Aftershock Predictions Held Back From Public
The NZ Herald reporting on the Christchurch earthquake inquiry have said that GNS scientists held back from making predictions about another powerful aftershock following the Boxing Day 2011 quake.
“Government earthquake experts held back forecasts of a massive aftershock for Christchurch following the magnitude 4.9 Boxing Day jolt because they didn’t want to alarm the already traumatised population.”
GNS scientist Dr Kelvin Berryman admitted under cross examination that
“information was withheld from the public, on advice from social scientists scared for the beleaguered city’s collective mental health.”
The Herald reports that Christchurch lawyer Marcus Elliott said that after the 22 February 6.3 magnitude aftershock which killed 182 people, GNS made public statements warning of the possibility of an aftershock of one order of magnitude less.
He then asked the panel of four scientists if they considered issuing the same warning after the December 26 shake.
Mr Elliott asked: “If someone had come to GNS after Boxing Day and said, `we want to give people the Christchurch a people of understanding if this one less magnitude earthquake occurred under the city’, could GNS have calculated the likely ground forces and given people an understanding of what they might expect?”
The panel confirmed they could provide such information.
But GNS Scientist Dr Terry Webb said the idea of a issuing a warning was thought to be”unhelpful”.
Dr Webb admitted: “In the first couple of weeks (after the Boxing Day shake), social science advice was basically that we’ve got a traumatised population and what can you do to help them cope best, and that really was to get them coping with aftershocks.
“They had a need and a right to know, and that’s why we readily talked about the possibility of a six, so that certainly wasn’t hidden.
“But what was thought of as unhelpful at the time, was talking about the possibility of an event bigger than Darfield (magnitude 7.1 on September 4) itself, in terms of magnitude.” … you can find the entire Herald report here
However, if you look back to this news report from January you’ll see that there is no mention of the possibility of a magnitude 6 aftershock, people were being told to expect tremors of up to magnitude 5 every month to six weeks.
“Flurry of aftershocks hits nerves” 21/01/2011
Christchurch has been rattled by its 10th aftershock in 24 hours after a magnitude 4.4 quake struck this morning…
…GNS Science seismologist John Ristau warned people to expect aftershocks of up to magnitude 5.0 every month to six weeks.
He said aftershocks could go on for “months, a year or maybe even over a year”.
The report goes on to talk about the psychological effect the quakes were having and the high degree of anxiety some people were experiencing. This had been heightened by the Boxing Day quake.
But as the New Year holiday season drew to a close and people started going back to work fears began to grow. A month and a day before the 22 February quake people were voicing their concerns about returning to workplaces and entering high-rise buildings:
“The general manager of counselling and trauma support organisation Employee Assistance Programmes Services, Rod Berry, said some people were still apprehensive about returning to their workplace.
“There are some people naturally nervous about going into any buildings at the moment, particularly high-rise buildings,” he said.
The ACC will pay for counselling only if a a person is physically injured in the quake or can show a mental injury arose from the physical injury.
A Canterbury District Health Board anxiety disorders unit spokesman said there had not been a noticeable increase in referrals.”
If the scientists had provided the information and predictions, which they told the inquiry that had at their disposal, could more lives have been spared on 22 February?
Would people have still occupied damaged buildings if they were fully aware that a magnitude 6 quake was likely to strike at any time?