Post by SA Hunter on Jun 7, 2016 10:23:50 GMT 10
www.adelaidenow.com.au/ipad/adelaide-earthquake-where-the-faults-lie/story-fn3o6wog-1226027404800
ADELAIDE'S last earthquake 57 yeas ago caused widespread damage - the next one could be worse.
THOSE who were awake that night would afterwards talk of the unnatural stillness in the air. Sounds seemed to carry for miles. Then out of that stillness came a humming sound, a bit like a far-away aeroplane. But instead of fading it grew louder and louder. Finally, one man recalled, the noise became an almighty rumbling, like a continuous drum roll; then a strange quivering started, before the veranda, the walls, and floor of his house started to move - gently at first, but then vigorously as the weatherboard building started bulging and swaying.
All across the city, the strange movement jolted people from their sleep. It was 3.40am. Some felt plaster falling on their beds, others headed outside to see brick walls collapsing, the tinkling sound of shattering glass was everywhere. The fire brigade chief was startled awake by the sound of the chimney collapsing on to the station's roof. Policemen on the beat were thrown to the ground. Watchmen at a city department store were terrified the building was about to collapse.
Such was the scene in Adelaide in the early hours of March 1, 1954.
Despite a lack of sophisticated measuring equipment it was estimated the city was hit by an earthquake around a magnitude of 5.5 on the Richter scale, with the epicentre somewhere near Darlington, about 12km south of the CBD. It unleashed nowhere near the power of the enormous shocks that have struck Chile, New Zealand and Japan since early last year. But until the Newcastle earthquake of 1989, the Adelaide quake was the most damaging recorded in Australia, and is a reminder that we are considered the most likely big Australian city at risk of a significant shock.
At the Victoria Hotel at Tapleys Hill the quake devastated the old pub. "It's the first time I've ever heard my wife scream," publican Alf Gibbons said later. "But when you see cracks opening in the walls and you hear a sound like a bomb going off, it's pretty frightening."
The St Francis Xavier Cathedral in Wakefield St was badly damaged; at the new Blackwood Community Hospital every room apart from the operating theatre was affected; in Mt Barker springs appeared in fields where none had been seen previously. In the city, the GPO clock's face was damaged. That was 57 years ago now, and time has perhaps dulled the impact the earthquake had on Adelaide. But the bill in today's dollars was about $150 million.
Since settlement, South Australia has experienced four damaging quakes. The biggest was a 6.5 jolt near Beachport in the South East which caused chaos at the nearby town of Kingston and was felt in Adelaide.
The story of the four quakes is recorded by former teacher Tom Dyster in his book, Strong Shock of Earthquake. Dyster was a young teacher in Kingston in 1948 when he first started to hear the story of the tremor which shook the town in 1897. More than 50 years later one of the students who was at the school that day would tell Dyster how frightening it all was. "Lew Jarman, who was one of those caught up in the crush, used to say how terrified he was as bigger children trampled on him and the plaster kept falling in chunks from the ceiling as he tried desperately to get on his feet and flee for safety."
Dyster's book covers the Mt Barker quake of 1883, Kingston in 1897, Warooka on the Yorke Peninsula in 1902 and Adelaide in 1954 and can be read on the Department of Primary Industries website. He is now 85 but still keeps an eye on earthquakes. "None of the earthquakes in SA was serious by the standard we are being introduced to at the moment overseas, but they are serious to the people on the spot," he says.
No one was killed in the 1954 tremor but if a similar quake was to strike Adelaide today we would perhaps not be so lucky. Judith Carr is as an executive director within the State Government but is also the Earthquake Hazard Leader for SA. It means she has examined all the risks and liaised with other departments such as the police to generate a response plan if the worst happens. "There has been significant residential and commercial development over the last 50 or so years and so a greater impact than occurred in 1954 would be expected," she says. "We have scenarios of damage likely for various earthquake magnitudes and, for exercise purposes only, assume that damage from an earthquake event would be similar to that of the 1989 Newcastle earthquake." That earthquake was the worst in Australian history. The damage bill was $1.5 billion and 13 people were killed.
Of course building standards have improved since 1954. In 1983 SA became the first state to adopt national standards to make buildings more earthquake resistant. Don Freeman, who is general manager of building policy in the Department of Planning, says this is a recognition that the state is at higher risk than the rest of the country. "Adelaide as a capital city has been recognised of all the capital cities as having a higher risk than probably all the others," he says. Freeman reckons most of the buildings constructed since 1983 would survive a quake, particularly those with a post-disaster function such as hospitals. They are designed to be flexible, rather than rigid, allowing them to absorb the energy of a tremor. Other older buildings, such as the SA Museum and the Town Hall, have been strengthened as well. He says most modern, well-designed homes should be OK but that there are weak points in older houses, particularly chimneys.
Despite all this, SA is regarded as geologically stable. There are no crashing tectonic plates such as those that produced the earthquakes in Japan and New Zealand. The Japanese earthquake, which measured 9.0, was about 178,000 times stronger than the tremor which hit Adelaide in 1954. The Japan quake was also about 11,220 times stronger than the 6.3 magnitude shock which devastated Christchurch last month.
