The Charlevoix Seismic Zone (CSZ) is the most active intraplate seismic region in Eastern Canada, characterized by the reactivated St. Lawrence rift and a crust fractured by a Devonian meteorite impact. With a probabilistic return period of ~145 years for magnitude ≥6 earthquakes, accurately quantifying seismic hazard is critical. Current assessments often rely on empirical Ground Motion Models (GMMs) that average wave propagation effects over diverse regions and may fail to account for the unique local site effects and complex 3D wave propagation inherent to the CSZ. To address this gap, we are developing a physics-based simulation framework using the SW4 finite-difference code. The framework centers on constructing a regional 3D velocity model by integrating depth slices of P- and S-wave velocity maps from a recent ambient noise tomography study with regional 1D models. To calibrate this structure, we processed available waveforms from moderate-magnitude (MN 4–5) earthquakes, applying instrument response correction and benchmarked them against NGA-East GMMs. Since the source parameters are established, we then compare synthetic waveforms from our simulations with these empirical records to calibrate the 3D velocity model. Results indicate observed PGV often exceeds the NGA-East median, confirming region-specific 3D modelling is necessary for the CSZ. Although few in Canada perform such simulations and no regional 3D velocity model has been assembled, we show that by maximizing the little earthquake data we have and integrating it with ambient noise tomography, now is the time to build a robust 3D velocity model for earthquake ground motion simulations.