Experimental images (top) and calculated images (bottom) for a modulated structure in a Sr2CuO3 superconductor, along [001]. The two-dimensional modulated structure results from metal ion shear displacements with half sine waves (Sr ion) and half cosine waves (Cu ion) along the [110] directions of the primary tetragonal La2CuO4-type structure. Oxygen occupancy and position have been derived in imperfect CuO1+x layers and calls into question the requirement of intact CuO2 sheets for superconductivity in High Tc cuprates.