While the full impact of the devastating Christchurch earthquake in New Zealand continues to unfold, some interesting environmental effects are being revealed.
The Christchurch earthquake caused a 30-million-tonne chunk of ice to break off from the Tasman Glacier, 200 km away in Aoraki/Mount Cook National Park on the west coast of the South Island. The 1.2 km long slab of ice plunged into Tasman Lake.A group of tourists on a boat in the lake at the time were walloped by giant 3.5 m waves created by the calving. The ice broke up in the water, forming several icebergs, one 250 m long.
The 30-million-tonne chunk of ice
Earthquakes are most destructive at the surface of the Earth, where the energy is released as the ground shaking. This means that when the epicentre is close to the surface, there's not much rock or earth for the tremor to travel through and act as a shock absorber.
Earthquakes do occur in Australia even though the nation does not sit on a tectonic plate boundary like in New Zealand.
The nearest boundary passed through Papua New Guinea to the north, into the Pacific Ocean and south to New Zealand.
Australia experiences "intraplate earthquakes" along fault lines dating back millions of years when parts of the country were on or near plate boundaries.
The greatest earthquake risk in Queensland is in Central Queensland.
A fault line just 30 kilometres west of Bundaberg ( the origin of a quake at least 5.4 in magnitude in 1935 ) has the potential for another large earthquake.
According to Seismologist Dr Kevin McCue of Central Queensland University in Rockhampton, the Australian continent is hit by a magnitude 6 earthquake every five to six years and currently, one is overdue, " so we're just waiting to see what will happen in Victoria ", and he thinks that it is just luck we haven't had an earthquakes under Melbourne and Sydney.
On December 28, 1989, a magnitude 5.6 earthquake struck Newcastle N.S.W, causing extensive damage and killing 13 people.
Earthquakes frequently occur close to plate boundaries, where the plates that make up the earth's crust push and slide against each other.
Despite sitting in the middle of a tectonic plate, scientists say Australia is subjected to the stresses and strains from movements at the edges of plate boundaries. "Compared to Canada, US, South Africa, central Africa and India, Australia is more active.
The warning comes after two moderate-sized earthquakes recently struck the Gippsland town of Korumburra in southeast Victoria. 06/03/2009
Both were felt 120 kilometres away in the city of Melbourne.
The earthquakes registered magnitude 4.6 on the Richter scale, with another small earthquake felt in the area in January 2009. Both struck 15 kilometres below ground and were associated with uplift of the Strzelecki Ranges.
Australian Earthquake warning, two separate geological studies have concluded that an area from Adelaide to south-east Victoria is seismically active and the next 'big one' could endanger lives and infrastructure.
