Global‐scale analysis of the mantle <i>Pds</i> phases

Chevrot, Sébastien; Vinnik, Lev; Montagner, Jean‐Paul

doi:10.1029/1999jb900087

Cited by 159 publications

(193 citation statements)

References 63 publications

(6 reference statements)

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“…model (Kennett and Engdahl, 1991) and repeated in the global study of Chevrot et al (1999). This suggests that the 410 and 660 km discontinuities beneath Kimberley occur very close to their namesake depth, i.e.…”

Section: Transition Zone Thickness and Wavespeedmentioning

confidence: 95%

“…In a global study, Chevrot et al (1999) found this time difference to vary between 41.8 and 48.7 s. This spread can be largely explained by lateral velocity variations in the upper mantle (that is, at depth < 400 km). They found that most of the observed times between 41.8 and 43.0 s are for stations located on Precambrian cratons.…”

Section: The 410 520 and 660 Km Discontinuitiesmentioning

confidence: 99%

“…Teleseismic seismograms are projected on the L, Q, and T axes, where L is along the principal motion direction, Q is comprised in the vertical direction and normal to L, and the transverse component, T is normal to both L and Q (Chevrot et al, 1999), and should not contain significant amounts of energy-if it does, there is a strong possibility there was a problem with the seismometer when the event was recorded. The components are then deconvolved by the principal component of the P-wave measured for a single event at all available stations.…”

Section: Methodsmentioning

confidence: 99%

“…To observe converted Ps and other secondary phases we used a technique introduced by Vinnik (1977), which was also used in the global-scale analysis of Chevrot et al (1999). Teleseismic seismograms are projected on the L, Q, and T axes, where L is along the principal motion direction, Q is comprised in the vertical direction and normal to L, and the transverse component, T is normal to both L and Q (Chevrot et al, 1999), and should not contain significant amounts of energy-if it does, there is a strong possibility there was a problem with the seismometer when the event was recorded.…”

Section: Methodsmentioning

confidence: 99%

“…In their global study of Ps phases, Chevrot et al (1999) found that most P 660 s move-out corrected (with a reference slowness of 6.4 s/degree) phases arrive between 65.6 and 72.7 s after the direct P-wave. The iasp91 model predicts it at 68.0 s. The arrivals in this study were even less clear then those of P 410 s, with only 15 of the stations registering convincing peaks near the expected time.…”

Section: The 410 520 and 660 Km Discontinuitiesmentioning

confidence: 99%

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Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

Stankiewicz

Chevrot

Hilst

et al. 2002

Physics of the Earth and Planetary Interiors

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The technique of receiver function analysis is applied to the study of crustal and upper mantle structures beneath the Kaapvaal craton in southern Africa and its surroundings. Seismic data were recorded by the seismic array of 82 sites deployed from April 1997 to April 1999 across southern Africa, as well as a dense array of 32 sites near Kimberley, in operation from December 1998 to June 1999. Arrival times for phases converted at the Moho are used to determine crustal thickness. The Moho depth in the south-western section of the craton was found to vary between 37 and 40 km, except for one station that recorded a depth of 43 km (SA23). Farther north along the western block of the craton (into Botswana) the depth increases up to 43 km. The depth increases even further in the north-eastern section of the craton, where results vary from 40 to 52 km. Just north of the Kaapvaal craton, in the neighbouring Zimbabwe craton, the crustal thickness drops significantly. The results obtained there varied from 36 to 40 km. For the Kimberley area, using the dense array, the Moho depth was found to be 37.3 km. Arrivals of the Ps and Ppps phases were used to determine the Poisson's ratio in the region. This was found to be 0.26 ± 0.01. Arrivals of phases from the 410 and 660 km mantle discontinuities are used to interpret the relative positions of these discontinuities, as well as for comparison of mantle temperatures and seismic velocities in the region with global averages. In the Kimberley area the 410 and 660 km discontinuities were found at their expected depth, implying that mantle temperatures in the region are close to the global average. The seismic velocities above the '410' were found up to 5% faster than the averages from the global iasp91 model, which is fast even by Precambrian standards. In other sections of the Kaapvaal craton, the velocities are also faster than global averages, but not as fast as beneath Kimberley. In these sections, the '410' is also slightly elevated, while the '660' is depressed, which implies a slightly lower mantle temperature relative to the global average. Beneath the Kaapvaal craton we find evidence suggesting the presence of a zone with a reduced wavespeed gradient at an upper bound of approximately 300 km, which may mark the lower chemical boundary of the craton.

