Meteoritics & Planetary Science 38, 989--1003 (2003)
The Moravka meteorite fall:
2. Interpretation of infrasonic and seismic data
P. G. Brown1, P. Kalenda2,
D. O. ReVelle3, and J. Borovicka4
1Department of Physics and Astronomy, University
of Western Ontario, London, Ontario N6A 3K7, Canada
2CoalExp, Kosmonautu 2, 70030 Ostrava 3, The Czech Republic
3Los Alamos National Laboratory, P.O. Box 1663, MS J557, Los
Alamos, New Mexico
87545, USA
4Astronomical Institute
of the Academy of Sciences, 25165 Ondrejov, The Czech Republic
Abstract. The sound production from the Morávka fireball
has been examined in detail making use of infrasound and seismic data.
A detailed analysis of the production and propagation of sonic waves
during the atmospheric entry of the Morávka meteoroid
demonstrates that the acoustic energy was produced both by the
hypersonic flight of the meteoroid (producing a cylindrical blast wave)
and by individual fragmentation events of the meteoroid which acted as
small explosions (producing quasi-spherical shock waves). The deviation
of the ray normals for the fragmentation events was found to be as much
as 30° beyond that expected from a purely cylindrical line
source blast. The main fragmentation of the bolide was confined to
heights above 30 km, with a possible maximum in acoustic energy
production near 38 km. Seismic stations recorded both the direct
arrival of the airwaves (the strongest signal) as well as air coupled
P-waves and Rayleigh waves (earlier signals). In addition, deep
underground stations detected the seismic signature of the fireball.
The seismic data alone permit reconstruction of the fireball trajectory
to a precision of order a few degrees. The velocity of the meteoroid is
much less well determined by these seismic data. The more distant
infrasonic station detected three distinct signals from the fireball,
identified as a thermospheric return, a stratospheric return and an
unusual mode propagating through the stratosphere horizontally and then
leaking to the receiver.
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