SA has a multitude of faults - basically just cracks in the rock - which have produced about 20 tremors so far this year. Most are tiny, ranging from a 1.3 magnitude shake near Swan Reach on March 13 to one measuring 3.5 about 25km from Orroroo in the Flinders Ranges on February 20. The most significant quake to hit the state in recent times happened near Mt Barker in April last year when a 3.8 magnitude tremor struck. It was felt widely across the metropolitan area.
There are two main fault lines in Adelaide. The Para line comes towards North Adelaide from the Gawler area, while the Eden-Burnside fault is essentially the Hills face zone. The Hills are the result of the fault: two sides have squeezed together, forcing up the land.
The 1954 quake happened because intense pressures underground caused the rock to crack and move. The fissure caused by the 1954 earthquake is estimated to have been about 6km long and 4km deep, although there is no certainty about the precise point it occurred because of a lack of measuring equipment at the time.
Scientists are still grasping for a way of predicting when earthquakes are going to strike. David Love, a seismologist in the geological survey at the Department of Primary Industries, says "around the world people are working on all sorts of methods to try and predict earthquakes, but to date success has been extremely limited".
Some scientists are working on a method that measures radon gas releases as it shows granite may be fracturing. Others are monitoring land slippage using GPS equipment, some are looking at water bore heights and electromagnetic fields.
Others believe earthquakes are linked. The theory is that the New Zealand quake may have helped trigger the slippage in Japan as they are all linked through the Pacific. By this measure the next big one will be on the San Andreas fault in California.
Love says geologically SA is close to being a solid structure but movement will still occur. "All our faults are shorter, all our earthquakes are smaller, we don't have a massive flat boundary fault running through the country," he says.
Surprisingly, in SA there is no easy correlation between where an earthquake may originate and where fault lines are. This is different to California where most tremors start along the fault line. So even though the 1954 earthquake was thought to have started in the Eden-Burnside fault, there is no certainty about that either. SA tremors are more likely to occur in the hilly areas and less on the plains. The Adelaide metropolitan area is also protected by being built on heavy clay which reduces the likelihood of the tremor being amplified and causing greater damage. One of the problems for Newcastle was that it was built on softer, sandy soil which is better for transmitting the shock of earthquake.
Love won't talk predictions but he will talk probabilities. "We have had slight damage in Adelaide city three times since settlement," he says. "Certainly getting to anything as severe as what they got in Christchurch is a very low probability. It can't be entirely ruled out, but the probability is very, very low."
ADELAIDE'S last earthquake 57 yeas ago caused widespread damage - the next one could be worse.
THOSE who were awake that night would afterwards talk of the unnatural stillness in the air. Sounds seemed to carry for miles. Then out of that stillness came a humming sound, a bit like a far-away aeroplane. But instead of fading it grew louder and louder. Finally, one man recalled, the noise became an almighty rumbling, like a continuous drum roll; then a strange quivering started, before the veranda, the walls, and floor of his house started to move - gently at first, but then vigorously as the weatherboard building started bulging and swaying.
All across the city, the strange movement jolted people from their sleep. It was 3.40am. Some felt plaster falling on their beds, others headed outside to see brick walls collapsing, the tinkling sound of shattering glass was everywhere. The fire brigade chief was startled awake by the sound of the chimney collapsing on to the station's roof. Policemen on the beat were thrown to the ground. Watchmen at a city department store were terrified the building was about to collapse.
Such was the scene in Adelaide in the early hours of March 1, 1954.
Despite a lack of sophisticated measuring equipment it was estimated the city was hit by an earthquake around a magnitude of 5.5 on the Richter scale, with the epicentre somewhere near Darlington, about 12km south of the CBD. It unleashed nowhere near the power of the enormous shocks that have struck Chile, New Zealand and Japan since early last year. But until the Newcastle earthquake of 1989, the Adelaide quake was the most damaging recorded in Australia, and is a reminder that we are considered the most likely big Australian city at risk of a significant shock.
At the Victoria Hotel at Tapleys Hill the quake devastated the old pub. "It's the first time I've ever heard my wife scream," publican Alf Gibbons said later. "But when you see cracks opening in the walls and you hear a sound like a bomb going off, it's pretty frightening."
The St Francis Xavier Cathedral in Wakefield St was badly damaged; at the new Blackwood Community Hospital every room apart from the operating theatre was affected; in Mt Barker springs appeared in fields where none had been seen previously. In the city, the GPO clock's face was damaged. That was 57 years ago now, and time has perhaps dulled the impact the earthquake had on Adelaide. But the bill in today's dollars was about $150 million.
Since settlement, South Australia has experienced four damaging quakes. The biggest was a 6.5 jolt near Beachport in the South East which caused chaos at the nearby town of Kingston and was felt in Adelaide.
