Assessing the geodynamics of strongly arcuate subduction zones in the eastern Caribbean subduction setting

2020 ◽  
Author(s):  
Menno Fraters ◽  
Wim Spakman ◽  
Cedric Thieulot ◽  
Douwe Van Hinsbergen
Keyword(s):  
Stress Field ◽  
Subduction Zones ◽  
Focal Mechanisms ◽  
North American Plate ◽  
Plate Motion ◽  
Caribbean Region ◽  
The North ◽  
Eastern Caribbean ◽  
Subduction Setting ◽  
Subduction System

<p>The eastern Caribbean Lesser-Antilles subduction system is a strongly arcuate subduction system. We have investigated the dynamics of this system through numerical modelling, demonstrating the developed capabilities and computational feasibility for assessing the 3D complexity and geodynamics of natural subductionsystems and applied this to the eastern Caribbean region. We show the geodynamic feasibility of westward directed trench-parallel slab transport through the mantle, i.e. slab dragging, on the northern segment of the slab, while the eastern segment of the slab is subducting by a mantle-stationary trench. The resistance of the mantle against slab dragging by the North American plate motion, as well as the deformation associated with the arcuate geometry of the slab, creates a complex 3D stress field in the slab that deviates strongly from the classical view of slab-dip aligned orientation of slab stress. More generally this means that the process of slab dragging may reveal itself in the focal mechanisms of intermediate and deep earthquakes. The characteristics of the arcuate subduction such as slab dragging and a complex 3D stress field as studied in the Caribbean region can be more generically applied to other arcuate subduction systems as well, such as the Izu-Bonin-Marianas or the Aleutians-Alaskasystems, where anomalous focal mechanisms of slabs are observed.</p>

Fractures in the northern plains, stream patterns, and the midcontinent stress field

1987 ◽  
Vol 24 (6) ◽  
pp. 1086-1097 ◽  
Author(s):  
Mel R. Stauffer ◽  
Don J. Gendzwill
Keyword(s):  
Stress Field ◽  
Horizontal Stress ◽  
The Body ◽  
North American Plate ◽  
Plate Motion ◽  
Viscous Drag ◽  
Near Surface ◽  
The North ◽  
Elastic Rebound ◽  
Western North Dakota

Fractures in Late Cretaceous to Late Pleistocene sediments in Saskatchewan, eastern Montana, and western North Dakota form two vertical, orthogonal sets trending northeast–southwest and northwest–southeast. The pattern is consistent, regardless of rock type or age (except for concretionary sandstone). Both sets appear to be extensional in origin and are similar in character to joints in Alberta. Modem stream valleys also trend in the same two dominant directions and may be controlled by the underlying fractures.Elevation variations on the sub-Mannville (Early Cretaceous) unconformity form a rectilinear pattern also parallel to the fracture sets, suggesting that fracturing was initiated at least as early as Late Jurassic. It may have begun earlier, but there are insufficient data at present to extend the time of initiation.We interpret the fractures as the result of vertical uplift together with plate motion: the westward drift of North America. The northeast–southwest-directed maximum principal horizontal stress of the midcontinent stress field is generated by viscous drag effects between the North American plate and the mantle. Vertical uplift, erosion, or both together produce a horizontal tensile state in near-surface materials, and with the addition of a directed horizontal stress through plate motion, vertical tension cracks are generated parallel to that horizontal stress (northeast–southwest). Nearly instantaneous elastic rebound results in the production of second-order joints (northwest–southeast) perpendicular to the first. In this manner, the body of rock is being subjected with time to complex alternation of northeast–southwest and northwest–southeast horizontal stresses, resulting in the continuous and contemporaneous production of two perpendicular extensional joint sets.

scholarly journals Plate Motion and Earth Orientation

1988 ◽  
Vol 129 ◽  
pp. 363-364
Author(s):  
A. Mallama ◽  
M. Kao
Keyword(s):  
A Priori ◽  
Terrestrial Reference Frame ◽  
North American Plate ◽  
Plate Motion ◽  
Earth Orientation ◽  
Root Mean Square Residual ◽  
The North ◽  
Tectonic Motion ◽  
Analysis System ◽  
Simple Rotation

Earth orientation series are linked to the terrestrial reference frame in which the observing site locations are measured. The effect of tectonic motion is a simple rotation for any given plate, but the overall effect depends on the distribution of sites. The magnitude of this motion is large enough to be evident in the data. For example, the coefficient of rotation for the North American plate around the Earth's Y-axis is −0.8 millarcseconds per year in the AMO-2 plate motion model of Minster and Jordan. The VLBI analysis system at NASA/GSFC for computing earth orientation series has recently been enhanced by including the Minster and Jordan model for a priori tectonic effects. Tests indicate that the weighted-root-mean-square residual of observations to the solution is decreased by using this model.

