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Array measurements of P velocities in the lower mantle

Johnson, Lane R. (1969) Array measurements of P velocities in the lower mantle. Bulletin of the Seismological Society of America, 59 (2). pp. 973-1008. ISSN 0037-1106.

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The extended array at the Tonto Forest Seismological Observatory in central Arizona has been used to measure dT/dΔ of direct P waves from 212 earthquakes in the distance range between 30 and 100°, and these data have been inverted to obtain a velocity model for the lower mantle. Travel times calculated for this model are in good agreement with empirical travel times. The dT/dΔ data from different azimuths and from different focal depths are all in reasonably good agreement with the exception of anomalously large values from earthquakes on the mid-Atlantic ridge. The effect of the core on the measured values of dT/dΔ at distances greater than 90° is shown to be significant, and a correction is made for this effect. A curve fit to the dT/dΔ data contains anomalous regions near the epicentral distances of 34.5, 40.5, 49.5, 59.5, 70.5, and 81.5° which may correspond to increased velocity gradients near the depths of 830, 1000, 1230, 1540, 1910, and 2370 km. PcP times were used to estimate a core radius of 3481 km.

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Additional Information:Copyright © 1969, by the Seismological Society of America. Manuscript received October 3, 1968. I am grateful to Don Anderson for many helpful discussions throughout the course of this study. I was supported by a National Science Foundation Graduate Fellowship during part of the study, and the research was supported by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under AFOSR contract AF-49(638)-1337.
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NSF Graduate Research FellowshipUNSPECIFIED
Air Force Office of Scientific Research (AFOSR)AF-49(638)-1337
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Caltech Division of Geological Sciences1569
Issue or Number:2
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ID Code:47860
Deposited By: George Porter
Deposited On:04 Aug 2014 15:31
Last Modified:03 Oct 2019 06:57

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