tracing a meteoric trajectory with infrasound
DESCRIPTION
Tracing a meteoric trajectory with infrasound. Läslo Evers and Hein Haak [email protected] http://www.knmi.nl/~evers Royal Netherlands Meteorological Institute (KNMI) Seismology Division. The presented work is under review with Geoph. Res. Lett. Dutch Infrasound Arrays. 2003 February 19 - PowerPoint PPT PresentationTRANSCRIPT
Tracing a meteoric trajectory with infrasound
Läslo Evers and Hein Haak
[email protected]://www.knmi.nl/~evers
Royal Netherlands Meteorological Institute (KNMI)Seismology Division
The presented work is under review with Geoph. Res. Lett.
Dutch Infrasound Arrays
Meteoric Infrasound in DBN
2003 February 1918h18m24.08s GMT
Detections at DBN
Meteoric Infrasound in DIA
2003 February 1918h17m59.31s GMT
Detections at DIA
Resolution I: Fisher ratio response
Resolution II: best beams at DIABest beam 1st arrival: 1.0 deg and 359.9 m/s
Best beam 2nd arrival: 359.0 deg and 335.6 m/s
Summary of the observations
2003.02.1918h17m57.28s
1.0o
359.9 m/s359.0o
335.6 m/s
32.3o
341.5 m/s 35.8o
373.5 m/s
Localization through cross bearing
What can be used for validation?• Reported time of occurrence of 18h13m05s• Observed approximate direction from S to N
What is known?• Arrival times of the different phases at DBN and DIA• Bearing and range from cross bearing
How?• Least squares optimization of observed and modeled differential traveltimes for different heights
• 4D source characteristics: location and time. Is the source moving (bolide) or static (nuclear test)?
What might be derived and why?
Atmospheric models
Raytracing for the 1st arrival DIA
Differential traveltime modeling
Observed Δt: 2.94±0.01 sMinimum at 0.03 s: 32, 56 km
Observed Δt: 3.37±0.15 sfound at 0.22 s: 27, 57 km
Trajectory reconstruction
Conclusions and discussion
The source is identified as moving, this bolide could be located in 4D by two nearby arrays.
Reported time of occurrence and path confirmed. Only convergent solutions found for ECMWF
models. snr of 17 in DBN and 2 in DIA: spatial coherence
lost in larger aperture array, resp. 60 and 1500 m. Average of DBN and DIA origin time correct, but an
absolute difference of ~8 sec caused by uncertainties in model and bearings.