Hi,
Yes, you can easily (though "easily" depends a bit on how comfortable you are with this matter) set an initial deformation surface (NOT a "height contour") with the tools in "Seismology -> Elastic deformation -> Draw fault", or import a fault trace, or import a slip model.
If you select the draw fault, after drawing it, right-click on the line and select the "Mansinha" option. Next, fill out the boxes and compute the deformation model.
Use this grid and the bathymetry grid, a by the way you should do the previous step on a figure with the bathymetry to ensure that the two grids are compatible, as in puts to the "Tsunami -> TINTOL" tool