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| Author: | Wayne Edwards |
| Institution: | Dept. of Geology & Geophysics, University of Calgary |
| Email: | edwards@astro.uwo.ca |
| Authors: | Edwards W. N. and Hildebrand A. R. |
Abstract Title:
"Locating bolide fragmentations and terminal explosions using arrival times of acoustic waves" |
Abstract:
When large bolides of diameters 0.1 – 10 m penetrate into the denser regions of the Earth’s atmosphere the ever increasing pressures acting upon them often cause the objects to explode violently. These explosions can either occur as a series of individual fragmentations along its trajectory or as a single large explosion/ terminal burst. Seismographs, microphones and microbarometers located nearby can often record the arrival of acoustic waves produced by these explosions as they reach the Earth’s surface. If several, adequately separated observations of these acoustic arrivals are made it is then possible to locate the source position in 4 dimensions (3 spatial + 1 temporal), the supracenter. This process is similar to locating earthquakes in the solid Earth, but is complicated by the anisotropic effects of atmospheric winds and sound velocity gradients on wave propagation.
We have developed a computer program (SUPRACENTER) that locates atmospheric explosions using direct ray arrival times and ray tracing through realistic atmospheres. In addition, should several fragmentations be recorded and their positions found, trajectory information may be obtained along with the bolide’s velocity. SUPRACENTER has demonstrated this utility through the analysis of several seismically recorded bolide events including: (1) the October 9, 1997 El Paso fireball and (2) the January 25, 1989 Mt. Adams fireball. Results from these two events suggest that the presence of large unidirectional winds in the atmosphere at the time of the bolide cause source locations to differ by 2-3 km in an upwind direction from static atmosphere locations. This so-called “wind drift” is significant as this is comparable to the widths of known meteorite strewn fields.
With the ability to rapidly compute of terminal burst positions and potentially trajectory information during the early days after a fall, researchers now have a new tool to guide them in meteorite recovery efforts.
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| Keywords: | bolide, seismic, acoustic waves, supracenter, terminal burst, fragmentation |
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