Earthquake notifications are provided by Geoscience Australia, who analyse and reports on earthquakes within Australia and internationally. This is done on a 24/7 basis by Duty Seismologists for the purposes of tsunami warnings and to alert governments, emergency services and the general public of earthquakes in Australia and overseas.
Earthquake notifications for Western Australia can be found on the Geoscience Australia website.
There is no accepted method to predict earthquakes, however, some regions are more prone to earthquakes than others due to their location in proximately to earthquake faults. When an earthquake occurs, Geoscience Australia and the Western Australia State Emergency Service will work together to notify the community.
Geoscience Australia monitors seismic data from over 60 stations on the Australian National Seismic Network and over 130 stations worldwide. This is done in near real-time, 24 hours a day. Seismic data is also freely provided by overseas Governments who have national seismic networks. Geoscience Australia uses data provided by the Governments of New Zealand, Indonesia, Malaysia, Singapore and China. Data from global seismic networks are also provided by USA, Japan, Germany and France.
The seismic data is collected and analysed automatically and then immediately reviewed by Geoscience Australia’s Duty Seismologist. For earthquakes that have the potential to generate a tsunami, preliminary earthquake details are computed within 15 minutes. All other earthquakes are generally computed within 30 minutes
Earthquakes that can be located in Australia are catalogued and published on the Geoscience Australia website. The analysis includes the origin time and date of the earthquake, its location (latitude, longitude and depth) and its magnitude. Earthquakes outside Australia, but within our region, are published only for earthquakes with a magnitude of 5 or greater. Earthquakes occurring anywhere internationally with a magnitude of 6 or greater are also catalogued and published on the Geoscience Australia website.
The size of earthquakes is determined by measuring the amplitude of the seismic waves recorded on a seismograph. A formula is applied to these which converts them to a magnitude scale, a measure of the energy released by the earthquake. For every unit increase in magnitude, there is roughly a thirty-fold increase in the energy released. For instance, a magnitude 2.0 earthquake releases 30 times more energy than a magnitude 1.0 earthquake, while a magnitude 3.0 earthquake releases 900 times (30×30) more energy than a magnitude 1.0.
A magnitude 8.6 earthquake releases energy equivalent to about 10,000 atomic bombs of the type developed in World War II.
The effects of an earthquake depend on many factors, such as the distance from the epicentre (the point on the Earth’s surface directly above where the earthquake originated within the Earth) and the local ground conditions. Generally, for locations near the epicentre, the following effects may be observed:
|Magnitude||Description of Effects|
|Less than 3.4||Usually felt by only a few people near the epicentre|
|3.5 – 4.2||Felt by people who are indoors and some outdoors, vibrations similar to passing a truck|
|4.3 – 4.8||Felt by many people, windows rattle, dishes disturbed, standing cars rock|
|4.9 – 5.4||Felt by everyone, dishes break and doors swing, unstable objects overturn|
|5.5 – 6.1||Some damage to buildings, plaster cracks, bricks fall, chimneys damaged|
|6.2 – 6.9||Much building damage, houses move on their foundations, chimneys fall, furniture moves|
|7.0 – 7.3||Serious damage to buildings, bridges twist, walls fracture, many buildings collapse|
|7.4 – 7.9||Causes significant damage, most buildings collapse|
|8.0 and over||Causes extensive damage, waves seen on the ground’s surface, objects thrown into the air|