Coupled Numerical Simulation of Teleseismic Wave Propagation Incorporating Local Structural Features

Tomography and full waveform inversion studies are dependent on synthetic datasets. However, simulating teleseismic wave propagation in 3D remains computationally challenging, particularly when small-scale local structure is incorporated into the model. To overcome this issue, a range of strategies - including hybrid methods and coupling techniques - have been explored in recent years.

In this work, we evaluate RegHyM, an open-source package that couples AxiSEM with SPECFEM3D. Previous work using the package has demonstrated the feasibility of simulating P waves from explosive sources, but this has not been systematically validated. To expand the range of applications of the package for seismological studies, we model body and surface waves for earthquake sources and compare the synthetic waveforms with observed seismological data. In the present work, high-resolution 3D regional models are developed numerically accounting for surface topography and 3D velocity model. Simulations are carried out for the Alpine region as the region is not only seismically active but also hosts a widespread network of seismic stations with openly available data. Moreover, the region has been explicitly explored in the past to determine subsurface velocity models. The synthetic data simulated for different earthquakes is then validated through systematic comparison with real data up to frequency of 0.1 Hz.

In addition, we further extended the package to record spatial gradients of the wavefield, including strains and rotations, and present successful cases of these new capabilities within RegHyM. The complete package, now accompanied by a user manual, enables regional and teleseismic wave propagation at reduced computational cost, while preserving the detailed structure of the 3D local model.

Future work will focus on extending the validation of the package to telesismic wave propagation at higher frequencies and assessing the reliability of the synthetic surface waves through comparisons with seismological data.