Case 6B: Episodic Aseismic Strain Signal Precursors to the Japan Sea Earthquake of 1983

  1. Max Wyss
  1. A. T. Linde,
  2. K. Suyehiro,
  3. S. Miura,
  4. I. S. Sacks and
  5. A. Takagi

Published Online: 3 APR 2013

DOI: 10.1029/SP032p0028

Evaluation of Proposed Earthquake Precursors

Evaluation of Proposed Earthquake Precursors

How to Cite

Linde, A. T., Suyehiro, K., Miura, S., Sacks, I. S. and Takagi, A. (1991) Case 6B: Episodic Aseismic Strain Signal Precursors to the Japan Sea Earthquake of 1983, in Evaluation of Proposed Earthquake Precursors (ed M. Wyss), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP032p0028

Author Information

  1. Tohoku, Geophys. J., 31, 29-41, 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

Episodic aseismic strain signals were recorded at a borehole strainmeter site in Tohoku over a period of several months preceding the Japan Sea earthquake, magnitude 7.7, which occurred on 26 May 1983. The site is about 90 km from the epicenter and about 100 events were recorded. The frequency of occurrence was about 1 per day in the 3 weeks immediately preceding the earthquake. The signals were bay-like, had amplitudes of tens of nanostrain and durations about 3 hours. They are consistent with aseismic slip on a planar deep extension of the earthquake fault plane, which dips at about 20°to the east. Such a source is also consistent with other observations of crustal deformation. The geometry of the source region is suggestive of subduction in the Japan Sea. We hypothesize that episodic aseismic slip events are an important mechanism for stress redistribution in seismically active regions.