The Tectonics and Active Faulting of Haiti from Seismicity and Tomography (original) (raw)
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Seismic hazard of the Enriquillo-Plaintain Garden Fault in Haiti inferred from paleoseismology
Nature Geoscience, 2010
The Enriquillo–Plantain Garden fault zone is recognized as one of the primary plate-bounding fault systems in Haiti1,2. The strike-slip fault runs adjacent to the city of Port-au- Prince and was initially thought to be the source of the 12 January 2010,Mw 7.0 earthquake. Haiti experienced significant earthquakes in 1751 and 1770 (refs 3–5), but the role of the Enriquillo–Plantain Garden fault zone in these earthquakes is poorly known. We use satellite imagery, aerial photography, light detection and ranging (LIDAR) and field investigations to document Quaternary activity on the Enriquillo–Plantain Garden fault. We report late Quaternary, left-lateral offsets of up to 160 m, and a set of small offsets ranging from 1.3 to 3.3m that we associate with one of the eighteenth century earthquakes. The size of the small offsets implies that the historical earthquake was larger than Mw 7.0, but probably smaller than Mw 7.6. We found no significant surface rupture associated with the 2010 earthquake. The lack of surface rupture, coupled with other seismologic, geologic and geodetic observations6,7, suggests that little, if any, accumulated strain was released on the Enriquillo–Plantain Garden fault in the 2010 earthquake. These results confirm that the Enriquillo– Plantain Garden fault remains a significant seismic hazard.
2012
Historical records indicate frequent seismic activity along the north-east Caribbean plate boundary over the past 500 years, particularly on the island of Hispaniola. We use accounts of historical earthquakes to assign intensities and the intensity assignments for the 2010 Haiti earthquakes to derive an intensity attenuation relation for Hispaniola. The intensity assignments and the attenuation relation are used in a grid search to find source locations and magnitudes that best fit the intensity assignments. Here we describe a sequence of devastating earthquakes on the Enriquillo fault system in the eighteenth century. An intensity magnitude MI 6.6 earthquake in 1701 occurred near the location of the 2010 Haiti earthquake, and the accounts of the shak-ing in the 1701 earthquake are similar to those of the 2010 earthquake. A series of large earthquakes migrating from east to west started with the 18 October 1751 MI 7.4–7.5 earthquake, probably located near the eastern end of the faul...
Transpressional rupture of an unmapped fault during the 2010 Haiti earthquake
Nature Geoscience, 2010
On 12 January 2010, a M w 7.0 earthquake struck the Port-au-Prince region of Haiti. The disaster killed more than 200,000 people and caused an estimated $8 billion in damages, about 100% of the country's gross domestic product 1. The earthquake was initially thought to have ruptured the Enriquillo-Plantain Garden fault of the southern peninsula of Haiti, which is one of two main strike-slip faults inferred to accommodate the 2 cm yr −1 relative motion between the Caribbean and North American plates 2,3. Here we use global positioning system and radar interferometry measurements of ground motion to show that the earthquake involved a combination of horizontal and contractional slip, causing transpressional motion. This result is consistent with the long-term pattern of strain accumulation in Hispaniola. The unexpected contractional deformation caused by the earthquake and by the pattern of strain accumulation indicates present activity on faults other than the Enriquillo-Plantain Garden fault. We show that the earthquake instead ruptured an unmapped north-dipping fault, called the Léogâne fault. The Léogâne fault lies subparallel to-but is different from-the Enriquillo-Plantain Garden fault. We suggest that the 2010 earthquake may have activated the southernmost front of the Haitian fold-and-thrust belt 4 as it abuts against the Enriquillo-Plantain Garden fault. As the Enriquillo-Plantain Garden fault did not release any significant accumulated elastic strain, it remains a significant seismic threat for Haiti and for Port-au-Prince in particular. The M w 7.0 Haiti earthquake of 12 January 2010 is the largest event to strike the southern