Fig. 4

b-values estimated in region B for each analysis window: before the 2011 eruption (period 1: January 1, 2007–January 18, 2011); during and immediately after the 2011 eruption (period 2: January 19, 2011–December 31, 2011); before the 2017 eruption (period 3: January 1, 2012–September 30, 2017); and immediately before and during the 2017 eruption (period 4: October 1, 2017–October 26, 2017). The analyzed region is located 7.0–8.0 km northwest of the summit (region B). n and b in the figures indicate the number of events and representative b-values of each analysis period, respectively