What happened in the New Zealand earthquake? And is the supermoon to blame?

Earthquake damage to State Highway One, near Ohau Point on the South Island's east coast. Image: AFP/Getty.

At least two people have died in the magnitide 7.5 earthquake that struck New Zealand’s South Island early on Monday, local time. Preliminary modelling suggests that the earthquake was caused by a rupture of a northeast-striking fault that projects to the surface offshore. But this may be a complex event, involving several faults on the South Island.

The northern part of the South Island straddles the boundary between the Pacific and Australian tectonic plates. The jostling between these plates pushes up rocks that create mountains including the southern Alps and the beautiful Seaward Kaikoura Range, one of New Zealand’s most rapidly uplifting mountain ranges.

The plate motion forces the oceanic crust of the Pacific plate beneath the Australian plate on thrust faults, and also causes the plates to slide laterally with respect to one another on strike-slip faults. The region affected by the recent earthquake has been one of the most seismically active in New Zealand over the past few years, including earthquakes that occurred as part of the Cook Strait earthquake sequence in 2013. It is likely that these sequences are related given their close spatial and temporal association.

What slipped during the earthquake?

The preliminary analysis strongly suggests that most of the energy release during this earthquake was sourced from the rupture of a roughly 200km-long fault system. This fault system is aligned northeast and dips to the northwest, beneath the northern part of the South Island. It coincides roughly with the subduction thrust in this area.

The potential for large earthquakes on the subduction fault in the lower North Island and upper South Island of New Zealand was recently highlighted by GNS Science, New Zealand’s geological survey. It published evidence for two similar events in the Blenheim area roughly 520-470 years ago, and 880-800 years ago.

Given its setting, this latest earthquake may be structurally complex, involving a mixture of plate boundary thrusting, lateral slip on strike-slip faults, and thrusting within the Pacific plate close to the epicentre, some 15km northeast of Culverden. The largest aftershocks suggest a mixture of thrusting and strike-slip movements.

The damage caused by the earthquake

 

Earthquake damage to State Highway One and the parallel railway tracks near Ohau Point on the South Island's east coast. Image: AFP/Getty.

 

Because the fault system was large, and the earthquake apparently started at the southwest end of the fault and propagated to the northeast, the seismic energy was released over a period of up to two minutes.

Large earthquakes produce more long period wave energy than smaller events. The 2011 Christchurch earthquake contained a lot of high-frequency energy and very strong ground accelerations, exposing more than 300,000 people to very strong to intense ground shaking.

In contrast, this recent earthquake was manifested in Christchurch as lower-frequency rolling, and due to the sparse population density in the earthquake region, roughly 3,000 people in the upper South Island experienced strong ground shaking equivalent to the Christchurch earthquake.

Reports are emerging of at least one major fracture in the ground surface that could be related to strike-slip faulting in the Clarence region. More traces may yet be found given the complexity of the earthquake. Tide gauge analysis will help to understand if a similar trace offshore caused the tsunami.

The earthquake has also triggered liquefaction in coastal areas and in susceptible sediments, and landsliding of up to a million cubic metres along steep susceptible cliffs in the northern South Island.

There are reports of extensive road damage including in the area between Hanmer Springs and Culverden, much of State Highway 1 and even Wellington, on the North Island. Most of this damage is probably caused by strong ground shaking, which causes weak ground to move en masse and has resulted in numerous slips and road closures in the central and northern South Island.


Earthquakes, aftershocks and the pull of the moon

Given the earthquake happened on the eve of a supermoon full moon, wthe closest the Earth has come to a full moon will be since 1948, it wasn’t long before some tried to make a connection. But the tidal triggering of earthquakes has been investigated since the 19th century and remains a challenging and controversial field.

Small amplitude and large wavelength tidal deformations of the Earth due to motions of the sun and moon influence stresses in Earth’s lithosphere.

It is possible that, for active faults that are imminently close to brittle failure, small tidal force perturbations could be enough to advance rupture relative to the earthquake cycle, or to allow a propagating rupture to travel further than it might otherwise have done.

But the specific time, magnitude and location of this or any other large earthquake has not been successfully predicted in the short-term using tidal stresses or any other possible precursory phenomenon. Deliberately vague predictions that provide no specific information about the precise location and magnitude of a future earthquake are not predictions at all. Rather, these are hedged bets that get media air time due to the romantic misinterpretation that they were valid predictions.

 

Damage at the Waiau Lodge Hotel, in Waiau, 120 kms north of Christchurch. Image: AFP/Getty.

Most earthquake scientists, including those that research tidal triggering of earthquakes, highlight the importance of preparedness over attempts at prediction when it comes to public safety. To this end, GNS Science uses a system of operational earthquake forecasts to communicate earthquake risk to concerned New Zealand residents during an aftershock sequence such as we are now entering.

These forecasts are based on earthquake physics and statistical seismology. The current operational forecast indicates an 80 per cent probability of:

A normal aftershock sequence that is spread over the next few months. Felt aftershocks (e.g. M>5) would occur from the M7.5 epicentre near Culverden, right up along the Kaikoura coastline to Cape Campbell over the next few weeks and months.

