1. A method of analysing seismic data from a geological volume divided into a plurality of voxels, for each voxel a respective neighbourhood being defined that includes that voxel and a predetermined arrangement of neighbouring voxels, the method including the steps of: calculating, for each voxel, the respective normal vectors of a seismic attribute vector field derived from the seismic data; calculating, for each voxel, a respective local structure tensor based on the normal vectors of the voxels of the respective neighbourhood; displaying a barycentric map having vertices corresponding to different anisotropy shape metrics of eigenvalues of the respective local structure tensor; calculating, for each voxel, the values of the anisotropy shape metrics for the eigenvalues of that voxel, such that each voxel has a corresponding location on the map; and showing a population density distribution of the corresponding locations of the voxels on the map.