3D dynamic rupture modeling of the 2021 Haiti earthquake used to constrain stress conditions and fault system complexity

The 2021 Mw7.2 Haiti earthquake was a devastating event which occurred within the Enriquillo Plantain Garden Fault Zone (EPGFZ). It is not well-understood why neither the 2021 nor the prior Mw7.0 2010 earthquake were simple strike slip events and, instead, ruptured with distinct patches of dip slip and strike slip motion on largely separate fault planes. We develop several 3D dynamic rupture simulations of the 2021 earthquake to test which conditions may have controlled the complex rupture. The major characteristics of the earthquake rupture include: the characteristic spatial and temporal separation of strike-slip and dip-slip motion, rupture transfer to the Ravine du Sud Fault (RSF), and a multi-peak source time function. We construct a detailed fault system geometry which includes a north-dipping Thrust Fault (TF) and near-vertical RSF, along with surrounding regional and secondary faults. We find that along-strike changes to the frictional strength of the TF are needed to focus the slip to reproduce the scale and pattern of deformation observed with InSAR. Lateral changes in the regional stress shape and orientation are key to reproducing the observed rupture transfer from the TF to the RSF while maintaining the rake required to reproduce the broad InSAR surface deformation pattern and multi-peak source time function. The dynamic rupture modeling results suggest that significant variability in fault stress and strength as well as complexities of the subsurface geometry may have been key controls on the dynamics of the 2021 rupture.