Large-scale PDE simulations using high-order finite-element methods on unstructured meshes are an indispensable tool in science and engineering. The widely used open-source PETSc library offers an efficient representation of generic unstructured meshes within its DMPlex module. This paper details our recent implementation of parallel mesh reading and topological interpolation (computation of edges and faces from a cell-vertex mesh) into DMPlex. We apply these developments to seismic wave propagation scenarios on Mars as an example application. The principal motivation is to overcome single-node memory limits and reach mesh sizes which were impossible before. Moreover, we demonstrate that scalability of I/O and topological interpolation goes beyond 12'000 cores, and memory-imposed limits on mesh size vanish.

23 pages, 11 figures