This refers to mechanical collapse of certain structures, e.g. building, bridges etc. This causes people to get buried in the debris. Possible presence of live beings in the debris does not allow the use of heavy earth moving equipments, and, manual rummaging through heavy concrete structures is very effort prone as well as time consuming.
Usually, structural collapse does not happen suddenly. There are signs given – which when ignored – could lead to structural collapse. Structural collapse could happen – because:
1. old building and bridges etc. have not been given proper care and preventive maintenance has been ignored for a long while
2. alterations are made to the civil structure, without considering the load bearing capacity
If you are working/residing in a building, which does not seem to be well-maintained, you might be at risk of getting caught in, when the building collapses. Its much better to get the building repaired appropriately, before its too late.
If you are making renovations to your building – causing structural changes, its best to do these under the guidance of appropriately qualified Structural Engineers, Civil Engineers or Architects. This will significantly reduce the chances of the collapse. Since this kind of disaster mostly preventable (and, has a certain degree of predictability), it should be avoided.
However, in case, one is still stuck in a situation of collapsing structure, the primary aim should be to save oneself from instantaneous damage. Usually, help would start arriving in a few hours (maximum). If you have survived the immediate impact, most probably, you might get rescued soon, and, might get medical attention.