Abyssally Generated T Phases1

  1. Leon Knopoff,
  2. Charles L. Drake and
  3. Pembroke J. Hart
  1. Rockne H. Johnson,
  2. Roger A. Norris and
  3. Frederick K. Duennebier

Published Online: 18 MAR 2013

DOI: 10.1029/GM012p0070

The Crust and Upper Mantle of the Pacific Area

The Crust and Upper Mantle of the Pacific Area

How to Cite

Johnson, R. H., Norris, R. A. and Duennebier, F. K. (2012) Abyssally Generated T Phases1, in The Crust and Upper Mantle of the Pacific Area (eds L. Knopoff, C. L. Drake and P. J. Hart), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM012p0070

Author Information

  1. Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 20 APR 2012

Book Series:

  1. Geophysical Monograph Series

Book Series Editors:

  1. Waldo E. Smith

ISBN Information

Print ISBN: 9780875900124

Online ISBN: 9781118663738



  • Aleution slope;
  • Magnetic tabe recordings;
  • Power-level variation;
  • Rays;
  • Refracted surface-reflected (RSR);
  • Spectral contour plot;
  • T phases


Two distinct types of signals have been identified from studies of T-phase spectra and source locations. One, with its source at a shoaling slope of the ocean bottom and with dominant frequencies near 4 cps, is the previously recognized and described classic T phase. The other, with its source in deep water and with dominant frequencies near 30 cps, is newly identified and is here termed the abyssally generated, or abyssal, T phase. Scattering from the sea surface is proposed as a mechanism for producing rays which propagate through the ocean with an apparent velocity equal to sofar velocity. It is hypothesized that the sea surface roughness shapes the spectrum of the abyssal T phase. A synthesis of the power-level record relates the degree of sharpness of the abyssal T-phase peak with focal depth.