Predicting bathymetry from Geosat-ERM and shipborne profiles in the South Atlantic Ocean     

Woo-Yeol Jung  Peter R. Vogt 《Tectonophysics》1992,210(3-4):235-253

Portions of two Geosat-ERM altimeter tracks and corresponding suborbital shipboard gravity and bathymetry profiles in the South Atlantic Ocean were analyzed: one across the Walvis Ridge (about 1100 km long) and the other in the Brazil Basin (about 2300 km long). Together, these profiles sample those types of sea-floor topography which dominate the gravity signature at wavelengths of 20 to 300 km. The Walvis Ridge is a massive aseismic ridge and the Brazil Basin profile crosses both an old seamount (emplaced at the time the crust was young) and a very young mid-plate volcano. Both profiles cross fracture zones. After the gravity and bathymetry profiles were split into subprofiles, various cross-spectral characteristics could be determined by FFT techniques. Analysis showed that observed admittance is not well constrained by either an Airy-type or flexural compensation models across the Walvis Ridge, but those over the Brazil Basin can be readily explained by an Airy-type model with a mean crustal thickness of about 20 km.

A theoretical filter was then designed, based on a priori geological knowledge, and used to predict bathymetry from the high-passed gravity/geoid anomalies.

Not surprisingly, the predicted bathymetry shows more detailed and correct short-wavelength (20–300 km) features than those predicted from the historical data base, as represented e.g., by the DBDB5 gridded bathymetric model. For areas where historical shipboard bathymetry measurements are widely spaced (longer than about 10 km for single-beam data) but where some regional geologic information is available (such as the relative ages of mid-plate volcanoes and crust), bathymetry predicted from altimetric data can be used to upgrade regional bathymetrie data bases, on which regional geologic/geophysical understanding depends.  相似文献   

Arctic margin gravity highs: Deeper meaning for sediment depocenters?     

Vogt  Peter R.  Jung  Woo-Yeol  Brozena  John 《Marine Geophysical Researches》1998,20(5):459-477

Morphologic, gravity, and seismic reflection/refraction data from ca. 10,000 km of Arctic passive continental margins suggest that the numerous oval free-air gravity anomalies, their +50–150 mGal extrema typically located just landward of shelf breaks, are caused by combinations of rapidly deposited Plio-Pleistocene glacial marine sediment loads, older post-breakup sediments, and perhaps causally related density anomalies (mascons) in the underlying oceanic crust. Dispersed seismicity associated with some gravity highs may reflect ongoing brittle, flexural adjustment to the loads. Multi-channel-seismic-controlled depocenter models for several prominent highs (including the Hornsund gravity high re-examined here) suggest that sediments alone do not suffice to explain the gravity highs, unless depocenter seismic velocities have been significantly underestimated. A flexural backstripping model for the Hornsund anomaly only roughly replicates observed gravity. Subjacent 'mascons', if present below some depocenters, may be caused by (1) anomalous subsidence of initially formed dense/thin crust; (2) depocenter blanketing of early-formed crust, mitigating hydrothermal fracturing and related density reduction; or (3) metastable phase transitions, converting basalt/gabbro to denser phases (Neugebauer–Spohn hypothesis), while cracks close or fill under the increased pressures and temperatures.  相似文献