South Australian town tops annual list of Australian earthquakes two years in a row
The small town of Ernabella (Pukatja) in South Australia has recorded the largest earthquake in the nation for two consecutive years, experiencing a 5.7 magnitude event in both 2012 and 2013.
Geoscience Australia highlighted this event as one of 579 earthquakes recorded nationally during 2013. As in previous years, Western Australia was the most seismically active state, experiencing 332 earthquakes for this period. New South Wales recorded 94 events, South Australia recorded 88 and Victoria recorded 30.
Ernabella - a remote South Australian community in the northern part of the state has experienced three earthquake events in the past 27 years larger than magnitude 5.5. "Ernabella's seismic activity makes it one of the few areas in Australia to have experienced multiple large earthquakes in our recorded history," said Geoscience Australia Seismologist Hugh Glanville.
"The Ernabella earthquakes are unusual in that built up stress is being released through occasional larger earthquake events, rather than smaller more regular ones, as experienced in other parts of the country. Geoscience Australia will continue to investigate this area through the deployment of seismic monitoring equipment, and hopefully the recorded data will be able to shed some light on the earthquakes occurring there," said Mr Glanville.
Western Australia's high level of seismic activity can be attributed to the occurrence of earthquake "swarms" in its Wheatbelt region. Swarms are small earthquakes that occur multiple times per week or month in a confined geographic area with no associated foreshock or aftershock.
While Australia seems to experience a high number of earthquakes per year, most of the earthquakes are under magnitude 4.0, which are considered small as they don't usually cause damage. "We don't tend to experience large earthquakes in Australia as we do not sit on the edge of a tectonic plate, where larger earthquakes are more frequently experienced," said Mr Glanville.
"Australia's earthquakes are caused by the Indo-Australian plate being pushed northeast about 7cm per year, colliding with the Eurasian, Philippine and Pacific plates. This movement causes the build-up of stress in the interior of the Australian plate, which is then released during earthquakes," he continued.
Internationally, there were a number of large earthquakes recorded during 2013, including an 8.3 magnitude event in the Western Pacific region and a 7.7 magnitude event in Pakistan in September that created a temporary mud volcano island in waters near Gwadar, Pakistan.
Geoscience Australia monitors, analyses and reports on significant earthquakes to alert emergency managers in the Australian Government, State and Territory Governments and the public about earthquakes in Australia and overseas so that the appropriate level of emergency response and assistance can be dispatched. Geoscience Australia also operates the Joint Australian Tsunami Warning Centre with the Bureau of Meteorology.
You can help Geoscience Australia by reporting if you had felt an earthquake or know of an earthquake that recently occurred. More information can be found on our website at www.ga.gov.au/earthquakes/ or follow us on Twitter @EarthquakesGA.