Seismic Records of the Major Events in Manhattan
Seismographers recorded the five major events in Manhattan on September 11. Here are seismograms recorded by Lamont-Doherty Earth Observatory of Columbia University, in Palisades, NY (PAL). 1 A detailed description of how the data was collected is available here. What these charts indicate about the timelines of the Towers' destruction is explored here.
Note that the vertical axes of the charts are not all to the same scale. The charts for the leveling of WTC 1 and 2 have one-tenth the vertical magnification of the three other charts. Note also that the times given on the charts are in Greenwich Mean Time (GMT), which is four hours ahead of Eastern Daylight Time (EDT), the time in which events of the 9/11/01 attack are usually reported.