Broadband Strong Ground Motion Simulation For a Potential Mw 7.1 Earthquake on The Enriquillo Fault in Haiti

Abstract:

The devastating 2010 Haiti earthquake showed the need to be more vigilant toward mitigation for future earthquakes in the region. Previous studies have shown that this earthquake did not occur on the Enriquillo Fault, the main plate boundary fault running through the heavily populated Port-au-Prince region, but on the nearby and previously unknown Léogâne transpressional fault. Slip on that fault has increased stresses on the Enriquillo Fault mostly in the region closer to Port-au-Prince, the most populated city of the country. Here we investigate the ground shaking level in this region if a rupture similar to the Mw 7.0 2010 Haiti earthquake occurred on the Enriquillo fault. We use a finite element method and assumptions on regional stress to simulate low frequency dynamic rupture propagation for a 53 km long segment. We introduce some heterogeneity by creating two slip patches with shear traction 10% greater than the initial shear traction on the fault. The final slip distribution is similar in distribution and magnitude to previous finite fault inversions for the 2010 Haiti earthquake. The high-frequency ground motion components are calculated using the specific barrier model, and the hybrid synthetics are obtained by combining the low-frequencies (f < 1Hz) from the dynamic rupture simulation with the high-frequencies (f > 1Hz) from the stochastic simulation using matched filtering at a crossover frequency of 1 Hz. The average horizontal peak ground acceleration, computed at several sites of interest through Port-au-Prince, has a value of 0.35g. We also compute response spectra at those sites and compare them to the spectra from the microzonation study.