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Research
Infrasound publications
A seismoacoustic analysis of the gas-pipeline explosion near
Ghislenghien in Belgium
Läslo G. Evers, Lars Ceranna, Hein W. Haak, Alexis Le Pichon and Rod W. Whitaker Abstract A high pressure gas-pipeline exploded near Ghislenghien in Belgium, on 2004, July 30. Seismic energy of this event was recorded at three nearby seismometers. The origin time of the explosion was determined by analyzing the Rayleigh waves and found to be 06h55m27+-2 s UTC. Ground truth of the explosion was invoked to assess the accuracy of the location derived from infrasound data recorded over Western Europe. Different infrasonic phases were identified by using array processing techniques and raytracing through atmospheric models. The analysis showed that the derived location was situated 13 km from the true location. The total area of the uncertainty ellipse, or area to be searched if the source was of unknown origin, was 690 km2. Next to the origin time and location, the yield was calculated by comparing infrasonic stratospheric amplitudes to those from a high explosives dataset and was estimated at 40.9 tons high explosives equivalent. In summary, this study illustrates the capability of seismic and infrasound data in forensic investigations. Furthermore, the potential of infrasound as a monitoring or verification technique is addressed.
Figure caption: Results from raytracing through HWM (left) and ECMWF (right) models for wind and temperature. The lower frame shows rays leaving the source in the direction of Flers. Rays bend towards the earth's surface between 40 and 55 km height, i.e. the stratosphere and from 120 km upwards, i.e. the thermosphere. The sound speed is plotted right of the lower frame. The effective sound speed (Veff in black) accounts for both wind and temperature (Vt in gray). Refractions occur from regions where Veff becomes larger than the sound speed at the surface (Vs) as indicated by the dashed line. The middle frame gives the traveltime for the rays. The upper frame shows the bounce point of the rays on the earth's surface. Rays shot from the source [0,0] to Flers [379,0] km are deviated towards the west by zonal cross winds. The azimuthal deviation follows from this representation by taking the tangent of the offset and range.
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