The paper discusses the modeling of phonon-mediated quasiparticle (QP) poisoning in superconducting qubit arrays, which is a significant challenge for quantum error correction due to the correlated errors caused by ionizing radiation. The authors describe a comprehensive strategy for numerically simulating the dynamics of phonons and QPs after an impact, using the GEANT4 Condensed Matter Physics (G4CMP) software. They compare the simulations with experimental measurements of phonon-mediated QP poisoning and demonstrate that their modeling captures the spatial and temporal footprint of QP poisoning for various configurations of phonon downconversion structures. The study focuses on four experimental superconducting qubit devices with different levels of phonon mitigation, including devices with and without back-side metallization and those with different thicknesses of Cu islands. The simulations reveal that the presence of Cu islands significantly reduces the QP poisoning footprint and recovery time compared to devices without back-side metallization. The authors also extend their modeling to a dense grid of hypothetical qubits and simulate the burst of phonons following a gamma-ray impact, characterizing the QP poisoning footprint and showing that effective phonon downconversion can significantly reduce the impact of QP poisoning. The results inform designs for future superconducting qubit arrays and phonon-based sensors of rare events.The paper discusses the modeling of phonon-mediated quasiparticle (QP) poisoning in superconducting qubit arrays, which is a significant challenge for quantum error correction due to the correlated errors caused by ionizing radiation. The authors describe a comprehensive strategy for numerically simulating the dynamics of phonons and QPs after an impact, using the GEANT4 Condensed Matter Physics (G4CMP) software. They compare the simulations with experimental measurements of phonon-mediated QP poisoning and demonstrate that their modeling captures the spatial and temporal footprint of QP poisoning for various configurations of phonon downconversion structures. The study focuses on four experimental superconducting qubit devices with different levels of phonon mitigation, including devices with and without back-side metallization and those with different thicknesses of Cu islands. The simulations reveal that the presence of Cu islands significantly reduces the QP poisoning footprint and recovery time compared to devices without back-side metallization. The authors also extend their modeling to a dense grid of hypothetical qubits and simulate the burst of phonons following a gamma-ray impact, characterizing the QP poisoning footprint and showing that effective phonon downconversion can significantly reduce the impact of QP poisoning. The results inform designs for future superconducting qubit arrays and phonon-based sensors of rare events.