scholarly journals Vertical tectonic motions in the Lesser Antilles: linking short- and long-term observations

2021 ◽  
Author(s):  
Elenora van Rijsingen ◽  
Eric Calais ◽  
Romain Jolivet ◽  
Jean-Bernard de Chabalier ◽  
Richard Robertson ◽  
...  
Keyword(s):  
Historical Earthquakes ◽  
Lesser Antilles ◽  
Accretionary Wedge ◽  
South American ◽  
Slab Geometry ◽  
The North ◽  
Tectonic Erosion ◽  
Interseismic Coupling ◽  
Short And Long Term ◽  
Gps Velocities

<p>Horizontal GPS velocities show that the Lesser Antilles subduction zone is currently experiencing low interseismic coupling, meaning that little to no elastic strain is building up as the North- and South American plates subduct beneath the Caribbean plate. However, geological data on Quaternary coral terraces and active micro-atolls in the central part of the arc reveal slow subsidence over the past 125,000 to 100 years, likely tectonic in origin. It has been proposed that coupling along the subduction interface could be responsible for this geological subsidence. We use forward elastic models with a realistic slab geometry to show that a locked subduction interface would actually produce uplift of the island arc, which contradicts these geological observations. We also show that vertical GPS data in the Lesser Antilles indicates a subsidence of 1-2 mm/yr of the entire arc. This short-term subsidence is in agreement with the ~100-year trend of 1.1 mm/yr subsidence derived from coral micro-atolls in eastern Martinique. Since locking of the subduction interface is inconsistent with this observed subsidence of the arc, we explore other mechanisms that could this observation, such as postseismic effects of historical earthquakes, slab retreat, tectonic erosion, accretionary wedge collapse or extension in the overriding plate. </p>

Frontal accretionary wedge structure from seismic reflection imaging in the Lesser Antilles, Guadeloupe-Antigua sector

2020 ◽  
Author(s):  
Lianjun Li ◽  
Hélène Carton ◽  
Nathalie Feuillet ◽  
Gaëlle Bénâtre ◽  
Yaocen Pan
Keyword(s):  
Seismic Data ◽  
Plate Boundary ◽  
Lesser Antilles ◽  
Accretionary Wedge ◽  
Northern Flank ◽  
The North ◽  
Air Gun ◽  
Data Compilation ◽  
Splay Faults ◽  
The Time Domain

<p>The Lesser Antilles Subduction Zone (LASZ), forming the plate boundary between North and South American plates and the Caribbean plate, has not produced any recent large instrumentally recorded thrust earthquake. The 1843 earthquake event (~M<sub>w</sub> 8.5) located offshore Guadeloupe is possibly subduction thrust related. Previous studies in the north-central LASZ based on active source seismic data have examined the overall configuration of the forearc domain, especially the geometry of the backstop and effect of subducted oceanic ridges. However, the detailed architecture of the accretionary wedge is still poorly known, as are wedge structures like splay faults that may host slip during future megathrust ruptures. In this study, we use selected re-processed deep multichannel seismic (MCS) profiles from the SISMANTILLES surveys (2001, 2007) and higher-resolution MCS profiles from the CASEIS survey (2016) complemented by a bathymetric data compilation. Analysis of this combined dataset yields a more comprehensive characterization of the accretionary wedge offshore Guadeloupe and reveals features that had not been previously described in this area.</p><p>The time-domain seismic data processing sequences was performed on selected MCS profiles from the SISMANTILLES surveys (profiles H, I and K) to mitigate the strong background noises and the ringy effect from the single-bubble air-gun source. The reprocessed images clearly show the presence of arcward-dipping splay faults extending from décollement to the seafloor. The most prominent one roughly delineates a boundary between the more topographically elevated inner wedge and the less-elevated frontal domain of the accretionary wedge. We estimate an along-strike (N-S) extent of ~168 km for the identified splay faults, between 16°12′N and 17°21′N; their northward continuation is then disturbed by the subducting Barracuda Ridge. In the vicinity of the northern flank of the Barracuda Ridge, landward of the deformation front, we observe a duplex-type structure above the décollement. Its geometry is reminiscent of the initial stage of the development of underplating duplexes as observed in analog models. We suggest that the evolution of such underplating basal duplex may result from the increase in friction due to the subduction of Barracuda Ridge and the increase in sedimentary loading on its northern flank. This observation highlights the complex role played by the Barracuda Ridge on the shaping and deformation of the frontal prism.</p>

Seismogenic behaviour in the Lesser Antilles: Insights from geodetic observations

2020 ◽  
Author(s):  
Elenora van Rijsingen ◽  
Eric Calais ◽  
Romain Jolivet ◽  
Jean-Bernard de Chabalier ◽  
Jorge Jara ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Temporal Distribution ◽  
Historical Earthquakes ◽  
Lesser Antilles ◽  
Model Parameters ◽  
Megathrust Earthquakes ◽  
Interseismic Coupling ◽  
Actual Degree ◽  
Block Models ◽  
Gps Time Series

