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Detection, Propagation, and Modeling

Detection, Propagation, and Modeling. Infrasound Technology Workshop Bermuda, 2008. Detection using Infrasound and Seismic Station Hedlin et al. Detection of a Bolide Event using novel configuration of Seismic and Infrasound Stations. Locations Determined from Seismic Detections

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Detection, Propagation, and Modeling

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  1. Detection, Propagation, and Modeling Infrasound Technology Workshop Bermuda, 2008

  2. Detection using Infrasound and Seismic StationHedlin et al. • Detection of a Bolide Event using novel configuration of Seismic and Infrasound Stations. • Locations Determined from Seismic Detections • Signals at infrasound and seismic stations well correlated. • General characteristics of atmospheric propagation understood, but not every detail • Acoustic to seismic coupling is variable.

  3. Automated Detection and LocationLars Ceranna et al., • Again novel network configuration with IMS and auxiliary stations. • 630,000 detections w/ 180,000 in the IMS bandpass • Seasonal variability explained with 80% ducted in the Stratospheric waveguide • Assumed constant Celerity in the inversion procedures.

  4. Multiple Explosion in EuropeDavid Green et al. • Four events investigated with multi-station detection for each. • Again seismic information (ground-truth). • Delectability followed expected seasonal patterns. • Observed coda for several closely spaced events nearly identical. • Not all detections for one event could not be predicted.

  5. Effects of Turbulence at Long Distances + Results from ISTC project #2845Kulichcov et al. • Observation of disposal of missile and ordnance. • Gravity waves/turbulence effects important consideration in network detection and location. • Multipath arrivals modeled and understood • Excellent complement of radiosondes and rocketsondes to resolve fine atmospheric structure.

  6. Acoustic-Gravity Waves from MeteorsDoug Revelle • Airwave objects • Give up on the Pierce-code (no leaky modes, exclusively linear theory) • Bolides multiple events per year (~20-30) • Review of source function for these events • “What you assume determines what you get”.

  7. Numerical Simulation of Attenuation and Non-linearlity • Finite-difference time-domain (FDTD) • Refraction and attenuation depends on frequency • Dispersion with altitude – attenuated computed to be less than Sutherland and Bass.

  8. Near-Field Clutter reductionSzuberla et al. • Identify signals that are too close to be of interest • Initial paper used the array to check for wave front curvature • New approach add additional element at distance

  9. InfraMonitor2.0Arrowsmith et al. • New detector accounts for temporal variability of correlated noise. • Signal association and location via a grid search algorithm with bounding constraints on celerity and back azimuth. • Application to regional infrasound network and ground-truth events (ordnance disposal) in Utah. • Improved detection and location statistics over existing approaches.

  10. Infrasound from Railroad BridgesMcKenna et al. • Near field portable array deployment to investigate acoustic radiation from railroad bridges. • Highly instrumented source with supporting meteorological observations. • Nocturnal inversion layers are important.

  11. Time Domain Parabolic Equation to Model Ground-truth eventsGibson et al. • Incorporation of gravity wave fluctuations in TDPE explain previously unexplained observed phases. • Improved phase identification. • Gardener Spectrum, independent of location and time.

  12. Ground Truth Events from Quarry BlastsHee-il Lee et al. • Various industrial sources in South Korea, original source locations near quarry region out in the ocean. • Seismo-acoustic event detection over all seasons. • Obtained ground-truth event information with deployment of near-field array. • Reexamined detection and location with regional information obtained improved results including local meterological information, observed celerities generally as expected. • Surface wind fields did not seem to effect detectability.

  13. Common Themes • Seismo-acoustic monitoring for improved detection and location • Internal Gravity-wave important to explain stratospheric refraction in some circumstances, also invoked to explain scattering out of elevated ducts • Beginning to think incorporation of more detailed propagation models in detection and location location algorithms.

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