Elastic Wave Velocities in Hawaiian Rocks at Pressures to Ten Kilobars

  1. Leon Knopoff,
  2. Charles L. Drake and
  3. Pembroke J. Hart
  1. Murli H. Manghnani and
  2. George P. Woollard

Published Online: 18 MAR 2013

DOI: 10.1029/GM012p0501

The Crust and Upper Mantle of the Pacific Area

The Crust and Upper Mantle of the Pacific Area

How to Cite

Manghnani, M. H. and Woollard, G. P. (2012) Elastic Wave Velocities in Hawaiian Rocks at Pressures to Ten Kilobars, 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/GM012p0501

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

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Keywords:

  • Basalts;
  • Birch's relationship;
  • Bulk density;
  • Elastic moduli;
  • Elastic wave velocities;
  • Hawaiian rocks;
  • Hysteresis effect

Summary

Bulk density pb, particle density pp, and compressional-wave and shear-wave velocities Vp and V8 measured for 165 specimens of Hawaiian rocks at atmospheric conditions are used to derive values of porosity η and elastic moduli. The rock specimens include tholeiitic, alkalic, and nephelinitic basalts, as well as ultrabasic inclusions such as dunite and eclogite. The variations in the parameters pb, pp, Vp, V8 , η, and elastic moduli for rocks at atmospheric conditions are significantly large, because of changes in porosity and mineral composition. The basalts exhibit an appreciable degree of anisotropy. Basalts show high initial compressibility and some remnant compressibility to 10 kb. The hysteresis effect, as defined by the velocity values with increasing and decreasing pressure, is small, suggesting that in basalts with low porosity the compressibility effect is related to elastic deformation rather than to collapse of the vesicle walls. Density change in basalts to 10 kb amounts to only a few per cent. The Vp values for basalts to 10 kb range from 5.42 km/sec for a trachyte to 7.01 km/ sec for a nephelinite, and show dependence on the olivine content. For all the rocks with low porosity (η<1–7%), the relationship between velocity at 10 kb and bulk density and chemical composition shows good agreement with Birch's relationship, Vp = a + bp for m ∼ 21.6. For the relatively more porous rocks (η = 7–19.7%), there appears to be no systematic relationship between velocity, density, and mean atomic weight.