Contribution a l'etude geologique de la partie orientale du massif de la Hotte (presqu'ile du Sud d'Haiti) : synthese structurale des marges de la presqu'ile a partir de donnees sismiques

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

From neogene thin-skin to recent thick-skin deformation in Haiti fold-and-thrust belt (Western Hispaniola)

International audienceHaiti lies along the North Caribbean plate boundary, marked by two major left-lateral strike-slip faults. A southwest-verging Trans-Haitian fold-and-thrust belt (FTB), mostly affecting tertiary carbonate platform, developed in central Haiti between the two faults, south of the Massif du Nord and the San Juan–Los Pozos Fault Zone, as a result of north-south shortening. The large NW-SE antiformal Gonâve Island and Ridge mark the southwest termination of the FTB as it encountered the Southern Peninsula and Enriquillo-Plantain Garden Fault Zone. We show that this collision resulted in a tightening of the deformed wedge and thrust faults rooted deeper into the crust, leading to a transition from thin-skinned to thick-skinned tectonics in the Pliocene. These short- (3–6 km) and long- (15–30 km) wavelength folding deformations are temporally distinct in the north and more concomitant in the south, where compressional thin-skinned deformation is still active. The thick-skinned shortening was mostly expressed during the Quaternary, as shown by the formation of folds and uplift of terraces between 1.7 Ma and today. This thick-skinned detachment is characterised by a stronger imprint of strike-slip component, dragging the FTB to a more E-W direction in its northwest and southeast extremities. Understanding of the fault zone geometry of the recent 2010 Haiti earthquake (M = 7.2) could be reconsidered in the light of this tectonic transition

How transpressive is the northern Caribbean plate boundary?

International audienceTranspressive deformation at the northern Caribbean plate boundary is accommodated mostly by two major strikeslipfaults, but the amount and location of accommodation of the compressional component of deformation is still debated.We collected marine geophysical data including multi-beam bathymetry and multichannel seismic reflection profiles alongthis plate boundary around Hispaniola, in the Jamaica Passage and in the Gulf of Gonâve. The data set allows us to imagethe offshore active strike-slip faults as well as the compressional structures. We confirm that the Enriquillo-Plantain-GardenFault Zone (EPGFZ) in the Jamaica Passage has a primary strike-slip motion, as indicated by active left-lateral strike-sliprelatedstructures, i.e.: restraining bend, asymmetrical basin, en echelon pressures ridges and horsetail splay. Based ontopographic cross-sections across the EPGFZ, we image a very limited compressional component, if any, for at least thewestern part of the Jamaica Passage. Toward the east of the Jamaica Passage, the fault trace becomes more complex and weidentify adjacent compressional structures. In the Gulf of Gonâve, distributed folding and thrust faulting of the most recentsediments indicate active pervasive compressional tectonics. Estimates of shortening in the Jamaica Passage and in the Gulfof Gonâve indicate an increase of the compressional component of deformation towards the east, which nonetheless remainsvery small compared to that inferred from block modelling based on GPS measurement

The northern Caribbean plate boundary in the Jamaica Passage: structure and seismic stratigraphy

International audienceMultibeam bathymetry data and multichannel seismic reflection profiles have been collected at the end of 2012 along the Enriquillo-Plantain-Garden Fault Zone (EPGFZ) in the Jamaica Passage, between Jamaica and Hispaniola. Analysis of the data set reveals the tectonic evolution and the stratigraphic complexity of the northern Caribbean boundary. Stratigraphic correlations with previous marine and on land studies are proposed to place the identified seismic sequences in their regional tectonic history. Two distinct crustal domains are interpreted. Typical stratigraphic sequences for the rifted blocks of the Eastern Cayman Trough margin are identified in five basins of the Jamaica Passage, highlighting the eastward limit of the Cayman Trough margin. These inherited basins are deformed and folded during a first phase of compression that could correspond to the regional tectonic rearrangement recorded in the early Miocene (about 20 Ma). A distinct crustal domain that we propose to relate to the Carib Beds (Caribbean typical reflectors A′′,B′′ and V) is identified in the southern part of the Jamaica Passage, indicating that the Caribbean Large Igneous Province could extend up to the extreme northeast part of theLower Nicaragua Rise. The left-lateral EPGFZ currently cuts acrosstwo pre-existing basins, the Morantand Matley basins. During the activity of the EPGFZ, these basins are deformed and folded indicating a second phase of compression. In contrast, the Navassa basin, located in the middle of the Jamaica Passage, results from the strike-slip motion of the EPGFZ and is interpreted as an asymmetricalbasin bordered by the EPGFZonly on its northern sid

Polyphase tectonic history of the Southern Peninsula, Haiti: from folding-and-thrusting to transpressive strike-slip

International audienceThe Southern Peninsula of Haiti is a seismically active east-west trending transpressive mountain range with elevations over 2 km. Present-day deformation is mainly partitioned along the left-lateral Enriquillo-Plantain Garden Fault Zone (EPGFZ) and associated oblique reverse faults and/or folds. The configuration of these faults, their respective timing, and the role of structural heritage on their development is poorly understood. To address these questions we present the results of extensive field campaigns, combined with satellite imagery interpretation and published data, which allows us to constrain the Cenozoic evolution of the Southern Peninsula. Our results show a polyphase tectonic history consisting of three major tectonic events: 1) Maastrichtian to early Paleocene crustal-scale folding that developed coevally with predominantly north to northeast dipping thrusts, resulting in uplift and erosion of the Cretaceous sedimentary cover in large parts of the Southern Peninsula. 2) Early Miocene uplift and erosion, which was strongest in the southwestern part of the peninsula and 2 decreased eastwards, did not affect the Massif de la Selle. Uplift is most likely unrelated to strike-slip activity but resulted from folding in response to NE-SW shortening that possibly reactivated older, predominantly N-to NE-dipping thrusts. 3) Late Miocene to present-day deformation and uplift. Spatially distributed strike-slip started during the late Miocene and became progressively focused along the EPGFZ in the latest Miocene. Oblique and thrust faults locally postdate strike-slip activity from the Pliocene onward. Increase in compressional deformation from west to east is reflected by a change in structural style, with predominantly strike-slip faults in the west and transpressional faults in the east, the latter possibly rooted on the EPGFZ at depth. Paleo-stresses associated with a strike-slip regime are at a significantly high angle to the trace of the EPGFZ, indicating that the EPGFZ is a mechanically weak fault

