Yes, Buried pipe in CII model is restrained by soil springs, and if ground shaking and whole soil and pipe will shake together, you can image the situation like Richard's example.
what your project should do that depend on your project specification and engineer judagement, we normally not consider seismic on plant design,
only pipeline project (such as cross country from USA to Canada) is considered to do seismic analys for buried pipe.
only issue is ground fault cause pipe break, that is not CII can do,
you have to go FEA with specific model, Abaqus or Anasys by Mohr-Coulomb model or PSI model.
Regards,
Limin