Accelerations, velocities, or displacements of the ground produced by seismic waves radiating away from earthquake sources.
NOTE A fixed offshore structure is founded in or on the seabed and consequently only seabed motions are of significance. The term ground motions is used rather than seabed motions for consistency of terminology with seismic design for onshore structures.
Source:API RP 2EQ, Seismic Design Procedures and Criteria for Offshore Structures, First Edition, November 2014. Global Standards