Furthermore, the causal mechanisms and nature of earthquake-related injuries are difficult to determine precisely, as are the appropriate variables and indicators describing such injuries. One must consider hazard exposure; construction types and their performance during earthquakes; the influence of nonstructural components, building components, and building contents; building occupancy and the behavior of occupants; emergency and rescue response; and medical treatment provided. Not surprisingly, one is soon faced with the problem that such information is very difficult to collect because it must be collected immediately after the impact when conditions are most chaotic and all qualified personnel are directed to the primary life-saving effort (132). This use of personnel is, in most cases, justifiable; however, without the active assistance of search and rescue personnel, "backtracking" injuries from hospitals to specific building-collapse sites may be impossible.