Jarillo Michel, O. and Tsvankin, I., 2015. Estimation of microseismic source parameters by 2D anisotropic waveform inversion. Journal of Seismic Exploration, 24: 379-400. Waveform inversion (WI), which has been used primarily for high-resolution velocity analysis, can also be employed to obtain the source parameters of microseismic events. Here, we implement WI to estimate the location, origin time, and seismic moment tensor of microseismic sources embedded in VTI (transversely isotropic with a vertical symmetry axis) media. The algorithm operates with 2D multicomponent wavefields modeled using an elastic anisotropic finite-difference code. The gradient of the objective function for the three classes of parameters is calculated with the adjoint-state method. Although in the current algorithm the VTI parameters are assumed to be known, they can be included in WI at almost no additional cost. Synthetic tests for data from layered VTI media recorded by vertical receiver arrays show that it is possible to tightly constrain all source parameters, if a sufficiently accurate initial model is available. In particular, the source location can be estimated simultaneously with the moment tensor. The resolution of event location, however, somewhat decreases when the origin time is unknown or there is an error in one of the VTI parameters.