Regularization by Digital Topography and by Estimating Crustal Parameters from Gravity Field Data: Example of Switzerland

Abstract

In this paper emphasis is put on the determination of crustal parameters by gravity anomalies. The determined parameters may also be used for the gravity field interpolation. The crustal parameters will be restricted in our case to densities and reference depth of the Mohorovicic discontinuity in the swiss alpine area. A procedure similar to the well known ‘Nettleton’- profiling for determination of the homogeneous density of a small scale topographic structure will be generalized to two dimensional datasets and varying density. The method will still be limited to small areas. Elsewhere similar approaches are used for gravity prediction, where in some way the correlation of height and anomaly is used, too. The estimate of the parameters, which may include also density and trendparameters is done by least-square adjustment or by least-square collocation. In this approach different components of all the methods can be identified. The basic idea consists in reducing the gravity field anomalies by physically meaningful parameters, which have to be estimated, to a more or less stochastic remainder. The applied model consists of horizontally varying crustal density, mantle density, reference depth of MohoDiscontinuity and known disturbing mass distributions like the ‘Ivrea’ body in the southern part of Switzerland. Similar calculations are carried out to treat the deflection of the vertical. The regularization of the deflections by topographic masses is clearly demonstrated, especially in rugged topography.