General 2D gravity inversion with density contrast varying with depth

Guspí, Fernando

doi:10.1016/0016-7142(90)90007-f

Cited by 26 publications

(12 citation statements)

References 12 publications

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“…Whereas the inversion of gravity anomalies is usually formulated to estimate the shape of a causative body [e.g., Oldenburg, 1974;Granser, 1987;Guspi, 1990], we showed that an alternative formulation to estimate density is particularly useful when reliable seismic information is available. Our success in this systematic approach is, however, somewhat fortuitous because the bounding approach largely depends on having well-constrained oceanic crust within the transect.…”

Section: Mooneymentioning

confidence: 99%

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Korenaga¹

2000

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This thesis studies the dynamics of mantle melting during continental breakups by geophysical, geochemical, and numerical analyses. The first part focuses on the mantle melting and crustal accretion processes during the formation of the Southeast Greenland margin, on the basis of deep-crustal seismic data. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a compressional velocity structure, and a long-wavelength structure with strong lateral heterogeneity is successfully recovered, including 30-to 15-km-thick igneous crust within a 150-km-wide continent-ocean transition zone. A nonlinear Monte Carlo analysis is also conducted to establish the absolute uncertainty of model parameters. The derived crustal structure is first used to resolve the origin of a margin gravity high, with new inversion schemes using both seismic and gravity constraints. Density anomalies producing the gravity high seem to be confined within the upper crust, not in the lower crust as suggested for other volcanic margins. A new robust framework is then developed for the petrological interpretation of the velocity structure of igneous crust, and the thick igneous crust formed at the continentocean transition zone is suggested to have resulted from vigorous active upwelling of mantle with only somewhat elevated potential temperature. In the second part, the nature of mantle melting during the formation of the North Atlantic igneous province is studied on the basis of the major element chemistry of erupted lavas. A new fractionation correction scheme based on the Ni concentrations of mantle olivine is used to estimate primary melt compositions, which suggest that this province is characterized by a large degree of major element source heterogeneity. In the third part, the nature of preexisting sublithospheric convection is investigated by a series of finite element analyses, because the strength of such convection is important to define the "normal" state of mantle, the understanding of which is essential to identify any anomalous behavior of mantle such as a mantle plume. The results suggest that small-scale convection is likely in normal asthenosphere, and that the upwelling velocity in such convection is on the order of 1-10 cm/yr. 271 Introductory NotesThis thesis is composed of three parts, all of which are related to the dynamics of mantle melting during continental breakups. In the first part, rifting magmatism associated with the opening of the North Atlantic (at -60 Ma) is investigated on the basis of deep-crustal seismic data collected across the Southeast Greenland continental margin. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a two-dimensional velocity structure (Chapter 1). Several key issues in travel time tomography such as velocity-depth ambiguity and absolute parameter uncertainty are identified, and a practical strategy is presented to resolve them. The derived crustal velocity structure is the...

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Section: Mooneymentioning

confidence: 99%

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Korenaga¹

2000

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“…This problem was first considered by Cordell (1979) who tentatively proposed a sedimentary model with a gradational decrease of density from the fault basinwards over a distance of about 5 km and up to a depth of 3 km. Cordell 1973;Murthy and Rao 1979;Granser 1987;Guspí 1990), in certain cases it may occur that more complicated functions are necessary in order to model satisfactorily in geophysical terms, the geology of the prospect target. Cordell 1973;Murthy and Rao 1979;Granser 1987;Guspí 1990), in certain cases it may occur that more complicated functions are necessary in order to model satisfactorily in geophysical terms, the geology of the prospect target.…”

Section: Geophysical Examplementioning

confidence: 99%

“…recrystallization, cementation, compaction) influence the density of the rocks. Murty and Rao 1979;Murty, Rao and Ramakrishna 1989;Pan 1989;Guspí 1990). Athy 1930).…”

Section: Introductionmentioning

confidence: 99%

Complex polynomials for the computation of 2D gravity anomalies

Oliva

Ravazzoli

1997

Geophysical Prospecting

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We present an efficient algorithm using a complex variables formulation for the computation of the gravity effect of 2D polygonal bodies having densities varying both laterally and with depth. The first derivatives of the gravity effect are also provided in order to enable the computation of the Jacobian matrix, which is necessary for linear inverse gravity problems. A geophysical example based on numerical assumptions about the density contrast on a well‐studied basin area shows the applicability of the algorithm.

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“…(1990). Guspi (1990) used polynomial density-depth functions for inverting gravity anomalies into 2-D polygons in the space domain.…”

Section: Derivation Of Basic Formulasmentioning

confidence: 99%