Thoughts on Processing and Related Items R. W. Whitaker and D. O. ReVelle

1. Thoughts on Processing and Related Items R. W. Whitaker and D. O. ReVelle Los Alamos National Laboratory Infrasound Workshop University of Hawaii Kona, Hawaii 11/12-15/01

2. Early Infrasound

3. Monitoring and Research • Processing for monitoring role is not the same as processing for research • Research will make monitoring better and refine processing in general (at least if done well) • Some types of signals may not be of interest in monitoring but may be quite valuable for research • Very short impulses (unless very large amplitude) • Nearly monochromatic signals (except for background microbaroms) • Single station detections • Automated monitoring tasks can and do use these aspects

4. Processing Environment • Monitoring task means detecting at as large range as possible (low SNR) • May have additional signals (events or noise) • Relatively small number of elements (degrees of freedom) • Detection by sparse arrays at low SNR events in potentially multiple signal environment • Need a variety of tools

5. Some Packages in Use • NOAA slowness plane correlation (LANL since ‘83) • DFX • Infra_tool • PMCC • UAF codes plus pure state filter • FK, STA/LTA, power, F statistic

6. Other Tools • Frequency filtering (by default) • Signal subtraction - very effective in some cases • Wavelets • Principle components, SVD, eigenvalues etc. • Neural nets • High resolution beamformers • (work by G. Smart on multiple signal FK)

7. Test Cases • Desire robust and effective processing • Test cases for exercising software • monitoring type events - duration, f, etc • ground truth • good SNR and low SNR • A role for synthetics? • False alarms, rates and measures

8. Summary • Testing of analysis approaches can be done as more stations come on line, with well observed signals • Need progress in automated and analyst tools • Need to try some novel tools • Need framework and test cases for comparisons and evaluations