Mark Quigley's long, cold year

GEOLOGIST MARK QUIGLEY
Last updated 16:32 17/02/2012
Daniel Tobin

Dr Mark Quigley, a Lecturer in Active Tectonics and Tectonic Geomorphology at Canterbury University, talks about the professional excitement and personal loss of living through Canterbury's earthquakes.

Mark Quigley
JOHN KIRK-ANDERSON\Fairfax NZ
GEOLOGIST: Mark Quigley with an earthquake-induced fracture in the Harper Hills north west of Hororata.

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The Earth

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Reflecting back on 2011 is not an enjoyable task. For me it was a blurred, restless year; a year of punctuated traumatic events separated by cold, sleepless nights in a house and suburb destined for condemnation.

It was a year of icy visits to the port-a-loo and (the worse option) emptying the chemical toilet, showers into a bucket, silty water from the taps, bumpy dusty roads and many long days and nights without power, water, sewerage, and drainage.

Throughout the year there was a mutual feeling of communal sadness as one-by-one our neighbours moved out of their houses and our suburb became quieter and darker.

Eventually, a few months after the Red Zone decision was announced, we too vacated our first house.

It was a year of shovelling that dull-grey, fine-grained sand that re-introduced itself to us every time a local earthquake exceeded M¬L 5.5 and local ground accelerations exceeded 0.13 g.

I often joked to people that I spent more time with my shovel than I did with my partner in 2011; there were times when this was not untrue.

As someone in the unusual position as both a victim and intellectual benefactor of this seismological unrest, I was asked by The Press to share some of my personal and scientific experiences and thoughts for the future.

By the start of February 2011, I was feeling pretty good about things.

Together with my colleagues and students, we had published several research papers on the September Darfield earthquake and we were feeling excited about our newly established partnerships and future research plans.

Having presented over 20 different earthquake lectures around the world, including lectures at the University of Canterbury and James Hay Theatre that each attracted more than a thousand Cantabrians, I was feeling that I had effectively contributed to the 'recovery' phase.

For a researcher and teacher, the acquisition and sharing of geological knowledge was a gratifying experience. 

As a community, we were focused on what land remediation techniques might be suitable for our suburb.

There were feelings of optimism, although continued aftershock activity beneath the central city and to the south and west was reminding us that the redistribution of crustal stresses following the September main shock and its aftershocks was still an ongoing process.

At 12:51pm on Tuesday, February 22, 2011, I was in the corridor outside my office on the third floor of the Geological Sciences department at the university.

My colleague Ben and I were about to head out for lunch when a rush of seismic energy surged through the building.

We each grabbed an adjacent doorframe, looking at each other with a mixture of curiosity and fear.

When the shaking stopped, the building popped and groaned, and we could see dust dropping from the ceiling. We knew that this was a big earthquake.

We grabbed keys, phones, and wallets and quickly evacuated the building into the parking lot.

A massive aftershock caused the parking lot to sway up and down, cars bobbing around like small ships in a violent sea.

I knew my partner Candice was in the central city and overheard someone saying that there had been building collapses and deaths there.

I tried to call her repeatedly but could not get through. My phone started ringing with interview requests from the major networks and radio stations.

I asked them to call my partner and ring me back; which one producer did.

Candice had been trapped in a sushi restaurant on Colombo Street and witnessed buildings collapsing around her, but she was ok and driving home.

I rode my bike through the city and saw the devastation everywhere; I felt numb.

I thought "maybe the liquefaction won't be as bad this time", as I raced home. But when I got close to Avonside and saw the flooding, I knew it would be worse.

We had more than a foot of water throughout our property and twice-as-much sand as in September.

There was certainly of feeling of "we can't go through this again" as Candice and I sat on our veranda, looking out at the suburb. But we did. And we knew that many were much worse off than us.

On the next day, I was part of an earthquake response team that conducted reconnaissance observations throughout the city from helicopter.

We observed large cracks in residential parts of the eastern Port Hills that we interpreted as 'head scarps', meaning that these potential detachment surfaces could fail in additional aftershocks.

Evacuations of some of these areas were based in part on our observations.

Some of these features failed in the June magnitude 6.0 aftershock, demonstrating the importance of basic geological field observations.

In the following weeks I explored the area looking at rockfalls and searching for clear geological evidence of surface rupture, which I didn't find, and surface uplift, which was evident in the Ferrymead area and along the coastline to the south.

I was inundated with media requests, most of which I obliged, and I spent a lot of time communicating with the public via blogs on my personal website.

The university was closed and we were tackling the problem of how to teach the students effectively.

We turned down repeated offers to bunk in with friends because we just wanted to have some normality in our lives, even if it meant living in a house with no services.

The arrival of the student and farmy armies, the Victorian police, and our friends at our doorstep with shovels in tow bolstered our spirits.

We had the discussions that all couples have, mainly centred around, "What should we do?", and, "What is going to happen to our home?"

A year on, and we have settled with CERA and our insurance company and largely moved on, although there are still claims to chase and phone calls to be made.

To those in the Red and Orange Zones, I can only say that there is a light at the end of the tunnel, no matter how dim this light may seem to be at times.

An important lesson for all New Zealanders is that low annual probability seismic events such as the Canterbury earthquake sequence actually DO happen, and when they do, the region will be at an elevated level of seismic risk for years following the mainshock.

Christchurch's seismic hazard was similar to our neighbouring cities of Ashburton and Timaru prior to the Darfield earthquake; have we learned a 'hard lesson' that will enable these cities to be better prepared?

The possibility of magnitude 7 or more earthquakes on faults beneath the Canterbury Plains was accounted for in the NZ National Seismic Hazard Model and the location of these faults, while not known previously, was not unexpected.

Our fault mapping and preliminary calculations have revealed that these are complex zones of strong faults with low slip rates (probably on the order of 0.1 mm a year) and long earthquake recurrence intervals (probably 12,000-25,000 years).

Fault junction zones appear to have played an important role in triggering subsequent earthquakes, although the time lag between successive earthquakes has ranged from seconds to months.

The mechanics of earthquake triggering require further research.

The September earthquake began on a fault that is seemingly too steep (~75 degrees) to initiate rupture based on traditional fault theory; this is an ongoing focus of study. Some scientists are still concerned about ongoing seismicity in the area between the eastern tip of the Greendale fault and western tip of the Port Hills Fault that ruptured in February, and studies are ongoing there.

However, most of the Christchurch area that experienced early aftershocks following the Darfield earthquake, indicating the presence of faults with high stress states, has gone relatively quiet following the major earthquakes of the last year, which is a good sign.

I am optimistic for a seismologically quieter and less frantic 2012.