<p>The Lesser Antilles subduction zone is a challenging region when it comes to unravelling its seismogenic behaviour. Over the last century, it has been seismically quiet, with no large thrust events recorded, leading to the question whether this subduction zone is able to produce large interplate earthquakes or not. The slow subduction velocity of ~20 mm/yr complicates this even further, as mega-earthquake recurrence times would be up to many hundreds of years in the case of a fully locked subduction interface, and up to several thousands of years for a partially locked interface. The record of two large historical earthquakes, a M ~8 in 1839 and M ~8.5 in 1843, is often referred to as evidence supporting the seismic character of the Lesser Antilles subduction zone. It remains, however, questionable whether these events actually occurred along the subduction interface.</p><p>Here we use GPS data acquired on various islands within the Antilles to infer interseismic coupling along the Lesser Antilles Arc. Previous block models have suggested low coupling of the subduction interface, making the occurrence of large megathrust earthquakes less likely. However, the non-uniqueness of these inversions, as well as uncertainties related to the distance between GPS stations and the subduction trench, cast doubts on how well the inferred coupling represents the actual degree of locking along the subduction interface. In this study, we attempt to improve these estimates, by using a Bayesian approach to derive a meaningful set of uncertainties on the distribution of interseismic coupling. By exploring the entire range of model parameters, we are able to provide a probabilistic estimate of interseismic coupling. To further improve our analysis with respect to previous models, we incorporate a layered elastic structure, as well as a more realistic fault geometry, testing two different slab models.</p><p>Our results suggest that the subduction interface of the Lesser Antilles subduction zone is most likely to be uncoupled. A sensitivity analysis highlights the deeper part of the interface (i.e., 30-60 km depth) as the region with higher sensitivity, since the GPS stations are distributed mostly above that portion of the subduction. A test regarding the proposed 1843 rupture contour reveals that this area is very unlikely to be locked. This apparent aseismic character of the Lesser Antilles raises questions about the role of slow slip along the interface. We therefore also analyse GPS time series to assess the spatial and temporal distribution of transient deformation signals in the region.</p>

Diversification of the North American Doellingeria-Eucephalus Clade (Astereae: Asteraceae) Inferred from Molecular and Morphological Evidence

2019 ◽  
Vol 44 (4) ◽  
pp. 930-942
Author(s):  
Geraldine A. Allen ◽  
Luc Brouillet ◽  
John C. Semple ◽  
Heidi J. Guest ◽  
Robert Underhill
Keyword(s):  
North American ◽  
Sequence Data ◽  
Phylogenetic Analyses ◽  
Sister Group ◽  
Morphological Evidence ◽  
South American ◽  
New Combinations ◽  
The North ◽  
Hybridization Event ◽  
Ancient Hybridization

Abstract—Doellingeria and Eucephalus form the earliest-diverging clade of the North American Astereae lineage. Phylogenetic analyses of both nuclear and plastid sequence data show that the Doellingeria-Eucephalus clade consists of two main subclades that differ from current circumscriptions of the two genera. Doellingeria is the sister group to E. elegans, and the Doellingeria + E. elegans subclade in turn is sister to the subclade containing all remaining species of Eucephalus. In the plastid phylogeny, the two subclades are deeply divergent, a pattern that is consistent with an ancient hybridization event involving ancestral species of the Doellingeria-Eucephalus clade and an ancestral taxon of a related North American or South American group. Divergence of the two Doellingeria-Eucephalus subclades may have occurred in association with northward migration from South American ancestors. We combine these two genera under the older of the two names, Doellingeria, and propose 12 new combinations (10 species and two varieties) for all species of Eucephalus.

RESOLVING SOURCE-TO-SINK DYNAMICS BY MULTI-PROXY DATA FROM THE NORTH AND SOUTH AMERICAN CONTINENTAL SEDIMENTARY ARCHIVES

2020 ◽  
Author(s):  
Barbara Carrapa ◽  
◽  
Andrea Stevens Goddard ◽  
Scott Meek ◽  
Peter G. DeCelles
Keyword(s):  
South American ◽  
Proxy Data ◽  
The North ◽  
Source To Sink ◽  
North And South

scholarly journals Distribution of interseismic coupling along the North and East Anatolian Faults inferred from InSAR and GPS data

2020 ◽  
Author(s):  
Quentin Bletery ◽  
Cavalié Olivier ◽  
Jean Mathieu Nocquet ◽  
Théa Ragon
Keyword(s):  
Gps Data ◽  
The North ◽  
Interseismic Coupling

scholarly journals Regionally extinct species rediscovered: the bush dog Speothos venaticus in Minas Gerais, south-eastern Brazil

Oryx ◽  
2014 ◽  
Vol 49 (1) ◽  
pp. 60-63 ◽  
Author(s):  
Guilherme Braga Ferreira ◽  
Marcelo Juliano Rabelo Oliveira ◽  
Rogério Cunha de Paula ◽  
Flávio Henrique Guimarães Rodrigues ◽  
Érica Daniele Cunha Carmo
Keyword(s):  
Protected Areas ◽  
Minas Gerais ◽  
The State ◽  
South American ◽  
North West ◽  
South Eastern ◽  
The North ◽  
Eastern Brazil ◽  
Bush Dog ◽  
Speothos Venaticus

