Fig. 7

Cumulative probability and frequency density distribution of the time difference (\(\Delta t\)) and the epicentral distance (\(\Delta r\)) between the largest foreshock and mainshock for long-term data. a, c Time difference (\(\Delta t\)) and b, d epicentral distance (\(\Delta r\)). a, b Cumulative probability distribution. b, d Probability density distribution. The dashed lines have slopes of − 1.0, − 1.5, and − 2.0, as indicated in the figure. The black dots, blue triangles, and red crosses indicate that the magnitude of the largest foreshock is above 1.0, 1.5, and 2.5, respectively