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| | Abstract | | Monitoring the tendency of acoustic emission (AE) associated with water injection into geothermal fields to track the flow of injected water is an important survey for investigating changes in underground conditions. In this study, to investigate the tendency of AEs during water injection, the distribution of AEs and b-value (the slope of the parameter of the Gutenberg-Richter (G-R) law) were measured using nine seismic stations around the OkuAizu Geothermal Field, Fukushima Prefecture. From these results, we examined the relationship between water injection and the tendency of AE occurrences. As a result, the water injection operations and the tendency of changes in b-value showed locality. For instance, the change of b-value around the water feed point showed a characteristic change compared with that for a wider area. It is considered that the number of AEs around the water feed point is likely to be controlled by the water injection operations. It will be possible to estimate the changes in the properties of AEs precisely by analyzing AEs during the longer-term water injection test that currently being carried out. |
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