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Kelvin Berryman 100

An extended Labour weekend that included a return crossing of Cook Strait and the chance to contemplate the mysteries of the landscape in the northern South Island provide the catalyst for this monolo◊gue. It is about ‘what we know and what we don’t know’ as it applies to active faults and earthquake hazard, but it could apply to many aspects of our natural hazard research.

Scientists like facts, but….

We know that our communication as scientists strongly influences the public’s comprehension and preparedness to natural hazards, and this ultimately influences the impact of inevitable future earthquakes, volcanic eruptions, tsunami and extreme weather. Scientists like to assemble all the facts before discussing research in the public arena, but what happens if all the facts cannot be found to the scientist’s satisfaction? This delay could limit science communication opportunities.

Give the message some staying power

More and more I am observing that waiting until all the facts have been assembled followed by a carefully scripted communication, often leads to only a brief flurry of media interest, and little long term improvement in preparedness. Scientists need to prepare their advice so that it has some staying power. I believe that updating the public, elected officials, and policy makers on a frequent basis as research is progressing could be effective.

Sometimes not everything is clear cut

While in Marlborough, I was reminded of work done by Russ Van Dissen and myself at least a decade ago, noting that the distance between the Wairau Fault and the Awatere Fault is about twice that of the other Marlborough faults. One explanation is that there is a ‘hidden’ fault – we suspect it’s is there but with little to go on. Other ‘hidden’ faults for which we have some evidence occur near Gisborne, beneath Palmerston North, and near Levin. And until recently, the Aotea fault in Wellington harbour was hidden from view. (LINK ♦)

There will also be times when we will only be "wise with hindsight", such as the Christchurch Fault which gave rise to the 22 February earthquake (LINK ♦). Similarly, the clear alignment of the aftershocks of the 2013 Cook Strait and Lake Grassmere earthquakes suggest reactivation of existing fault or faults with research still underway to reveal those features.

Thus, the vexing question of how many more ‘surprises’ are out there

We can say with confidence that much of New Zealand’s future earthquake activity will lie within a belt extending from the Bay of Plenty and East Cape regions diagonally through the country to Fiordland, as depicted in New Zealand’s National Seismic Hazard Map (right).

National seismic hazard model v3 with caption

NSHM update for 2010 showing peak ground acceleration expected with a 475 year return period on Class C sites. Hazard estimates in units of g.

But outside the high hazard zone (red and yellow shading), damaging events can still occur. Magnitude 6 earthquakes occur on average ten times more frequently than magnitude 7. Science cannot pinpoint where or when these events will occur, so earthquakes always have the potential to surprise, as in Christchurch. So I suggest an important part of the earthquake hazard conversation is to talk openly about the potential for future surprises in a positive and proactive way.

Putting things into perspective

The Aotea Fault was met with great interest that petered out just as quickly. There may have been a missed opportunity to open the discussion on an even greater hazard – the subduction fault. This megafault is the movement zone between the Pacific and Australian Plates that slopes down beneath the eastern North Island and is only 22 km beneath our feet in Wellington (VIDEO LINK ♦). It is a close cousin to features that produced the megaquakes in Indonesia on Boxing Day 2004 or the Tohoku earthquake offshore of Japan in 2011.

The subduction fault is a colossal feature compared with the Aotea Fault. So to give the public a balanced approach we need to bring them along on the scientific journey - what we know or don’t know, what organisations are involved, and how the public can do their part.

Only through frequent and ongoing discussion will there be rational preparedness compared with headlines that have a single day of consciousness, with little or no ensuing action. There are opportunities to engage with Science Media Centre, and the re-emergence of science pages in several of the national newspapers is a welcome opportunity.

Listen in on some of the discussion at the recent Media Disasters and the Public. (LINK ♦)

Kelvin Berryman - Director, Natural Hazards Research Platform / Principal Scientist, GNS Science