I thought to start off my blog, I would write a bit about my home town. I live in Christchurch, New Zealand (have done all my life). As a “Cantabrian”, I am now very familiar with a geological phenomenon called Earthquakes. So this blog is going to look at the science behind what causes earthquakes, as well as some post-earth quake tourist information for Christchurch.
So, here we go!
The outer surface of the earth is called the crust, and it is not a continuous piece. It is made up of 7-8 major plates, as well as many minor ones. The plates sit on a molten layer, called the mantle, and the edges of these plates are called plate boundaries.
New Zealand as a whole sits on a pretty major plate boundary, between the Pacific and the Australian plates. These two plates are slowly moving relative to each other. At the end of the South Island, the Australian plate is moving underneath the Pacific plate, while at the tip of the North Island the Pacific plate is moving under the Australian plate. This creates a pretty large area (most of the length of the south island in fact), where the plates are grinding against each other. This creates the Alpine fault line, which is a large fracture caused by plate movement.
However there are tons of smaller fault lines all over New Zealand, including one that was discovered on September 4th 2011, when the pressure from the plate movement became so great that the fault ruptured, causing an earthquake measuring 7.1 on the Richter scale.
(By the way, GNS Science has an awesome interactive map showing the active faults in New Zealand. You can check it out here)
But what does a 7.1 magnitude earthquake mean? Well as somewhere who has been through it, it means the earth quakes! However we can break it down into more empirical terms. There are two things that influence how strong an earthquake seems to us; the magnitude of the seismic movements, and the depth at which they occurred. Magnitude is normally measured by the Richter scale, which is a log scale from 1-10 specifically for seismic movement. A log scale means that each number on the scale refers to an earthquake 10 TIMES GREATER than the number before it. So a magnitude 7 earthquake is 10 times stronger than a magnitude 6.
Up on the earth’s surface, you probably won’t feel any earth quakes under a magnitude of 3. Small earthquakes happen all the time, and are only recorded by very precise instruments called seismographs. The magnitude 7.1 and 6.3 earthquakes in Christchurch caused A LOT of damage, and while no one died in the September earthquake, 185 people died in the 6.3 earthquake on February 22nd.
Hang on, if the February earthquake was smaller, then why was it worse? Well this comes back to depth. The February earthquake was closer to the surface, and closer to the city. The direction of the movement can also play a part in the amount of damage caused.
(There is another interactive map that illustrates earthquake occurrences across Christchurch. This includes buttons to replay the earthquake activity seen on September 4th and February 22nd, so you can compare them to a normal day. View it here).
“That all sounds awful. Why would you ever want to visit Christchurch?”
Well the earthquakes were 5 years ago, and even though there is still a lot of rebuilding going on, there have been some really cool things “pop up” in Christchurch. In fact, we created a whole culture around it.
As the central city has opened back up, the buildings left standing have been painted with a variety of large murals. Everything from traditional graffiti style to a detailed ballerina! These won’t be around forever, as they will slowly be obscured by new buildings, however it adds an incredible dash of colour to the city. Check out Scape Public Art for more information on these works.
A Container Mall has also opened in the city, called Re:Start. The entire mall is built out of shipping containers, painted all colours of the rainbow. It’s a really cool place to wander around, with funky clothing stores, coffee shops, and food stalls. The Re:Start mall also has Quake City, which is a special exhibition by the Christchurch Museum, focused on the Christchurch Earthquakes. So if I have peaked your interest on geology, you can check out some cool interactive activities there. Including measuring your own seismic activity by jumping on a specially designed sensor! You can find more information about retailers at the Re:Start Malls website.
If you’re into the outdoors, and some epic views, the Port Hills in Christchurch offers scenic views over both Christchurch and Lyttleton Harbour. The Lyttleton and Akaroa harbours are formed by two extinct volcanoes (I know, New Zealand is full of awesome geological phenomenons!). There is a gondola that goes up the side of the hills, and they have a nice restaurant at the top. The gondola will also transport mountain bikes, so you can take your bike to the top and enjoy a breath taking ride down. Price and transport information is available on the Welcome Aboard Christchurch website, as well as information on other Christchurch attractions.
There are plenty of other things to do in Christchurch, and the surrounding district of Canterbury. I have been caving and rock climbing in the north of the district, had fudge at the beautiful French town of Akaroa, and relaxed in hot pools at Hanmer. You can find out information on all of these things and more at the Christchurch Information Center. Or Leave a comment about a spot that interests you! I would be glad to write a post about it – includes a free science lesson!