Deriving a New Crustal Model of Northern Adria: The Northern Adria Crust (NAC) Model

Abstract

We presented a new 3D model of the geophysical properties of the crust (namely depth of the Moho and V P , V S , density, Young's modulus, and shear modulus) of the northern tip of the Adria microplate that we called NAC (Northern Adria Crust). The horizontal dimensions of the physical properties variations are optimized at 5 × 5 km and the vertical dimension at 1 km. NAC has been built by critically choosing and integrating all available information about the depth of the main interfaces and the physical properties of the crust. We started from a V P dataset, and we converted it in V S and density by using empirical relations, tuned through the comparison with the available data from local tomographic inversion, and taking into account the lithologies of the area. Uncertainties and reliability of the model are quantified, taking into account the data quality and the interpolation procedure. NAC has two versions, different in the structure of the Moho interface: the first considers one continuous surface for the whole area, while the second implies three separate surfaces for the Adria microplate, Eurasia, and the Pannonian fragment. The differences between the two models are minimal, but the available data better sustain the solution of the fragmented crust. For its characteristics of multiparametric information and resolution, NAC can be precious for any purpose and use where a detailed knowledge of the crustal structure of this area is required. Moreover, it is easy to improve NAC, including new information on the crustal structures, when they will be available.

High-Resolution Crustal S-wave Velocity Model and Moho Geometry Beneath the Southeastern Alps: New Insights From the SWATH-D Experiment

“…The concentration of the seismic activity in the narrow velocity band is also in agreement with the occurrence of large earthquakes in the upper-crustal density domain boundaries and the regions of the highest geodetic strain rate (Spooner et al, 2019). This supports the hypothesis that the faster middle and lower crust of Adria in this area is more rigid than the Southeastern Alps, while the faster upper crust of southeastern Alps is more rigid than Adria (e.g., Brückl et al, 2007Brückl et al, , 2010Marotta and Splendore, 2014;Magrin and Rossi, 2020).…”

“…depths, respectively (Christensen and Mooney, 1995;Brocher, 2005;Moschetti et al, 2010;Molinari and Morelli, 2011;Macquet et al, 2014;An et al, 2015;Guidarelli et al, 2017;Magrin and Rossi, 2020;Planès et al, 2020). Part of this discrepancy originates from the lack of single definitions of the discontinuities and the trade-off between the S-wave velocity and the depth of the discontinuities.…”

“…We compared SEA-Crust with those of NAC (Magrin and Rossi, 2020) and Kästle et al (2018) (hereafter KST18) through the calculation of their relative changes (Supplementary Figures S5-S7) for fixed-depth slices. Mapping the local differences in the upper crust (5 and 10 km depth, Supplementary Figure S5), NAC is faster than SEA-Crust almost everywhere in the Po and Venetian-Friuli plains (more than 20% at 5 km depth).…”

“…During the last two decades, important efforts were made to determine the crustal thickness of the Alps through different approaches (e.g., Kummerow et al, 2004;Spada et al, 2013;Hetényi et al, 2018b;Kästle et al, 2018;Lu et al, 2018Lu et al, , 2020Spooner et al, 2019;Magrin and Rossi, 2020). The Moho model of Spada et al (2013) is derived from a combination of receiver function and controlled source seismological studies.…”

“…A new high-resolution crustal model is computed down to a depth of 60 km and its relation with the main geologic and tectonic features are discussed. The estimated crustal thickness in the Southeastern Alps and external Dinarides is compared with those included in the Northern Adria crust (NAC) model (Magrin and Rossi, 2020) and the Moho map of Spada et al (2013).…”