This aftershock sequence will probably (98 per cent) include several large aftershocks: some greater than magnitude 6 have already occurred. And, for each magnitude 6 aftershock we expect 10 more magnitude 5 aftershocks over the coming days and weeks.The Conversation

Brendan Duffy is a lecturer in applied geoscience, and Mark Quigley an associate professor, at the University of Melbourne.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Can you have capitalism without capital? Brighton, Ankara, Ghent and the intangible economy

The Fusebox, Brighton. Image: WiredSussex.

As you head north out of Brighton on the A23 things take a distinctly granular turn. The cool bars and trendy eateries give way to second-hand shops and nail bars.

Looming over the area, New England House, an eight-storey brutalist office block, is home to Wired Sussex, a collection of digital and media companies, as well as its offshoot The Fusebox. Here, a collection of entrepreneurs, tech visionaries and creative technologists are seeking to transform their ideas into successful businesses. This island of cutting-edge thinking, surrounded by the evidence of the glaring consequences of austerity, could stand as a synecdoche for the suddenly vogueish concept of the “intangible economy”.

Towards the end of last year, on Radio 4’s Start The Week, Jonathan Haskel, author of Capitalism Without Capital, laid out the features of this brave new economy. The ideas are scalable, have sunk costs, their benefits spill over, and they have synergies with other intangible assets. All of these things are, to a greater or lesser extent, attributes featured in the virtual reality games, apps for care home workers, and e-commerce ideas mapped out by the bright sparks in the Fusebox.

Its manager, Rosalie Hoskins, explains that it exists to support the work of small companies doing creative work. Within these clean white walls they can bounce their ideas off each other and reap the fruits of collaboration. “We’ll provide the doors,” she says. But “it’s up to them to open them.”

One innovative thinker hoping to make her entrance is Maf’j Alvarez. She tells me she studied for a masters in digital media arts at the University of Brighton, and describes herself as an ‘interactive artist’. “Right now I am playing with virtual reality,” she tells me. “There’s a lot of physics involved in the project which explores weight and light. It definitely has a practical application and commercial potential. VR can be used to help people with dementia and also as a learning tool for young people.”

The Fusebox, she says, is “about collaboration. The residents of the Fusebox are in all a similar situation.”

The willingness to work together, identified by Haskell as a key element of the intangible economy, is evident in the Fusebox’s partnership with like minded innovators in Ankara. Direnç Erşahin from İstasyon, a centre for “social incubation” based in the Turkish capital, visited the Fusebox toward the end of last year.

“It was a good opportunity to exchange knowledge about the practice of running a creative hub – managing the place, building a community and so on,” he says.

Erşahin and his colleagues have launched a fact-checking platform – teyit.org – which he believes will provide “access to true information”. The co-operation between the Fusebox in Brighton and İstasyon in Ankara  is “a good opportunity to reinforce a data-oriented approach and university and society interaction,” he argues.

But the interaction between wider society and the denizens of the intangible world is often marked by friction and, ironically, a failure of communication.

This point is underlined by Aral Balkan, who runs a company called indie.ie which aims to develop ethical technologies. “There’s a good reason we have a trust problem,” he says. “It’s because people in mainstream technology companies have acted in ways that have violated our trust. They have developed systems that prey upon individuals rather than empowering them.”

A former Brighton resident, Balkan is almost a walking definition of Theresa May’s “citizen of nowhere”. He is a regular speaker on the TED and digital circuits, and I crossed paths frequently with him when I covered the industry for Brighton’s local newspaper. He left the city last year, chiefly, he tells me, in protest over the UK government’s overweening “snooper’s charter” laws.


He has Turkish and French citizenship and is now based in Malmö, Sweden, while working with the city of Ghent on a radical redevelopment of the internet. “Ghent is a beautiful example of how location affects the work,” he tells me. “They don’t want to be a smart city, they want to encourage smart citizens. We are exploring alternatives.”

Karl-Filip Coenegrachts, chief strategy officer at the City of Ghent, is another believer in the synergies made possible by the intangible economy. “The historic perspective has impacted on the psychology and DNA of the city,” he says. “The medieval castle built to protect the nobility from the citizens not the other way around. People in Ghent want to have their say.”

Left out of this perspective, of course, are those who cannot make their voice heard or who feel they are being ignored. The fissures are easy to find if you look. The future of Belgium’s coalition government, for example, is threatened by Flemish nationalists in the wake of a scandal over the forced repatriation of 100 Sudanese migrants. In Ankara, President Recep Tayyip Erdogan has purged local government and continues to stamp on any dissent.

In the UK, the gig economy makes headlines for all the wrong reasons. Back in the area around the Fusebox, the sharp observer will notice, alongside the homeless people curled up in sleeping bags in charity shop doorways, a stream of gig-worker bikers zooming from one order to another.

The intangible economy throws up all-too tangible downsides, according to Maggie Dewhurst, vice chair at the Independent Workers Union of Great Britain. She gives short shrift to the idea of ‘capitalism without capital’.

“It does get a bit irritating when they muddy the waters and use pseudo academic definitions. They pretend tangible assets don’t exist or are free.”

In fact, she adds, “The workers are a human resource.”