The story of the four quakes is recorded by former teacher Tom Dyster in his book, Strong Shock of Earthquake. Dyster was a young teacher in Kingston in 1948 when he first started to hear the story of the tremor which shook the town in 1897. More than 50 years later one of the students who was at the school that day would tell Dyster how frightening it all was. "Lew Jarman, who was one of those caught up in the crush, used to say how terrified he was as bigger children trampled on him and the plaster kept falling in chunks from the ceiling as he tried desperately to get on his feet and flee for safety."
Dyster's book covers the Mt Barker quake of 1883, Kingston in 1897, Warooka on the Yorke Peninsula in 1902 and Adelaide in 1954 and can be read on the Department of Primary Industries website. He is now 85 but still keeps an eye on earthquakes. "None of the earthquakes in SA was serious by the standard we are being introduced to at the moment overseas, but they are serious to the people on the spot," he says.
No one was killed in the 1954 tremor but if a similar quake was to strike Adelaide today we would perhaps not be so lucky. Judith Carr is as an executive director within the State Government but is also the Earthquake Hazard Leader for SA. It means she has examined all the risks and liaised with other departments such as the police to generate a response plan if the worst happens. "There has been significant residential and commercial development over the last 50 or so years and so a greater impact than occurred in 1954 would be expected," she says. "We have scenarios of damage likely for various earthquake magnitudes and, for exercise purposes only, assume that damage from an earthquake event would be similar to that of the 1989 Newcastle earthquake." That earthquake was the worst in Australian history. The damage bill was $1.5 billion and 13 people were killed.
Of course building standards have improved since 1954. In 1983 SA became the first state to adopt national standards to make buildings more earthquake resistant. Don Freeman, who is general manager of building policy in the Department of Planning, says this is a recognition that the state is at higher risk than the rest of the country. "Adelaide as a capital city has been recognised of all the capital cities as having a higher risk than probably all the others," he says. Freeman reckons most of the buildings constructed since 1983 would survive a quake, particularly those with a post-disaster function such as hospitals. They are designed to be flexible, rather than rigid, allowing them to absorb the energy of a tremor. Other older buildings, such as the SA Museum and the Town Hall, have been strengthened as well. He says most modern, well-designed homes should be OK but that there are weak points in older houses, particularly chimneys.
Despite all this, SA is regarded as geologically stable. There are no crashing tectonic plates such as those that produced the earthquakes in Japan and New Zealand. The Japanese earthquake, which measured 9.0, was about 178,000 times stronger than the tremor which hit Adelaide in 1954. The Japan quake was also about 11,220 times stronger than the 6.3 magnitude shock which devastated Christchurch last month.
SA has a multitude of faults - basically just cracks in the rock - which have produced about 20 tremors so far this year. Most are tiny, ranging from a 1.3 magnitude shake near Swan Reach on March 13 to one measuring 3.5 about 25km from Orroroo in the Flinders Ranges on February 20. The most significant quake to hit the state in recent times happened near Mt Barker in April last year when a 3.8 magnitude tremor struck. It was felt widely across the metropolitan area.
There are two main fault lines in Adelaide. The Para line comes towards North Adelaide from the Gawler area, while the Eden-Burnside fault is essentially the Hills face zone. The Hills are the result of the fault: two sides have squeezed together, forcing up the land.
The 1954 quake happened because intense pressures underground caused the rock to crack and move. The fissure caused by the 1954 earthquake is estimated to have been about 6km long and 4km deep, although there is no certainty about the precise point it occurred because of a lack of measuring equipment at the time.
Scientists are still grasping for a way of predicting when earthquakes are going to strike. David Love, a seismologist in the geological survey at the Department of Primary Industries, says "around the world people are working on all sorts of methods to try and predict earthquakes, but to date success has been extremely limited".
Some scientists are working on a method that measures radon gas releases as it shows granite may be fracturing. Others are monitoring land slippage using GPS equipment, some are looking at water bore heights and electromagnetic fields.
Others believe earthquakes are linked. The theory is that the New Zealand quake may have helped trigger the slippage in Japan as they are all linked through the Pacific. By this measure the next big one will be on the San Andreas fault in California.
Love says geologically SA is close to being a solid structure but movement will still occur. "All our faults are shorter, all our earthquakes are smaller, we don't have a massive flat boundary fault running through the country," he says.
Surprisingly, in SA there is no easy correlation between where an earthquake may originate and where fault lines are. This is different to California where most tremors start along the fault line. So even though the 1954 earthquake was thought to have started in the Eden-Burnside fault, there is no certainty about that either. SA tremors are more likely to occur in the hilly areas and less on the plains. The Adelaide metropolitan area is also protected by being built on heavy clay which reduces the likelihood of the tremor being amplified and causing greater damage. One of the problems for Newcastle was that it was built on softer, sandy soil which is better for transmitting the shock of earthquake.
Love won't talk predictions but he will talk probabilities. "We have had slight damage in Adelaide city three times since settlement," he says. "Certainly getting to anything as severe as what they got in Christchurch is a very low probability. It can't be entirely ruled out, but the probability is very, very low."
