Illustration of the model domain Ω (for d = 3) and boundary Γ, which is further decomposed into the part coinciding with the surface of the rocky object, Γ_s, the lateral boundary Γ_l, and the bottom boundary Γ_b. While there are generally no restrictions on the choice of the model domain, in this work we construct Ω by vertical extrusion of parts of the surface of the rocky object with a constant depth. Therefore, the surface topography is also illustrated on the bottom boundary Γ_b.