A study of lateral inhomogeneities in the upper mantle by multiple Scs travel‐time residuals

Emile A. Okal*, Don L. Anderson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

An analysis of records of multiply reflected ScS phases from ten deep‐focus earthquakes yields near‐vertical one‐way travel‐time residuals varying from +5.0 to −3.5 s. Continental and oceanic residuals overlap and both indicate large lateral variations. Similar values are found for the older oceanic basins and for continental shields. Most, if not all, of the variations can be attributed to differences in the lithosphere and asthenosphere. The mantle under Hawaii, Iceland and Trindade (South Atlantic) Islands is anomalously slow, all being postulated hotspots. In the case of Trindade, petrological data is consistent with a pronounced low‐velocity zone and large S delays. Some recent studies assumed that stations on oceanic islands were representative of the ocean as a whole and it has been suggested that continent‐ocean differences extend deeper than 400 km. The present results indicate that oceanic islands are anomalous, and that differences between oceans and continents need not extend below 200 km. This does not rule out the existence of deep lateral inhomogeneities, but only the proposal that continents, in general, are faster than oceans to depths greater than 400 km.

Original languageEnglish (US)
Pages (from-to)313-316
Number of pages4
JournalGeophysical Research Letters
Volume2
Issue number8
DOIs
StatePublished - Aug 1975

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

Fingerprint Dive into the research topics of 'A study of lateral inhomogeneities in the upper mantle by multiple Scs travel‐time residuals'. Together they form a unique fingerprint.

Cite this