Wednesday, February 21, 2007

Tonight, an earthquake

Tonight we had an earthquake.

It wasn’t the first earthquake I’d felt in
New Zealand, but it was first I’d felt in Auckland. It also felt the strongest.

The first earthquake I felt was on July 19, 2004 (I wrote it down) when we were living in Paeroa. There was a swarm of earthquakes in the Bay of Plenty region. They were generally at a shallow depth and mostly too gentle for humans to feel. One shock, however, was 5.4 on the Richter Scale, and about 5km underground. It was strong enough for us to feel something like 60km away. I felt like a leaf floating in a pond when a pebble is thrown in—a gentle wave rolled me slightly.

This time, there were two earthquakes closer to us. The first was at 8.24pm. It was 3.7 in magnitude, about 6km in depth, and centred 30km east of Orewa, a resort town about 30 minutes or so north of us. We didn’t feel this quake.

The second quake, at 9:00pm, was different. It was 4.5, 15km deep and in roughly the same location as the 8.24 quake. This one was a sudden jolt that rattled the entire house and sent our dog running to see what was up. We felt this one. It felt like a big truck had driven past the house, just missing it. It felt bigger than the 2004 one mostly because this time we were closer to it.

Earthquakes in NZ aren’t unusual, of course. The country is sometimes called “the shaky isles” due to the large number of earthquakes reported. Up to and including the 9pm quake, there were four recorded today on the GeoNet site listing recent NZ earthquakes. Some days there are more, and some days they may be less.

We’re constantly reminded to be prepared, as I’m sure people in Hawaii and California are. Many of us don’t think about it—until we get a gentle reminder, like tonight. Where are the torches? Do we have extra batteries? Do we have emergency water? How’s our supply of emergency food?

It surprised me a bit that I lived in New Zealand for nearly nine years before I felt my first earthquake. The second was two and a half years later, not that it means anything (totally different regions and epicentres).

Nevertheless, one day there will be a huge event in New Zealand—an earthquake or volcanic eruption. Although the odds of either happening in my lifetime aren’t great, they could happen at any time. Tomorrow I’m going to make sure we’re prepared, though I know we mostly are. One of these days, there could be a much bigger event.

The star on the map at top shows the epicentre of tonight's earthquakes. Below is the wave from the second one. Both are from GeoNet and can be seen here.

As it happens, this is my 200th post since I began this blog last September. I didn't realise it this would be such an earth shattering thing.

Update: There was another earthquake at 11.23pm. Same location, magnitude 3.8, depth 7km. I didn't feel this one at all. The NZ Herald website has published reader reactions here. According to Stuff, the runways at Auckland airport were checked for damage (there was none, of course). Right: three eartquakes at roughly the same place over three hours seems a little weird to me.

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