Hospitals are an integral part of a society’s critical functions designed to respond to man-made and natural disasters. Effective hospital capacity planning can significantly enhance the capability and effectiveness of treatment for emergency patients with injuries resulting from a disaster. Such information can be used for patient/ambulance routing, resource planning, and emergency operations management. In the current paper, we develop a generic simulation model that is capable of representing the operations of a wide range of hospitals given an earthquake disaster situation. Using results from our simulations, generalized regression equations are fitted to obtain steady-state hospital capacities. A parametric metamodel is then developed to predict transient capacity for multiple hospitals in the disaster area in a timely manner, as demanded by emergency operations management for guiding the routing and treatment of injured people.