Imaging of subducted lithosphere beneath South America

Engdahl, E. R.; Hilst, Robert D. van der; Berrocal, Jesús

doi:10.1029/95gl02013

Cited by 76 publications

(48 citation statements)

References 11 publications

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“…The subhorizontally deflected slab seems to begin to descend deeper beyond the uppermost lower mantle. See Fukao et al (2001) for the earlier references for the Peruvian slab images including Engdahl et al (1995). Slab penetration is clearly imaged but subhorizontal deflection of the penetrated slab is less clear in a recent P-velocity model of Li et al (2008).…”

Section: Slab Signature In the Uppermost Lower Mantlementioning

confidence: 95%

Deep Earth Structure - Subduction Zone Structure in the Mantle Transition Zone

Fukao

Obayashi

2015

Treatise on Geophysics

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Section: Slab Signature In the Uppermost Lower Mantlementioning

confidence: 95%

Deep Earth Structure - Subduction Zone Structure in the Mantle Transition Zone

Fukao

Obayashi

2015

Treatise on Geophysics

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“…Composite E‐W profile of P wave anomalies. Top: map showing the location of the profile “3f” of Engdahl et al [1995] and the profile FF′ below. Shallow, intermediate, and deep earthquakes are shown by red circles, yellow squares, and white triangles, respectively (1964–1995 data of Engdahl et al [1998]).…”

Section: The Travel Time Inversionmentioning

confidence: 99%

Seismic velocity anomalies beneath SE Brazil from P and S wave travel time inversions

2003

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[1] We present the result from teleseismic travel time inversions for P and S wave data mainly recorded at portable broadband stations in SE Brazil. The stations were deployed at 45 sites within an area 1000 Â 1700 km during the years 1992-1999. More than 10,000 relative P and S wave arrival times, including core phases, were obtained from the waveforms using a new coherence functional. These P and S relative phase times are independently inverted for slowness perturbations, earthquake relocations, and station corrections. The final models represent the least amount of structure required to explain the residuals within a defined standard error. The robust and consistent features in the velocity anomaly models are interpreted and their resolution is tested with synthetic case inversions. We confirm the existence of a cylindrical low-velocity anomaly beneath the Paraná basin, which has been interpreted by VanDecar et al. [1995] as the fossil conduit through which the initial Tristan da Cunha plume head traveled to generate the Paraná -Etendeka flood basalts about 130 Ma. We now show that this low-velocity cylindrical structure seems to be confined to the upper mantle. Beneath the upper mantle, the velocity anomalies show a N-S oriented pattern, which we interpret as due to the Nazca plate subducted slab. At lithospheric depths, the Archean, southern part of the São Francisco craton, shows high velocities down to 200-300 km. All areas with Late Cretaceous postrift alkaline intrusions are characterized by low velocities at lithospheric depths.INDEX TERMS: 7218 Seismology: Lithosphere and upper mantle; 8180 Tectonophysics: Tomography; 9360 Information Related to Geographic Region: South America; KEYWORDS: seismic regional tomography, SE Brazil, Paranã-Etendeka flood basalts, Tristan da Cunha plume, subducted Nazca plate, alkaline intrusions Citation: Schimmel, M., M. Assumpção, and J. C. VanDecar, Seismic velocity anomalies beneath SE Brazil from P and S wave travel time inversions,

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“…Assuming that these high S velocities are caused predominantly by lower temperatures [Jordan, 1988] ] in this region and with results from James and Snoke [1990]. Teleseismic arrival time tomography shows more uniform resolving power below 100 km for the subducting Nazca plate [Engdahl et al, 1995;VanDecar et al, 1995b;Bijwaard et al, 1998] than our predominantly continental body and surface waveform tomography.…”

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confidence: 99%

Upper mantle S velocity structure of central and western South America

Lee¹,

James²,

Silver³

2001

J. Geophys. Res.

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Abstract. We have used broadband seismograms recorded at portable and permanent seismic stations in South America to image the three-dimensional S velocity stmcture beneath central and western South America. We have interactively fitted the waveforms of S and surface wave trains in >500 seismograms from 90 earthquakes and 60 different stations. The constraints on upper mantle S velocity structure provided by the waveform fits have been combined with independent estimates of depth to the Mohorovi•id discontinuity, yielding model SA99. The S velocity stmcture of SA99 reveals a highly heterogeneous upper mantle with a maximum peak to peak difference of 1 km/s above 100 km. The heterogeneity seems to be correlated with tectonic and geologic domains. SA99 shows high lithospheric S velocities for the Precambrian cratons. The Amazon basin is also undefiain by high S velocities, while three other intraplatform basins are undedain by low S velocities at various depths. SA99 shows extremely low velocities in the mantle wedge beneath the volcanically active Andes. We explain these low S velocities as originating from realistic amounts of volatiles, released by the subducting Nazca crest, and resulting amounts of partial melt within the peridotitic mantle wedge, without requiring elevated temperatures. While SA99 could be consistent with diffuse influx for comer flow in the mantle wedge, it does not support models that require influx of subcontinental upper mantle into the mantle wedge through a laterally uniform low-viscosity channel.

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Imaging of subducted lithosphere beneath South America

Cited by 76 publications

References 11 publications

Deep Earth Structure - Subduction Zone Structure in the Mantle Transition Zone

Deep Earth Structure - Subduction Zone Structure in the Mantle Transition Zone

Seismic velocity anomalies beneath SE Brazil from P and S wave travel time inversions

Upper mantle S velocity structure of central and western South America

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