scholarly journals Along‐Arc Heterogeneity in Local Seismicity across the Lesser Antilles Subduction Zone from a Dense Ocean‐Bottom Seismometer Network

2019 ◽  
Vol 91 (1) ◽  
pp. 237-247 ◽  
Author(s):  
Lidong Bie ◽  
Andreas Rietbrock ◽  
Stephen Hicks ◽  
Robert Allen ◽  
Jon Blundy ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Lesser Antilles ◽  
Seismogenic Zone ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Plate Interface ◽  
Local Seismicity ◽  
Slow Spreading ◽  
Lesser Antilles Arc

Abstract The Lesser Antilles arc is only one of two subduction zones where slow‐spreading Atlantic lithosphere is consumed. Slow‐spreading may result in the Atlantic lithosphere being more pervasively and heterogeneously hydrated than fast‐spreading Pacific lithosphere, thus affecting the flux of fluids into the deep mantle. Understanding the distribution of seismicity can help unravel the effect of fluids on geodynamic and seismogenic processes. However, a detailed view of local seismicity across the whole Lesser Antilles subduction zone is lacking. Using a temporary ocean‐bottom seismic network we invert for hypocenters and 1D velocity model. A systematic search yields a 27 km thick crust, reflecting average arc and back‐arc structures. We find abundant intraslab seismicity beneath Martinique and Dominica, which may relate to the subducted Marathon and/or Mercurius Fracture Zones. Pervasive seismicity in the cold mantle wedge corner and thrust seismicity deep on the subducting plate interface suggest an unusually wide megathrust seismogenic zone reaching ∼65  km depth. Our results provide an excellent framework for future understanding of regional seismic hazard in eastern Caribbean and the volatile cycling beneath the Lesser Antilles arc.

Evolution of Caribbean subduction from P-wave tomography and plate reconstruction

2020 ◽  
Author(s):  
Robert Allen ◽  
Benedikt Braszus ◽  
Saskia Goes ◽  
Andreas Rietbrock ◽  
Jenny Collier ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Plate Boundary ◽  
P Wave ◽  
Lesser Antilles ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Equatorial Atlantic ◽  
The North ◽  
The Caribbean ◽  
Plate Reconstruction

<p>The Caribbean plate has a complex tectonic history, which makes it  particularly challenging to establish the evolution of the subduction zones at its margins. Here we present a new teleseismic P-wave tomographic model under the Antillean arc that benefits from ocean-bottom seismometer data collected in our recent VoiLA (Volatile Recycling in the Lesser Antilles) project. We combine this imagery with a new plate reconstruction that we use to predict possible slab positions in the mantle today. We find that upper mantle anomalies below the eastern Caribbean correspond to a stack of material that was subducted at different trenches at different times, but ended up in a similar part of the mantle due to the large northwestward motion of the Americas. This stack comprises: in the mantle transition zone, slab fragments that were subducted between 70 and 55 Ma below the Cuban and Aves segments of the Greater Arc of the Caribbean; at 450-250 km depth, material subducted between 55 and 35 Ma below the older Lesser Antilles (including the Limestone Caribees and Virgin Islands);  and above 250 km, slab from subduction between 30 and 0 Ma below the present Lesser Antilles to Hispaniola Arc. Subdued high velocity anomalies in the slab above 200 km depth coincide with where the boundary between the equatorial Atlantic and proto-Caribbean subducted, rather than as previously proposed, with the North-South American plate boundary. The different phases of subduction can be linked to changes in the age, and hence buoyancy structure, of the subducting plate.</p>

A Significant Increase in Interplate Seismicity near Major Historical Earthquakes Offshore Martinique (FWI)

2021 ◽  
Author(s):  
Jordane Corbeau ◽  
O’Leary Gonzalez ◽  
Nathalie Feuillet ◽  
Anne-Marie Lejeune ◽  
Fabrice R. Fontaine ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Plate Boundary ◽  
Historical Earthquakes ◽  
Seismogenic Zone ◽  
Plate Interface ◽  
Seismicity Rate ◽  
Rupture Area ◽  
Interplate Seismicity ◽  
Statistical Studies

ABSTRACT Understanding the processes that may be at the origin of major earthquakes in subduction zones is highly challenging, especially in the case of slowly converging areas such as the Lesser Antilles subduction zone. Our study reveals a recorded increase in seismicity rate and cumulative seismic moment over the last two decades offshore Martinique island and, particularly, in the presumed rupture area of the major historical 1839 earthquake. This sustained seismicity is shared between extensive intermediate depth activity since the 2007 Mw 7.4 earthquake that occurred about 20 km north of Martinique and a compressive seismic cluster located in the seismogenic zone of the subduction zone. We also observe a downward migration of the seismicity along the plate interface up to a 60–65 km depth and a recorded increase in the magnitudes of the earthquakes. All these observations may indicate ongoing changes along the plate boundary interface near the area of the historical major rupture of 1839, although more detailed statistical studies and additional data are necessary to confirm this trend.

