Processing a Partially Coherent Large Seismic Array for Discrimination
Abstract
A stochastic model has been proposed to characterize the telesceismic short period P-wave signal variations observed within a Large Aperture Seismic Array (LASA). The model asserts that, in the frequency domain, the received signal is equal to some average signal multiplied by a random gain and phase. Within a Montana LASA sub-array the mean value of the modulus squared of the random term can be roughly approximated by 1 + 0.18f squared, where f is frequency. For sensors drawn from the full LASA aperture the value is approximately 1 + 2.0f squared. An incoherent signal processing method, spectraforming, is introduced as a viable alternative to beamforming for obtaining spectral information at frequencies above about 1.0Hz. The spectraform is essentially the average power in sensors with a correction subtracted for background noise power contributions. It is demonstrated that although beamforming will give more noise rejection than spectraforming the latter can be superior in terms of output signals to noise ratio when input signal variations between sensors are large. Expressions have been obtained for the signal power spectral density expected from various modes of processing.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 27, 1970
- Accession Number
- AD0715917
Entities
People
- Guy T. Kuster
- Richard T. Lacoss
Organizations
- Massachusetts Institute of Technology