part of Hispaniola since the 15 September 1751, 21 November 1751 and 3 June 1770 events, which also severely affected Port-au-Prince. Although the location of these historical events is poorly constrained, they are thought to have ruptured the Muertos-Enriquillo-Plantain Garden fault system 5 (Fig. 1b). They were followed on 7 May 1842 by a M w 8.0 event farther north, inferred to occur on the offshore section of the Septentrional fault along the northern coast of Haiti, then by a sequence of M w 7.5-8.1 events between 1946 and 1953 on the subduction fault to the northeast of the Dominican Republic (Fig. 1b). These large earthquakes highlight the three main fault systems that accommodate the Caribbean-North America relative plate motion in the northeastern Caribbean (Fig. 1a), at the transition between frontal subduction of the North American plate beneath the Caribbean plate in the Lesser Antilles and roughly eastwest strike-slip motion along the Cayman trough 6-9. Global positioning system (GPS) studies show that the interior of the Caribbean plate moves east-northeastwards (N70 E) at a rate of
Bulletin of the Seismological Society of America, 2013
ABSTRACT Haiti has been the locus of a number of large and damaging historical earthquakes. The recent 12 January 2010 M-w 7.0 earthquake affected cities that were largely unprepared, which resulted in tremendous losses. It was initially assumed that the earthquake ruptured the Enriquillo Plantain Garden fault (EPGF), a major active structure in southern Haiti, known from geodetic measurements and its geomorphic expression to be capable of producing M 7 or larger earthquakes. Global Positioning Systems (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data, however, showed that the event ruptured a previously unmapped fault, the Leogane fault, a north-dipping oblique transpressional fault located immediately north of the EPGF. Following the earthquake, several groups installed temporary seismic stations to record aftershocks, including ocean-bottom seismometers on either side of the EPGF. We use data from the complete set of stations deployed after the event, on land and offshore, to relocate all aftershocks from 10 February to 24 June 2010, determine a 1D regional crustal velocity model, and calculate focal mechanisms. The aftershock locations from the combined dataset clearly delineate the Leogane fault, with a geometry close to that inferred from geodetic data. Its strike and dip closely agree with the global centroid moment tensor solution of the mainshock but with a steeper dip than inferred from previous finite fault inversions. The aftershocks also delineate a structure with shallower southward dip offshore and to the west of the rupture zone, which could indicate triggered seismicity on the offshore Trois Baies reverse fault. We use first-motion focal mechanisms to clarify the relationship of the fault geometry to the triggered aftershocks.
Seismic hazard of the Enriquillo–Plantain Garden fault in Haiti inferred from palaeoseismology
The Enriquillo–Plantain Garden fault zone is recognized as one of the primary plate-bounding fault systems in Haiti. The strike-slip fault runs adjacent to the city of Port-au- Prince and was initially thought to be the source of the 12 January 2010,Mw 7.0 earthquake. Haiti experienced significant earthquakes in 1751 and 1770, but the role of the Enriquillo–Plantain Garden fault zone in these earthquakes is poorly known. We use satellite imagery, aerial photography, light detection and ranging (LIDAR) and field investigations to document Quaternary activity on the Enriquillo–Plantain Garden fault. We report late Quaternary, left-lateral offsets of up to 160 m, and a set of small offsets ranging from 1.3 to 3.3 m that we associate with one of the eighteenth century earthquakes. The size of the small offsets implies that the historical earthquake was larger than Mw 7.0, but probably smaller than Mw 7.6. We found no significant surface rupture associated with the 2010 earthquake. The lack of surface rupture, coupled with other seismologic, geologic and geodetic observations, suggests that little, if any, accumulated strain was released on the Enriquillo–Plantain Garden fault in the 2010 earthquake. These results confirm that the Enriquillo– Plantain Garden fault remains a significant seismic hazard.