AbstractThe bush dog Speothos venaticus, a rare Near Threatened South American canid that lives in packs, was thought to be extinct in Minas Gerais state, south-eastern Brazil, until recently. Here, we report four recent records of the species in Minas Gerais, the first in the state since the description of the species in 1842. All records are from the Cerrado ecosystem in the north and north-west of the state; two are from animals found dead, one from footprints and another from a camera trap. Three of the records were inside or close (< 10 km) to strict protected areas, in a region recognized as the Protected Areas Mosaic Sertão Veredas–Peruaçu, where we expect any new records of the bush dog to be found. We discuss the low probability of detecting the bush dog and the main regional threats to the species, and emphasize the need to protect large and interconnected natural areas and keep them free of domestic dogs to avoid the extinction of the bush dog in Minas Gerais.

Inversion of regional surface-wave spectra for source parameters of aftershocks from the 1992 Petrolia earthquake sequence

1995 ◽  
Vol 85 (3) ◽  
pp. 705-715
Author(s):  
Mark Andrew Tinker ◽  
Susan L. Beck
Keyword(s):  
Surface Wave ◽  
Focal Mechanism ◽  
Source Parameters ◽  
Strike Slip ◽  
Earthquake Sequence ◽  
Fault System ◽  
Accretionary Wedge ◽  
Wave Spectra ◽  
The North ◽  
Gorda Plate

Abstract Regional distance surface waves are used to study the source parameters for moderate-size aftershocks of the 25 April 1992 Petrolia earthquake sequence. The Cascadia subduction zone had been relatively seismically inactive until the onset of the mainshock (Ms = 7.1). This underthrusting event establishes that the southern end of the North America-Gorda plate boundary is seismogenic. It was followed by two separate and distinct large aftershocks (Ms = 6.6 for both) occurring at 07:41 and 11:41 on 26 April, as well as thousands of other small aftershocks. Many of the aftershocks following the second large aftershock had magnitudes in the range of 4.0 to 5.5. Using intermediate-period surface-wave spectra, we estimate focal mechanisms and depths for one foreshock and six of the larger aftershocks (Md = 4.0 to 5.5). These seven events can be separated into two groups based on temporal, spatial, and principal stress orientation characteristics. Within two days of the mainshock, four aftershocks (Md = 4 to 5) occurred within 4 hr of each other that were located offshore and along the Mendocino fault. These four aftershocks comprise one group. They are shallow, thrust events with northeast-trending P axes. We interpret these aftershocks to represent internal compression within the North American accretionary prism as a result of Gorda plate subduction. The other three events compose the second group. The shallow, strike-slip mechanism determined for the 8 March foreshock (Md = 5.3) may reflect the right-lateral strike-slip motion associated with the interaction between the northern terminus of the San Andreas fault system and the eastern terminus of the Mendocino fault. The 10 May aftershock (Md = 4.1), located on the coast and north of the Mendocino triple junction, has a thrust fault focal mechanism. This event is shallow and probably occurred within the accretionary wedge on an imbricate thrust. A normal fault focal mechanism is obtained for the 5 June aftershock (Md = 4.8), located offshore and just north of the Mendocino fault. This event exhibits a large component of normal motion, representing internal failure within a rebounding accretionary wedge. These two aftershocks and the foreshock have dissimilar locations in space and time, but they do share a north-northwest oriented P axis.

scholarly journals A short introduction to historical earthquakes in Libya

2009 ◽  
Vol 47 (2-3) ◽  
Author(s):  
A. S. Suleiman ◽  
P. Albini ◽  
P. Migliavacca
Keyword(s):  
Historical Earthquakes ◽  
Historical Seismicity ◽  
Historical Sources ◽  
Short Introduction ◽  
North Central ◽  
The North ◽  
Lack Of Information ◽  
Macroseismic Effects ◽  
Instrumental Recording ◽  
Earthquake Effects

As a result of the relative motion of the African and European plates, Libya, located at the north central margin of the African continent, has experienced a considerable intraplate tectonism, particularly in its northern coastal regions. If the seismic activity of the last fifty years, at most, is known from instrumental recording, macroseismic effects of those earthquakes which affected Libya in the past centuries are still imperfectly known. To try and partly overcome this lack of information, in this contribution we present a short introduction to historical earthquakes in Libya, focusing on the period up to 1935. According to the studies published in the last twenty years, the earliest records of earthquakes in Libya are documented in the Roman period (3rd and 4th century A.D.). There is a gap in information along the Middle and Modern Ages, while the 19th and early 20th century evidence is concentrated on effects in Tripoli, in the western part of nowadays Libya. The Hun Graben area (western part of the Gulf of Sirt) has been identified as the location of many earthquakes affecting Libya, and it is in this area that the 19 April 1935 earthquake (Mw = 7.1) struck, followed by many aftershocks. Further investigations are needed, and some hints are here given at historical sources potentially reporting on earthquake effects in Libya. Their investigation could result in the needed improvement to lay the foundations of a database and a catalogue of the historical seismicity of Libya.

Sign in / Sign up

Export Citation Format

Share Document