Earthquake warning system may save lives
JOHN EDENS IN QUEENSTOWN
Last updated 05:00 05/03/2011
An earthquake early-warning system is conceivable for the South Island alpine fault and could give people 30 seconds to get out of buildings.
Geologists and researchers agree an alpine fault earthquake poses the main seismic hazard in the South Island.
GNS Science tectonic geologist Dr Rupert Sutherland – the project manager of a multi-disciplinary team investigating results from instruments embedded deep within boreholes along the fault – says an early-warning system is conceivable.
"In practice, you do not need that much warning if you want to stop a train or turn a power station off.
"You only need seconds to prepare."
The borehole project was not conceived with early-warning systems in mind but the topic was being discussed in geological circles, Dr Sutherland said.
Whereas last month's 6.3-magnitude Christchurch earthquake was a sudden, no-warning event, shallow and close to the city, an alpine fault event was different, he said.
A rupture could take minutes to run along the entire length of the fault, in either direction, or rupture in stages.
"An alpine fault event is unusual, it could be hundreds of kilometres long, it could take two minutes for the fault to unzip so you then have a little bit of time as the waves travel.
"Conceivably, with good instruments, you could get a minute's warning," he said.
University of Otago geologist Professor Richard Norris – a member of the university's borehole project team – said a system using high-sensitivity equipment, high-speed computers and radio or satellite communications could pinpoint a quake in seconds.
An early-warning system could give parts of the South Island between 30 seconds and 2 minutes to prepare, Prof Norris said.
"It might allow people to get out of buildings, it might give just enough warning to help immediate responses.
"It might take three minutesto rupture from Hokitika to Milford – you could give people warning."
Technology was available but it was not clear how the information would be quickly conveyed to people, he said.
The alpine fault is a 650km-long split in the earth's crust between Fiordland and Marlborough.
It marks the point where the Pacific plate and Indo-Australian Plate meet, roughly following the western edges of the Southern Alps.
The quake recurrence rate is about once every 300 years, with the most recent event in 1717, which means a large earthquake of up to magnitude 8 is possible this century.
Japanese authorities use a seismometer network as an early-warning system and last month a sensor array trial started in California to give people seconds or longer if the San Andreas fault ruptured.
In California, a test system in the Coachella Valley uses a network of sensors and high-speed communications to send alerts, potentially warning people seconds or up to a minute before a quake.
Sensors detect early-stage waves from an earthquake before more damaging seismic waves propagate.
- The Southland Times