M7.0 Christchurch Earthquake

Just after half four on the morning of September 4th, a M7.0 earthquake epicentered 40km west of Christchurch, thoroughly shaking the region and causing an estimated $2 billion in damages. East Christchurch was hit especially hard due to ground liquefaction and an abundance of brick buildings. Miraculously no one was killed and I only heard reports of two people being injured. Some impressive images of the damage can be found on the web.

This earthquake caught all geologists off-guard as there was zero evidence for active faulting in the area and Christchurch was thought to have a relatively low seismic hazard compared to the rest of the South Island. This earthquake changes everything and throws a wrench in established models of seismic hazard in NZ. It's a good time to be a pessimistic geologist!

I was passing through the general area on the morning of the 11th with my parents so we decided to take a detour to see the surface rupture along the country roads. By this time all of the roads were unfortunately repaired such that the cracks were no longer present in the road. For about 20km, formerly straight roads now have a noticeable kink to the right when you cross the fault. Large stands of trees in forestry blocks were mostly intact apart from trees within about 30m of the fault trace, which had either been uprooted or, in some cases, snapped on their trunks. Visible damage to nearby structures was minor apart from a few brick walls and buildings. Focal mechanisms and surface ruptures both show dextral strike-slip (horizontal) offset (of up to 4m) with a slight reverse (vertical) component on a steep-dipping fault plane. Good images can be found on GNS Science's website.

Above: En echelon tension gashes rupture a ~15m wide zone in a paddock along the fault rupture.

Dextral road offset of a whole lane (~3m)

Heaphy Sept 7-9

The Heaphy track is one of New Zealand's 9 Great Walks- perfectly-graded, immaculately-manicured tracks that traverse some of New Zealand's finest and most varied landscapes. The Heaphy is known for being the longest of these tracks at 78km and for traversing the most diverse landscapes. The track connects Golden Bay to the top of the West Coast and follows one of the oldest routes Maori took to collect West Coast jade and was later used by Europeans as a route to the goldfields. Typically the track these days is done in 4-6 days (staying at a hut each night), but due to time constraints we opted to do it in 3 days. I had always wanted to walk the track since I first heard of it, but was always put off by the logistics of ending up about a 6 hour drive from where you start. This turned out to be a good time of year to go as the track and huts were clear of tourists and we only saw one group a day- not bad for such a well-known track.

The heavy rains that hit us on the West Coast also pelted Kahurangi, and the stream crossings had barely dropped low enough that we could drive to the eastern start of the track. We set out in our rain gear as light rain worked its way through the already soaked forest canopy. For several hours dark skies showed no signs of letting up as we steadily climbed through varied beech forests, occasionally glimpsing the Aorere River far below. As we neared the highest part of the track, the rain cleared to reveal glorious blue skies and white cumulous clouds that fortuitously stayed with us the rest of the trip. From Perry Saddle the track descends through stunted sub-alpine vegetation before emerging onto the expansive red tussock flatlands of the Gouland Downs. The Downs are an exposed erosional surface cut into quartzite with occasional remnants of overlying limestone delineated by hummocky hills of stunted silver beech, such as near the Gouland Downs Hut, the small old hut where we spent our first night.







Gouland Downs




Gouland Downs Hut at center


The Heaphy boot pole (note roller blades and high heels)




Day 2 I spent a small part of the morning examining the small caves and karst near the track (5 caves go directly underneath it!), then we continued across the Downs and into a beautiful landscape of mixed tussock fields and stunted beech with the occasional rock outcrop. Expansive views of the Tasman Sea and Heaphy River mouth could be seen at intervals. From James McKay Hut the forest changes dramatically on the long downhill to the Heaphy River. The beech trees become less abundant as rimu, podocarps and tree ferns become more abundant in the lush West Coast rainforest. We ended the long, but varied, second day at Lewis Hut on the confluence of the Heaphy and Lewis Rivers, where I had a brisk swim. Here enormous rata jut out of the forest at intervals, carrying a whole forest of their own on their large branches and vines.









The third day I set off at first light to try and find a cave based on some vague directions. I passed several beautiful blue limestone bluffs, some with enticing entrances in the cliff faces. I quickly found three marked trails where there should have only been one and after about 45 minutes of crashing through the bush I had to walk back out to meet my parents at the Heaphy Hut on the river mouth. In the end I was probably less than 50m away from the cave. Upon arriving at the coast we were immediately greeted by sandflies. The last 5 hours are along beautiful pristine beaches lined with extensive groves of Nikau palms. It was the warmest day I had had in months and the palms and blue waters and heat of the sun temporarily transported me somewhere tropical.

