Figure 12. (a) The "old" and "new" digitized versions near the beginning of the vertical trace of the 1994 Northridge record at Sylmar Converter Station, Valve Hall Floor. The difference between the two versions is probably due to smoothing effects of the automatic trace following algorithm, more pronounced for lower threshold levels. (b) Illustration of differences in data digitized by the LeAuto software caused by different threshold levels, for a portion of the trace shown in part (a). The image was scanned with 600 dpi resolution and 256 level gray scale.