, the mass density model does not affect the accuracy of the geoid. This second result indicates that the effect of variable density Manuscript + tables + figuresPage 2 of 44 A c c e p t e d M a n u s c r i p t 2 models on geoid determination may apply only to extensive areas of high terrain and not to smaller topographic units such as single volcanoes. The high-precision gravity model and gravimetric geoid for Azores (AZGEOD07) generated in this study will allow the conversion of old orthometric heights to ellipsoidal heights at precisions useful for the monitoring of vertical deformation. The geoid will also have application to investigations of ocean circulation modulation and of dynamic processes of Earth's mantle.

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Gravimetric determination of an intrusive complex under the Island of Faial (Azores): some methodological improvements

Cited by 34 publications

References 31 publications

A new gravity inversion method for multiple subhorizontal discontinuity interfaces and shallow basins

A new gravity inversion method for multiple subhorizontal discontinuity interfaces and shallow basins

Structure of Alluvial Valleys from 3-D Gravity Inversion: The Low Andarax Valley (Almería, Spain) Test Case

Sensitivity analysis of the gravity geoid estimation: A case study on the Azores plateau

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