Figure 6

Characteristics of total earthquake energy and its correlation with ²²²Rn concentration. (a) Change of total earthquake energy with radius, determined using the earthquakes (Figure 1) within a radius from the center of measurement point locations. The energy at a point was defined by the earthquake magnitude, which was converted to energy using the Gutenberg-Richter law and then divided by the square of the distance from the hypocenter. (b) Positive correlation between the total earthquake energy and the median of the number of ²²²Rn for each active fault area. The ²²²Rn data at the 11 points on IM-3 (Figure 1) are not included because they are not located on an active fault (the Izumi Fault).