Our Changing World

Three seismologists from GeoNet reflect on the decade of big earthquakes that began 10 years ago with the Darfield earthquake in Canterbury.

Go to this episode on rnz.co.nz for more details

Ten years after the Darfield earthquake, three seismologists from GeoNet reflect on a decade of big earthquakes and what we've learnt from them.

Darfield. Christchurch. Cook Strait. Kaikōura.

In the past decade, New Zealand has experienced four major earthquake sequences that have caused loss of life, as well as extensive damage to land and buildings.

In this Our Changing World earthquake special, three GNS Science seismologists from GeoNet recollect their experience of the Big Ones and talk about the lessons we have learned from these ten shaky years.

Find Our Changing World on Apple Podcasts, Spotify, Stitcher, iHeartRADIO, Google Podcasts, RadioPublic or wherever you listen to your podcasts

We really are the shaky isles here in New Zealand. We live in a very tectonically active part of the world and our history books are full of big earthquakes.

The largest on record - but certainly not the largest ever - was the magnitude 8.2 Wairarapa earthquake of 1855. Much of current downtown Wellington, as well as State Highway 2 from Wellington to the Hutt Valley, became useable real estate only after it was uplifted in that jolt.

The magnitude 7.8 quake in Murchison in 1929, was closely followed by our deadliest earthquake, with 256 deaths - that was the magnitude 7.8 Hawkes Bay earthquake of 1931.

Let's fast forward past the magnitude 7.1 Inangahua earthquake of 1968, and skip several big Fiordland shakes to get to this week's anniversary.

Darfield earthquake

At 4.36am on the 4th of September 2010, Canterbury was rudely woken by a magnitude 7.1 earthquake, which would become known as the Darfield quake. It was a shallow quake, just 10 kilometres deep.

A seismic recorder located almost at the epicentre recorded the strongest earthquake ground-shaking ever recorded in New Zealand at the time, with the ground near the epicentre moving up 1.25 times the acceleration due to gravity.

The Darfield earthquake took everyone by surprise.

"We wouldn't have really expected a major earthquake in Canterbury," says GeoNet seismologist John Ristau. "The big thing we would have expected would have been an earthquake along the West Coast of the South Island, with the Alpine Fault."

John was on duty at GeoNet that morning and he says that "when I first saw this map indicating everything was happening in Canterbury, around Christchurch, my first thought was 'this can't be right'."

The Darfield earthquake happened on an unknown fault, hidden beneath a layer of thick sediments, which would become known as the Greendale Fault. It last moved about 18,000 years ago…

Go to this episode on rnz.co.nz for more details

A time-travelling climate scientist is using dead corals to investigate past marine climates in the Pacific.

Go to this episode on rnz.co.nz for more details

Dead corals cast up the shore of Aitutaki, in the Cook Islands, provide a window into the Pacific Ocean's marine climate hundreds of years ago.

Ancient corals are the keepers of past climate records that can shed light on future climate changes.

Find Our Changing World on Apple Podcasts, Spotify, Stitcher, iHeartRADIO, Google Podcasts, RadioPublic or wherever you listen to your podcasts

A tropical coral reef is a vibrant patchwork of colourful corals, sponges, fish and a diverse range of other creatures.

Stony corals such as Porites grow slowly, over hundreds of years, to become mounds several metres across, often becoming mini atolls in their own right.

They are the coral reef equivalent of a canopy tree in a forest. Just like a tree's trunk, the hard coral skeleton under the thin veneer of living polyps lays down annual growth rings that are a record of that year's climate.

On average, says NIWA climate scientist Andrew Lorrey, a Porites coral grows about a centimetre a year, so a 75 centimetre-long core taken from a dead coral spans about 75 years.

About a thousand years ago, a storm or tsunami uprooted Porites from the lagoon of Aitutaki, in the southern Cook Islands, and cast them up on the shore, where they have remained like giant bleached cauliflowers.

For Andrew and colleagues, these ancient fossilised coral skeletons are a treasure trove that could shed light on past climate events in this little-known part of the Pacific.

