Gravity Signal of the Crust-Mantle Boundary and Density Structures in this Region

Abstract

The mass sources that are responsible for the longwavelength gravity field of the Earth are not yet fully understood. The biggest candidate to describe these anomalies is mantle convection, yet models that can explain the mantle convection and the gravity field are not available. Another candidate is the core-mantle boundary with a density contrast of 4500 kg/m3 between the ferrous core and the silicate mantle. Due to the high density contrast variations in the core-mantle boundary can have a great impact on the gravity field. Also, density anomalies above the core-mantle boundary are large enough to be seen in the gravity field. The geometry of these anomalies amount to hundreds of km’s with density contrast up to 100 kg/m3. Sensitivity tests using similar dimensions and density contrasts show that gravity anomalies of 10-100 mGal can be computed, which is in the same as the longwavelength part of the gravity field. We argue that the gravity signal from structures at the deepest part of the lower mantle should be part of any global analysis. During the 3D Earth project, we will use seismic models of the core-mantle region to simulate more realistic geometries and density anomalies to study their effect on the global gravity field. This presentation is part of the ESA Support To Science Element - 3D Earth – which is presented by Jörg Ebbing