Microseismic mapping of hydraulic fractures is improved by use of crosswell data to calibrate or verify dipole-sonic velocity data. The microseismic technique uses an array of triaxial receivers to detect microearthquakes induced by a fracture treatment to provide a real-time image of the fracture and the direction in which it propagates. To apply this technique, receiver orientation must be determined by detecting perforations or other energy sources in the treatment well. The ultimate goal is improved accuracy in microseismic mapping, but the results are useful in assessing the applicability of dipole-sonic logs.