Effective Seismic Weight per ASCE 7-16 §12.7.2

A structure's effective seismic weight, W, should include the dead load and a minimum of 25% of the floor live load.

If a building sways during an earthquake, only that portion of the mass or weight that is physically tied to the structure needs to be considered effective. Also, certain types of live loads, such as storage loads, may develop inertial forces, particularly where they are densely packed.