Electron spin resonance signals from earthquake-affected clays were analyzed. One signal was attributed to an hydroxyl radical, (HOHC; Si-OoH), which bonded with an H2O+ ion that was obtained by ionizing inter-layer water in montmorillonite (Si-OoH3O+). The O hole center, (OHC; Si-Oo), combined with an hydronium ion (H3O+) and was split into quartet lines (with intensity ratios of 1:3:3:1) by hyperfine coupling of 3 equal protons (I = ½). It was recalled that the quartet signal had often been detected from hydrothermal silicas or weathered feldspars. Another signal could be attributed to a CO33- radical that was stabilized by an exchangeable cation which existed in the inter-layer and was detected only by artificial irradiation; due to its low thermal stability. All of these electron spin resonance signals increased uniformly during irradiation with X-rays.

T.Fukuchi: Japanese Journal of Applied Physics, 1996, 35[1-3], 1977-82