The question of whether Australia is a safe place of an earthquake is still controversial. Australia is not located in an active seismic zone. In fact, Australia is not at the plate border but in the middle of plate tectonics . However, earthquakes still occur in small strength each day. According to seismologist it has been predicted that a large earthquake in Australia occur once every 100 years.
The worst earthquake in Australia was an earthquake that occurred in the state of New South Wales (NSW) over Newcastle, precisely in the date of 28 December 1989. This earthquake measuring 5.6 magnitude and was regarded as the most destructive earthquake. Estimated losses incurred approximately 4 billion dollars. There were precisely 13 fatalities and 160 people injured. The area of the damage was reaching as far as 800 kilometers including Sydney. There were 35.000 houses to be damaged, including 70.000 other damaged buildings in the same region and 300 houses collapsed. This earthquake is an earthquake with a magnitude of small but big effects because of the unstable ground and the old housing conditions that were not earthquake resistant.
A large earthquake could occur in Australia but was rare because the earthquake with great strength over 8.0 Magnitude occurs at tectonic plate boundaries. Low seismicity did not mean just a small earthquake occurred but large earthquakes happen in infrequent period.
The presence of the deadly earthquake in 1989 in Newcastle became evident that the earthquake had a large impact hazard on Australia. Since then, Australia has adopted earthquake-resistant structures as well as building since 1994.
Newcastle Earthquake Australia
Australia was right in the middle of the Indo-Australian plate which collided in the east with the Pacific plate and in the north with the Eurasian plate.
This condition makes the earthquake in the plate interior or so-called intra-plate earthquake which occur very rarely compared to the earthquake in the border of tectonic plates or so-called inter-plate earthquakes where a big earthquake often occur in areas such as active seismic zone, namely in countries over plate boundary such as in South America in Chile, in Asia which are Japan, China, and Indonesia, as well as New Zealand and the Himalayas or Nepal.
Earthquake Australia occurred because it is located in one of the lithospheric plates moving among the other plates in the earth’s outer crust layer. Mountain and fault generated by the pressure inside the crust in the plate boundary and the right in the interior of the plate as a result of the movement of the lithospheric plates.
Large earthquakes generated by a large pressure generated between the lithospheric plates engaged with each other. The motion of plate has resulted in convergent, divergent, and transform. Convergent produce a collision between the plates. Divergent produce separation and transform produces movement through each other. Earthquake in the plate boundary generates 90 percent of earthquakes worldwide.
Because the tectonic plates in earth’s crust are around 100 kilometers, earthquake normally is produced by the rupture of a layer of rock in the earth’s crust called a fault line which has different names in each region.
Seismologists in researching events that recur at fault’ rupture in Australia was hindered by thick blocking layers of soil and sediment.
Compared with other intra-plate earthquake region, Australia has a medium to high risks.