HR: 0830h
AN: U31B-0006    [PDF]
TI: Infrasound Signal Coherence Observations From Distant Sources - Source Effects, Path Effects and Near-Receiver Noise
AU: * McCormack, D A
EM: cormack@seismo.nrcan.gc.ca
AF: Geological Survey of Canada, 7 Observatory Crescent, Ottawa, On K1A 0Y3 Canada
AB: The numbers of modern infrasound arrays has been increasing rapidly in recent years. The availability of data from these arrays has resulted in a substantial increase in the number of both planned and opportunistic recordings of large sources at long ranges. This work presents a systematic study of signal coherence measured across baselines of 100 metres to 3 km from sources at ranges of 10$^{2}$ to 10$^{4}$ km. Coherence estimates can be robustly made at frequencies between roughly 0.4 and 4 Hz. At lower frequencies coherent noise makes coherence estimates unstable, and at higher frequencies signal to noise is too low. As well as coherence measurements which scale with frequency, signals show systematic variations with source type which may be useful for example for bolide signal identification. In addition, signals have a clear coherence dependence on range which we interpreted as due to atmospheric scattering. Coherence measurements are affected by local noise bursts at individual elements of an infrasound array. We compare observations of noise fields at infrasound arrays with simulations to develop a noise model that permits estimates of the probability of interference of a signal observation with noise bursts, and apply this to the question of optimal infrasound array configuration.
DE: 0394 Instruments and techniques
DE: 3322 Land/atmosphere interactions
DE: 3360 Remote sensing
DE: 3394 Instruments and techniques
SC: U
MN: 2003 Fall Meeting