HR: 1330h
AN: ED42A-1198    [PDF]
TI: Correlation Between Radon Outgassing and Seismic Activity Along the Hayward Fault Near Berkeley, California
AU: * Holtmann-Rice, D
EM: flyingtabmow@comcast.net
AF: Lawrence Hall of Science, University of California, Berkeley, CA 94720
AU: Cuff, K
EM: kcuff@uclink4.berkeley.edu
AF: Lawrence Hall of Science, University of California, Berkeley, CA 94720
AB: Results from previous studies indicate that radon concentration values are significantly higher over selected sections of the Hayward fault than adjacent areas. This phenomenon is believed to be attributed to the presence of abundant fractures in rock associated with the fault, which act as pathways for radon as it migrates from depth towards the earth?s surface. In an attempt to determine whether or not a relationship exists between seismicity along the fault, the production of microfractures, and emanation of radon, a radon outgassing monitoring study was conducted along an active section of the Hayward fault in Berkeley, California. The study was carried out by using an alphaMETER 611, which is a device capable of accurately measuring radon concentrations every 15 minutes. The alphaMETER was placed at the bottom of a sealed one meter deep well, in close proximity to a section of the Hayward fault located along the northwestern face of the Berkeley Hills. Once per week for several months data collected by the alphaMETER was downloaded into a laptop computer. Data from the alphaMETER was then compared with seismic data recorded by local seismometers to see if any correlation existed. A general correlation between variation in radon concentration and the occurrence of small earthquakes was found. Significant peaks in radon concentration were observed within an approximately one week period before the occurrence of small earthquakes. Concentration values then decreased dramatically just prior to and during periods when the earthquakes occurred. Such correlation is very similar to that recently observed in association with a magnitude five earthquake along the Anatolian Fault, reported by geoscientists working in Turkey using similar instrumentation (Inan, 2003, personal communication). The most plausible explanation for the observed correlation is as follows: 1) prior to a given earthquake, stress build up within a particular fault region leads to the formation of microfractures, which results in an increase in radon emisions; 2) during and immediately following an earthquake, stress release occurs, which then results in the closing of micro-fissures; 3) closure of microfractures leads to a subsequent decrease in radon emission. While data collected along the Hayward and Anatolian faults convincingly supports the notion that a relationship between radon outgassing and seismic activity does indeed exist, further research is necessary to better constrain the nature of this relationship.
DE: 6605 Education
SC: Education and Human Resources [ED]
MN: 2003 Fall Meeting