What is an earthquake?

A rock breakage, usually deep within the earth, which causes a sudden shaking of the earth's surface.

Causes of an earthquake

Stresses built up from movement deep within the earth are released in the earth's brittle crust.

Types of earthquake

• Surprisingly, earthquakes do differ, depending on the part of the world in which they occur. Australian earthquakes have a shallow focus, the site of the earth's crust where the earthquake occurs.
• Shallow earthquakes wreak the most damage.

Likely impact of an earthquake

• Depends on where a person is when the earthquake occurs.
• Falling objects and debris cause many casualties, because the shaking damages buildings. The longer an earthquake lasts, the more extreme the damage.
• Many deaths occur because people move prematurely during an earthquake and are struck by falling objects.
• Fallen power lines can leave communities without power.
• Broken chimneys, gas or electrical lines can cause fires. Chemical spills create hazards, and broken water mains can cut water supplies.
• Earthquakes can trigger landslides, seismic sea waves (tsunamis). If dams fail, flash flooding can occur.

Warnings

• There is no accepted method to predict earthquakes. Be prepared.
• Some regions are more earthquake-prone than others.
• Parts of South Australia -- including Adelaide and the mid-north -- are an earthquake hazard area with a high potential for future earthquakes.
• Earthquakes have been reported in South Australia since 1837, one year after white settlement, and formally since 1897.

Emergency action: earthquake

Before

• Check that your insurance policy covers earthquake damage and that you are fully insured.
• If buying a house, remember that brick veneer is more flexible and earthquake resistant than double brick and stone, and old mortar may deteriorate.
• In existing buildings, check for unsupported masonry parapets, gables and chimneys, and repair loose roof tiles and cracks in walls.
• Brace tall, free-standing bookshelves and water heaters to stop them falling over.
• Store breakables, heavy items and hazardous liquids on bottom shelves.
• Secure suspended cupboard doors with heavy latches.
• Have battery powered radio and torch by your bed.
• Know the safest areas during earthquakes (see 'During').
• List emergency numbers: police, State Emergency Services, fire, ambulance; and gas, power and water supplies.

During

• If indoors, stay there (keep clear of falling debris outside).
• Keep clear of windows, chimneys and overhead fittings.
• Shelter under (and hold onto) a sturdy table, bench or doorframe.
• In high-rise buildings, stay clear of windows and outer walls. Get under a desk.
• Don't use lifts because you may be trapped.
• In crowded areas or buildings, don't rush for the doors. Move clear of overhead fittings and shelves.
• If outside, keep well clear of buildings, overhead structures, walls, bridges, power lines and trees.
• In a city street, shelter from falling debris under strong archways or doorways of buildings. Don't stand under awnings or parapets because they may collapse.
• In a vehicle, stop in an open area until the shaking stops. Beware of fallen power lines, damaged roads, including overpasses and bridges; and landslides.
• Listen to your car radio before moving.

After

• Watch for hazards and tend to injuries.
• Turn off electricity and water. Don't light matches and check for fuel leaks and damaged wiring.
• Check for injuries. Apply first-aid. Don't move the seriously injured unless in immediate danger.
• Check for broken water, sewerage or electrical mains.
• Don't use the phone immediately (to avoid congestion) unless there is a serious injury or fire.
• Check for cracks and damage in the roof, walls and chimneys.
• Expect aftershocks, so evacuate if the building is damaged.
• Listen to the local radio and heed warnings or advice on damage, service disruptions and evacuation.
• Don't waste food or water because the supply may be interrupted.
• Collect emergency water supplies from heaters, ice cubes, toilet tanks and canned foods.
• Avoid driving unless for an emergency (keep the streets clear for emergency services).
• Don't go sightseeing or enter damaged buildings.
• Stay calm and help others if possible.

South Australia's earthquake history

• The Richter Scale is a measure of the energy released at an earthquake's focus. The focus is the site in the earth's crust where the earthquake occurs.
• Since white settlement (1836), anecdotal records tell of earthquakes from 1837. Formal records indicate earthquakes at Beachport in 1897, 6.5 on the Richter scale; Warooka (1902: 6.0: two killed); Robe (1948: 5.6); Adelaide (1954: 5.6: damage $350 million); Wilpena (1972: 5.2); Tennant Creek (1988: 6.2: damage $10 million).
  
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