When an earthquake takes place, data from seismograms measuring ground motion are collected by a worldwide network of more than 1,800 seismographic stations operated by members of the international Federation of Digital Seismograph Networks. The earthquake’s location, depth and intensity also are determined. The Princeton system, called the ShakeMovie, will now collect these recordings automatically using the internet.
The scientists will then input the recorded data into a computer model that creates a virtual earthquake. The videos will incorporate both real data and computer simulations known as synthetic seismograms. These simulations fill the gaps between the actual ground motion recorded at specific locations in the region, providing a more complete view of the earthquake.
The animations rely on software that produces numerical simulations of seismic wave propagation in sedimentary basins. The software computes the motion of the Earth in three dimensions based on the actual earthquake recordings, as well as what is known about the subsurface structure of the region.
After the 3D simulations are computed, the software program plugs in data capturing surface motion, including displacement, velocity and acceleration, and maps it onto the topography of the region around the earthquake. The movies are then automatically published via the ShakeMovie portal.
Earthquake movies will be available for download about one-and-a-half hours after the occurrence of a quake of magnitude 5.5 or greater.
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