The U. S. Geological Survey (USGS) ShakeCast system is a freely-available, post-earthquake situational awareness application that automatically retrieves earthquake shaking data from ShakeMap, compares intensity measures against users' facilities, sends notifications of potential damage to responsible parties, and generates facility damage assessment maps and other Web-based products for emergency managers and responders. The ShakeMap/ShakeCast combined system allows a consistent approach for the evaluation of facility performance using the ShakeMap methodology by combining observations with ground motion predictions and covers major geographic regions and earthquakes, real-time, historical, and scenario, worldwide. We present common approaches to assessing facility impact estimates by combining measured or estimated ground-motion parameters with vulnerability functions. Vulnerability functions can be pre-computed, use one of these ground-motion parameters as input, and produce a multi-state discrete output of damage likelihood (or, inspection priorities). Two custom modules for evaluating Arias Intensity and Newmark landslide displacements are presented as examples of using the ShakeCast application with more advanced, customized damage functions. ?? 2009 ASCE.