On isostatic geoid anomalies

Haxby, W. F.; Turcotte, Donald L.

doi:10.1029/jb083ib11p05473

Cited by 305 publications

(194 citation statements)

References 12 publications

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“…These are all relative geoid lows confirming the correlations found by Nakanishi and Anderson [1984]. Dense regions of the mantle that are in isostatic equilibrium also generate geoid lows [Haxby and Turcotte, 1978;Hager, 1983]. Dense regions in dynamic equilibrium generate geoid lows if the viscosity does not increase too rapidly with depth [Hager, 1984].…”

Section: Introductionsupporting

confidence: 71%

Mapping convection in the mantle

Tanimoto¹,

Anderson²

1984

Geophysical Research Letters

187

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Abstract. Long-period (100-250 sec.) Love and Rayleigh waves are used to map heterogeneity and azimuthal anisotropy in the upper mantle. Spherical harmonic descriptions of anisotropy up to £ = m = 3 and 28 are derived. Azimuthal anisotropy obtains values as high as 1 Yz OJo. There is good correlation of fast Rayleigh wave directions with upper mantle return flow directions derived from kinematic considerations. This is consistent with the a-axis of olivine being aligned in the flow direction. The main differences between the flow models and the Rayleigh wave azimuthal variation maps occur in the vicinity of hotspots. Hawaii, for example, appears to perturb the return flow. There is strong correlation of the geoid and surface wave velocity at £ = 4 and 5. Slow regions at this scale are associated with geoid highs and high heat flow, consistent with upwelling convective flow or with isostatically compensated regions of low density. The correlation of azimuthal anisotropy with upper mantle return flow directions, rather than with plate directions, suggests that part of the return flow is in the upper mantle and this, in turn, implies a low viscosity channel.

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Section: Introductionsupporting

confidence: 71%

Mapping convection in the mantle

Tanimoto¹,

Anderson²

1984

Geophysical Research Letters

187

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“…The models usually used in discussing the isostatic geoid (7)(8)(9)17) are obtained by assuming 1) that the half-space equation (3) is applicable, and 2) that only local density contrasts (the k -0 wavenumber) is important. This is equivalent to assuming a one-dimensional density model.…”

Section: Discussionmentioning

confidence: 99%

“…Oceanic heat flow can be explained by these models if hydrothermal activity at the ridge is taken into account (6); recently it has been demonstrated that the short wavelength change in geoid elevation over ridges predicted by these simple models is also readily observed (7)(8)(9).…”

Section: Introductionmentioning

confidence: 99%

Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere

Hager

1983

Earth and Planetary Science Letters

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Commonly used one-dimensional geoid models predict that the isostatic geoid anomal y over old ocean basins for the boundary-layer thernil model of the lithosphere is a factor of two greater than that for the plate mode 1. Calculations presented here, using; the spherical analogues of the plate and boundary-layer thermal models, show that for the actual global distribution of plate ages, one-dimensional models are not accurate and a spherical, tull y three-dimensional treatment is necessar y . The maximum difference in geoid heights predicted for the two models is onl y about two meters.The thermal structure of old lithosphere is unlikely to he resolvable using global geoid anomilies.Stripping the effects of plate aging; and a hypothetical uniform, 35 km, tsostatically-compensated continental crust from the observed geoid emphasizes that the largest-amplitude geoid anomaly is the geoid low of almost 120 m over West Antarctica, a factor of two greater than the low of 60 m over Ceylon.

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“…The geoid data are known to relate linearly to the topography between wavelengths 400 km and 4000 km (Sandwell and Renkin, 1988), therefore, the GTR analysis for these wavelengths can be used to understand the mode of compensation of topographic features such as swells, plateaus and aseismic ridges (Haxby and Turcotte, 1978;Sandwell and McKenzie, 1989;Coblentz et al, 2011). In general, low GTR values (0-2 m/km) indicate shallow level of compensation, whereas, the intermediate GTR values (2-6 m/km) suggest that the compensation takes place at deeper level by lithosphere thinning (Crough, 1978).…”

Section: Geoid-topography Ratio (Gtr)mentioning

confidence: 99%

Lithosphere structure and upper mantle characteristics below the Bay of Bengal

et al. 2016

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SUMMARY:The oceanic lithosphere in the Bay of Bengal (BOB) formed 80 -120 Ma following the breakup of eastern Gondwanaland. Since its formation, it has been affected by the emplacement of two long N-S trending linear aseismic ridges (85 o E and Ninetyeast) and by the loading of ca.20-km of sediments of the Bengal Fan. Here, we present the results of a combined spatial and spectral domain analysis of residual geoid, bathymetry and gravity data constrained by seismic reflection and refraction data. Self-consistent geoid and gravity modeling defined by temperature-dependent mantle densities along a N-S transect in the BOB region revealed that the depth to the Lithosphere-Asthenosphere boundary (LAB) deepens steeply from 77 km in the south to 127 km in north, with the greater thickness being anomalously thick compared to the lithosphere of similar-age beneath the Pacific Ocean. The Geoid-Topography Ratio (GTR) analysis of the 85°E and Ninetyeast ridges indicate that they are compensated at shallow depths.

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On isostatic geoid anomalies

Cited by 305 publications

References 12 publications

Mapping convection in the mantle

Mapping convection in the mantle

Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere

Lithosphere structure and upper mantle characteristics below the Bay of Bengal

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