A 22° long seismic profile for the study of the top of D'

Freybourger, Marion; Achauer, U.

doi:10.1029/1999gl010827

Cited by 10 publications

(9 citation statements)

References 15 publications

(2 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We show PK d KP traveltimes for the model PWDK [ Davis and Weber , 1990] and a model (PSA1) that provides a slightly better fit to the data in Figure 4a due to smaller traveltime and slowness. PSA1 is similar to several other models of D″ in different regions of the Earth [ Young and Lay , 1987b; Gaherty and Lay , 1992; Sidorin et al , 1999; Freybourger et al , 1999]. The two models PWDK and PSA1 differ only slightly in the depth of the D″ discontinuity but strongly in regard to the velocity gradients.…”

Section: Traveltimessupporting

confidence: 71%

Detection of a D″ discontinuity in the south Atlantic using PKKP

Rost

Revenaugh

2003

Geophysical Research Letters

View full text Add to dashboard Cite

[1] A strong arrival in the early coda of major-arc PKKP ab is observed on recordings of earthquakes in the Banda Sea region from the short-period, small-aperture Yellowknife array. The arrival has a move-out close to PKKP ab with an average delay of $12 s. We show that the phase is most likely an underside reflection from a D 00 discontinuity above the PKKP reflection point at the core-mantle boundary beneath the southern Atlantic on the edge of the African superplume. Differential travel times between PKKP ab and PK d KP (the underside reflection at the D 00 discontinuity) is used to constrain potential D 00 velocity models. The high amplitude of PK d KP requires proximity to the b-caustic adding further velocity control. We find that a P-velocity model with a sharp positive velocity jump $280 km above the core-mantle boundary, and a negative velocity gradient closer to the core-mantle boundary, fits the data well.INDEX TERMS: 7207 Seismology: Core and mantle; 7200 Seismology; 8124 Tectonophysics: Earth's interiorcomposition and state (1212). Citation: Rost, S., and J. Revenaugh, Detection of a D 00 discontinuity in the south

show abstract

Section: Traveltimessupporting

confidence: 71%

Detection of a D″ discontinuity in the south Atlantic using PKKP

Rost

Revenaugh

2003

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…The variations in depth of the discontinuity are uncertain due to the lack of constraint on velocity above and below the discontinuity, but some variation appears to exist. Thin high-velocity or low-velocity lamella models appear to fit some P-wave observations at least as well as first-order velocity discontinuity models (Freybourger et al, 1999;Thomas et al, 1998;Weber, 1994), but this has not been demonstrated convincingly for S-wave observations. It has been argued that the D 00 discontinuities are actually globally extensive, with lateral variations in depth and strength being the result of lateral temperature variations and interactions with upwelling and downwelling flow (e.g., Nataf and Houard, 1993;Sidorin et al, 1998Sidorin et al, , 1999.…”

Section: Seismic Wave Triplicationsmentioning

confidence: 89%

“…The reflector that produces this extra arrival varies globally in depth by several Depth (km) Figure 6 Radial profiles of S-wave velocity in the lowermost mantle: PREM (Dziewonski and Anderson, 1981), SLHE, SLHA (Lay and Helmberger, 1983a), SYL1 (Young and Lay, 1987a), SGHP (Garnero et al, 1988), SWDK (Weber and Davis, 1990), SYLO (Young and Lay, 1990), and SGLE (Gaherty and Lay, 1992). hundred kilometers (e.g., Kendall and Shearer, 1994) and appears to have regional-scale lateral variations of on the order of a hundred kilometers that may produce scattering rather than simple reflections (e.g., Emery et al, 1999;Freybourger et al, 1999;Hutko et al, 2006;Krü ger et al, 1995;Lay et al, 1997Lay et al, , 2004aScherbaum et al, 1997;Thomas et al, 2004a,b;Weber, 1993;Yamada and Nakanishi, 1998). Shear velocity increases of 2.5-3.0% are found in regions under Eurasia (SWDK and SGLE), Alaska (SYLO), Central America (SLHA), the Indian Ocean (SYL1), and the central Pacific (SGHP).…”

Section: Seismic Wave Triplicationsmentioning

confidence: 99%

Deep Earth Structure: Lower Mantle and D″

Lay

2015

Treatise on Geophysics

View full text Add to dashboard Cite

“…Siberia is not entirely unexplored in terms of lower mantle and CMB structure. The lowermost mantle under Siberia has been examined in several studies of earthquake P wave data from the Pacific subduction zones recorded at various sites in western Europe [ Weber and Davis , 1990; Gaherty and Lay , 1992; Weber , 1993; Thomas and Weber , 1997; Thomas et al , 1998; Freybourger et al , 1999, 2001; Thomas et al , 2002]. The reflection points for PcP are clustered around 80°E mostly under Siberia and the Kara Sea, east of the trace of the Ural Mountains and north of the location of the Peaceful Nuclear Explosion profiles.…”

Section: Introductionmentioning

confidence: 99%

Reflection seismic profiles of the core‐mantle boundary

2004

View full text Add to dashboard Cite

[1] High amplitude, high frequency, and laterally coherent seismic phases from the coremantle boundary (CMB) are observed on data from Peaceful Nuclear Explosions in Siberia. These arrivals are observed at 2600-4000 km offset with travel times and moveouts consistent with CMB reflections (PcP) and are readily correlated because of the small station interval of 10 km. The duration and complexity of the arrivals are inconsistent with a simple reflection from a single CMB interface. They require the combination of PcP and a complex precursor phase (PdP) from the top of an ultralowvelocity zone (ULVZ) despite the fact that earthquake recordings indicate that there is no ULVZ present beneath this part of Siberia. Lateral variations in the waveform imply that the thickness and physical properties of the ULVZ change with a wavelength of 150-200 km and an amplitude of up to 8 km. We find at least one location where there is no ULVZ present. At another well-sampled location, the precursor has higher frequency content than the primary arrival. Reflectivity modeling of these PcP/PdP phases shows that kilometer-scale layering may be required in the ULVZ to explain the seismic waveform and the frequency split. The modeling shows very low velocity in the ULVZ with reductions of 25 and 40% for P and S waves, respectively. This indicates higher percentages of partial melt in the ULVZ than hitherto interpreted. Our observations indicate that the ULVZ may be present over wide areas of the Earth with a thickness below the resolution limit of seismological data with a lower frequency content. INDEX TERMS:7207 Seismology: Core and mantle; 7219 Seismology: Nuclear explosion seismology; 7203 Seismology: Body wave propagation; KEYWORDS: core-mantle boundary, ultralow velocity zone, nuclear explosion Citation: Ross, A. R., H. Thybo, and L. N. Solidilov (2004), Reflection seismic profiles of the core-mantle boundary,

show abstract

A 22° long seismic profile for the study of the top of D'

Cited by 10 publications

References 15 publications

Detection of a D″ discontinuity in the south Atlantic using PKKP

Detection of a D″ discontinuity in the south Atlantic using PKKP

Deep Earth Structure: Lower Mantle and D″

Reflection seismic profiles of the core‐mantle boundary

Contact Info

Product

Resources

About