West Coast Sept 4-6 &10

We made the few obligatory stops crossing Haast Pass and then drove down to Jackson Bay to give my parents an idea of my field area. We walked down a shallow, meandering creek to one of my favorite West Coast beaches to watch the Fiordland Crested penguins waddling to their nests at the end of the day. A few waited around on the beach and would comically run down to the water's edge to greet their buddies each time one appeared from the surf. We were fortunate with a slight break in the weather, which gave off a soft golden light and beautiful sunset. The penguins seemed to enjoy it equally.





We stayed the night in a troubled Fox Glacier township, which had just seen a plane crash killing 9 people (5 locals) earlier that day. The following day we stopped at Hokitika Gorge where many improvements had been made to the trail since my last visit. I was quite impressed with what they were able to do with it and that much of it was made handicapped accessible. Here the improvements seemed welcome over the packed 1.5 lane road with insufficient parking I encountered previously. The water was as creamy and as blue as I remembered it. Someday when I am here on a warm day I will jump in.



We stayed the night at a precariously-situated bach half a stone's throw to both the highway and the roaring Tasman Sea. Just to its north a small creek cascades past the front door, a large rock pinnacle immediately seaward provides some semblance of protection and glass windows and patios look out on the coast in two directions. What an impressive place to sit out a storm! The noise of the sea was distinctly constant like a waterfall, rather than the rhythmic rolling of a more orderly swell. We went for a few short walks the following morning and drove up Bullock Creek to where the road was flooded in well over a meter of water. Then a long drive on to the caver hut on Takaka Hill where we readied ourselves for 3 days on the Heaphy track.









Post-Heaphy track we went for a drive and hike in the Oparara Basin, one of the most spectacular landscapes on the West Coast. Here several limestone arches and caves abound, and the red-brown tannin-brewed waters are in stark contrast to the grey flaggy limestone and vibrant greens of some of New Zealand's lushest rainforest. It is a special place to me, which I why I was horrified to see tourist improvements here- signage overkill and carefully-managed trails taking away from the rugged beauty of this place. Worst of all, revisiting a small, but very photogenic creek, I found an old photo of mine is no longer reproducible as it now has a bridge crossing the shot. Sometimes I wonder if it is better to never revisit a place.

Milford & Routeburn Sept 1-3

I finally escaped Dunedin after more than 2 months bound in its wintry grasp, to take my visiting parents on a 1.5 week road trip around the South Island. The weather was the cold, wet and bleak variety much of the time, but at least the days were finally getting to be a bit longer. The first stop was the lakeshore town of Te Anau and a day trip out to Milford Sound. We made a quick stop at Mirror Lakes and opted for a several hour walk to Lake Marian, both places where I became fascinated by the crisp reflections. Lake Marian was oddly low, the surface being perhaps 30m below its spill over.

No alteration to the next images apart from a 180° rotation










Then onward to Milford where the weather had already arrived. Due to several dry days prior, Milford was drier than I had ever seen and the usually intangible number of waterfalls could be counted. At least the touristas were limited in quantity as well. We opted for a boat tour, something I had yet to do. The Sound was a shadowy, gray tunnel- two vertical walls of rock and trees, a floor of rough dark blue-black sea and a hazy roof of thick gray and diagonal rain. It was nice although I had previously been spoiled by several geology-related helicopter flights in the area. We were fortunate in our timing because we drove through Homer Tunnel hours before it started snowing and the following day the road was closed for several days due to snow.









The following day we drove through the Queenstown gauntlet and on to the road to Glenorchy and the eastern start of the Routeburn track. Despite a rather vague and uncertain weather forecast, we set off for an overnight trip up to the Routeburn Falls Hut. As with all Great Walks, the Routeburn was perfectly graded such that significant elevation was gained with relative ease. The track passes through mature beech forest, skirts the edge of a blue-watered river gorge, opens out on expansive river flats and then continues to climb to a second hanging valley, at the lip of which sits the Routeburn Falls Hut. The hut sits right at tree line, lower here than elsewhere due to the strong winds blasting down from Harris Saddle. The panoramic view of the main valley below and peaks above from the hut's balcony is really quite a sight. A grim wood supply and enormous hut ensured we slept early to combat the cold. The morning we awoke to find ourselves in a winter wonderland, surrounded by 10cm of snow, which continued to lightly fall from the sky.









The walk back in the snow was thoroughly pleasant, as well as the drive back through Glenorchy under dark and heavy skies. After four parking spaces (30 minute time limit), we finally put Queenstown (QTrap as I call it) behind us for the much more manageable Arrowtown. Overnight we slept through the M7.0 Christchurch earthquake, which caused quite a stir for that city (more on this later). Then over a snowy Crown Range to Wanaka and on to the West Coast.