Wednesday, July 04, 2012

PS it's an Earthquake

So about this time last night, I'm sitting at my workbench in the study, Fi is pottering in the kitchen, and the kids are asleep upstairs. All is quiet when the model shelves beside me start rattling. They do that from time to time in response to low frequency noises like passing vehicles, the washing machine, or earthquakes. Whenever they start their noisemaking my earthquake spidey senses go all a-tingle, but they usually stop after a second or two and I go back to whatever I was doing. This time they don't stop.

After taking a second or two to tune in I notice that we are indeed rocking gently to and fro, and having an earthquake. After discussing this with friends later we'll figure out this was the P wave arriving and doing it's thing. The whole P and S wave (link) aspect of earthquakes is something I learned years ago but haven't thought about for a while and we're about to get a reminder of how they work.

I note the time for later reference, and that Fi hasn't said anything, so I calmly call out "earthquake" to the kitchen without leaving my seat. She doesn't hear me, so I call out again, and this time she responds by rushing to the doorway and urging me to do the same. That I have time to call out twice isn't something I notice at the time, but in hindsight it means the tremor has already gone on longer than usual. It hasn't got much worse yet and I'm thinking it's a pretty good nudge, (but not that bad) but it will probably end in a few seconds so I'll see what it does and ride it out. Fi is a little less blase, and getting insistent, so I get up and head to the doorway.

I've just gotten to the doorframe when the S waves start arriving and the shaking really kicks off, the worst we've ever experienced in this house. Fi suggests we head upstairs to get the kids, but I'm still thinking this will only go for a few more seconds (ignoring the fact that this is already one of the longest tremors I've ever experienced), so again suggest we ride it out. That's when the shaking kicks up another notch, we hear something glass fall over in the kitchen (later determined to be empty beer bottles in the recycling), the house starts creaking and we are both heading upstairs to rescue the little ones. Quite what we would do if the house started collapsing at this point I haven't figured out, especially having just left a spot of relative safety, but parental instinct is a great driver. We've just gotten to the top of the stairs and are about to go charging into the girl's bedroom to grab one each when the shaking eases and stops, followed by that wierd period when you aren't quite sure if the shaking really has stopped, or your adrenalised senses are tricking you into thinking it is still going.

Having determined that the land has returned to a state of quiescence, we look into the girl's room and immediately have to drop our voices as we calm each other down. The bebes slept through the whole thing. One of them may have rolled over, but that is all :).

It turns out to have been a deep magnitude 7.0, which is starting to get up there in terms of destructive potential, but luckily the depth mitigated it a bit. A much lesser magnitude, but many times shallower tremor wrought all the havoc in Christchurch last year.

There's a Geonet backgrounder here, with the Geonet quake report proper here.

And if you want to hear what it sounded like in a Wellington church, the earthquake was captured during a recording session here (lasting a lot longer than I realised at the time).

It was a doozy.

No comments: