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Long-term premonitory seismicity patterns in Tibet and the Himalayas

Keilis-Borok, V. and Knopoff, L. and Allen, C. R. (1980) Long-term premonitory seismicity patterns in Tibet and the Himalayas. Journal of Geophysical Research. Solid Earth, 85 (B2). pp. 813-820. ISSN 2169-9313. doi:10.1029/jb085ib02p00813.

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An attempt is made to identify seismicity patterns precursory to great earthquakes in most of Tibet as well as the central and eastern Himalayas. The region has considerable tectonic homogeneity and encompasses parts of China, India, Nepal, Bhutan, Bangladesh, and Burma. Two seismicity patterns previously described were used: (1) pattern Σ is a peak in the sum of earthquake energies raised to the power of about 2/3, taken over a sliding time window and within a magnitude range less than that of events we are trying to predict; and (2) pattern S (swarms) consists of the spatial clustering of earthquakes during a time interval when the seismicity is above average. Within the test region, distinct peaks in pattern Σ have occurred twice during the 78‐year‐long test period: in 1948–49, prior to the great 1950 Assam‐Tibet earthquake (M = 8.6), and in 1976. Peaks in pattern S have occurred three times; in 1932–1933, prior to the great 1934 Bihar‐Nepal earthquake (M = 8.3), in 1946, and in 1978. The 1934 and 1950 earthquakes were the only events in the region that exceeded M = 8.0 during the test period. On the basis of experience here and elsewhere, the current peaks in both Σ and S suggest the likelihood of an M = 8.0 event within 6 years or an M = 8.5 event within 14 years. Such a prognostication should be viewed more as an experimental long‐term enhancement of the probability that a large earthquake will occur than as an actual prediction, in view of the exceedingly large area encompassed and the very lengthy time window. Furthermore, the chances of a randomly occurring event as large as M = 8.0 in the region are perhaps 21% within the next 6 years, and the present state of the art is such that we can place only limited confidence in such forecasts. The primary impact of the study, in our opinion, should be to stimulate the search for medium‐ and short‐term precursors in the region and to search for similar long‐term precursors elsewhere.

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Additional Information:© 1980 by the American Geophysical Union. Paper number 9B1195. Received March 6, 1979; revised August 9, 1979; accepted August 13, 1979. The present study was carried out as a part of Project III of the program of Soviet-American cooperation in earthquake prediction while one of the US (V.I.K-B.) was a visiting scientist at the Seismological Laboratory of the California Institute of Technology, where he was a Sherman Fairchild Distinguished Scholar, and at the Institute of Geophysics and Planetary Physics of the University of California, Los Angeles. The visit of Keilis-Borok to the United States was supported by the Fairchild Foundation through Caltech and by the U.S. Geological Survey. W. Lee provided us with invaluable consultations on the seismicity of China. The assistance of M. French is gratefully acknowledged. E. R. Engdahl and W. Rihenhart helped us to obtain recent supplements to the NOAA earthquake file. We appreciate critical comments by D. L. Anderson. Contribution number 3177, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125. Publication number 1876, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90024.
Group:Seismological Laboratory
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Sherman Fairchild FoundationUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences3177
Issue or Number:B2
Record Number:CaltechAUTHORS:20190912-101905872
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Official Citation:Keilis‐Borok, V., Knopoff, L., and Allen, C. R. (1980), Long‐term premonitory seismicity patterns in Tibet and the Himalayas, J. Geophys. Res., 85(B2), 813–820, doi:10.1029/JB085iB02p00813
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98607
Deposited By: Tony Diaz
Deposited On:12 Sep 2019 18:32
Last Modified:16 Nov 2021 17:40

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