The Travel Times of P Seismic Waves and Their Relevance to the Upper Mantle Velocity Distribution

1972 ◽  
pp. 447-482 ◽  
Author(s):  
ANTON L. HALES
Keyword(s):  
Velocity Distribution ◽  
Upper Mantle ◽  
Seismic Waves ◽  
Travel Times ◽  
Mantle Velocity

An analysis of the travel times of S waves to North American stations in the distance range 28° to 82°

1967 ◽  
Vol 57 (4) ◽  
pp. 761-771 ◽  
Author(s):  
H. A. Doyle ◽  
A. L. Hales
Keyword(s):  
United States ◽  
Upper Mantle ◽  
Univariate Analysis ◽  
Western United States ◽  
Travel Times ◽  
Eastern United States ◽  
S Waves ◽  
Distance Range ◽  
Time Term ◽  
Mantle Velocity

abstract The travel times of S waves from 20 earthquakes to stations in North America in the distance range 28° to 82° have been studied. The deviations from J-B times were analyzed into station, source and distance components using the least-squares time-term approach of Cleary and Hales. Station anomalies had a range of about eight seconds, as compared to three seconds for the P anomalies, and are believed to be caused largely by variations in the upper mantle velocity distribution. S residuals, like the P residuals, were generally positive in the western United States, and negative in the central and eastern United States. P and S residuals at the same station correlated with a coefficient of 0.75, the slope of the regression of S anomaly on P anomaly being 3.72. Corrections to J-B times for S were of the order of the standard errors of the determinations. Within the distance range of 28° to 82° large changes of the S travel times, such as were required by the lower mantle velocities proposed by MacDonald and Ness (1961), are not permitted by the present data. The analysis was checked by carrying out a univariate analysis of variance of the same data.

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

Intensities and travel times of seismic rays in a sphere with a linear velocity function

1977 ◽  
Vol 67 (1) ◽  
pp. 33-42
Author(s):  
Mark E. Odegard ◽  
Gerard J. Fryer
Keyword(s):  
Velocity Profile ◽  
Travel Time ◽  
Upper Mantle ◽  
Intensity Ratio ◽  
Computation Time ◽  
Spherical Body ◽  
Travel Times ◽  
Velocity Function ◽  
Intensity Ratios ◽  
Distance Travel

Abstract Equations are presented which permit the calculation of distances, travel times and intensity ratios of seismic rays propagating through a spherical body with concentric layers having velocities which vary linearly with radius. In addition, a method is described which removes the infinite singularities in amplitude generated by second-order discontinuities in the velocity profile. Numerical calculations involving a reasonable upper mantle model show that the standard deviations of the errors for distance, travel time and intensity ratio are 0.0046°, 0.057 sec, and 0.04 dB, respectively. Computation time is short.

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.

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