Field Detection of Microcracks to Define the Nucleation Stage of Earthquake Occurrence

Figure 9

Evolution of the cumulative numbers 𝑁1(𝑡), 𝑁2(𝑡), and 𝑁3(𝑡) for B-1, B-2, and B-3, respectively. B-2 type tend to dominate as approaching to final rupture. But there are no big changes in partial importance in the activity.