Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 

What Lies Beneath? Earthquake Expert Talks Rocks

20 October 2003

What Lies Beneath? Earthquake Expert Talks Rocks
Geology Professor Rick Sibson to give Distinguished Research Medal Lecture

“What unknown affinity
Lies between mountain and sea
In country crumpled like an unmade bed?”

The answer to that Denis Glover poem* is, quite simply, “Plate Tectonics”.

Plate Tectonics? Indeed, says Rick Sibson. He should know -- he’s been studying the fault zones crumpling this nation’s bed for over 25 years. A University of Otago Professor of Geology, and one of only seven living New Zealanders made a Fellow of the Royal Society of London, Sibson will be presenting his Distinguished Research Medal Lecture at the University this week: Inside an Earthquake: the Rock Evidence.

His audience will accompany Sibson on his life-long journey in search of rocks from ancient and active fault zones. Not just any old rocks, mind you, but ones that help us map the movement of past earthquakes, and which provide us some understanding of the forces that drive that action.

The Outer Hebrides, the hills of Juneau Alaska, the Makran region of Iran, the deep mines of Val D’Or, Quebec, the Mt Isa mining district of Australia, California’s San Andreas Fault, and the trails of Westland, have all been Sibson’s “laboratory”. Earthquakes, both ancient and modern, have left a distinctive geological imprint on each of these regions, convincing Sibson that earthquakes are just “too important” to be left to seismologists alone.

People often associate the study of earthquakes with the jagged lines scratched on a seismograph. But Sibson argues that earthquakes are more properly the domain of geology, touching as they do every crease and wrinkle and fold on the surface of the earth. They are also quite astonishingly “useful”, he says.

Wellington Harbour, for example, which provides safe sanctuary to moored vessels, is the result of continuing earthquake activity along a series of major faults. And every miner knows that you find gold and other valuable minerals along old fault zones. The legendary Californian, Australian, and Canadian Gold Rushes, as well as smaller deposits in Otago such as Macraes Mine, occurred because ancient earthquake ruptures allowed massive amounts of very hot, pressurised water to flow intermittently through narrow fault zones, creating the mineralisation we now prize.

“Wellington Harbour contains about one cubic kilometre of water” Sibson explains. “If you heated the water up to about 300 degrees, and it flowed from the right source rocks through the Wellington fault, it might result in a rather puny gold deposit of about 10 tonnes.”

By contrast, the gold now being mined at Macraes Mine probably resulted from fluid flowing in many thousands of pulses following successive earthquakes, the total fluid volume being equivalent to about 10 Wellington Harbours.

“The significance of these studies,” he says, “is that in at least some settings earthquakes are triggered not only by stress accumulating, but also by (water) pressure build up”.

Earthquakes have other important uses as well. Without them, the South Island would simply not exist. “We exist only because we are being actively shortened east-west along the plate boundary. If that didn’t happen, we wouldn’t be above sea level.”

But such activity has its risks, he concedes. Lurking beneath the stunning valleys and mountains of Westland and Fiordland is enough potential force to release about 30 times as much energy as the earthquake Southerners experienced last August. “And the shaking will go on perhaps 10 times as long.” The last earthquake of such magnitude occurred around 1717.

Hold on to your beds…

WHAT: Distinguished Research Medal Lecture – “Inside an Earthquake: The Rock Evidence”
WHO: Professor Richard Sibson, Department of Geology, University of Otago
WHEN: Wednesday 22 October, 5.00 pm
WHERE: Castle Lecture Theatre 1, Albany St.

* From Arawata Bill – The Search in Denis Glover, Selected Poems edited by Bill Manhire, (Victoria University Press)

© Scoop Media

 
 
 
Business Headlines | Sci-Tech Headlines

 

Stats NZ: Consents For New Homes At All-Time High

A record 41,028 new homes have been consented in the year ended March 2021, Stats NZ said today. The previous record for the annual number of new homes consented was 40,025 in the year ended February 1974. “Within 10 years the number of new homes ... More>>

Stats NZ: Unemployment Declines As Underutilisation Rises

The seasonally adjusted unemployment rate decreased to 4.7 percent in the March 2021 quarter, continuing to fall from its recent peak of 5.2 percent in the September 2020 quarter but remaining high compared with recent years, Stats NZ said today. ... More>>

ALSO:

Digitl: The Story Behind Vodafone’s FibreX Court Ruling

Vodafone’s FibreX service was in the news this week. What is the story behind the Fair Trading Act court case? More>>

Reserve Bank: Concerned About New Zealand's Rising House Prices

New Zealand house prices have risen significantly in the past 12 months. This has raised concerns at the Reserve Bank of New Zealand – Te Putea Matua about the risk this poses to financial stability. Central banks responded swiftly to the global ... More>>

Westpac: Announces Strong Financial Result

Westpac New Zealand (Westpac NZ) [i] says a strong half-year financial result has been driven by better than expected economic conditions. Chief Executive David McLean said while the global COVID-19 pandemic was far from over, the financial effect on ... More>>

MYOB: SME Confidence In Economic Performance Still Cautious

New insights from the annual MYOB Business Monitor have shown the SME sector is still cautious about the potential for further economic recovery, with two-in-five (41%) expecting the New Zealand economy to decline this year. The latest research ... More>>