Interpretation of the lithospheric structure beneath the Indian Ocean from gravity gradient data

摘要

Global geoidal undulations are often used as the constraining parameter to model the mantle convection pattern, while gravity data are typically applied to interpret the lithospheric structure. In more recent studies, especially after launching the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite gravity-gradiometry mission, gravity gradient measurements have also been used in various geoscience applications. The main motivation of using gravity gradients is to provide a more conclusive information about a spatial localization of investigated phenomena. In geophysical studies, such implications are particularly related to a probably better detection of investigated lithospheric structures, such as active tectonic margins. In this study, we address this aspect by comparing interpretational characteristics from gravity and gravity gradient information. The Bouguer and mantle gravity gradients are used for this purpose to interpret the lithospheric structure beneath the Indian Ocean as well as the (adjacent) continental lithospheric structures (such as the East African Rift System). Our results confirm that gravity gradient more closely reproduces some tectonic and volcanic features, such as oceanic subductions, volcanic island arcs, and convergent continental tectonic margins. Similarly, mid-oceanic spreading ridges are localized slightly better in the gravity gradient map. Our findings also indicate that the interpretational quality cannot be improved by using directly observed gravity gradients. The reason is that these interpretations require applying gravimetric forward modelling techniques in order to enhance a particular lithospheric structure.