A method of analysing seismic data from a geological volume is provided. The geological volume is divided into a plurality of voxels. For each voxel a respective neighbourhood is defined which includes that voxel and a predetermined arrangement of neighbouring voxels. For each voxel, the respective normal vectors of a seismic attribute vector field derived from the seismic data are calculated. For each voxel, a respective local structure tensor based on the normal vectors of the voxels of the respective neighbourhood is calculated. For each voxel, the value of an expression which includes one or more of the eigenvalues (λ1, λ2, λ3) of the respective local structure tensor is calculated. The method can be used for seismic surveying, or to manage operation of or drilling of a subterranean well.