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Section: Transition Zone Thickness and Wavespeedmentioning

confidence: 95%

Section: The 410 520 and 660 Km Discontinuitiesmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: The 410 520 and 660 Km Discontinuitiesmentioning

confidence: 99%

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Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

Stankiewicz

Chevrot

Hilst

et al. 2002

Physics of the Earth and Planetary Interiors

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The mantle transition zone beneath West Antarctica: Seismic evidence for hydration and thermal upwellings

Emry

Nyblade

Julià

et al. 2015

Geochem Geophys Geosyst

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Although prior work suggests that a mantle plume is associated with Cenozoic rifting and volcanism in West Antarctica, the existence of a plume remains conjectural. Here we use P wave receiver functions (PRFs) from the Antarctic POLENET array to estimate mantle transition zone thickness, which is sensitive to temperature perturbations, throughout previously unstudied parts of West Antarctica. We obtain over 8000 high-quality PRFs using an iterative, time domain deconvolution method filtered with a Gaussian width of 0.5 and 1.0, corresponding to frequencies less than 0.24 and 0.48 Hz, respectively. Single-station and common conversion point stacks, migrated to depth using the AK135 velocity model, indicate that mantle transition zone thickness throughout most of West Antarctica does not differ significantly from the global average, except in two locations; one small region exhibits a vertically thinned (210 6 15 km) transition zone beneath the Ruppert Coast of Marie Byrd Land and another laterally broader region shows slight, vertical thinning (225 6 25 km) beneath the Bentley Subglacial Trench. We also observe the 520 discontinuity and a prominent negative peak above the mantle transition zone throughout much of West Antarctica. These results suggest that the mantle transition zone may be hotter than average in two places, possibly due to upwelling from the lower mantle, but not broadly across West Antarctica. Furthermore, we propose that the transition zone may be hydrated due to >100 million years of subduction beneath the region during the early Mesozoic.

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Crust beneath the northwestern Deccan Volcanic Province, India: Evidence for uplift and magmatic underplating

2015

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The northwestern Deccan Volcanic Province of India and its pericratonic rift basins were reactivated during different stages after the breakup of India from the Gondwanaland and collision with the Asian plate. In this study, we present results of crustal thickness and average crustal V p /V s ratios beneath this plume-affected region using common conversion point imaging and H-k stacking analysis of 6893 receiver functions using data from a network comprising 58 broadband seismic stations sited on diverse tectonic terrains. We find large variations in crustal thickness, with the Moho depths varying from 28 to 43 km in the Kachchh rift, 28 to 38 km in the Cambay rift, 39.5-41.5 km in the north and eastern parts of the Cambay rift, and 29 to 39 km in the Saurashtra region and South Gujarat. A Moho upwarp of 6 to 7 km in the Saurashtra region can be attributed to positive buoyancy and uplift due to thermal influx affected by the Reunion plume. High crustal V p /V s ratios beneath the Kachchh rift (1.8 to 2.05), coastal areas of Saurashtra (1.75 to 2.06), and North Gujarat (1.81 to 1.85) indicate dominance of a mafic/ultramafic crust. High regional heat flow, high electrical conductivity, large intracrustal S wave velocity reduction, and high average crustal Poisson's ratios are consistent with partial melt related to the process of magmatic underplating in the lower crust. At other stations, the crust appears to be felsic with V p /V s ratios in the range of 1.57 to 1.76.

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Global‐scale analysis of the mantle Pds phases

Abstract: Abstract.A

Cited by 159 publications

References 63 publications

Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

The mantle transition zone beneath West Antarctica: Seismic evidence for hydration and thermal upwellings

Crust beneath the northwestern Deccan Volcanic Province, India: Evidence for uplift and magmatic underplating

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