Bulletin of the Seismological Society of America, 2013
The 12 January 2010 M w 7.0 Haiti earthquake ruptured the previously unmapped Léogâne fault, a secondary transpressional structure located close to the Enriquillo fault, the major fault system assumed to be the primary source of seismic hazard for southern Haiti. In the absence of a precise aftershock catalog, previous estimations of coseismic slip had to infer the rupture geometry from geodetic and/ or seismological data. Here we use a catalog of precisely relocated aftershocks beginning one month after the event and covering the following 5 months to constrain the rupture geometry, estimate a slip distribution from an inversion of Global Positional Systems (GPS), Interferometric Synthetic Aperture Radar (InSAR) and coastal uplift data, and calculate the resulting changes of Coulomb failure stress on neighboring faults. The relocated aftershocks confirm a north-dipping structure consistent with the Léogâne fault, as inferred from previous slip inversions, but with two subfaults, each corresponding to a major slip patch. The rupture increased Coulomb stresses on the shallow Enriquillo fault parallel to the Léogâne rupture surface and to the west (Miragoâne area) and east (Port-au-Prince). Results show that the cluster of reverse faulting earthquakes observed further to the west, coincident with the offshore Trois Baies fault, are triggered by an increase in Coulomb stress. Other major regional faults did not experience a significant change in stress. The increase of stress on faults such as the Enriquillo are a concern, as this could advance the timing of future events on this fault, still capable of magnitude 7 or greater earthquakes.
Geophysical Research Letters, 2011
Haiti earthquake, we deployed a mainly offshore temporary network of seismologic stations around the damaged area. The distribution of the recorded aftershocks, together with morphotectonic observations and mainshock analysis, allow us to constrain a complex fault pattern in the area. Almost all of the aftershocks have a N-S compressive mechanism, and not the expected left-lateral strike-slip mechanism. A first-order slip model of the mainshock shows a N264°E north-dipping plane, with a major left-lateral component and a strong reverse component. As the aftershock distribution is sub-parallel and close to the Enriquillo fault, we assume that although the cause of the catastrophe was not a rupture along the Enriquillo fault, this fault had an important role as a mechanical boundary. The azimuth of the focal planes of the aftershocks are parallel to the northdipping faults of the Transhaitian Belt, which suggests a triggering of failure on these discontinuities. In the western part, the aftershock distribution reflects the triggering of slip on similar faults, and/or, alternatively, of the southdipping faults, such the Trois-Baies submarine fault. These observations are in agreement with a model of an oblique collision of an indenter of the oceanic crust of the Southern Peninsula and the sedimentary wedge of the Transhaitian Belt: the rupture occurred on a wrench fault at the rheologic boundary on top of the under-thrusting rigid oceanic block, whereas the aftershocks were the result of the relaxation on the hanging wall along pre-existing discontinuities in the frontal part of the Transhaitian Belt. Citation: Mercier de Lépinay, B., et al. (2011), The 2010 Haiti earthquake: A complex fault pattern constrained by seismologic and tectonic observations, Geophys. Res. Lett., 38, L22305,
Geosphere, 2019
The boundary between the Caribbean and North American plates in the Hispaniola region is the northwestern termination of the North American plate subduction evolving from westward subduction in the Lesser Antilles to southward subduction in the Greater Antilles and oblique collision against the Bahamas platform in Cuba. We analyze P waveforms recorded by 27 broadband seismic temporary stations deployed during the Trans-Haiti project. Seismicity recorded by the temporary network from June 2013 to June 2014 is used to locate the earthquakes. A total of 514 events were identified with magnitudes ranging from 1 to 4.5. Twenty-six moment tensors were calculated by full waveform inversion using the ISOLA software. The analysis of the new moment tensors for the Haiti upper lithosphere indicates that normal, thrust and strikeslip faulting are present but with a majority of thrust faulting. The mean P and T axes for the moment tensors indicated that the current compressional deformation is mainly N-S to NNE-SSW. Moreover, a dozen intermediate-depth earthquakes (>70 km) are located under Haiti, with one event in the south of the island reaching 260 km depth. The seismic data of the Haiti network, over a one-year time period, tend to confirm the existence of a lithospheric slab inherited from southward subduction under the Greater Antilles. The scarcity of the intermediate-depth seismic events in this area may be the effect of the lack of a dense seismic network or may indicate that we image the western slab edge. ■ 1. INTRODUCTION Recently, the Mw 7.0 2010 Haiti transpressional earthquake prompted several geological and geophysical studies to constrain the fault geometry and the crustal structure in the area of the main shock near the capital city Port-au
