3D gravity modelling of the crust in the Eastern and eastern-Southern Alps using density data derived from compressional-wave velocities obtained by Local Earthquake Tomography

Detailed crustal structures and causative kinematic processes in the Alps continue to be a matter of ongoing research. Of particular interest is the crustal structure of the Adriatic indenter, the northern tip of the Adriatic plate that collided with and significantly deformed the Eastern Alpine Orogen in the Oligo-Miocene.

As part of the “Mountain Building in 4D” (4DMB/AlpArray) project, a high-density network of seismic stations was previously used to produce 3-D models of compressional wave velocity (Vp) of the crust and upper mantle in the Eastern and eastern Southern Alps using Local Earthquake Tomography (LET). This LET model shows a thickened high velocity zone within the lower crust beneath the Periadriatic fault, which is expected to relate to the local gravity field variations.

Here, we present results of gravity modelling using the IGMAS+ software and densities derived from the P-wave velocities of the LET model. Different possible empirical relationships between Vp and density are explored and compared to previous models as well as the AlpArray Gravity measurements to further constrain the present lithological and tectonic structures in the Eastern and eastern-Southern Alps. Strengths and weaknesses of the LET model and the gravity response of the derived densities, in particular regarding uncertainties of structures at greater depths, will be discussed.