Wednesday, 23 February 2011

Christchurch, NZ

My comrade in words the Angry Exile brought this site to my attention which kind of tells a greater story about the Christchurch Earthquake than the one currently being covered in the mainstream.

Often when an Earthquake is reported, all you see are the headlines, like '200 people killed in quake horror' for example. When you read the associated articles, they skim over the surface, glossing over important details that might be actually useful, apart from generating mere sympathy for the victims. The really interesting thing about the Christchurch tremors is the concentration of seismic activity and where it is happening.

What really did the damage was not one big quake, like the 7.1 magnitude on the picture from 4th September 2010, but a series of rapid hammer blows of 3-4+ magnitude after the main shocks of 6.3 and 5.7, which occurred within twelve minutes of one another. They were followed by a 5.9 magnitude quake less than two hours later. If you run through the sequence of tremors, you can see that the vast majority of the recent shocks recorded are in what is known to be the northern caldera wall of an extinct volcano. Having run through the recent sequences, I'd hazard a guess that what is happening under the Southern edge of Christchurch is a widespread collapse of the old volcanic vent system and magma chambers in the 2-12km depth range. Perhaps even slippage in the faults within the caldera walls as they 'settle'. Not directly related to the nearby Greendale fault at all.

I'm only an amateur observer of such phenomena, but that's what it looks like to me. Go look for yourselves. Run the sequence of 22nd February and you'll see what I mean.


Angry Exile said...

I watched the extended director's cut from 4/9/10, and the two things that struck me as a far more amateurish amateur were the sheer numbers of aftershocks and the speed at which they hit. On moderate to high speed with about half of both South Island and North Island in the picture it looked like that one area is being machine gunned, with the odd stray, an unrelated quake I guess, appearing much further off. Another thing was that Kaikoura to the north of Christchurch got quite a few shakes in mid September. A knock on effect from the activity around Christchurch perhaps? If so I wouldn't want to be around Kaikoura for a bit.

Bill Sticker said...

I watched the past 7 day plot with the 'sticky dot' enabled feature. Shows the concentration of seismic activity beautifully.

Great site. Now if only the data on the audio frequency of the tremors was available, we could test out this interesting little hypothesis.

Related Posts with Thumbnails