Earthquake Weather

If you don't care for geology-obsessed rantings, you may want to stop reading here. However, if you like the rantings of someone who is completely and utterly, head-over-heels for his major, then this might be quite the thing to witness.

I'll set the mood for you first. It's late - about 1:30 am, to be precise - and I'm just minding my own business, sitting on the couch, browsing Facebook (are you really surprised?) while KC and Page are watching Troy. Then, all of a sudden, it happened: an EARTHQUAKE. Well, I couldn't be entirely sure at first, because I'll admit, it was hard to tell if I really felt it or maybe I was just woozy from being tired. It was (and still is) late, after all. It felt like the couch was gently oscillating below me - a little bit of a rolling motion, while moving side to side, for about 6 seconds. What's that, you say? Sounds just like Rayleigh and Love waves? That's why I thought too! Goodness, we sure know our seismology, don't we?

Naturally, I asked KC and Page if they'd felt the shaking too, even mentioning that it could have been an earthquake, but I think they were too engrossed in the death of Achilles to have noticed. Their loss! At this point, though, I was getting excited about the possibility of having finally felt my first earthquake. For a long time, I've always wanted to feel one, even before I went to college, just because it would be cool (ironic for someone interested in hazard management). Honestly, the only reason why I chose to go to school in Southern California and the South Island(PDF) of New Zealand is because both of these places are really prone to earthquakes. I mean, really, what else is there to care about?

Being the investigative person I am, I immediately went to the USGS Earthquake site - nothing there. Frustrated that I might have been thwarted once again (by a large passing truck, perhaps?) I tracked down the NZ version of the USGS, the Institute of Geological and Nuclear Sciences (GNS). Quickly navigating through the EQ site, I found a fantastic page with the seismic readouts of a set of 15 seismometers throughout NZ - just a representative sample. There weren't any readings on them, but it was also at least 6 or 7 minutes old, before I felt anything. My thoughts were confirmed, though, when I saw the individual readout of the WNZ (Wanaka) drum - one I knew would be close to any EQ action, which went up to 1:30 am, showing a solitary, large, red line. That was it! Within a few minutes, all of the stations' drums were showing this (huge) blip. Money in the bank.

Still, I didn't know where this happened, or even what the magnitude was. It was about this time that the USGS world EQ map updated - this time with a satisfyingly large, red box over Fiordland (map). Clicking with anticipation, I clicked and was blown away to see a big, bold '7.0' on the EQ page. And there it was. Of course, I knew that this would probably change, since most magnitudes are revised with time, after a lot of different seismometers have been analyzed, so in the mean time I went to the GNS and USGS sites, filling out 'felt reports' like a good little geology student - after all, these are important in calculating things like the Modified Mercalli index of the quake. It came out to pretty much a III. Shockingly, within 45 minutes of the quake, there had been well over 200 felt reports from all over NZ - that's by 2:15 am. Well done, Kiwis. Dunedin, for those who don't know, is the concentration of dots in the center-right of the above map.

To get a little more into the geological nitty-gritty of this quake, at this point, the magnitude has been placed at 6.8 - a pretty decent showing. It was centered just off the coast of Fiordland (maps here), clearly along the boundary between the Pacific and Australian Plates. This fault, the Alpine Fault, runs from here and forms the nearly linear western boundary of the Southern Alps - see some fantastic evidence of this here, here and here. It's a right lateral fault, but with a lot of oblique motion - the Pacific plate is essentially being thrust over the Australian plate (45 degree dip in places), hence the Alps. It's also the reason why we see these two moment tensor solutions - both indicating convergence along a SW-NE plane. Hmmm...funny how these things have a way of working themselves out. It's a good feeling, really.

Alright, that's enough from me. The USGS page on this quake can be found here, and the GNS one here. Check out some of the accompanying maps and other goodies - they're good times. Also, more on the Alpine Fault from our friends at the Otago Geology Dept. Alright, now I really need to sleep...being able to study for my final on Friday - for my metamorphism class, no less - would probably be a nice thing.