A thorough description of how to process microseismic data and the underlying theory, of what can and cannot be inferred, and to what level of certainty, the discussion follows the passage of a seismic wave – from a source triggered by hydraulic stimulation, through hydrocarbon-bearing formations, towards motion sensors. Over the past decade, microseismic monitoring, a technology used to evaluate the completions of wells drilled to produce hydrocarbons from unconventional reservoirs, has grown increasingly popular among oil and gas companies. Microseismic Monitoring, by Vladimir Grechka and Werner M. Heigl, presents a thorough description of how to process microseismic data and the underlying theory, of what can and cannot be inferred, and to what level of certainty. The layout of the book follows the passage of a seismic wave – from a source triggered by hydraulic stimulation, through hydrocarbon-bearing formations, towards motion sensors. The analysis of various approaches to harvesting the source-related information from microseismic records has singled out the accuracy of the velocity model as the most critical ingredient for the quality of microseismic deliverables and our understanding of the information contained in those. An accurate velocity model, fully accounting for the strong elastic anisotropy of hydraulically fractured shales, is a prerequisite for obtaining precise event hypocenters and interpretable seismic moment tensors. The ray theory complemented by its modern extensions, the paraxial ray tracing and Frechet ray tracing, provides the only practical means available today for building such models. This book was written for geophysicists interested in learning advanced microseismic data-processing techniques.