Rupture Segmentation of the 14 August 2021 Mw 7.2 Nippes, Haiti, Earthquake Using Aftershock Relocation from a Local Seismic Deployment

The 14 August 2021 Mw 7.2 Haiti earthquake struck 11 yr after the devastating 2010 event within the Enriquillo Plantain Garden (EPG) fault zone in the Southern peninsula of Haiti. Space geodetic results show that the rupture is composed of both left-lateral strike-slip and thrust motion, similar to the 2010 rupture; but aftershock locations from a local short-period network are too diffuse to precisely delineate the segments that participated in this rupture. A few days after the mainshocks, we installed 12 broadband stations in the epicentral area. Here, we use data from those stations in combination with four local Raspberry Shakes stations that were already in place as part of a citizen seismology experi-ment to precisely relocate 2528 aftershocks from August to December 2021, and derive 1D P- and S-crustal velocity models for this region. We show that the aftershocks delineate three north-dipping structures with different strikes, located to the north of the EPG fault. In addition, two smaller aftershock clusters occurred on the EPG fault near the hypocenter area, indicative of triggered seismicity. Focal mechanisms are in agreement with coseismic slip inversion from Interferometric Synthetic Aperture Radar data with nodal planes that are consistent with the transpressional structures illustrated by the aftershock zones.

Automated summary

This article investigated the aftershock activity of the Mw 7.2 earthquake in Haiti in August 2021 and derived crustal velocity models for the region based on data from installed stations. The study revealed the delineation of three north-dipping structures with different strikes located to the north of the Enriquillo Plantain Garden fault, as well as two smaller aftershock clusters on the fault near the hypocenter area indicative of triggered seismicity. Focal mechanisms were consistent with coseismic slip inversion from Interferometric Synthetic Aperture Radar data.