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The delineation and interpretation of the earth's gravity field (Document No: 19870013632)
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Marsh, Bruce D. |
| Copyright Year | 1987 |
| Description | The geoid and topographic fields of the central Pacific were delineated and shown to correlate closely at intermediate wavelengths (500 to 2500 km). The associated admittance shows that anomalies having wavelengths less than about 1000 km are probably supported by the elastic strength of the lithosphere. Larger wavelength anomalies are due to dynamic effects in the sublithosphere. Direct modeling of small scale convection in the asthenosphere shows that the amplitudes of observed geoid and topographic anomalies can be independently matched, but that the observed admittance cannot. Only by imposing an initial regional variation in the thermal regime is it possible to match the admittance. It is proposed that this variation may be due to differences in the onset time of convection beneath the lithosphere of different ages. That is, convection beneath thickening lithosphere is strongly dependent on the rate of thickening (V) relative to the rise time for convection. The critical Rayleigh number contains the length scale K/V, where K is thermal diffusivity. Young, fast growing lithosphere stabilizes the underlying asthenosphere unless it has an unusually low viscosity. Lithosphere of different age, separated by fracture zones, will go unstable at different times, producing regional horizontal temperature gradient that may strongly influence convection. Laboratory and numerical experiments are proposed to study this form of convection and its influence on the geoid. |
| File Size | 576171 |
| Page Count | 17 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19870013632 |
| Archival Resource Key | ark:/13960/t0rr6r07z |
| Language | English |
| Publisher Date | 1987-06-25 |
| Access Restriction | Open |
| Subject Keyword | Geophysics Viscosity Earth Gravitation Rheology Lithosphere Pacific Ocean Gravitational Fields Geoids Convection Topography Asthenosphere Thermodynamic Properties Heat Transfer Anomalies Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Technical Report |
