3D Microseismic Wavefield Imaging Using the Energy Imaging Condition

Summary In passive monitoring of microseismicity, full-wavefield imaging offers a robust approach for the estimation of source location and subsurface properties. With multicomponent data and the 3D elastic wave equation, the coexistence of P- and S-modes at the source location in time-reversal wavefield extrapolation allows the development of imaging conditions that identify the source position based on migration principles. The correlation between decomposed P- and S-wavefields is the most common imaging condition used in passive elastic wavefield imaging. However, the PS imaging condition produces a nodal plane at the source location and requires Helmholtz decomposition, which is not feasible for anisotropic media. We propose an imaging condition for passive wavefield imaging that is based on energy conservation of the elastic wave equation. Our imaging condition also compares the different modes present in the displacement field, but produces a strong and focused correlation at the source location without wave-mode decomposition at each time step. Numerical 3D synthetic experiments demonstrate the advantages of the proposed imaging condition (compared to PS correlation with decomposed wave modes), its sensitivity with respect to velocity inaccuracy, its quality and efficacy in estimating the source location.