Kids-induced earthquake today at Parliament House
16 October 2002
Scientists were in the right place at the right time today, witnessing a rare and unusual type of earthquake, estimated to occur in Australia only once per year at the most.
The epicentre is believed to be located on the lawn in front of Parliament House in Canberra, close to Canberra's well-known Deakin Fault.
Seismologists at Geoscience Australia say that this particular seismic event has a unique and unmistakable signature, which indicates that this earthquake is related to the exuberant jumping of some 200 young children.
Smaller aftershocks of the group's natural ebullience were also detected soon after the initial event, when the children began heading off to their tours of Parliament House. Other after-effects of the quake also became apparent following the earthquake, such as irrepressible smiling by parliamentary staff.
The children seemed to spontaneously congregate and jump for joy in celebration of international Earth Science Week, which started on Sunday this week and continues until October 19.
Preliminary estimates of the local magnitude are being calculated by seismologists at Geoscience Australia.
What is an earthquake?
An earthquake occurs when rocks break under the stress created by the constant movement and collision of the thin jigsaw-like tectonic plates that form the surface of the Earth. Most earthquakes occur at the boundaries of tectonic plates. However, some earthquakes take place in the middle of plates - such as on the Australian continent - and these are called intraplate earthquakes.
The shaking of large earthquakes can cause considerable damage to buildings, and even the loss of life. Although the level of seismic activity in Australia is low compared to places such as Japan or New Zealand, earthquakes of magnitude 6 or greater occur in Australia on average about once every five years.
The epicentre of an earthquake is the point on the Earth's surface directly above the source of the earthquake, which can be as deep as 700 kilometres.
Australia's first-reported earthquake
The first reported earthquake in Australia was felt at Port Jackson (Sydney) in June 1788, when Governor Phillip reported:
"The 22nd of this month we had a slight shock of an earthquake; it did not last more than 2 or 3 seconds. I felt the ground shake under me and heard a noise that came from the southward, which I at first took for the report of guns fired at a great distance."
Similar earthquakes were felt in the early days of Adelaide (1837), Melbourne (1841), Hobart (1827) and Perth (1849).
How do we record earthquakes?
The instrument used to measure an earthquake is called a seismometer. Seismometers are devices attached to or buried in the ground, which convert the earthquake vibrations into an electrical signal. This signal can then be sent by telephone, radio or satellite to a recording device called a seismograph. The seismograph converts the electrical signal into a computer or paper readout, called a seismogram, which can be analysed by scientists.
Geoscience Australia operates a network of 32 seismometers around Australia. They provide information about earthquakes in Australia and our region.
What is a fault?
A fault is a fracture in the Earth's crust caused from the breaking of rocks. Once a fault forms, the rocks on either side may continue to grind along the same fault over many thousands or millions of years. The Earth's crust is riddled with small faults, most of which are not currently active and therefore do not produce earthquakes. Some of these faults can be seen at the surface but most are buried underground.
Faults can be uncovered during the building of road cuttings and other excavations, such as those found in State Circle near Parliament House in Canberra.
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