UQ seismographs record huge earthquake

University of Queensland seismograph stations recorded an earthquake of magnitude 7.9 near the Santa Cruz Islands, in the southwest Pacific Ocean, at 10:02 p.m.(Queensland time) Monday night 21 April 1997.

The earthquake was located approximately 2160 km northeast of Brisbane and 2250 km east-north-east of Cairns.

The huge earthquake was recorded by the Charters Towers and Mt Nebo International seismograph stations managed by the Queensland University Advanced Centre for Earthquake Studies (QUAKES). The stations also recorded numerous after-shocks.

QUAKES' seismologist Dr. Steven Jaume said Monday's earthquake was the largest recorded in the world this year.

"Earthquakes of this size only occur about once a year," he said.

"The Santa Cruz Islands are part of the so-called Pacific 'Ring of Fire', a zone of earthquake and volcanic activity that surrounds the Pacific Ocean. About 75% of the earthquake energy released worldwide occurs in this zone.

"While earthquakes occur less frequently in Australia than around the Pacific Ocean, earthquakes as large as an estimated magnitude 7.2 have occurred within Australia. These 'intraplate' earthquakes pose a significant hazard, as evidenced by the 1989 Newcastle earthquake which killed 13 people and caused 3 to 4 billion dollars damage."

Dr Jaume said QUAKES conducted a reassessment of earthquake hazard in Queensland last year and the results revealed the earthquake hazard in the state was much higher than previously recognised. Queensland's largest earthquake occurred in 1918 and had a magnitude of 6.3, the largest recorded in eastern Australia.

Not enough was known about earthquakes in Queensland and an upgraded earthquake monitoring system was needed to collect the type of data needed for accurate earthquake hazard assessment, Dr. Jaume said.

"QUAKES is working with the Australian Geological Survey Organisation (AGSO) to improve earthquake monitoring and improve understanding of the earthquake hazard in Queensland, he said.

"Two new seismometer stations were installed in Cairns last month and new stations have been recently established at the Gold Coast. New seismometers are scheduled to be installed in Brisbane later this year."

Dr Jaume said QUAKES was developing a strong observational seismology program in addition to its already world-class program in advanced computer simulation of earthquakes.

"The combination of first-class programs in both computational and observational seismology will give us a unique ability to answer fundamental questions about earthquake predictability and earthquake hazard assessment," he said.

For further information, please contact: Dr Steven Jaume seismologist, QUAKES (Queensland University Advanced Centre for Earthquake Studies (telephone 07 3365 2176 fax 07 3365 7347).