Spatial Variations in Crustal and Mantle Anisotropy Across the North American-Caribbean Boundary on Haiti

International audienceHaiti, on the island of Hispaniola, is situated across the North American-Caribbean plate boundary at the transition point between oblique subduction in the east and a transform plate boundary in the west. Here we use shear wave splitting measurements from S waves of local (0-50 km) and intermediate depth (50-150 km) earthquakes as well as SK(K)S phases from teleseismic earthquakes to ascertain good spatial and vertical resolution of the azimuthal anisotropic structure. This allows us to place new constraints on the pattern of deformation in the crust and mantle beneath this transitional region. SK(K)S results are dominated by plate boundary parallel (E-W) fast directions with~1.9 s delay times, indicating subslab trench parallel mantle flow is continuing westward along the plate boundary. Intermediate depth earthquakes originating within the subducting North American plate show a mean fast polarization direction of 065°and delay time of 0.46 s, subparallel to the relative plate motion between the Caribbean and North American plates (070°). We suggest a basal shear zone within the lower ductile crust and upper lithospheric mantle as being a potential major source of anisotropy above the subducting slab. Upper crustal anisotropy is isolated using shear wave splitting measurements on local seismicity, which show consistent delay times on the order of 0.2 s. The fast polarization directions indicate that the crustal anisotropy is controlled by the fault networks in close proximity to the major strike-slip faults, which bisect the north and south of Haiti, and by the regional stress field where faulting is less pervasive

Haiti-Drill: an amphibious drilling project workshop

International audienceThe Haiti region – bounded by two strike-slip faults expressed both onshore and offshore – offers a unique opportunity for an amphibious drilling project. The east–west (EW)-striking, left lateral strike-slip Oriente–Septentrional fault zone and Enriquillo–Plantain Garden fault zone bounding Haiti have similar slip rates and also define the northern and southern boundaries of the Gonâve Microplate. However, it remains unclear how these fault systems terminate at the eastern boundary of that microplate. From a plate tectonic perspective, the Enriquillo–Plantain Garden fault zone can be expected to act as an inactive fracture zone bounding the Cayman spreading system, but, surprisingly, this fault has been quite active during the last 500 years. Overall, little is understood in terms of past and present seismic and tsunami hazards along the Oriente–Septentrional fault zone and Enriquillo–Plantain Garden fault zone, their relative ages, maturity, lithology, and evolution – not even the origin of fluids escaping through the crust is known. Given these unknowns, the Haiti-Drill workshop was held in May 2019 to further develop an amphibious drilling project in the Haiti region on the basis of preproposals submitted in 2015 and their reviews. The workshop aimed to complete the following four tasks: (1) identify significant research questions; (2) discuss potential drilling scenarios and sites; (3) identify data, analyses, additional experts, and surveys needed; and (4) produce timelines for developing a full proposal. Two key scientific goals have been set, namely to understand the nature of young fault zones and the evolution of transpressional boundaries. Given these goals, drilling targets were then rationalized, creating a focus point for research and/or survey needs prior to drilling. Our most recent efforts are to find collaborators, analyze existing data, and to obtain sources of funding for the survey work that is needed

The tectonics and active faulting of Haiti from seismicity and tomography

Oblique convergence of the Caribbean and North American plates has partitioned strain across a major transpressional fault system that bisects the island of Hispaniola. The devastating MW 7.0, 2010 earthquake that struck southern Haiti, rupturing an unknown fault, highlighted our limited understanding of regional fault segmentation and its link to plate boundary deformation. Here we assess seismic activity and fault structures across Haiti using data from 33 broadband seismic stations deployed for 16‐months. We use travel‐time tomography to obtain relocated hypocenters and models of Vp and Vp/Vs crustal structure. Earthquake locations reveal two clusters of seismic activity. The first corresponds to aftershocks of the 2010 earthquake and delineates faults associated with that rupture. The second cluster shows shallow activity north of Lake Enriquillo (Dominican Republic), interpreted to have occurred on a north‐dipping thrust fault. Crustal seismic velocities show a narrow low‐velocity region with an increased Vp/Vs ratio (1.80‐1.85) dipping underneath the Massif de la Selle, which coincides with a southward‐dipping zone of hypocenters to a depth of 20 km beneath southern Haiti. Our observations of seismicity and crustal structure in southern Haiti suggests a transition in the Enriquillo fault system from a near vertical strike‐slip fault along the Southern Peninsula to a southward‐dipping oblique‐slip fault along the southern border of the Cul‐de‐Sac‐Enriquillo basin. This result, consistent with recent geodetic results but at odds with the classical seismotectonic interpretation of the Enriquillo fault system, is an important constraint in our understanding of regional seismic hazard

Monitoring Haiti’s Quakes with Raspberry Shake

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