Migration-Based Local Event-Location Workflow for Ocean-Bottom Seismometer (OBS) Records in Subduction Zones: A Practical Approach for Addressing a Large Number of Events

2021 ◽  
Author(s):  
Shinji Yoneshima ◽  
Kimihiro Mochizuki
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Real Data ◽  
Japan Trench ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
S Waves ◽  
Local Earthquakes ◽  
Ocean Bottom Seismometers ◽  
Event Location

ABSTRACT An efficient event-location workflow is highly desired to analyze large numbers of local earthquakes recorded by ocean-bottom seismometers (OBSs) in subduction zones. The present study proposes a migration-based event-location approach for evaluating OBS records to examine local subduction-zone earthquakes. This approach can significantly reduce the amount of manual time picks compared with conventional methods. The event-location workflow was designed to detect arrival onsets of both P and S phases. Synthetic tests have shown that the proposed migration-based event-location method is robust against different types of noise, such as environmental noise and local spike noise. This workflow was then applied to real OBS data in the off-Ibaraki region at the southern end of the Japan trench. The results show that this approach is applicable to real data from subduction-zone events: It gives reasonable agreement with manual time picks for both P and S waves and reasonable error bars, and it demonstrates a clear down-dip trend of seismicity. The results also show fair agreement with event distributions from previous studies of the off-Ibaraki region. This proposed workflow can be used to examine the seismicity of local earthquakes around the subduction zone using OBSs. This approach is especially effective when the seismicity is high and/or in cases in which long-term OBS monitoring has recorded a large number of events.

Subduction zone heterogeneity observed across the magnitude spectrum for megathrust earthquakes

2021 ◽  
Author(s):  
Susan Bilek ◽  
Emily Morton
Keyword(s):  
Spatial Heterogeneity ◽  
Subduction Zone ◽  
Stress Drop ◽  
Subduction Zones ◽  
Cascadia Subduction Zone ◽  
Ocean Bottom ◽  
Small Earthquake ◽  
Megathrust Earthquakes ◽  
Seismic Slip ◽  
Subduction Zone Earthquakes

<p>Observations from recent great subduction zone earthquakes highlight the influence of spatial geologic heterogeneity on overall rupture characteristics, such as areas of high co-seismic slip, and resulting tsunami generation.  Defining the relevant spatial heterogeneity is thus important to understanding potential hazards associated with the megathrust. The more frequent, smaller magnitude earthquakes that commonly occur in subduction zones are often used to help delineate the spatial heterogeneity.  Here we provide an overview of several subduction zones, including Costa Rica, Mexico, and Cascadia, highlighting connections between the small earthquake source characteristics and rupture behavior of larger earthquakes.  Estimates of small earthquake locations and stress drop are presented in each location, utilizing data from coastal and/or ocean bottom seismic stations.  These seismicity characteristics are then compared with other geologic and geophysical parameters, such as upper and lower plate characteristics, geodetic locking, and asperity locations from past large earthquakes.  For example, in the Cascadia subduction zone, we find clusters of small earthquakes located in regions of previous seamount subduction, with variations in earthquake stress drop reflecting potentially disrupted upper plate material deformed as a seamount passed.  Other variations in earthquake location and stress drop can be correlated with observed geodetic locking variations. </p>

scholarly journals Isotopic Compositions of Plagioclase From Plutonic Xenoliths Reveal Crustal Assimilation Below Martinique, Lesser Antilles Arc

2021 ◽  
Vol 9 ◽  
Author(s):  
J. R. Brown ◽  
G. F. Cooper ◽  
G. M. Nowell ◽  
C. G. Macpherson ◽  
I. Neill ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Lesser Antilles ◽  
Sr Isotope ◽  
Crustal Assimilation ◽  
Arc Magmas ◽  
Isotopic Compositions ◽  
Mantle Sources ◽  
Show Evidence ◽  
Sediment Addition ◽  
Lesser Antilles Arc

