By Sid Perkins
New computer models developed to analyze how seismic vibrations travel through Earth’s crust can also be used to identify and track heavy vehicles such as tanks and trains.
Stig O. Hestholm, a seismologist at the Massachusetts Institute of Technology, and his colleague Bent O. Ruud of the University of Bergen in Norway developed new formulations of equations for estimating the effect of hills and valleys on the magnitude of ground motions caused by earthquakes. In their model, the researchers use a large, three-dimensional grid to represent a section of Earth’s crust. They can shape the upper surface of the grid to match any terrain.
Supercomputer simulations of seismic waves traveling through the grid show that ground motions are greater atop hills and smaller in large basins or valleys compared with flat terrain. This type of information could be useful in disaster-response planning and establishing building codes, says Hestholm.
The same modeling techniques could help defense analysts estimate the size of ground movements caused by sources of vibration on Earth’s surface. For example, the scientists could use the simulations to predict how the vibrations from a 20-ton armored tank will travel through different terrains.
In reverse, this technique could analyze the ground vibrations collected by a small regional network of seismometers. Such data could determine the location, number, speed, and possibly even the size and weight of sources of vibration such as trains, heavy trucks, and tanks.
