Case 7B: Temporal Change in Scattering and Attenuation Associated with the Earthquake Occurrence—A Review of Recent Studies on Coda Waves

  1. Max Wyss
  1. Haruo Sato

Published Online: 3 APR 2013

DOI: 10.1029/SP032p0054

Evaluation of Proposed Earthquake Precursors

Evaluation of Proposed Earthquake Precursors

How to Cite

Sato, H. (1991) Case 7B: Temporal Change in Scattering and Attenuation Associated with the Earthquake Occurrence—A Review of Recent Studies on Coda Waves, in Evaluation of Proposed Earthquake Precursors (ed M. Wyss), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP032p0054

Author Information

  1. Pure Appl. Geophys., 126,465–497,1988

Publication History

  1. Published Online: 3 APR 2013
  2. Published Print: 1 JAN 1991

ISBN Information

Print ISBN: 9780875907840

Online ISBN: 9781118667873

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Keywords:

  • Earthquake prediction—Evaluation

Summary

The study of coda waves has recently attracted increasing attention from seismologists. This is due to the fact that it is viewed as a new means by which the stress accumulation stage preceding a large earthquake can be measured, since the scattering paths nearly uniformly cover a fairly large region around the focus and observation stations, compared with the direct ray paths. To date, we have had many reports on the temporal variation of the relation between coda duration and amplitude magnitude, and that of the coda attenuation Qc −1 which is estimated from coda amplitude decay. Some of these have shown a precursor-like behavior, however, others seem to have shown a coseismic change. We have critically reviewed these reports, and discussed what these observational facts tell us about the change in the heterogeneous crust. We found significant temporal variations, not only in the mean but also in the scatter of Qc −1, associated with the mainshock occurrence. The formation of new cracks, the reopening and growing of existing cracks, the interaction of these cracks, and the pore water movement through these cracks might correspond to such variations. In addition, we may expect an inhomogeneous distribution of crack clusters in a fairly large region, compared with the aftershock region. The gradual appearance of such crack clusters seems to be the most plausible mechanism by which coda decay gradients are caused to largely scatter in the stress accumulation stage. (For additional supporting evidence see references.)