Active fault characterization and seismotectonic zoning of the Hispaniola island
Journal of Seismology
Designing a seismic source model based on the most complete description of potentially active faults and on the kinematics of their latest movements is an essential requirement in seismic hazard studies, at regional and local scales. A study to characterize active faults in the Hispaniola island (today’s Haiti and Dominican Republic) has been conducted in the framework of the probabilistic seismic hazard assessment for Santo Domingo (capital of the Dominican Republic). In this work, we present a seismotectonic map of Hispaniola and its surroundings, based on a compilation and synthesis of geological, geophysical, geodetic and seismological data. Based on these data, distinct seismic zone sources are proposed and classified as either intercrustal domains, major active faults or subduction zones. Each seismic source is described according to several parameters, including its mechanism and current rate of deformation, the associated seismicity and its estimated maximal magnitude. These...
Natural Hazards, 2014
The San Ramón Fault is an active west-vergent thrust fault system located along the eastern border of the city of Santiago, at the foot of the main Andes Cordillera. This is a kilometric crustal-scale structure recently recognized that represents a potential source for geological hazards. In this work, we provide new seismological evidences and strong ground-motion modeling from hypothetic kinematic rupture scenarios, to improve seismic hazard assessment in the Metropolitan area of Central Chile. Firstly, we focused on the study of crustal seismicity that we relate to brittle deformation associated with different seismogenic fringes in the main Andes in front of Santiago. We used a classical hypocentral location technique with an improved 1D crustal velocity model, to relocate crustal seismicity recorded between 2000 and 2011 by the National Seismological Service, University of Chile. This analysis includes waveform modeling of seismic events from local broadband stations deployed in the main Andean range, such as San José de Maipo, El Yeso, Las Melosas and Farellones. We selected events located near the stations, whose hypocenters were localized under the recording sites, with angles of incidence at the receiver\5°and S-P travel times\2 s. Our results evidence that seismic activity clustered around 10 km depth under San José de Maipo and Farellones stations. Because of their identical waveforms, such events are interpreted like repeating earthquakes or multiplets and therefore providing first evidence for seismic tectonic activity consistent with the crustal-scale structural model proposed for the San Ramón Fault system in the area (Armijo et al. in Tectonics 29(2):TC2007, 2010). We also analyzed the ground-motion variability generated by an M w 6.9 earthquake rupture scenario by using a kinematic fractal k -2 composite source model. The main goal was to model broadband strong ground motion in the near-fault region and to analyze the variability of ground-motion parameters computed at various receivers. Several kinematic rupture scenarios were computed by changing physical source parameters. The study focused on statistical analysis of horizontal peak ground acceleration (PGAH) and ground velocity (PGVH). We compared the numerically predicted ground-motion parameters with empirical ground-motion predictive relationships from Kanno et al. (Bull Seismol Soc Am 96:879-897, 2006). In general, the synthetic PGAH and PGVH are in good agreement with the ones empirically predicted at various source distances. However, the mean PGAH at intermediate and large distances attenuates faster than the empirical mean curve. The largest mean values for both, PGAH and PGVH, were observed near the SW corner within the area of the fault plane projected to the surface, which coincides rather well with published hanging-wall effects suggesting that ground motions are amplified there.