On Tuesday I posted some pictures of New Zealand’s Tolkien-ish landscape. There are reasons why it’s so rugged. And at 10:36 last night, 3 July, one of them happened. New Zealand’s North Island was rocked by the biggest quake it’s had in many years.
It shook Wellington like a terrier rattling a bone. Listen for yourself – here’s the noise it made in a Wellington church during a recording session. The quake starts around 00:45: http://www.stuff.co.nz/national/7219667/Earthquake-captured-on-organ-recording
I was asleep when it hit, blasted awake by the jolt – and wondered whether it was local. There wasn’t any sound of stuff crashing around the house so – well, I went back to sleep. Hey, we’re used to these things. We’re prepared. It was nowhere near as sharp as one in December that caught She Who Must Be Obeyed and me in a masonry building (we dived under a table).
My personal ‘felt estimate’ for the intensity around our house was around IV/V on the Modified Mercalli scale (building creaks, dishes and plates rattle, people woken). But I wanted to know the absolute magnitude and epicentre. New Zealand has a fantastic seismic network. Our Geological and Nuclear Sciences department posts early estimates in near-real time. By the time we were up at 5.00 am this morning (discovering nothing dislodged around the house) they had a final figure for the quake and its location. It was a big one; magnitude 7.0, luckily off the Taranaki coast and very deep. Probably the Pacific plate moving.
It wasn’t expected, but there are several known faults around the country which are overdue to move, including one that will trigger the ‘big one’ in Wellington – a quake of 8+ magnitude with a likely ‘felt intensity’ of X on the MM scale. The lesson was brought home when Christchurch was devastated by a succession of quakes beginning in September 2010 – including one in February 2011 that killed 182. The official enquiry into why buildings collapsed is under way now.
There is a theory that the Christchurch sequence was triggered by a 7.8 magnitude quake that hit Fijordland in July 2009. It did no great damage in that remote location but seems, some geophysicists think, to have stressed the system – which then fractured in Christchurch. Whether the latest quake is going to do anything on the Wellington system is a moot point. GNS said today they haven’t the resources to look further into it just now.
But, to me, not it’s something to lose sleep over. We have to live with quakes, here in New Zealand. And volcanoes. And pointy sticks.
Well, actually not the pointy sticks. But definitely quakes and volcanoes. They’re gonna happen – we have to accept them. And be ready.
+++Coming up: a contest. Watch this space.+++
Copyright © Matthew Wright 2012