Since March 1972, a number of earth-strain episodes have been recorded at the Stone Canyon Geophysical Observatory, San Benito County, California. The episodes closely resemble recordings of nearby fault-creep episodes in shape and duration, suggesting similar source mechanisms. The episodes occur during a period of high tectonic strain release, as evidenced by increased seismicity and an accelerated rate of fault creep. On September 3 and 4, 1972, a creep episode was followed (after 20 hr) by a local earthquake of magnitude 4.6, which generated a distinct strain step and was followed (after 5 to 10 min) by a strain episode.

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