"We're using the chemistry of the corals to reconstruct past marine climates," says Andrew.

Stable isotopes of oxygen show what the salinity of the seawater was at the time, while trace element geochemistry - specifically the calcium and strontium ratio - is related to temperature. He says the coral might even show what winds were like at the time.

Andrew says salinity in this part of the Pacific is related to rainfall, so the higher the rainfall the lower the salinity. He says heavy rainfall comes from a climate feature known as the South Pacific convergence zone, which changes in intensity and location.

He says there is very little paleoclimate data from that part of the Pacific, which is important climatically as it lies in the core region of the El Nino southern oscillation or ENSO, and is also the birth place of tropical cyclones.

Andrew says the Aitutaki specimens span an historically warm period known as the medieval climate anomaly, which lasted from about 950 to 1250.

"This might be a past analogue for what our future holds with ENSO ."

Polynesian migrations

The medieval climate anomaly coincided with a period when Polynesians were actively migrating across the eastern Pacific…

Go to this episode on rnz.co.nz for more details

Scientists at the Centre for Green Chemical Science at the University of Aukalnd, are developing cleaner greener processes and products.

Go to this episode on rnz.co.nz for more details

From safer solvents to make better batteries, to catalysts that can clean up wastewater, green chemists are developing better ways of making stuff.

James Wright and Cameron Weber are passionate advocates of an area of chemistry known as 'green chemistry.'

"It's where we design new processes and products that don't harm the environment," says James, who is Director of the Centre for Green Chemical Science at the University of Auckland.

Find Our Changing World on Apple Podcasts, Spotify, Stitcher, iHeartRADIO, Google Podcasts, RadioPublic or wherever you listen to your podcasts

Traditional chemical processes, used at an industrial scale to make everything from shampoo and mobile phones to clothes and packaging, are often polluting and energy intensive.

Starting in the 1990s, chemists began to develop green solutions that were better, safer and more sustainable.

"We are both trying to minimise the environmental impact of chemistry and the chemical industry," says Cameron, "and also use chemistry to solve some environmental problems."

Cameron works with solvents, which traditionally are volatile. "You open a paint can, for example, and you get the fumes from the solvents that are present there."

Cameron says that solvents are often hazardous to health and flammable, as well as being derived from fossil fuels.

One approach, says Cameron, is to create solvents that will work at lower temperatures. This saves energy and is less hazardous.

He is also keen to develop new solvents that will allow more than one reaction to happen at the same time.

Ionic solvents are made from salts, which normally melt at very high temperatures. But if the solvent is made from large, asymmetrical ions you can create a salt that is liquid at room temperature and is inherently non-volatile.

Ionic solvents conduct electricity and could be used to make better batteries that are non-flammable.

Cameron says that another advantage is they can be made from common, widely available ingredients.

Ionic solvents made from iron are magnetic, and after it has done its job the solvent can be removed using a magnet.

Deep eutectic solvents are a special kind of ionic solvent which have a much lower melting point than the constituent ingredients. Choline chloride and urea have respective melting points of 302°C and 133°, but in combination their melting point is a mere 12°, which effectively means that two compounds that are solid at room temperature create a liquid when they are mixed together.

Cameron likens his job to being a designer, creating new compounds with interesting properties that might then be picked up and used by industry…

Go to this episode on rnz.co.nz for more details

The sensory lab at AUT is used for food testing and tests can involve all the senses, including sound.

Go to this episode on rnz.co.nz for more details

Food scientist Nazimah Hamid from AUT says that the sound of the space we eat in can have surprising effects on the taste of food.

Eating is a sensory experience that involves our eyes, mouth - and even our ears.

Find Our Changing World on Apple Podcasts, Spotify, Stitcher, iHeartRADIO, Google Podcasts, RadioPublic or wherever you listen to your podcasts

Professor Nazimah Hamid is a food scientist at Auckland University of Technology. She says that when we eat we use all five senses.

