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Science 13 December 1974:
Vol. 186. no. 4168, pp. 1031 - 1034
DOI: 10.1126/science.186.4168.1031
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Articles

Tilt Precursors before Earthquakes on the San Andreas Fault, California

M. J. S. Johnston 1 and C. E. Mortensen 1

1 U. S. Geological Survey, National Center for Earthquake Research, Menlo Park, California 94025

An array of 14 biaxial shallow-borehole tiltmeters (at 1O-7 radian sensitivity) has been installed along 85 kilometers of the San Andreas fault during the past year. Earthquake-related changes in tilt have been simultaneously observed on up to four independent instruments. At earthquake distances greater than 10 earthquake source dimensions, there are few clear indications of tilt change. For the four instruments with the longest records (> 10 months), 26 earthquakes have occurred since July 1973 with at least one instrument closer than 10 source dimensions and 8 earthquakes with more than one instrument within that distance. Precursors in tilt direction have been observed before more than 10 earthquakes or groups of earthquakes, and no similar effect has yet been seen without the occurrence of an earthquake.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Stress Anomaly Accompanying the 1979 Lytle Creek Earthquake: Implications for Earthquake Prediction.
B. R. Clark and B. R. CLARK (1981)
Science 211, 51-53
   Abstract »    PDF »
Geodetic tilt measurements along the San Andreas Fault in central California.
J. C. SAVAGE, W. H. PRESCOTT, J. F. CHAMBERLAIN, M. LISOWSKI, and C. E. MORTENSEN (1979)
Bulletin of the Seismological Society of America 69, 1965-1981
   Abstract »    PDF »
Meteorological noise in wire strainmeter data from Parkfield, California.
N. R. GOULTY, P. M. DAVIS, R. GILMAN, and N. MOTTA (1979)
Bulletin of the Seismological Society of America 69, 1983-1988
   Abstract »    PDF »
Deadline for Nominations: 15 September 1977 AAAS-Newcomb Cleveland Prize: Contest Year Is Nearly Over.
(1977)
Science 197, 154
   PDF »
Observations of creep-related tilt, strain, and water-level changes on the central San Andreas fault.
C. E. MORTENSEN, R. C. LEE, and R. O. BURFORD (1977)
Bulletin of the Seismological Society of America 67, 641-649
   Abstract »    PDF »
Earthquake precursors.
T. RIKITAKE (1975)
Bulletin of the Seismological Society of America 65, 1133-1162
   Abstract »    PDF »
Premonitory changes in ts/tp due to anisotropy and migration of hypocenters.
I. N. GUPTA (1975)
Bulletin of the Seismological Society of America 65, 1487-1493
   Abstract »    PDF »


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Science. ISSN 0036-8075 (print), 1095-9203 (online)