Detailed gravity interpretation in selected areas of the Eastern Alps

In the recent decades gravity investigation in Austria has been focused on acquiring a modern data set for detailed gravity studies. In most even high Alpine areas data coverage corresponds to 1 station/10 km2 today that enables to develop detailed models of the upper crust. During the project new gravity stations have been installed in order to complete homogeneous and dense data coverage in Austria, which permits now to compile the planned new gravity map. The main task of this project was to start three-dimensional modeling in selected areas of special interest. As a first step data homogenization had to be performed by applying modern mass correction methods and high- resolution digital terrain models. Qualitative interpretation followed in terms of investigating reduction anomalies due to wrong density assumptions and incomplete height reduction. The equivalent source principle as well as new approaches to field continuation downwards have been applied. Main target of three-dimensional modeling was the Inn valley and it`s surrounding. This area is an important example of an over-deep Alpine valley where seismic and gravity information could be combined. A preliminary 3D model of the uppermost crust has been derived based on a stripped gravity map after subtracting long-wavelength features caused by sources of the middle and lower crust and the crust-mantle boundary.