Trique, M. and Richon, P. and Perrier, F. and Avouac, J. P. and Sabroux, J. C. (1999) Radon emanation and electric potential variations associated with transient deformation near reservoir lakes. Nature, 399 (6732). pp. 137-141. ISSN 0028-0836 http://resolver.caltech.edu/CaltechAUTHORS:20120907-155928570
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Two of the most often cited earthquake precursors are radon emanation and electric potential variations, but these few reported examples have generally been deemed questionable. If a mechanism relating crustal deformation to radon emanation or electrical signals does indeed exist, it is thought to involve fluids. Some preliminary insight has been gained into these processes from the study of natural systems under controlled mechanical and hydrological conditions. Here we report electric potential variations, radon emanation and deformation measurements recorded since 1995 in the French Alps in the vicinity of two artificial lakes which have strong seasonal variations in water level of more than 50 metres. We observe that electric potential variations and radon emanations are repeatedly associated with transient deformation events induced by variations in lake levels. These events are characterized by a change in ground tilt which deviates from the expected elastic response, and are associated with periods of accelerating strain, which suggests that accelerated loading can enhance fluid transport properties. Qualitatively, this behaviour can be accounted for by a model in which straining induces fluid overpressure and dynamic flow in cracks. These observations may shed light on the sensitivity of rock transport properties to deformation.
|Additional Information:||© 1999 Macmillan Magazines Ltd. Received 13 August 1998; Accepted 4 March 1999. We thank Y. Caristan, A. Meesters and R. Pican for support, and EDF for its water level data and access to the lakes. We also thank the members of the technical team from the Département Analyse et Surveillance de l'Environment, CEA, for their dedication in performing their work in often difficult weather conditions.|
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|Deposited By:||Tony Diaz|
|Deposited On:||07 Sep 2012 23:13|
|Last Modified:||26 Dec 2012 16:08|
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