Figure 6

Application of FFM to SBL. (a) The daily SBL at SMN belonging to the clusters related to volcanic activity (Gn, Rn1, Rn2, and Kn). The colors are the same as in Fig. 5a. The light-magenta area shows the weekly smoothed SBL at SMN as in Fig. 2c. (b–d). The inverse of the data in (a), and the magnifications of the rectangles, (c) and (d). They exhibit linear slopes down toward the 2011 eruption (c) and the 2017 and 2018 eruptions (d). The dotted lines show the fitting of the weekly smoothed SBL by Eq. (1) with the parameters listed in Table 1.