An experiment to detect nonlinear seismic responses on exploration/monitoring scales

Summary One of the objectives of the 2012 CREWES/University of Calgary seismic field experiment, near Priddis AB, was to revisit the idea of measuring nonlinear seismic responses. Our approach involves comparing data from multiple sources activated individually and together. We consider the difference between responses from (1) the CREWES Envirovibe carrying out a linear sweep, (2) a standard (Geokinetics Mertz 22) vibe vibrating at a fixed 25Hz, and (3) the two simultaneously. If the Earth responds nonlinearly to seismic sources, the difference between (3) and (1)+(2) should be non-zero, though relatively small. We show examples of the uncorrelated data for these sweeps, and comparisons of norms of the data differences as above. Differences are visible, which must be examined to distinguish between true seismic nonlinearity and vibe feedback. Pursuing these potential explanations of our measurements is the near term research plan.