Modelling the density contrast and depth of the Moho discontinuity by seismic and gravimetric-isostatic methods with an application to Africa

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• 作者：Mohammad Bagherbandi^a ; ^b ; ^{mohbag@kth.se} ; Lars E. Sjö ; berg^a
• 关键词：Crust ; Density contrast ; Isostasy ; Moho ; Africa
• 刊名：Journal of African Earth Sciences
• 出版年：2012
• 期刊代码：4_1464343X
• 类别：ear
• 出版时间：15 June, 2012
• 卷：68
• 期：Complete
• 页码：111-120
• 文件大小：1700 K

摘要

The crustal thickness (Moho depth) is of interest in several geosciences applications, such as geography, geophysics and geodesy. Usually the crustal depth and density variations are estimated by seismic survey data. As such data collection is very time-consuming and expensive an attractive option could be to use a gravimetric/isostatic model. In this case, realistic estimates for the crustal density and Moho density contrast (MDC) are important. In this study, we first use the seismic crustal thickness of CRUST2.0 model as a known parameter in combination with gravimetric data in estimating the crust-mantle density contrast by the isostatic model of Vening Meinesz-Moritz. We present different models to estimate the MDC and its impact on the modelling of the gravimetric-isostatic Moho depth. The theory is applied to estimate the Moho depth of the African continental crust by using different models for the MDC: (a) constant value (0.6 g/cm³), (b) Pratt-Hayford鈥檚 model, (c) CRUST2.0 as input to three gravimetric/isostatic models based on Vening Meinesz-Moritz theory. The isostatic models agree by 5.8-7.1 km in the rms with the regional seismic model at a resolution of 2掳 脳 2掳, and the smallest rms difference at a resolution of 1掳 脳 1掳 is of 7.2 km. For comparison, the rms differences of CRUST2.0 and the regional seismic model are 8.8 and 9.1 km at the resolutions of 2掳 (interpolated) and 1掳, respectively. The result suggests that the gravimetric/isostatic Moho model can be used in densification of the CRUST2.0 Moho geometry, and to improve it in areas with poor data.