Ushnish Basu
Ansys Employee

More detailed answer is here: https://forum.ansys.com/forums/topic/drm-approach-in-soil-structure-interaction/

You can use INTERFACE_SSI__AUX to record free-field motions and forces in a free-field model, and then apply them to the soil-structure model using LOAD_SEISMIC_SSI_AUX