Saturday, 12 March 2011

Christchurch NZ subsidence

One of the things I've been thinking about regarding the recent February 22nd Earthquake in Christchurch, New Zealand, is if there was any collapse of an old magma chamber, surely there should be associated subsidence.

During the quake, according to the satellite image embedded in this article, the ground literally bounced half a metre. The soil underneath parts of the city briefly turned into a virtual liquid, leading to reported subsidence in the area of up to 300mm (1ft). This phenomena is not uncommon during large earthquakes.

Now having looked at the Quake distribution since the first 7.3 and the discovery (Reactivation?) of the Greendale Fault, my thought is that this fault is extending, and that the next 'big one' will occur either off shore or further towards the mountains as part of a more active fault system. Note the depth of the fault on the snagged graphic from the Christchurch Earthquake map site (You have to run the full sequence from Sept 4th). Most of the dots indicate a consistent fault depth of around 5-7.5 km, with a bias pointing towards the end of the Hikurangi trough subduction zone. See this page from the University of Canterbury Geology department.

Geologists of the British Geological Survey discuss the Christchurch Quake distribution in the video below.


Just as an aside; we've been having a lot of Solar flare activity over the past few months. Which allowing for a certain latency in any possible internal heating process, starts to look like there is a degree of real life correlation in the hypothesis. I think there may well be more large seismic events / Volcanic Eruptions to come in the next few months, globally speaking. As we keep on being told, we're in for a 'big one' over here in Southwestern BC, it may be a good idea to keep the old disaster kit on standby. It won't hurt if I'm wrong. Although we've been getting a steady trickle of small seismic shocks which relieve some of the stress building up down below. It could continue like this for another century. On the other hand......

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