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Earthquakes pose a major threat to the people of Haiti, as tragically shown by the catastrophic 2010 Mw 7.0 earthquake and more recently by the 2021 Mw 7.2 earthquake. Both events occurred within the transpressional Enriquillo–Plantain Garden fault zone (EPGFZ), which runs through the southern peninsula of Haiti and is a major source of seismic hazard for the region. Satellite-based Interferometric Synthetic Aperture Radar (InSAR) data are used to illuminate the ground deformation patterns associated with the 2021 event. The analysis of Sentinel-1 and Advanced Land Observation Satellite (ALOS)-2 InSAR data shows (1) the broad coseismic deformation field; (2) detailed secondary fault structures as far as 12 km from the main Enriquillo–Plantain Garden fault (EPGF), which are active during and after the earthquake; and (3) postseismic shallow slip, which migrates along an ∼40 km unruptured section of the EPGF for approximately two weeks following the earthquake. The involvement of secondary faults in this rupture requires adjustments to the representation of hazard that assumes a simple segmented strike-slip EPGF. This work presents the first successful use of phase gradient techniques to map postseismic deformation in a vegetated region, which opens the door to future studies of a larger number of events in a wider variety of climates.
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Sedimentary signatures of large earthquakes along the submerged Enriquillo–Plantain Garden transpressional plate boundary, northern Caribbean
Abstract The Enriquillo–Plantain Garden fault (EPGF), the southern branch of the northern Caribbean left-lateral transpressional plate boundary, has ruptured in two devastating earthquakes along the Haiti southern peninsula: the Mw 7.0, 2010 Haiti and the Mw 7.2, 2021 Nippes earthquakes. In Jamaica, the 1692 Port Royal and 1907 Great Kingston earthquakes caused widespread damage and loss of life. No large earthquakes are known from the 200-km-long Jamaica Passage segment of this plate boundary. To address these hazards, a National Science Foundation Rapid Response survey was conducted to map the EPGF in the Jamaica Passage south of Kingston, Jamaica, and east of the island of Jamaica. From the R/V Pelican we collected >50 high-resolution seismic profiles and 47 gravity cores. Event deposits (EDs) were identified from lithology, physical properties, and geochemistry and were dated in 13 cores. A robust 14C chronology was obtained for the Holocene. A Bayesian age model using OxCal 4.4 calibration was applied. Out of 58 EDs that were recognized, 50 have ages that overlap within their 95% confidence ranges. This allowed for their grouping in multiple basins located as much as 150 km apart. The significant age overlap suggests that EDs along the Enriquillo–Plantain Garden plate boundary resulted from large and potentially dangerous earthquakes. Most of these earthquakes may derive from the EPGF but also from thrust faulting at this strain-partitioned transpressional boundary. The recent increase in Coulomb stress on the EPGF from the Mw 7.2 Nippes earthquake in southwestern Haiti and the discoveries reported here enhance the significance for hazard in the Jamaica Passage.
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- Award ID(s):
- 2201417
- PAR ID:
- 10599000
- Publisher / Repository:
- www.gsapubs.org
- Date Published:
- Journal Name:
- Geology
- Volume:
- 52
- Issue:
- 10
- ISSN:
- 0091-7613
- Page Range / eLocation ID:
- 769 to 773
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Steckler, M (Ed.)The northern E-W boundary of the Caribbean Plate is primarily left lateral and has evolved through the Cenozoic from transtensive to transpressive. The southern branch of this boundary, the Enriquillo-Plantain Garden Fault (EPGF), traverses southern Haiti through the Jamaica Passage to Jamaica. Damaging earthquakes occurred in Haiti in 1751, 1770, 2010 and 2021, and in Jamaica in 1692 and 1907, yet the Jamaica Passage segment has little known seismicity with no large historic events. The EPGF in the Passage follows a 2-3 km deep trough that is less oblique to the plate motion, and was imaged previously by the 2012 HAITI-SIS seismic cruise. We present the results of an NSF-funded RAPID cruise carried out in January 2022 to the Jamaica Passage, that investigated the EPGF with a hi-res multichannel seismic system collecting >650 km of data and 47 sediment cores. We observe prominent scarps along the EPGF consistent with large seismogenic displacements, and discovered widely distributed event deposits in the cores (McHugh et al. abstract). Imaged Neogene shortening structures verge southward, and are consistent with reactivation under compression. Shortening decreases from east to west. The Matley (eastern) and Navassa (central) sub-basins feature imbricate thrusting along their northern flanks, and the Morant (western) sub-basin features open folding flanked by unfolded sediments in its central part. At the depths imaged by our data, the strain is mostly partitioned: The EPGF is sub-vertical with no consistent vertical offsets, thus accounting for only sinistral motion sub-parallel to the fault, while shortening is directed across the basins. Structures point to two distinct stress components: a regional one that drives transpression, and a spatially variable one close to the EPGF, possibly in response to minor bends along this fault. Extensional and contractional structures are superimposed at distinct times on the north flank of the EPGF, as expected of a fault that translates relative to the causative fault bends. This is an important feature related to the major fault bend west of the Morant Basin, marking the transition between the Passage and the Jamaica segment of the EPGF. The results will help us better understand the tectonics of the region and its earthquake history, and to assess the hazard for future events.more » « less
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ABSTRACT 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 experiment 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.more » « less
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How structural segment boundaries modulate earthquake behavior is an important scientific and societal question, especially for the Wasatch fault zone (WFZ) where urban areas lie along multiple fault segments. The extent to which segment boundaries arrest ruptures, host moderate magnitude earthquakes, or transmit ruptures to adjacent fault segments is critical for understanding seismic hazard. To help address this outstanding issue, we conducted a paleoseismic investigation at the Traverse Ridge paleoseismic site (TR site) along the ∼7-km-long Fort Canyon segment boundary, which links the Provo (59 km) and Salt Lake City (40 km) segments of the WFZ. At the TR site, we logged two trenches which were cut across sub-parallel traces of the fault, separated by ∼175 m. Evidence from these exposures leads us to infer that at least 3 to 4 earthquakes have ruptured across the segment boundary in the Holocene. Radiocarbon dating of soil material developed below and above fault scarp colluvial packages and within a filled fissure constrains the age of the events. The most recent event ruptured the southern fault trace between 0.2 and 0.4 ka, the penultimate event ruptured the northern fault trace between 0.6 and 3.4 ka, and two prior events occurred between 1.4 and 6.2 ka (on the southern fault trace) and 7.2 and 8.1 ka (northern fault trace). Colluvial wedge heights of these events ranged from 0.7 to 1.2 m, indicating the segment boundary experiences surface ruptures with more than 1 m of vertical displacement. Given these estimates, we infer that these events were greater than Mw 6.7, with rupture extending across the entire segment boundary and portions of one or both adjacent fault segments. The Holocene recurrence of events at the TR site is lower than the closest paleoseismic sites at the adjacent fault segment endpoints. The contrasts in recurrence rates observed within 15 km of the Fort Canyon fault segment boundary may be explained conceptually by a leaky segment boundary model which permits spillover events, ruptures centered on the segment boundary, and segmented ruptures. The TR site demonstrates the utility of paleoseismology within segment boundaries which, through corroboration of displacement data, can demonstrate rupture connectivity between fault segments and test the validity of rupture models.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1130/G52258.1
