Abstract
Abstract. In this study, we present an estimate of the gravity signal of the slabs beneath the Alpine mountain belt. Estimates of the gravity effect of the subducting slabs are often omitted or simplified in crustal-scale models. The related signal is calculated here for alternative slab configurations at near-surface height and at a satellite altitude of 225 km. We apply three different modelling approaches in order to estimate the gravity signal from the subducting slab segments: (i) direct conversion of upper mantle seismic velocities to density distribution, which are then forward calculated to obtain the gravity signal; (ii) definition of slab geometries based on seismic crustal thickness and high-resolution upper mantle tomography for two competing slab configurations – the geometries are then forward calculated by assigning a constant density contrast and slab thickness; (iii) accounting for compositional and thermal variations with depth within the predefined slab geometry. Forward calculations predict a gravity signal of up to 40 mGal for the Alpine slab configuration. Significant differences in the gravity anomaly patterns are visible for different slab geometries in the near-surface gravity field. However, different contributing slab segments are not easily separated, especially at satellite altitude. Our results demonstrate that future studies addressing the lithospheric structure of the Alps should have to account for the subducting slabs in order to provide a meaningful representation of the geodynamic complex Alpine area.
Highlights
Interpretation of gravity anomalies can reveal information on the architecture and tectonic setting of the lithosphere (e.g. Zeyen and Fernàndez, 1994; McKenzie and Fairhead, 1997; Holzrichter and Ebbing, 2006; Braitenberg, 2015; Spooner et al, 2019)
In the step, we try to concentrate on the seismic anomalies in the Alpine realm that can be related to the slab segments
The highest magnitude of the forward-calculated gravity signal is on the order of 110 mGal and is observed for a slab model with a density contrast of 80 kg m−3 and a constant slab thickness of 100 km, while the lowest signal is produced by a combination of 20 km m−3 density contrast and a slab thickness of 60 km
Summary
Interpretation of gravity anomalies can reveal information on the architecture and tectonic setting of the lithosphere (e.g. Zeyen and Fernàndez, 1994; McKenzie and Fairhead, 1997; Holzrichter and Ebbing, 2006; Braitenberg, 2015; Spooner et al, 2019). Babuška et al, 1990; Lippitsch et al, 2003; Spakman and Wortel, 2004; Mitterbauer et al, 2011; Karousová et al, 2013; Zhao et al, 2016; Kästle et al, 2018; El-Sharkawy et al, 2020). Those different studies suggest different configurations of slab segments Those different studies suggest different configurations of slab segments (see Sect. 1.1), al-
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