"We often associate eating with the sense of taste," says Nazimah. "We also eat with our eyes. If you eat crisps - think about it - ... it's what you hear."

But it isn't the crunch of crisps that inspires Nazimah. "My interest is how sound affects the flavour perception of food ... when I first started work here it was on music."

A research group from Oxford University had already done a study that found people associated the sound of a piano with sweetness while a trombone had bitter flavours. Another group in the USA, meanwhile, were looking at emotional states associated with food evoked by the sound of music.

To investigate these ideas further, Nazimah and her students embarked on a series of experiments, using chocolate gelato as their test food.

They offered their test subjects a choice of nine genres of music and asked them to rank them from favourite to most disliked.

Each person was then given three lots of chocolate gelato to eat, while they were played their most liked music, some music they weren't too fussed about and music they disliked. They were asked to rate their experience of the gelato.

Nazimah says gelato consumed to the strains of preferred music was rated as creamier, sweeter and more chocolatey. Disliked music evoked bitterness.

The effect was so marked the participants were sure they had been offered different types of gelato.

"We were the first group to discover that it's not the type of music you listen to," says Nazimah. "It's whether you like the music."

In another experiment, she decided to look at the effect of different sound environments on the sensory perception of food.

"When you think about it, we never eat in silence."

She selected a nearby bus stop on a busy road, a campus café and a quiet, relaxed area with a view of tree canopies, and asked the participants to rate the chocolate gelato consumed in each of these environments.

Not surprisingly, gelato eaten at a busy bus stop was a much less pleasant experience than one consumed in the congenial hubbub of a friendly café. The ice cream tasted bitter and people felt stressed at the bus stop…

Go to this episode on rnz.co.nz for more details

A panel of virologists from the University of Otago discuss research into covid-19.

Go to this episode on rnz.co.nz for more details

'Covid-19 unmasked: understanding the outbreak' is a panel discussion from the 2020 New Zealand International Science Festival.

University of Otago virologists and public health experts join William Ray for a coronavirus discussion at the 2020 New Zealand International Science Festival.

Find Our Changing World on Apple Podcasts, Spotify, Stitcher, iHeartRADIO, Google Podcasts, RadioPublic or wherever you listen to your podcasts

Studying SARS-CoV2

Miguel Quiñones-Mateu is a virologist in the Department of Microbiology and Immunology at the University of Otago.

He runs a secure Physical Containment lab (PC3) at the university, where researchers can safely isolate and grow SARS-CoV-2, the virus responsible for COVID-19, using samples taken from infected individuals.

He says he began work before New Zealand had its first case of covid-19, which made sourcing material difficult.

"But once we isolated the virus and we had it," he says, "then we started sharing the genetic material. ... It opened the door for projects like the vaccine initiative we're involved in."

"If we didn't have that opportunity of working with the virus, we wouldn't be where we are."

Race to develop vaccines

Vernon Ward is a virologist at the University of Otago. He is involved in the Oxford vaccine trial, which is one of the leading covid-19 vaccine possibilities that has just gone to stage 3 clinical trials.

He says the project is an international collaboration that involves experts around the world.

"There are many different labs working on this. No one country can do it by themselves."

"There's a huge amount of collaboration between the different parties," says Vernon

"One of my colleagues was asked if this was a race and he pointed out it's not a race between all the developers; it's actually a race against the virus."

Tracking the spread of the virus

University of Otago virologist Jemma Geoghegan is involved in sequencing samples of the coronavirus and by comparing mutations she is helping map the spread of the disease.

Jemma says that when a virus makes copies of itself it makes mistakes, which are mutations. These mutations then get passed on.

"If we look at the virus genome from all the cases then what we can do is reconstruct a family tree or evolutionary tree."

"We can use that to track who infected who," says Jemma, "and develop really accurate contact networks."

Jemma and colleagues at ESR sequence the genomes of covid-19 samples collected from returning travellers who are in managed isolation or in quarantine.

The rate at which coronavirus mutates…

Go to this episode on rnz.co.nz for more details