Seismic arrays permanently installed over a hydrocarbon reservoir can record data continuously, even in the absence of active seismic shooting. Here we study ambient-seismic noise tomography as a tool for continuous monitoring. This is of interest for both monitoring production-related changes over a long time scale (years), but it may also be a source of data for monitoring hazards over short time scales (days to weeks). We compare cross-correlations of partial recordings to cross-correlations of the full recording as a function of absolute recording time, inter-station distance and frequency. We use straight-ray tomography to image the virtual-seismic sources for travel times picked after band passes for various frequencies. The correlations converge faster for nearby receiver pairs and lower frequencies than for further receiver pairs and higher frequencies. The convergence rate also depends on the strength of the microseism energy in the ambient seismic field. Features visible in ambient-seismic noise tomography images of Scholte wave group-velocity for various frequency bands are compared to slices of a P wave velocity cube obtained from full waveform inversion of active seismic data. Clear similarities indicate that the Scholte wave group-velocity between
Hz forms an image up to a depth of
meters. Clear similarities indicate that the Scholte wave group-velocity between
Hz forms an image up to a depth of
meters. This study shows the feasibility of ambient-seismic noise tomography monitoring of the near surface.
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