Figure 4. Comparison of the influence of bin size. (a) Bin size selection, 1km (blue), 5km (red) and 10km (black) along strike and 1km depth range. (b) Corner frequency comparison between 10km bin and 1km (blue) and 5km (red) bin. (c) Stress drop comparison between 10km bin and 1km (blue) and 5km (red) bin. (d) ECSs solved from different bin sizes. Shaded areas in (b) and (d) represent frequency band outside the fitting range (higher than 60Hz, or lower than 2Hz). Black dashed lines in (b) and (c) indicate identical values. The comparison indicate 10 km along strike box can sufficiently account for attenuation at 1 km, and the 10km-by-1km area is selected for data analysis because of its high event density. The 10km test area is highlighted in Figure 6(a) as a black box.