Earthquakes are a sudden shaking, vibration or trembling of the Earth's crust caused by the release of huge stresses due to underground volcanic forces, the breaking of rock between the surface, or by a sudden movement along an existing fault line.
Earthquakes are unpredictable and strike without warning. They range in strength from slight tremors to great shocks lasting from a few seconds to a few minutes.
The size or magnitude of earthquakes is determined by measuring the amplitude of the seismic waves recorded on a seismograph and the distance of the seismograph from the earthquake. These are put into a formula which converts them to a magnitude, which is a measure of the energy released by the earthquake.
Earthquakes can occur anywhere, no part of Earth’s surface is free from earthquakes, but some regions experience them more frequently.
Many factors contribute to the effects of an earthquake including: the magnitude, the depth of the earthquake, topography and local ground conditions. For further details on effects of earthquakes refer to:
Electricity and telephone lines, gas, sewer and water mains can be damaged; landslides, faults, subsidence and even tsunamis (huge seismic waves) can be caused leaving many people dead, injured or homeless.
Most earthquake casualties result from falling objects or debris because shocks can damage or demolish buildings and other structures.
Know your local earthquake risk
What you should do
- Ask your local Council if tremors or earthquakes have ever occurred in your area and what damage resulted.
- Study that information and ask your local Council about ways to make your house safer in the event of an earthquake.
- Find out how and where to turn off power, gas and water supplies.
- Plan together where your family will meet if separated.
- Know your safe areas during an earthquake.
- Check that you have adequate household and contents insurance and which hazards are not covered by the policy.
Emergency Kit is an important step to prepare for, survive and cope with emergencies.
Watch for possible warning signs
- Erratic animal behaviour - scared or confused pets or birdcalls not usually heard at night may indicate that an earthquake is imminent.
- Ground water levels - watch for sudden water level changes in wells or artesian bores.
When an earthquake hits
- If you are indoors - stay there (clear of falling debris outside). Keep clear of windows, chimneys and overhead fittings. Shelter under and hold onto a door frame, strong table or bench.
- In high rise buildings, stay clear of windows and outer walls. Shelter under a desk near a pillar or internal wall.
DO NOT use elevators.
- In crowded areas or stores, do not rush for doors, but move clear of overhead fittingsand shelves.
- If outside, keep well clear of buildings, overhead structures, walls, bridges, powerlines, trees etc.
- In a city street, shelter from falling debris under strong archways or doorways of buildings. Don't go under awnings as they may collapse.
- In a vehicle, stop in an open area until shaking stops.
- Beware of downed powerlines and road damage, including overpasses and bridges. Listen to your car radio for warnings before moving.
After an earthquake
- Expect aftershocks.
- Listen to your local radio station and heed warnings and advice on damage and service disruptions.
- Turn off electricity, gas, water and DO NOT light matches in the event of a gas or fuel leak. Check for injuries and apply first aid. DO NOT move seriously injured people unless they are in immediate danger.
- DO NOT use the telephone immediately (to avoid congestion) unless there is a life threatening situation.
- Evacuate the building if it is badly damaged.
- Do not waste food and water as supplies may be interrupted. Collect emergency water from heaters, ice cubes, toilet tanks and canned foods.
- Do not go sightseeing or enter damaged buildings.
- Try to stay calm and help others if possible.
- After an earthquake, do not phone emergency numbers for general information and advice. Call only if you require emergency assistance.
Further information about earthquakes
Seismology Research Centre
Geoscience Australia: Earthquake Information
Get Ready Queensland