Microseismic waveforms and velocity heterogeneity: Towards full-waveform location algorithm

Seismic forward modeling is an integral component of microseismic location algorithms, yet there is generally no one correct approach, but rather a range of acceptable approaches that can be used. Since microseismic signals are band limited, the length scale of heterogeneities can significantly influence the seismic wavefronts and waveforms. This can be especially important when subsurface heterogeneity is strong and/or vary on scales lengths equivalent of less than the dominant source wavelength. In this paper, we show that ray-based approaches are not ubiquitously suitable for all microseismic applications and hence we argue that for advanced imaging techniques in unconventional reservoir settings, ray-based algorithms may not be suitably accurate. Here we focus on exploring the feasibility of using one-way wave equations as forward propagators for full waveform event location techniques. One-way wave equations are capable of modeling the evolution of important and observable wave phenomena and could represent efficient full waveform modeling tools. As a feasibility study, we focus on the acoustic wave equation to explore efficiencies and compare traveltime and amplitude errors. However, the results have implications for one-way wave equations for elastic and anisotropic media.