An earthquake is the sudden release of stress built up within the earth's crust. When the crust fails, energy waves are released which people and structures nearby experience as shaking.
Aftershocks are smaller earthquakes triggered by the initial shock. Aftershocks generally decrease in number and intensity over time.
Most earthquakes occur along plate boundaries. However, areas within plates, such as Australia, do experience occasional large intraplate earthquakes. WA has a long history of this type of event.
Earthquakes of magnitude 4 or less are reasonably common in Western Australia. Roughly one magnitude 4 earthquake occurs every five years in the Meckering area (~130 km east of Perth). The most active earthquake area in Australia is Burakin (~250 km north-east of Perth) where a magnitude 5.0 earthquake in September 2001 was followed by ~18,000 aftershocks over the following six months.
Scientists have never predicted a major earthquake. They don’t know how to and don’t expect to in the near future. However probabilities can be estimated for potential future earthquakes, looking at the likelihood that an earthquake will strike a particular area.
Possible impacts of an earthquake include:
The damage caused by an earthquake is dependent upon both the magnitude of an earthquake and the distance from the earthquake focus to vulnerable elements (e.g. buildings, people). Consequently, a smaller magnitude earthquake that is close to vulnerable elements can potentially cause more damage than a larger magnitude earthquake that is further away from vulnerable elements.
The nature of intraplate earthquakes make predicting risk difficult. However the history of earthquakes in the state demonstrates there is potential for large earthquakes.
MECKERING 1968 EARTHQUAKE
On 14 October 1968, a magnitude 6.9 earthquake struck the town of Meckering.
The town was destroyed and twenty people were injured but there were no deaths.
The earthquake caused ground movement which broke railway lines and ruptured major roads to Meckering.
Considerable shaking occurred in Perth alarming residents and causing damage to many older buildings.
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