Automated damage detection methods have application to instrumented structures that are susceptible to types of damage that are difficult or costly to detect. The presented method has application to the detection of brittle fracture of welded beam-column connections in steel moment-resisting frames (MRFs), where locations of potential structural damage are known a priori. The method makes use of a prerecorded catalog of Green’s function templates and a cross-correlation method to detect the occurrence, location, and time of structural damage in an instrumented building. Unlike existing methods, the method is designed to recognize and use mechanical waves radiated by the original brittle fracture event, where the event is not known to have occurred with certainty and the resulting damage may not be visible. An experimental study is conducted to provide insight into applying the method to a building. A tap test is performed on a small-scale steel frame to test whether cross-correlation techniques and catalogued Green’s function templates can be used to identify the occurrence and location of an assumed-unknown event. Results support the idea of using a nondestructive force to characterize the building response to high-frequency dynamic failure such as weld fracture.