Fig. 8

Change in amplitude during the period around the water injection experiments. The bottom row shows the temperature observed at the Gunka station. The blue background indicates the periods of the injection experiments. Red and Blue dots show the variation in amplitude for the 800-m and 1700-m sensors, respectively. Green dots show the variation in amplitude at the 800-m sensors after the reduction of the effects of atmospheric temperature. We make a vertical offset of 0.05 for this plot. The values of green dots are shown in the vertical axis in right side of the graphs. During the water injection experiment, the transfer function of the 1700-m sensor could not be analyzed because of the noise caused by the injection. The gap between horizontal lines with a pair of triangles on the right side of the panels show the mean error of the amplitude change