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

Harriet Zoe Yin , Mathilde Marchandon, Jennifer Susan Haase, Alice-Agnes Gabriel , Roby Douilly

The 2021 M_w7.2 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 2010 M_w7.0 earthquakes were pure strike slip events and, instead, ruptured with distinct patches of dip slip and strike slip motion on largely separate fault planes. 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 develop several 3D dynamic rupture simulations of the 2021 earthquake to analyze which conditions may have controlled the complex rupture. We construct a detailed fault system geometry with 17 fault segments, including 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 match the scale and pattern of surface deformation observed with InSAR. Lateral changes in the regional stress shape and orientation are key to generating the observed rupture transfer from the TF to the RSF while maintaining the rake required to match 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 controlling factors on the dynamics of the 2021 rupture.