Chris Bravo, Department of Defense environmental prototype evaluator, uses a seismic receiver to collect seismic waves caused by a passing train at Fort Eustis, Va., Sept. 10, 2015. The DoD team coordinated with the 733rd Mission Support Group as well as U.S. Army Rail to gather readings caused by locomotive traffic. (U.S. Air Force photo by Staff Sgt. Natasha Stannard/Released)