Otago is a province with a rich history of establishing firsts. We have led the way in many fields and that tradition continues. Researchers at the University of Otago are attracting international attention and some have been granted millions of dollars for cutting-edge projects. What are they up to? Reporter John Gibb, in a fortnightly series, does his own research on the researchers.
One of the most enduring images of Christchurch's major earthquakes has been not just of broken buildings, but of muddy water pouring endlessly out of the ground.
This is the now-notorious liquefaction.
Why this muddy mess should have been so vigorously ejected and so extensive - water in some cases spurting 5m into the air - has left many shocked observers scratching their heads.
The cost of replacing Christchurch's heavily damaged and destroyed buildings has recently been estimated at $40billion.
But liquefaction and related flooding has also damaged the land itself on a massive scale, amounting to many extra billions of dollars.
Some eastern Christchurch streets have become scenes from a ghost town, and big areas have been declared unfit for housing.
Dunedin scientist Dr Simon Cox was among many New Zealanders ''moved by the plight of the people as the earthquakes hit Christchurch''.
''Liquefaction returned time and time again and slowly broke people's souls,'' the GNS Science Dunedin principal scientist said.
He decided to use his skills as an earth scientist to understand what was happening.
The Dunedin-born Dr Cox, who surfs, and climbs mountains in his leisure time, did not always dream of achieving scientific feats.
As a boy, he hoped to be a professional football player for Newcastle United. Today, he is patrol captain at the Warrington Surf Life Saving Club.
And as an award-winning scientist, he is leading a national team of researchers, shedding light on why liquefaction, and the associated land damage, were much greater than expected.
It has long been known that if the water table is less than 4m deep, partly depending on other factors, such as soil type, liquefaction is likely in a major earthquake.
But Dr Cox and fellow researchers have shown the important role played by pressurised artesian groundwater at a much lower level, about 20m, in much of Christchurch.
He points out that, during quakes, such pressurised water can do several things, including:
• Contributing to ''subsurface fracturing and weakening of ground, developing pathways for escape of water from depth''.
• Providing a ''mechanism and driving force'' that carries the products of liquefaction to the surface where it makes a ''big mess''.
In late 2011, Dr Cox won the New Zealand Hydrological Society prize for his research paper involving the first of the recent major Canterbury earthquakes.
The paper focused on the effects on subsurface groundwater of the 7.1 magnitude earthquake, which hit at 4.35am in September 2010, causing extensive ground and property damage in Darfield, elsewhere in rural Canterbury, and in Christchurch itself, but killed nobody.
Dr Cox's research has been funded through a $490,000 grant under the Government's natural hazards research platform.
Extensive groundwater monitoring long carried out in Canterbury had made a crucial difference in showing links between liquefaction and groundwater pressure, he said.
The scientists found ''a very clear increase'' in the probability of material being ejected to the surface as deep groundwater pressure increased.
They measured the artesian pressures at various Christchurch sites, often down to about 20m.
Some higher pressures would lift water in a pipe 5m above ground level. By far the most destructive recent Canterbury quake was the magnitude 6.3 quake, which struck at 12.51pm on February 22, 2011, killing 185 people.
During the quake, liquefaction increased distinctly once groundwater pressure levels rose above ground level.
Christchurch's distinctive geography, geology and hydrology contributed to the high pressurisation of the deep groundwater.
An important contributor was ''simply the scale of the Canterbury Plains alluvial system'', to which the artesian water was connected, having run downhill towards the coast.
''Our work suggests artesian pressures played a significant role in the mess, and repeated mess, of sand, silt and dirty water that appeared in Christchurch.''
The geohydrology and extent of the hazard elsewhere in New Zealand had yet to be fully quantified, but Dr Cox expected the Christchurch situation to be significantly different from other main centres.
If regulatory authorities looked to Christchurch as an example, there was a ''very real chance'' that resulting regulations could ''over-engineer for the hazard'' in other areas.
South Dunedin and the Taieri Plain both had ''a very shallow water table'' and soft sedimentary soils that ''might be susceptible to liquefaction'' from an earthquake''.
Little detail was known about Dunedin's hydrology below about 20m, but it seemed unlikely Dunedin had ''high artesian pressures'' because nearby hills cut off the city from wider aquifer connections.
The Dunedin City and Otago Regional Councils had developed maps to differentiate areas of rock or firm sediments ''too strong to experience liquefaction'', from geologically weak areas that could be susceptible.
The hope is extensive geotechnical testing and groundwater monitoring will show how much potentially liquefiable ground is out there.
THE CHALLENGE
CLARIFYING THE ROLE OF PRESSURISED ARTESIAN GROUNDWATER IN THE RECENT MAJOR LIQUEFACTION PROBLEMS IN CHRISTCHURCH AND REDUCING FUTURE RISKS.
What is your research about?
Investigating the way pressurised artesian groundwater contributed to liquefaction and related flooding and land damage in the recent major Christchurch earthquakes.
Why is it important?
New Zealand has developed building codes and standards to mitigate the effects of earthquakes and lessen structural damage caused by shaking. But the recent major Christchurch earthquakes also caused extensive damage to land, including through liquefaction.
Most interesting aspect of your research?
If you drill a hole 40m deep there are places in eastern Christchurch where the groundwater will flow freely and reach more than 5m above ground.
It continually amazes me how many people have absolutely no understanding of this, and I am continually improving my own understanding of groundwater hydrology.
In what way is it unique?
Establishing links between artesian groundwater pressure and liquefaction had never before been conclusively demonstrated, and was likely to have ''ramifications worldwide''.
