Travel times to Australian stations from Pacific nuclear explosions in 1958

Doyle, H. A.; Webb, James

doi:10.1029/jz068i004p01115

Cited by 15 publications

(2 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Evidence for the existence of twin discontinuities with close correspondence to the ones suggested here have previously been presented by a number of investigators (see, for example, Doyle and Webb [1963]). With the commonly used technique of a few observations several degrees apart, it is extremely difficult to see the fine structure of the travel-time curve.…”

supporting

confidence: 86%

Upper mantle structure of western North America from apparent velocities ofPwaves

Niazi¹,

Anderson²

1965

J. Geophys. Res.

130

View full text Add to dashboard Cite

In a study of variation of the compressional velocity with depth in the C region of the upper mantle in western North America, we determined apparent velocities of first arrivals across the Tonto Forest array in Arizona for about 70 shallow‐focus earthquakes. The epicenters ranged from 10° to 30° in distance and were mostly south of the array. The method gives the slope of the travel‐time curve directly, the parameter required for a velocity‐depth determination. For this distance range we found that although the slope of the P wave travel‐time curve decreased substantially with distance, i.e., increasing apparent velocity, the variation was not uniform. Two relatively abrupt changes were observed at distances of about 17° and 24°. These are most readily interpreted as two second‐order discontinuities in the region of the mantle above 1000 km. Assuming an average crustal structure as derived from seismic refraction measurements and taking the uppermost 200 km of the mantle given by Gutenberg or Jeffreys, we investigated various possible forms of variation of the P wave velocity with depth. The discontinuities in the rate of change of velocity with depth which cause the observed breaks in the apparent velocity curve are found to be at depths of about 320 and 640 km. Although no absolute times are required in the method, the travel times for the various derived models are computed and compared with standard tables.

show abstract

supporting

confidence: 86%

Upper mantle structure of western North America from apparent velocities ofPwaves

Niazi¹,

Anderson²

1965

J. Geophys. Res.

130

View full text Add to dashboard Cite

show abstract

“…These new travel times show certain departures from the travel time tables of Jeffreys & Bullen (1958) in the distance range of A = 30" to 100". Most of these are listed in the literature as J-B residuals, a quantity which is the difference between the J-B travel time and the observed value at a given distance (Doyle & Webb 1963, Carder 1964, Cleary & Hales 1966, Herrin 1966, Carder e t al. 1966.…”

Section: T+ T[g$(t)+n-$] C ( T ) =mentioning

confidence: 99%

Inhomogeneities in the Earth's Mantle

1967

View full text Add to dashboard Cite

Using seismic body and surface waves, the velocity structure of the Earth's mantle is determined with the emphasis on regions of anomalous variations (so-called ' discontinuities '). In the upper mantle, the interpretation of Rayleigh and Love wave dispersion curves yields shear velocity profiles with discontinuities at depths 350 km and 700 km, and a low-velocity zone extending to 350km. In the lower mantle P-velocity profile is determined from dt/dA measurements using large aperture seismic array and travel times from Long Shot nuclear explosion for the Japan-Kuriles-Aleutian-Montana path. The velocity structure shows anomalous gradients or ' discontinuities ' at depths 700, 1200 and 1900 km, indicating that the lower mantle is not homogeneous.Lateral variations of the velocity structures are investigated. For the upper mantle studies the Earth is divided into three regions: oceanic areas, continental shields, and tectonic zones. Pure path phase velocities of Love waves are extracted from the composite dispersion data. The pure path shear velocity profiles obtained from these data are characterized by lower velocities under the oceans in the uppermost portion of the mantle. Shields have the highest velocities. These velocity differences are interpreted in terms of temperature variations. At a depth of 110 km the temperature of the oceanic mantle is higher (by 100-500" C depending on the temperature coefficient of the velocity) than that of the mantle under the shields. The presence of lateral heterogeneities in the mantle is demonstrated qualitatively by the differences ofdt/dA vs A curves for two separate paths.Undulations of the geoid as determined from satellite observations are investigated for determining the sources of the anomalies. It is concluded that the main sources of lateral density variations must be in the mantle at depths greater than about 100 km.

show abstract

Comparison of the 1968 P tables with times from nuclear explosions (II) the Marshall Islands and Sahara series

Muirhead

Cleary

1969

Earth and Planetary Science Letters

View full text Add to dashboard Cite

Travel times to Australian stations from Pacific nuclear explosions in 1958

Cited by 15 publications

References 11 publications

Upper mantle structure of western North America from apparent velocities ofPwaves

Upper mantle structure of western North America from apparent velocities ofPwaves

Inhomogeneities in the Earth's Mantle

Comparison of the 1968 P tables with times from nuclear explosions (II) the Marshall Islands and Sahara series

Contact Info

Product

Resources

About