Exposure

The first objective for a general earthquake protection programme is safeguarding human life. For this reason it is very important to assess the number of people involved, dead and/or injured.

There are various different causes for loss of human life: the collapse of buildings, bridges and other constructions and also road accidents. Then there are those linked to phenomena triggered by the earthquake, such as landslides, land liquefaction, tidal waves and fires. Various statistics obtained from major earthquakes around the world have shown that around 25% of deaths in an earthquake are due to none structural damage of buildings (falling partition walls, glass, cornices, roof tiles, etc.) and phenomena caused by the earthquake.

It can generally be estimated, with a certain margin for error and especially for more severe earthquakes, how many people were involved, using calculations based on the number of collapsed or damaged buildings. Several considerations are needed to be able to make these estimates:
• the number of people living in the buildings
• the time of the earthquake
• the possibilities of escape and/or protection
• how people were affected (dead or injured)
• the possibility of dying even after aid has been given.
It is very difficult to accurately estimate the consequences of an earthquake in terms of human lives at different times of the day and year. The number of people living in a house in fact varies from region to region, from the city to the countryside and depends on the size of families. Furthermore, in the daytime, the number of people present in a building depends on its use. For example, offices have maximum presence during the middle of the day and are virtually empty during the night. On the other hand, the number of people in a city dwelling in the evening and at night is, on average, lower than those present in a house in the countryside because cities offer more alternatives at these times, both for pleasure and work, often outside the home. Reference to the kind of buildings and relative inhabitants, however, may provide a global estimate acceptable for violent earthquakes that affect large areas.