1 / 18

Large Experimental Infrasound Array at Deelen, detection and signal analysis

Large Experimental Infrasound Array at Deelen, detection and signal analysis. Hein Haak and Läslo Evers haak@knmi.nl evers@knmi.nl http://www.knmi.nl/~evers. Measuring infrasound at KNMI. Distinguish between earthquakes and sonic sources (start of interest in 1985)

evadne
Download Presentation

Large Experimental Infrasound Array at Deelen, detection and signal analysis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Large Experimental Infrasound Array at Deelen, detection and signal analysis Hein Haak and Läslo Evers haak@knmi.nl evers@knmi.nl http://www.knmi.nl/~evers

  2. Measuring infrasound at KNMI • Distinguish between earthquakes and sonic sources (start of interest in 1985) • Research in the context of CTBT • Royal Airforce (Klu) driven research on sonic booms and chemical explosions • Couple seismology and atmospheric research • Provide public information on atmospheric events

  3. KNMI Microbarometer • Broad band: 0.002 – 30 Hz, low inlet volume • Robust, low cost ($2000), almost off the shelf

  4. Details of the KNMI microbarometer

  5. Planned and installed IS Arrays

  6. Array detection and analysis • Infrasound has generally low signal-to-noise ratios and amplitudes are hard to predict  efficient noise reducers signal stacking to enhance snr,  state of the art detectors: Fisher, PMCC • Array processing for source characterization arrival time, apparent sound speed and back azimuth, other? (frequency content, wavelet scale, duration)

  7. DIA: the Deelen Infrasound Array • 16 KNMI microbarometers • 1.5 km aperture • Porous hose noise reducer • Low cost test facility for infrasound

  8. Array design criteria • Isotropic or omni-directional response  circular shaped main lob • High resolution, minimal energy spreading delta-like main lob • Avoid spatial aliasing  side lobs low amplitude and far from main lob Monochromatic response to 0.2 Hz plane wave

  9. Fisher ratio Time domain Fisher analysis • Evaluation in the slowness domain

  10. Low S/N ratio signals • F: Fisher statistic value, SNR: Signal to Noise Ratio in terms of Power, N: Number of array elements • Usually, F > 3 indicates more than 90% change of a coherent signal (F may be lower than 3) • For N=16  SNR=0.125 (Amplitude Ratio=0.3)

  11. Infrasound from a meteor • Time since 2001.10.27 19u28m47.4s UT • From 400 to 500 s slight increase in amplitude and frequency • Band pass filter 0.5 to 1.5 Hz

  12. Time domain processing

  13. Frequency domain Fisher analysis • Frequency–slowness power spectrum • Fisher coherency

  14. Frequency-slowness analysis Single frequency slowness plot

  15. 24 hours of infrasound data Time axis starts on 2001, July 28

  16. Airplanes at close range

  17. Example of Etna’s infrasound

  18. Summary and outlook • Detection of small signals is essential in infrasound, the lowest yield explosions are of interest, wind and temperature profiles determine signal amplitudes • Many sources of infrasound are recorded, some are yet unknown • Back azimuth and arrival time are needed to localize infrasonic events, more parameters are helpful • High wind noise reducers may be small and smart arrays

More Related