There is no direct export feature for an interface in xyz representation, but there is an alternative way using the illumination maps. First a NORSAR3D ‘Eventset’ needs to be calculated in the NORSAR tracer (PP reflections for the interface which you want to export) then you can use this event set in the SMA (simulated migration amplitude) to calculate a SMA map.

In this process the interfaces will be resampled and thus the interfaces can be exported. While setting up the SMA you can underMapping surface geometry specify the sampling and dimensions of the desired grid. After the SMA is generated you can select under Export illumination map ASCII xyzf. Unfortunately you have to change the output by removing the SMA amplitude value afterwards, e.g., using awk '{print $1, $2, $3;}' grid.xyzf grid.xyz. That should provide you with the desired result.