The Morávka meteorite fall: 2. Interpretation of infrasonic and seismic data

Abstract

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 quasispherical 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 on the order of a few degrees. The velocity of the meteoroid is much less well-determined by these seismic data. The more distant infrasonic station detected 3 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.

Entry dynamics and acoustics/infrasonic/seismic analysis for the Neuschwanstein meteorite fall

“…Recently, infrasound records have been combined with satellite data to estimate bolide source energies, luminous efficiencies, and to calibrate influx rates observed by satellite systems (Brown et al 2002b), while multistation recordings have been employed for bolide geolocation (Brown et al 2002c). A recent analysis of the Morávka meteorite fall (BoroviËka et al 2003a;Brown et al 2003) has placed some limits on characteristics of the shock wave source at the fireball from both the ballistic wave and fragmentation events, suggesting that the deviation of the ray normals for the fragmentation events may be as much as 30° beyond that expected from a purely cylindrical line source blast.…”

“…11a and 11b. This numerical model has also been used previously for interpreting infrasonic data measured for the Morávka fireball (see Brown et al [2003] for more details).…”

Evidence for a meteoritic origin of the September 15, 2007, Carancas crater

“…For example, the Park Forest fireball (March 27, 2004) fragmented three times before reaching the ground ). The Neuschwanstein fireball (April 6, 2002) was also reduced into pieces at the end of its trajectory (Spurný et al 2003;Oberst et al 2004;ReVelle et al 2004), as did the Morávka (May 6, 2000) (Brown et al 2003), the Tagish Lake (January 18, 2000) (Brown et al 2002a), and the Peekskill (October 9, 1992) (Beech et al 1995;Ceplecha et al 1996) events. Such objects usually produce seismic and acoustic signals when they fragment or when the supersonic front shock sweeps the Earth's surface (Brown et al 2003).…”

Trajectory of the August 7, 2010 Biwako fireball determined from seismic recordings

“…Past atmospheric trajectories of reballs have been determined by visual recordings such as photographs and movies (Brown et al, 1994(Brown et al, , 2003, infrasound records (Brown et al, 2002;Le Pichon et al, 2002, and seismic records (e.g., Nagasawa, 1978;Nagasawa and Miura, 1987;Cevolani, 1994;Qamar, 1995;Brown et al, 2002;Cates and Sturtevant, 2002;Le Pichon et al, 2002Ishihara et al, 2003Ishihara et al, , 2004Rydelek and Pujol, 2004;Pujol et al, 2005). An object ying at supersonic velocity produces a sonic boom, and the acoustic-to-seismic coupled signal is often recorded by seismic arrays.…”