Mapping mantle flows underneath the North American and Caribbean Plates

2021 ◽  
Author(s):  
Hejun Zhu
Keyword(s):  
North American ◽  
Subduction Zones ◽  
Current Model ◽  
Waveform Inversion ◽  
Body Waves ◽  
Plate Motion ◽  
Cascadia Subduction Zone ◽  
Fast Axis ◽  
The North ◽  
Short Period

<p>In this talk, I will present a new 3-D azimuthally anisotropic tomographic model, namely US32, for the North American and Caribbean Plates. This model is constrained by using seismic data from USArray and full waveform inversion. The inversion uses data from 180 regional earthquakes recorded by 4,516 seismographic stations, resulting in 586,185 frequency-dependent phase measurements. Three-component short-period body waves and long-period surface waves are combined to simultaneously constrain deep and shallow structures. The current azimuthally anisotropic model US32 is the result of 32 pre-conditioned conjugate-gradient iterations. In the current model, I observe a complex depth-dependent pattern for fast axis directions across the North American and Caribbean Plates.<span>  </span>At shallow depths, these fast axis directions delineate local geological provinces, such as the Snake River Plain, Cascadia subduction zone, Rio Grand Rift, etc. At greater depths, the fast axis directions follow the absolute plate motion trajectories at most places. At depths around 700 km, the fast axis directions are perpendicular to the strikes of the mapped Farallon slab, suggesting the presence of 2-D corner flows induced by this ancient subduction underneath the mantle transition zone. In addition, underneath the Cascadia and Cocos subduction zones at depths from 250 to 500 km, the fast axis directions suggest the presence of toroid-mode mantle flows, following the geometry of fast downwelling materials.</p>

scholarly journals The role of arc migration in the development of the Lesser Antilles: A new tectonic model for the Cenozoic evolution of the eastern Caribbean

Geology ◽  
2019 ◽  
Vol 47 (9) ◽  
pp. 891-895 ◽  
Author(s):  
R.W. Allen ◽  
J.S. Collier ◽  
A.G. Stewart ◽  
T. Henstock ◽  
S. Goes ◽  
...  
Keyword(s):  
Large Scale ◽  
Lesser Antilles ◽  
Caribbean Region ◽  
Tectonic Model ◽  
Continental Arc ◽  
Show Evidence ◽  
Geochemical Variations ◽  
Eastern Caribbean ◽  
Two Phases ◽  
Subduction System

Abstract Continental arc systems often show evidence of large-scale migration both toward and away from the incoming plate. In oceanic arc systems, however, while slab roll-back and the associated processes of backarc spreading and arc migration toward the incoming plate are commonplace, arc migration away from the incoming plate is rarely observed. We present a new compilation of marine magnetic anomaly and seismic data in order to propose a new tectonic model for the eastern Caribbean region that includes arc migration in both directions. We synthesized new evidence to show two phases of backarc spreading and eastward arc migration toward the incoming Atlantic. A third and final phase of arc migration to the west subdivided the earlier backarc basin on either side of the present-day Lesser Antilles arc. This is the first example of regional multidirectional arc migration in an intra-oceanic setting, and it has implications for along-arc structural and geochemical variations. The back and forth arc migrations were probably due to the constraints imposed by the neighboring American plates on this isolated subduction system, rather than variations in subducting slab buoyancy.

