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Correlated radon and CO_2 variations near the San Andreas Fault

Shapiro, M. H. and Melvin, J. D. and Tombrello, T. A. and Fong-liang, Jiang and Gui-ru, Li and Mendenhall, M. H. and Rice, A. and Epstein, S. and Jones, V. T. and Masdea, D. and Kurtz, M. (1982) Correlated radon and CO_2 variations near the San Andreas Fault. Geophysical Research Letters, 9 (5). pp. 503-506. ISSN 0094-8276. doi:10.1029/GL009i005p00503.

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Correlations have been observed between groundwater radon and thoron concentrations and carbon dioxide discharges at the Lake Hughes station of the Caltech radon monitoring network. The Lake Hughes site is one of three radon monitoring stations located near the "big bend" segment of the San Andreas fault which began to record anomalous radon levels in August 1981. Two stations, Lake Hughes and Lytle Creek, recorded anomalous increases in radon while the third, Sky Forest, recorded an anomalous decrease. Several weeks after the onset of the anomaly, strongly correlated radon fluctuations began at Lake Hughes and Lytle Creek. These radon spikes also were found to be phase anti-correlated with barometric pressure fluctuations. Analyses of gas grab samples showed relatively high levels of CO_2 and ethylene in borehole air at Lake Hughes and Lytle Creek, while analyses of water samples showed relatively large increases in HCO_3^− at both sites. Isotopic analysis of one gas sample from Lake Hughes yielded a ^(13)C δ value of −22 ‰, which suggests that the CO_2 originates from the oxidation of organic material. The correlation in radon fluctuations at Lake Hughes and Lytle Creek and their common dependence on barometric pressure changes began shortly after the onset of the radon anomaly in August, and probably resulted from the simultaneous saturation of the water in these boreholes with carbon dioxide.

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Additional Information:© 1982 American Geophysical Union. Received February 9, 1982; accepted March 15, 1982. The work in this paper was supported in part by U.S. Geological Survey Contract 14-08-0001-19752 at Caltech. We thank the Earth Sciences Department at California State University, Fullerton for providing microbarograph data.
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U.S. Geological Survey (USGS)14-08-0001-19752
Issue or Number:5
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ID Code:44256
Deposited By: Ruth Sustaita
Deposited On:12 Mar 2014 14:36
Last Modified:10 Nov 2021 16:49

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