tremble

I guess if you were brought up here, you must get more used to it. But personally, I just can’t imagine getting used to being woken up by earthquakes. Following the big tsunami-inducing quake on the opposite side of the Australian plate, there has been an flurry of tectonic activity down here in New Zealand, on the Australian-Pacific plate boundary…

There was one a couple of months ago that managed to toss a book off my shelf, and to make the whole building wobble, leading to an unnervingly long-lived swaying up here on the top floor (the 13th floor in fact - glad I’m not superstitious). There have been many more earthquakes, but I seem to be a bit dull when it comes to noticing them. If I’m not sitting or lying down, I don’t seem to feel them.

The latest sequence of quakes that I actually managed to notice was on the 14th of March. Much of Wellington was rudely awakened by a sizable 6.4 at four in the morning. There were four more significant quakes in NZ that day, and the image above shows the two that could be felt in the Wellington area. It shows a very long time-line of seismic activity, folded over and moved up the plot every hour. The frighteningly red bit indicates that the wobbles were large enought to start obscuring the rest of the plot, and so were capped-off and painted red.

The image is taken from the excellent New Zealand GeoNet site, which has a set of seismic drums all over the country, as shown in the national overview. This one is nearest to Wellington. They also have a list of the most recent quakes, and make their historical data archive freely available via the web.

Just to remind you of how lively the rocks are hereabouts, GeoNet also hosts a set of Volcano cams, including the White Island Crater Cam (featuring Dino). White Island is the active volcano off the northern coast, which is said to act as a pressure valve for the rest of the country.

I’m not sure that is necessarily the case – certainly there’s no shortage of geothermal activity on the main island. There are the hot spring of Hamner and Rotorua, the latter of which is particularly exciting due to the sulphurous steaming streets, the hot pools, geysers and colourful thermal parks. Furthermore, Mt Ngauruhoe, Mt Ruapehu and Mt Egmont/Taranaki all serve as pointed reminders of the north island’s volcanic potential, especially when one remembers that the largest lake in NZ, Lake Taupo, was formed in a massive volcanic explosion not all that long ago (on a geological timescale).

The Kiwi’s are pretty cool about all this, and take the quakes in their stride. But despite this relaxed attitude to quakes in general, many clearly do worry about the possibility of ‘A Big One’. I think the last Big One around here was over a century ago, and raised the land upon which much of central Wellington was subsequently built. On average, quakes that size turn up every hundred years or so, so in a very woolly sense, we are overdue. Like everyone else, I hope it never comes.

Anj