Figure 5.  The vertical trace of the 1994 Northridge earthquake accelerogram at Sylmar Converter Station-Valve Group 1-6 (basement): (a) the beginning; (b) the beginning enlarged by macro-photography, showing gradual build up of optical density; (c) the beginning enlarged by a repeated Xerox process and the "old" digitized version of the record. The dashed line shows the "old" digitization.