Keywords: NCSTAR 1-9 Figure 12-77 Page 603.png en Downward velocity time graph of north face roofline as World Trade Center 7 began to collapse on September 11 2001 NIST NCSTAR 1-9 Figure 12-77 Page 603 2008-11-20 NIST NCSTAR 1-9 Figure 12-77 Page 603 Therese P McAllister et al PD-USGov Uploaded with UploadWizard Maps and diagrams of 9/11 7 World Trade Center 2006 |