  We present a highly scalable 3D fully-coupled Earth & ocean model of
earthquake rupture and tsunami generation. We model seismic, acoustic and
surface gravity wave propagation in elastic (Earth) and acoustic (ocean)
materials sourced by physics-based non-linear earthquake dynamic rupture.
Complicated geometries, including high-resolution bathymetry, coastlines and
segmented earthquake faults are discretized by adaptive unstructured
tetrahedral meshes. A Discontinuous Galerkin discretization with ADER local
time-stepping (ADER-DG) yields petascale computational efficiency and
high-order accuracy in time and space.
  We compare the 3D fully-coupled approach to a benchmark problem for 3D-2D
linked models that use 2D shallow-water modeling. We present a large-scale
fully-coupled model of the 2018 Sulawesi events that links the dynamics from
supershear earthquake faulting to elastic and acoustic waves in Earth and ocean
to tsunami gravity wave propagation in the narrow Palu Bay. And we demonstrate
scalability and performance of the MPI+OpenMP parallelization on three
petascale supercomputers.
