Late Holocene Structural Style and Seismicity of Highly Transpressional Faults in Southern Haiti

Abstract

The devastating 2010 Haiti earthquake (M w 7.0) was caused by rupture of the Léogâne, blind, thrust fault located 5 km north of the 1,200-km-long, left-lateral, Enriquillo-Plantain Garden fault zone (EPGFZ). Unexpectedly, the EPGFZ remained largely quiescent or slightly reactivated during the 2010 earthquake. Nevertheless, the EPGFZ still formed a major, crustal boundary between a coseismically uplifted lowland north of the EPGFZ and a subsided area in the highlands south of the fault.Here we use high-resolution sonar data from two Haitian Lakes that straddle the EPGFZ to demonstrate the presence of a 10-to 15-km-wide, 120-km-long, late Holocene fold-thrust belt which deforms clastic, lowland basins along the northern edge of the EPGFZ. In the eastern part of the study area, sonar results from Lake Azuey show that the linear trace of the EPGFZ cutting the Holocene lake bed is more deeply buried and less active than the adjacent, newly discovered, northwest striking, northeast dipping Jimani thrust fault that is part of the adjacent, transpressional belt of en echelon thrusts and folds. This structural relationship between a less active EPGFZ and more recently active, transpression-related Jimani thrust is remarkably similar to the 2010 epicentral area 70 km to the west between the less active EPGFZ and seismogenic, northeast-dipping, Léogâne thrust during the 2010 Haiti earthquake. In this complex transpressional zone, we propose that coseismic deformation alternates at recurrence intervals of centuries between oblique, transpression-related structures (Léogâne, Jimani, and Trois Baies thrusts) and the main strike-slip, plate boundary fault zone (EPGFZ).

The Tectonics and Active Faulting of Haiti from Seismicity and Tomography

“…In map view, a spatial separation of the clusters along the Léogâne fault may also indicate that the fault is segmented beneath the basin (Figure , profile BB' and CC'). Wang et al () suggest that the Léogâne fault forms a conjugate pair with southward‐dipping faults such as the Lamentin thrust, accommodating shortening across the region. Possible stress transfer between the faults during the 2010 earthquake (Saint Fleur et al, ) and the continued seismicity we observe on both faults is consistent with these fault systems being coupled.…”

“…The oblique convergence of the Caribbean and North American plates at 19 mm/year has resulted in a transpressive fault system that affects the island of Hispaniola (Haiti and Dominican Republic; Calais et al, ). Previous geophysical studies into crustal structure have mainly focused on the epicentral region of the M w 7.0, 12 January 2010 Haitian earthquake, revealing a network of subsurface faults which accommodates strain across the broader fault zone (Calais et al, ; Douilly et al, ; Wang et al, ). Regional crustal structure across Haiti has also been constrained by the use of receiver functions (Corbeau, Rolandone, et al, ).…”

“…It extends westward, forming the Gonâve Island as well as transpressive structures offshore (Corbeau, Rolandone, Leroy, Meyer, et al, ; Granja‐Bruña et al, ), and eastward up to the Muertos Trough (Byrne et al, ; Ladd et al, ). South of Gonâve Island, there is a series of southward dipping faults extending 50 km, known as the Trois Baies thrust system (Mercier de Lépinay et al, ; Momplaisir, ; Wang et al, ).…”

“…Cowgill et al () more recently observed a left‐lateral offset in the EPGF at a site to the east of Port‐au‐Prince, at the boarder of the CSE basin. In the CSE basin, Mann et al () and Wang et al () described curvilinear en echelon drag folds and interpreted them to mark the surface trace of the EPGF cross cutting the basin. East‐west linear structures observed in chirp sonar profiles from Lake Azuei and Lake Enriquillo have also been used to interpret the presence of the EPGF crossing the CSE basin (Rios et al, ; Wang et al, ).…”

Neotectonics of Southeast Jamaica Derived From Marine Seismic Surveys and Gravity Cores

“…Though the EPGF is thought to be the primary source for large magnitude (>M w 6) earthquakes, moderate to large earthquakes (e.g., 2010 M w 7 Haiti event) may have also occurred along previously unknown, blind, or poorly constrained faults that accommodate strain from the EPGF (Bakun et al, 2012;Hayes et al, 2010;Koehler et al, 2013;Wiggins-Grandison & Atakan, 2005). Recent studies also show that deformation is often concentrated along blind fault systems that are either adjacent to, extend away from, or connect at depth with the EPGF (e.g., Corbeau et al, 2016;Wang et al, 2018).…”