Structural Engineering · Engineering Glossary
Seismic load is the inertial force exerted on a building during an earthquake, caused by the acceleration of the building mass due to ground motion. Seismic loads are horizontal forces (and in some cases vertical) that the lateral force resisting system must resist without collapse.
The magnitude of seismic loads depends on the building's mass, its stiffness and period, the site's mapped acceleration values (Ss and S1 from ASCE 7), the soil site class, and the building's Seismic Design Category and Risk Category. ASCE 7 provides equivalent lateral force, modal response spectrum, and response history analysis procedures for determining seismic design forces. Seismic forces are applied at each floor level proportional to the story weight and height. Unlike wind loads, seismic forces depend on the building's own weight — heavier buildings attract larger seismic forces, which is one reason lightweight construction can be advantageous in high-seismic regions.
Apex Grid Engineering maintains this glossary as a resource for architects, contractors, developers, and property owners who encounter unfamiliar engineering terminology on their projects.
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