Application of frequency-dependent multichannel Wiener filters to detect events in 2D three-component seismometer arrays

Wang, J. and White, R. S. and Tilmann, F. and Bordoni, P. (2009) Application of frequency-dependent multichannel Wiener filters to detect events in 2D three-component seismometer arrays. Geophysics, 74 (9). V133-V141. DOI

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Hydraulic fracture-induced microseismic events in producing oil and gas fields are usually small, and noise levels are high at the surface as a result of the heavy equipment in use. Similarly, in nonhydrocarbon settings, arrays for detecting local earthquakes will benefit from reduced noise levels and the ability to detect smaller events will be increased. We propose a frequency-dependent multichannel Wiener filtering technique with linear constraints that uses an adaptive least-squares method to remove coherent noise in seismic array data. The noise records on several reference channels are used to predict the noise on a primary channel and then can be subtracted from the observed data. On a test with an unconstrained version of this filter, maximal noise suppression leads to signal distortion. Two methods of im-posing constraints then achieve signal preservation. In one case study, synthetic signals are added to noise from a pilot deployment of a hexagonal array (nine three-component seismometers, approximately 150×150 m) above a gas field; noise levels are suppressed by up to 11 dB (at 2–10 Hz). In a second case study, natural seismicity recorded at a dense array (~10 m spacing) in Italy is used, where the application of the filter improves the signal-to-noise ratio (S/N) more than 20 dB (at 2–15 Hz) using 35 stations. In both cases, the performance of the multichannel Wiener filters is significantly better than stacking, espe-cially at lower frequencies where stacking does not help to suppress the coherent noise. The unconstrained version of the filter yields the best improvement in signal-to-noise ratio, but the constrained filter is useful when waveform distortion is unacceptable.

Item Type: Article
Uncontrolled Keywords: 09AREP; IA58
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Geophysics
Volume: 74
Page Range: V133-V141
Identification Number:
Depositing User: Sarah Humbert
Date Deposited: 11 May 2009 16:51
Last Modified: 23 Jul 2013 09:54

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