In Hindsight

2011 was, overall, a year the like of which we will not see again soon. I know most of my friends in New Zealand couldn’t wait to see the end of it. For various reasons, a lot of people I know over here couldn’t either. And there’s not a few parts of it – the economy, the election, the earthquake, the earthquake, the earthquake – that I will be glad to put in the past, even if their effects linger on.

But, bittersweetly, 2011 has, on a purely personal level, been one of the best and most successful years of my life, and I think of Mike’s, too. It’s been the year we settled in to our lives over here, the year in which, in so many ways, we got everything we could possibly have wanted – financial security, professional validation and achievement, new experiences. We transitioned from near-poverty studenthood to a secure existence; we visited, between us, many of America’s great cities; we made friends; we did good work. Mike turned his technical expertise into a job he loves, and I got a NASA fellowship for my research, something I’ve been working at, in some ways, for half my life. For all the small (and not-so-small) frustrations, America has been good to us in 2011.

And yet. Drunk on the cheap subscriptions here (The Economist, $70 a year!), we get half a dozen political and financial magazines, more than we can read, honestly; they pile up around the house in guilt-inducing drifts. I’d demand we get them in online format only,  but that’s either not possible or more expensive than getting the hard copies as well.

All of them had end-of-year summaries, forecasts for 2012. They didn’t mention Christchurch, or gave it only a single line. I had a conversation, two or three months ago, with an American scientist who has traveled frequently through Christchurch to Antarctica, which included the sentence “Wasn’t there an earthquake or something?” I didn’t know whether to laugh or cry at that. The quake fundamentally shapes everything that has happened in New Zealand this year, almost every conversation I have about home. Over here, it might as well have never happened – but it has changed New Zealand forever. (Don’t even bother asking about the Rugby World Cup. That didn’t happen either.)

In light of that, I finally went back and looked at my notes from a course I took in my first year at university, 2005: Environmental Geohazards. It focused, naturally, on Christchurch and its environs. I threw out the accompanying booklet when I left Christchurch, certain I’d never need a map of Christchurch’s liquefaction potential, or any of my other accumulated notes from five years of university. I was wrong, as it happens, but fortunately, in 2005 I was young and mad enough to type up all the hand-written notes I took in class. (This was – be shocked – before it was quite acceptable to take laptops to class, though only by about a year.) And so I know what I was told, six years before the quake, about what might happen to Christchurch. It makes for interesting reading.

“The greatest hazard to Christchurch City is the hazard of an earthquake. The Canterbury region is riddled with faults (Figure 4) and the return time for a magnitude VI quake in the region – shaking severe enough to cause minor damage to most buildings – is just ten to twenty years (Figure 2). A MM VII-VIII earthquake, which has a very high probability of occurring in the next century, would completely knock out most of the city’s infrastructure, causing subsidence, landslides, liquefaction, and possibly a tsunami, not to mention damage across large parts of the entire South Island. This will only occur once, but will be devastating when it does.”

I’m not sure whether “MM” refers to the Moment Magnitude (what most people still think of as the “Richter” scale, the absolute magnitude of earthquakes) or the Modified Mercalli scale, that of impact, but I think it’s the latter. The “damage across large parts of the South Island” part was wrong, because this summary referred to the possibility of an Alpine Fault earthquake, but the rest was quite accurate.

“Liquefaction: this is very important in Christchurch, associated with sand and coarse silt. It causes settling and ‘sand volcanoes’, as well as deformation. It happens over geologically recent estuaries and coastal deposits, and is highly linked to the length of shaking. Longer, more liquefaction. Overlying caps of clay can break. Water is expelled for a more stable packing formation. There are engineering issues with settling – buildings can fall over, and these days are built with foundations 30 or 40 m deep. This is spectacular but not too dangerous….Christchurch has high liquefaction potential throughout most of the central city, due to the high groundwater table. But potential does not equal reality. The worst is near estuaries and near the river. There is a low groundwater table but the potential is much reduced: it is more central and near to the Avon and Heathcote due to lateral spreading.”

This is my summary of the lecturer’s words. It captures the possibility, but misses entirely the recurrence of liquefaction, and the back-breaking work of cleaning it up; dangerous it might not be, but from this distance it seems like one of the most psychologically damaging things about the earthquakes, the repeated clean-up, the dust and mud. The academic idea of it never made that clear.

“Vulnerability to shaking: the worst for buildings is when the frequency created is the same as the building’s natural frequency, or about 10 storeys is the WORST in Christchurch. Tilt-slab buildings are bad, and some soft storey buildings can pancake in on themselves. Modern buildings often collapsed. In Kobe 1995 local shaking made the motorway fall over.”

I don’t remember how high the CTV building was, but not ten stories, I think? Pancaking, of course, foreruns the PGC building. I don’t think I realised, when I took those notes, how many buildings in Christchurch this paragraph was applicable to.

“A local quake at less than 20 km would be M 5 to 5.5, like June 4 1869, which had an epicentre in the city, and less than 15 km deep, with 5 to 10 seconds of shaking, and MM 7 in the centre city rapidly decreasing and very localised. There would be some minor liquefaction, relatively minor damage, rockfalls and landslides in Sumner and the Port Hills, and M 4-4.5 aftershocks.

I don’t know where seismology went between 2005 and 2010, but this is patently not what happened. The quake was local, but the Darfield quake was a 7, and the February quake a 6.3; andthe damage was not minor. I haven’t quoted all my notes summarising the earthquake risk to Christchurch, but it focused largely on the Alpine Fault and others in the foothills; local faults were barely mentioned, apart from here.

“Impacts: Christchurch could be potentially affected by active faults within 200 km. The Hope and Alpine faults are the most active at 135 and 100-300 repeat times respectively. There is a probability of 65% of a quake in the next 50 years. Damage likely to cover most of the region including infrastructure and lifelines.
…Major concerns are the immediate destruction with no effective warning, evacuation, casualty treatment and loss of services. There is a long time-frame for recovery and normality, months or years. Christchurch has 150 year return cycle for a MM 7.5 to 8 quake and 1000 years fro a MM 9 quake.
…There will be lots of superficial damage to houses so you stay inside and under cover. Houses should remain standing though. There are services issues with water (leading to fires, like in Napier 1931), switchyards have been redesigned to cope with the shaking, and there will be large rock avalanches which will lead to long distance problems and aggregate on the floodplains, disrupting farming. Roads will be blocked, brick buildings badly damaged such as many in the city centre, and any tows on faults like Hamner will be devastated. Ruptures will take out roads. “

Again, this is all predicated on the idea that a major, destructive Christchurch quake would be an Alpine Fault quake, but it’s not inaccurate about the results in the city. If MM *is* Modified Mercalli, many areas of the east did experience MMIX-X shaking (see these GeoNet maps of peak ground acceleration.)

But this is the sentence that was absolutely right:

There is a long time-frame for recovery and normality, months or years.

When I learned about earthquakes, six years ago, I learned about the instant damage. Not the recovery. Last week’s aftershocks only emphasise how long that is.

Having gotten everything I could have asked for in 2011 – for myself, if not for anyone else – this is what I want for 2012: recovery, for Christchurch, for New Zealand, for everyone. Let it be the start of something better.