Tilt precursors before earthquakes on the San Andreas fault, California

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Abstract

An array of 14 biaxial shallow-borehole tiltmeters (at 10-7 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.

Suggested Citation

Johnston, M., Mortensen, C., 1974, Tilt precursors before earthquakes on the San Andreas fault, California: Science, v. 186, no. 4168, p. 1031-1034, https://doi.org/10.1126/science.186.4168.1031.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Tilt precursors before earthquakes on the San Andreas fault, California
Series title Science
DOI 10.1126/science.186.4168.1031
Volume 186
Issue 4168
Year Published 1974
Language English
Publisher American Association for the Advancement of Science
Description 4 p.
First page 1031
Last page 1034
Country United States
State California
Additional publication details