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Published June 10, 1980 | Published
Journal Article Open

Automated radon monitoring at a hard-rock site in the southern California transverse ranges


Data are presented from 20 months of near-real-time (three samples per day) radon monitoring at a hard-rock site in the Transverse Ranges of southern California. An annual cycle is evident in the data which is attributed to thermoelastic strains in the vicinity of the borehole site. Between April 1, 1977, and October 31, 1978, there were 11 earthquakes with magnitudes ≥2.0 within 25 km of the monitoring site. Three of these events appeared to be preceded by precursory signals, four were preceded by 'possible' precursory signals, and four were not preceded by any apparent precursors. Before the 4.6 M Malibu earthquake of January 1, 1979, a 'possible' precursory signal sequence of 40–50 days' duration was observed.

Additional Information

Copyright 1980 by the American Geophysical Union. (Received March 1, 1979; revised May 31, 1979; accepted June 12, 1979.) The authors wish to thank the staffs of the Kellogg Laboratory and the Seismological Laboratory for assistance throughout the course of this work. C. A. Barnes provided valuable information about counter technology and background levels during the development of the radon-thoron monitor. This research was supported in part by the National Science Foundation (PHY76-83685), Jet Propulsion Laboratory/ NASA contract 64598, the California Institute of Technology president's Venture Fund, and U.S. Geological Survey contract 14-08-0001-17734.

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