The term "earthquake" or seismic tremor is a good description of the natural phenomenon which suddenly strikes an area causing damage that varies according to the intensity of the quake and local geological conditions. Close to the epicentre of the quake, the damage is direct, resulting in immediate destruction, such as collapsed buildings and other infrastructure, and indirect or secondary, resulting, for example, in fires, landslides, ruptured water and gas mains, interruption of electricity supplies, floods, etc..
It should be noted that the main quake is regularly followed by after-tremors, which may occur a few hours, days or even months later and which can be as violent as the initial earthquake. These can cause considerable additional damage which, unless protective measures are taken by the political authorities and their intervening bodies, can result in numerous victims.
Seismic waves (usually known by their Japanese name, "Tsunamis" or tidal waves) are caused by severe underwater earthquakes, or by collapsing sea or lake beds which often result from an earthquake or volcanic eruption. The waves produced spread in all directions at high speed (several hundred kilometres an hour) and, even after having travelled several hundred kilometres from their underwater epicentre, may become very high (tens of metres) when they reach shallow coastal waters or narrow bays. They thus give rise to major dangers for the exposed population and coastal infrastructure, such as hotel resorts, port installations and buildings
on the coast.
2. Preventive and protective measures
Because man has no control over earthquakes they must be considered as unavoidable events.
The damage they cause can, therefore, only be limited by taking long-term security measures to avoid the collapse of homes and important infrastructure, such as, for example dams, nuclear power stations, reservoirs of toxic or inflammable materials, power lines, communication networks, bridges, etc. It is the same for tsunamis. It is clear that such long-term security measures will be adapted to the major dangers that threaten different regions. This is notably the case for areas subject to high tectonic pressure or situated over geological faults, the main causes of high seismic activity (for example the areas situated around the Pacific Ocean and the Mediterranean).
It is up to the governments of the states at risk to establish local seismic building standards ensuring that buildings are resistant to earthquakes, having a solid base and foundations with shock absorbers or dampers that can reduce the effects of seismic tremors. Building should also be flexible and resistant to horizontal and vertical tensions. However, the recent earthquakes in Kobe and Los Angeles have shown that full protection from earthquakes does not exist.
It should be noted that states with civil protection shelters for use in wartime have at their disposal an additional safety measure to protect their citizens in case of an earthquake and, more particularly, from the aftershocks.
Logically, precautions against tsunamis can only consist in the establishment of an observation and warning system along the coasts which have been shown in the past to be subject to this type of disaster.
3. Intervention and rescue measures
Short-term community protection measures are limited to the permanent monitoring of seismic activity in a state or region by a specialist institute having at its disposaI a reliable network of observation seismographs and acting as an earthquake information and alarm centre. It is important to have access to experts who, using traditional observation methods (animal behaviour, water courses and water tables) and the most modern techniques of
geophysics, are able to analyse the potential danger.
However, because the duration of an earthquake is extremely short (generally less than a minute) it is clear that in practice protective and rescue measures are very limited. Essentially, these consist of behavioural rules and instructions for the population and the co-ordinated intervention of the rescue teams available at different political levels. Management of the rescue operations should be in the hands of established political authorities assisted by a coordinating high command and by a head of operations who will have available personnel who know the conditions inherent to this type of disaster. It is important to ensure that specialised personnel (civil engineers) carry out a technical reconnaissance of the stricken area so as to identify the dangerous buildings and areas, warn of chemical or radioactive danger if need be and protect the public. There should also be reconnaissance, rescue, protection and assistance teams who will help to deal with the secondary effects of the earthquake and any subsequent tremors. Operational squads and management structures will be established accordingly.
4. Instructions for the population
4.1 In case of potential danger
- Respect seismic building standards and any laws on land development and environmental protection especially with regard to building restrictions or bans.
- Find out about the protective measures in force and above all know the alarm signaIs and evacuation procedures, especially for tsunamis. Adapt your behaviour to the circumstances of each incident.
- Always keep an emergency kit ready for the family. This should include identity papers, personal documents (medical certificates, vaccination certificates and blood group), personal medicines and a battery operated radio and pocket torch.
- Each occupant of a building should know where the cut off points for water and gas are, and how to operate them. They should also know where the main electricity switch/fuse box is and how to work it.
-In an area at risk, buildings and the infrastructure in general should be regularly checked in order to demolish unstable elements likely to fall on the occupants or on people outside.
4.2 During a strong earthquake
- If outside, be careful of collapsing buildings and falling materials and infrastructures (pylons, bridges, statues, etc.).
- If inside, make your way to a safe place as quickly as possible (doorways, solid tables, desks, beds) and protect yourself from falling objects (furniture, lamps, etc.).
- Protect yourself from the aftershocks.
- In case of a water or gas Ieak, switch off the mains. Be careful of rubble and of damaged electrical cables, wires or other materials that carry electricity. If possible, switch off the power.
- Do not use the telephone unless absolutely necessary (do not overload the lines).
- Leave coast areas (danger of Tsunamis).
4.3 After the earthquake
- Keep calm, do not panic.
- Check if there are any injured in the neighbourhood and if possible help them.
- Listen to the radio but do not use the telephone unnecessarily.
- Check if there are any fires in the building and try to put them out or alert the fire service.
- Secure objects or parts of buildings that have become dangerous as a consequence of the disaster (mark, reinforce or demolish unstable structures). If outside, beware of falling materials and keep away from walls.
- Prepare yourself for new tremors and protect the wounded and handicapped.
- Collaborate with the official rescue organs and with the services that are helping the homeless.