Propagation of Regional Seismic Phases in the Indian Shield: Constraints on Crustal and Upper Mantle Velocity Models

2004 ◽  
Vol 94 (1) ◽  
pp. 29-43 ◽  
Author(s):  
V. G. Krishna
Keyword(s):  
Upper Mantle ◽  
Indian Shield ◽  
Velocity Models ◽  
Mantle Velocity

Upper mantle velocity and its dynamic significance in the middle-southern segment of the Tan-Lu fault zone

2021 ◽  
Vol 804 ◽  
pp. 228771
Author(s):  
Qiguang Zhao ◽  
Xiaoping Fan ◽  
Yicheng He ◽  
Leiming Zheng ◽  
Yejun Sun
Keyword(s):  
Fault Zone ◽  
Upper Mantle ◽  
Mantle Velocity

Crustal structure in central New Mexico interpreted from the gasbuggy explosion

1976 ◽  
Vol 66 (3) ◽  
pp. 877-886
Author(s):  
Tousson R. Toppozada ◽  
Allan R. Sanford
Keyword(s):  
New Mexico ◽  
Upper Mantle ◽  
Rio Grande ◽  
Seismic Profile ◽  
Rio Grande Rift ◽  
Additional Information ◽  
Crustal Velocity ◽  
Crustal Model ◽  
Mantle Velocity ◽  
Record Section

abstract Interpretation of a seismic profile extending 548 km southward from the GASBUGGY nuclear test of December 10, 1967 resulted in a crustal model for central New Mexico. The crust is 39.9 km thick below the Paleozoic “basement”. It consists of an upper crust 18.6 km thick having P velocity 6.15 km/sec, and a lower crust 21.3 km thick having P velocity 6.5 km/sec. The apparent upper mantle velocity is 8.12 km/sec. This model applies near the crossover distance, 50 km west of Albuquerque. Additional information from earthquakes and explosions suggests that the upper crustal velocity drops to 5.8 km/sec in the Rio Grande rift, and that the true upper mantle velocity is 7.9 km/sec. The low upper crustal velocity in the Rio Grande rift can be detected on the record section of the GASBUGGY profile.

Shear velocity from differential travel times of short-period ScS-P in New Hebrides, Fiji-Tonga, and Banda Sea regions

1975 ◽  
Vol 65 (6) ◽  
pp. 1787-1796
Author(s):  
Mansur A. Choudhury ◽  
Georges Poupinet ◽  
Guy Perrier
Keyword(s):  
Upper Mantle ◽  
Focal Depth ◽  
Shear Velocity ◽  
Mean Value ◽  
Travel Times ◽  
Velocity Models ◽  
Depth Dependence ◽  
Short Period ◽  
New Hebrides ◽  
The Antarctic

abstract Behavior of P, S and ScS residuals as well as those of differential travel times of ScS-P from the Jeffreys-Bullen tables are analyzed. The phases have been read from short-period records of the Antarctic station, Dumont d'Urville (DRV); the earthquakes originating in New Hebrides, Fiji-Tonga, and Banda Sea regions. P residuals from all regions show a mean value of about −1 sec. On the contrary, S and ScS residuals, well correlated among themselves, show important regional as well as focal-depth dependence. ScS-P residuals from shallow and intermediate shocks are largely positive for New Hebrides and largely negative for Banda Sea; those from intermediate shocks are moderately positive for Fiji-Tonga. The anomalies disappear at depths greater than about 200 km. Upper mantle shear velocity models are presented for the three regions. The models are discussed in relation to a sinking lithosphere.

Upper-mantle discontinuity from amplitude data of P′P′ and its precursors

1973 ◽  
Vol 63 (2) ◽  
pp. 587-597
Author(s):  
Ta-Liang Teng ◽  
James P. Tung
Keyword(s):  
Upper Mantle ◽  
Body Waves ◽  
P Wave ◽  
Specific Reference ◽  
Amplitude Data ◽  
Surface Displacements ◽  
Short Period ◽  
Mantle Velocity ◽  
Mantle Discontinuity ◽  
Upper Mantle Discontinuity

abstract Recent observations of P′P′ and its precursors, identified as reflections from within the Earth's upper mantle, are used to examine the structure of the uppermantle discontinuities with specific reference to the density, the S velocity, and the Q variations. The Haskell-Thomson matrix method is used to generate the complex reflection spectrum, which is then Fourier synthesized for a variety of upper-mantle velocity-density and Q models. Surface displacements are obtained for the appropriate recording instrument, permitting a direct comparison with the actual seismograms. If the identifications of the P′P′ precursors are correct, our proposed method yields the following: (1) a structure of Gutenberg-Bullen A type is not likely to produce observable P′P′ upper-mantle reflections, (2) in order that a P′P′ upper-mantle reflection is strong enough to be observed, first-order density and S-velocity discontinuities together with a P-wave discontinuity are needed at a depth of about 650 km, and (3) corresponding to a given uppermantle velocity-density model, an estimate can be made of the Q in the upper mantle for short-period seismic body waves.

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