Experimental researches of degassing phenomene associated with rock deformation and fracturing

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The target of this research is to elucidate characteristics of degassing associated with earthquake and volcanic eruption, based on experimental investigations of micro-cracks and micro-pores in rocks. A new system has been developed for real-time monitoring of gas composition during rock deformation until the final rock fracturing. It was found that micro-crack formation and their mutual connection began at the time when the rock stress reached about 40% of the value of the rock strength, resulting in degassing from the rock samples which was continuously observed using the new system. The most interesting finding is that the degassing behavior at the final step before the rock failure was completely different from those at the previous steps. At the final step, degassing from the rock samples became continuous, which strongly suggested that spontaneous formation of micro-cracks started. Such a new finding should be important in understanding the mechanisms of various kinds of precursory phenomena of earthquakes.