Seismicity and focal mechanisms of the Arctic region and the North American plate boundary in Asia

2015 ◽  
pp. 79-118 ◽  
Author(s):  
Kazuya Fujita ◽  
David B. Cook ◽  
Henry Hasegawa ◽  
David Forsyth ◽  
Robert Wetmiller
Keyword(s):  
North American ◽  
Plate Boundary ◽  
Arctic Region ◽  
Focal Mechanisms ◽  
North American Plate ◽  
The Arctic ◽  
The North ◽  
The Arctic Region

scholarly journals NASA/Crustal Dynamics Project Results: Tectonic Plate Motion Measurements with Mark-III VLBI

1988 ◽  
Vol 129 ◽  
pp. 339-340
Author(s):  
J. W. Ryan ◽  
T. A. Clark
Keyword(s):  
West Germany ◽  
Marshall Islands ◽  
North American Plate ◽  
Plate Motion ◽  
Eurasian Plate ◽  
Owens Valley ◽  
Tectonic Plate ◽  
African Plate ◽  
The North ◽  
Crustal Dynamics

The NASA Crustal Dynamics Project (CDP) has been using VLBI on intercontinental baselines to measure tectonic plate motions since 1979. We report on measurements between sites on the North American plate (Haystack/Westford, MA; Owens Valley and Mojave, CA; Ft. Davis, TX and Gilmore Creek, AK), the Eurasian plate (Onsala, Sweden; Wettzell, West Germany, and Shanghai, China), the Pacific plate (Kauai, HI; Kwajalein in the Marshall Islands, and Vandenberg AFB, CA), the African plate (Hartebesthoek, RSA), and Japan (Kashima).

Complexity measures and variability of the seismicity monitored whithin the Mexican flat slab before the main shock occurred on 19 September 2017

2020 ◽  
Author(s):  
Alejandro Ramírez-Rojas ◽  
Elsa Leticia Flores-Márquez
Keyword(s):  
North America ◽  
Subduction Zones ◽  
Main Shock ◽  
Plate Boundary ◽  
North American Plate ◽  
Cocos Plate ◽  
Complexity Measures ◽  
Flat Slab ◽  
The North ◽  
Natural Time

<p>Several subduction zones exists in Earth, which have a more or less known dynamic, however each of them has its particularities, as in the case of the Mexican subduction zone, where the flat slab is of special interest. The present flat-slab area is located along the central part of the Cocos-North America plate boundary that the convergence rate between Cocos and North America. The Cocos plate is a remnant of the large Farallon plate, which began to split into smaller plates since 28 Myr ago approximately, when the East Pacific Rise began to interact with the North American Plate. Within such flat slab could be trigger large and destructives earthquakes like the main shock occurred close to Mexico City on September 19, 2017. In this work, we analyze, under the natural time domain, the seismicity registered within the Mexican flat slab since 1995 until the main shock occurred on September 19, 2017. We analyzed the fluctuations of order parameter for seismicity in order to provide some complex measures defined on natural time. Our analysis reveals a possible precursor measure switching on a few weeks before the main shock.  Also we have observed that in the flat slab region the number of earthquakes recorded is lesser than those observed along the total south Pacific Mexican coast.</p>

scholarly journals Population recovery changes population composition at a major southern Caribbean juvenile developmental habitat for the green turtle, Chelonia mydas

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jurjan P. van der Zee ◽  
Marjolijn J. A. Christianen ◽  
Mabel Nava ◽  
Ximena Velez-Zuazo ◽  
Wensi Hao ◽  
...  
Keyword(s):  
Green Turtle ◽  
Chelonia Mydas ◽  
Caribbean Region ◽  
Population Composition ◽  
Temporal Shift ◽  
The North ◽  
Southern Caribbean ◽  
Western Caribbean ◽  
Eastern Caribbean ◽  
North Western

Abstract Understanding the population composition and dynamics of migratory megafauna at key developmental habitats is critical for conservation and management. The present study investigated whether differential recovery of Caribbean green turtle (Chelonia mydas) rookeries influenced population composition at a major juvenile feeding ground in the southern Caribbean (Lac Bay, Bonaire, Caribbean Netherlands) using genetic and demographic analyses. Genetic divergence indicated a strong temporal shift in population composition between 2006–2007 and 2015–2016 (ϕST = 0.101, P < 0.001). Juvenile recruitment (<75.0 cm straight carapace length; SCL) from the north-western Caribbean increased from 12% to 38% while recruitment from the eastern Caribbean region decreased from 46% to 20% between 2006–2007 and 2015–2016. Furthermore, the product of the population growth rate and adult female abundance was a significant predictor for population composition in 2015–2016. Our results may reflect early warning signals of declining reproductive output at eastern Caribbean rookeries, potential displacement effects of smaller rookeries by larger rookeries, and advocate for genetic monitoring as a useful method for monitoring trends in juvenile megafauna. Furthermore, these findings underline the need for adequate conservation of juvenile developmental habitats and a deeper understanding of the interactions between megafaunal population dynamics in different habitats.

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