Variations in stable- isotope ratios of ground waters in seismically active regions of California

Measurements of D and ¹⁸O concentrations of ground waters in seismically active regions are potentially useful in earthquake prediction and in elucidating mechanisms operative during earthquakes. Principles of this method are discussed and some preliminary data regarding a magnitude 5.7 earthquake at the Oroville Dam in 1975 and a series of events near San Juan Bautista in 1980 are presented to support the utility of such measurements. After earthquakes, the D content of nearby ground waters increased by several permil while the ¹⁸O content remained constant. This increase implies that H₂O may have either decomposed or reacted to form molecular H₂ at depth. It is emphasized that many areas must be investigated for these effects in order to find a sufficient number of "sensitive" water wells and springs to permit a truly effective program of earthquake research.