What does a secondary cave-in refer to?

A secondary cave-in refers to the subsequent collapse that occurs after the initial collapse of a structure or an excavated area. This term is crucial in rescue operations, particularly in scenarios involving trench or structural collapse, because it underscores the risks rescuers face as they attempt to access victims or assess the situation. Understanding that a secondary cave-in can happen helps responders to implement appropriate safety measures and protocols to protect themselves and any potential victims still trapped within the collapsed area.

The other options do not accurately define a secondary cave-in. The idea of a rescue conducted after the first response refers to the actions taken by teams following the immediate emergency response, which is unrelated to cave-ins. Additional support structures relate to preventative measures taken to stabilize an excavation but do not define what a secondary cave-in is. A warning signal for rescuers could pertain to alerts regarding potential dangers, but again, this does not capture the nature of a secondary cave-in itself.