The chemical and isotopic compositions of volcanic arc lavas often show evidence for involvement of a sedimentary component during magma genesis. Determining where this sedimentary component is added to arc magmas is of vital importance for constraining the extent to which sediments and volatiles are recycled at subduction zones. Lavas from Martinique in the Lesser Antilles arc have wide ranging isotopic compositions extending to highly radiogenic values (e.g. 87/Sr/86Sr up to ∼0.710) that could, in principle, be explained by sediment addition to the mantle source or by crustal assimilation in the upper plate. We use Sr isotopic compositions of plagioclase from Martinique plutonic xenoliths to provide evidence supporting the crustal assimilation hypothesis. Plagioclase from plutonic xenoliths formed in the mid-crust (∼12 km) show a restricted range of unradiogenic Sr isotope ratios (87Sr/86Sr = 0.7041–0.7042) whereas plagioclase from upper crustal plutonic xenoliths (∼6 km) show greater intra-sample variation and more radiogenic Sr isotopic compositions up to 87Sr/86Sr = 0.7047. This trend is also observed in plutonic xenolith whole rock 87Sr/86Sr. Combined, these results indicate that the range of Sr isotope compositions becomes larger and more radiogenic in Martinique magmas as a result of sediment assimilation at shallow crustal levels. This is supported by Assimilation-Fractional Crystallization modeling, which shows that assimilation of chemically and isotopically heterogenous crustal sediments can produce the isotopic variation in Martinique plutonic xenoliths and lavas. Our results highlight the importance of constraining crustal contributions from the upper plate before using arc lava geochemistry to quantify sediment and volatile recycling at subduction zones and assessing potential heterogeneity of arc mantle sources.

Warm thermal structures in subduction zones lead to ample dehydration at the depths of deep slow slip and tremor and resultant transformations in viscous rheology 

2021 ◽  
Author(s):  
Cailey Condit ◽  
Victor Guevara ◽  
Melodie French ◽  
Adam Holt ◽  
Jonathan Delph
Keyword(s):  
Subduction Zones ◽  
Thermal Structure ◽  
Fluid Pressure ◽  
Plate Boundary ◽  
Pore Fluid ◽  
Seismogenic Zone ◽  
Plate Interface ◽  
Dehydration Reactions ◽  
Episodic Tremor And Slip ◽  
Increased Strength

<p>Feedbacks amongst petrologic and mechanical processes along the subduction plate boundary play a central role influencing slip behaviors and deformation styles. Metamorphic reactions, resultant fluid production, deformation mechanisms, and strength are strongly temperature dependent, making the thermal structure of these zones a key control on slip behaviors.</p><p> </p><p>Firstly, we investigate the role of metamorphic devolatilization reactions in the production of Episodic Tremor and Slip (ETS) in warm subduction zones. Geophysical and geologic observations of ETS hosting subduction zones suggest the plate interface is fluid-rich and critically stressed, which together, suggests that this area is a zone of near lithostatic pore fluid pressure.  Fluids and high pore fluid pressures have been invoked in many models for ETS. However, whether these fluids are sourced from local dehydration reactions in particular lithologies, or via up-dip transport from greater depths remains an open question. We present thermodynamic models of the petrologic evolution of four lithologies typical of the plate interface along predicted pressure–temperature (P-T) paths for the plate boundary along Cascadia, Nankai, and Mexico which all exhibit ETS at depths between 25-65 km. Our models suggest that 1-2 wt% H<sub>2</sub>O is released at the depths of ETS along these subduction segments due to punctuated dehydration reactions within MORB, primarily through chlorite and/or lawsonite breakdown. These reactions produce sufficient in-situ fluid across this narrow P-T range to cause high pore fluid pressures. Punctuated dehydration of oceanic crust provides the dominant source of fluids at the base of the seismogenic zone in these warm subduction margins, and up-dip migration of fluids from deeper in the subduction zone is not required to produce ETS-facilitating high pore fluid pressures. These dehydration reactions not only produce metamorphic fluids at these depths, but also result in an increased strength of viscous deformation through the breakdown of weak hydrous phases (e.g., chlorite, glaucophane) and the growth of stronger minerals (e.g., garnet, omphacite, Ca-amphibole). Lastly, we present preliminary data on viscosity along warm subduction paths showing the locations of these dehydration pulses correlate with viscosity increases in mafic lithologies along the shallow forarc.</p>

scholarly journals The Molybdenum Isotope System as a Tracer of Slab Input in Subduction Zones: An Example From Martinique, Lesser Antilles Arc

2017 ◽  
Vol 18 (12) ◽  
pp. 4674-4689 ◽  
Author(s):  
Richard M. Gaschnig ◽  
Christopher T. Reinhard ◽  
Noah J. Planavsky ◽  
Xiangli Wang ◽  
Dan Asael ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Lesser Antilles ◽  
Molybdenum Isotope ◽  
Isotope System ◽  
Lesser Antilles Arc
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