A method for mapping shear wave velocity in biological tissues includes using an ultrasound transducer to generate mechanical excitations at a plurality of locations in a region of interest. An MRI system is used to capture a phase image of each mechanical excitation, wherein motion encoding gradients (MEGs) of the MRI system encode a propagating shear wavefront caused by the mechanical excitation. A plurality of shear wave velocity maps is generated based on the phase images, wherein each shear wave velocity map depicts velocity between adjacent propagating shear wavefronts. The shear wave speed values are combined to generate a composite shear wave velocity map of the region of interest.