Radial variation of compressional and shear velocities in the Earth's lower mantle

Autor: Bruce R. Julian, M. K. Sengupta
Rok vydání: 1978
Předmět:
Zdroj: Geophysical Journal International. 54:185-219
ISSN: 1365-246X
0956-540X
DOI: 10.1111/j.1365-246x.1978.tb06763.x
Popis: Summary. This paper extends an earlier study (Sengupta & Julian) of travel times of P waves of deep-focus earthquakes to include shear waves. Primary advantage of deep-focus earthquakes is the reduction of anomalies caused by complex structures near the source. The standard deviations of travel times and station anomalies of this study are about half as large as those determined from the data of shallow-focus earthquakes (e.g. Herrin et al.; Hales & Roberts). Spherically-symmetric velocity models derived from the travel times by a linearized inverse technique have resolving lengths of about 70 km for standard errors in velocity of about 0.02 km/s. No pronounced reversal of either compressional or shear velocity was required at the base of the mantle to satisfy the data, though a small velocity decrease could not be entirely ruled out. Some anomalous rapid changes in compressional velocity gradient were, however, found centred around the depths of 2400 and 2600 km. The models derived in this study agree most closely with that of Herrin et al. for compressional velocity and the model 1066B of Gilbert & Dziewonski for shear velocity.
Databáze: OpenAIRE
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