3D crustal velocity model for the wider Zagreb area

The 3D structural model covers 60 km by 80 km area around the city of Zagreb, Croatia, and extends to the depth of 60 km. It describes seismologically relevant parameters, density, P- and S-wave velocity, on a working grid of 125 m in UTM (zone 33N) coordinate system. The model is represented by four main layers: sediments, upper crust, lower crust and mantle. The format of the model is suitable for simulations obtained using software package SPECFEM3D Cartesian (geodynamics.org/cig/software/specfem3d/; accessed Aug 2021). Description of the formatting of the file can be found on the SPECFEM3D 'engCartesian package documentation site: https://specfem3d.readthedocs.io/en/latest/13_changing_the_model/#using-external-tomographic-earth-models (accessed Aug 2021). 3D seismic model for the wider Zagreb area was assembled using publicly available geological and geophysical data. It describes in detail main structures observed in the uppermost part of the crust (e.g. sedimentary basins and high-velocity structures) and is embedded within the regional EPcrust crustal model (https://doi.org/10.1111/j.1365-246X.2011.04940.x). The performance of the model was tested by simulating ground motion for several moderate earthquakes. Results show that the 3D model is able to reproduce main characteristics of the ground motion, primarily shaking duration and amplification effects. Therefore, it is suited for simulation of shaking scenarios in the wider Zagreb area, mostly for T > 1 s.