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Friday, March 4, 2011

The Christchurch Earthquake

I'm writing this blog as if it is fact.  It isn't.  It is pure speculation.  Joining the dots if you like and perhaps I am seeing spots in front of my eyes.  Below is a tentative explanation of why the recent 6.3, highly destructive Christchurch earthquake occurred.

Many millions of years ago a volcano erupted on the continent of  Zelandia.  Many years later, despite the fact that the local people called it Te-ahu-patiki* a European explorer would name it  The Banks Peninsula.

*Actually, this is the name for one part of the Peninsula but it seems to be the nearest to a name that applies to the whole mountain.

The volcano erupted offshore and grew as more lava poured out of the earth. Erosion moved rock and soil down hill.  Eventually the eroded material joined the volcano to the nearby land aided by the material being washed seaward from the young rising mountain range to the west*.

*Because of the huge amount of material shed from the New Zealand Alps, the rivers, when they reach the plains are braided.  They fill up their stream beds and jump to a new path spreading new material back and forth across the plains like giant grouting machines.

The huge weight of this new mountain pushed down on the earth and the mountain sunk, trying to become isostatic with its surroundings.  Molten sills and dikes and the heat under the volcano helped with this process, making the material supporting the volcano a little less viscous than it otherwise would be.

In time, the volcano died, underground magma cooled and solidified and the volcano was locked into its surroundings.  All this time more material was washing off the volcano to be  deposited on land to the West and in the sea to the North, East and South.  The fast growing mountains to the West continued to wash material down around the volcano.  The volcano got lighter and lighter while the ground around it got heavier.

The volcano was no longer isostatic with its surroundings.  It wanted to rise but it was locked into the surrounding land.

On Sept 4, 2010 a nearby fault ruptured.  This fault had nothing to do with the volcano.  It is an east west fault coming off the north south plate-tectonic-fault that runs down the middle of the New Zealand Alps to the West.  Unfortunately, this fault points directly towards the north side of the Banks Peninsula right on the southern edge of Christchurch.  Following the Sept earthquake, after shocks just kept coming.  Between the Sept 4 quake and the Christchurch quake there were just under 5000 aftershocks.  Eventually the rock was sufficiently weakened that the volcano could pop up. The break in the rock was shallow so even thought the quake was only a 6.3, it caused huge vibration in the nearby area.  The Sept 4 quake was 40km from Christchurch, the 6.3, only 10km away.  Because it was a upward break on the volcano side and a downward break on the Christchurch side, it caused huge vertical accelerations.  It was akin to someone cracking a whip.  Unfortunately, parts of Christchurch are built on a swamp and the closer to the coast, the swampier it gets.  Further inland, the Alps have spread layer after layer of shingle (gravel) on top of the land, compressing and stabilizing it.

So far so good.  That's a theory but a Scientific theory is measured by how well it can make predictions so what would one predict if the above scenario is correct.

1.  The volcano: the Banks Peninsula, should have risen during this quake and will continue to rise as further after-shocks occur.  I must admit, I have cheated a little with this prediction.  Someone told me he had heard on a radio program that the Banks Peninsula had indeed risen.  That was what triggered off this blog.  So how about other predictions.

2.  The Banks Peninsula should have tilted.  While the North North West side should have risen, the South side should have hardly risen at all.  In fact as you go across the volcano from North West to South East, the amount of rise should be less and less.

3.  The rest of the volcano is still out of equilibrium with the surrounding rock.  One would expect more earth quakes which will center on the Western and southern rim of the volcano and possibly to the East.  Unfortunately, there is no way of predicting when, but a major earth quake might be preceded by some small ones on the other side of the peninsula from Christchurch as the rocks begin to rupture.  All the after shocks we are having,  continue to weaken the rock on the other rims of the volcano and the rock on the south rim will have been bent by the rise of the North Western side.

4.  Following any major quakes on the other rims of the Peninsula, that side would be expected to rise as well. The shore line of the Banks Peninsula should rise and the harbors become shallower.

5.  Communities to the West and South of Christchurch should expect some pretty large quakes, possibly in the near future and Christchurch will continue to experience shocks, some  fairly large, as the Banks Peninsula achieves equilibrium with its surroundings.  After-shocks should go on for a considerable time interspersed with some pretty large events on other sides of the peninsula.
It is likely that no quakes as devastating as the 6.3 will occur on the Christchurch side.

7.  The after shocks from this quake are unlikely to follow the same pattern as aftershocks from the Sept 4 event.  I have no idea whether they will be more or less but since the cause is different, the pattern should be different.  If they are greater and stronger, this would indicate that the volcano is actively trying to reach equilibrium and might increase the likelihood of large events radiating from other sides of the Banks Peninsula

Postscript.  Since writing this blog, I have come across a most interesting site from GNS Science.  Click here. 
Note that the north part of the banks peninsula moved up and to the west while the land to the North moved down and to the East.  If this blog is correct, sometime in the future one would expect to see other parts of the peninsula move upward and probably to the west with energy focused toward the land opposite the risen land.  This could be toward the ocean or toward Ashburton.


Anonymous said...

I know of an extraordinary event directly over the east coast plate boundary coincidentally some 8 hours before September 4th earthquake. witnesses provided exact coordinates to a high altitude sustained energy release reaction directly over the tectonic plate boundary to New Zealands goverment atmospherics science organizations as well as GNS in Wellington. The response to the witnesses was unusual for such an event. To date the science heads at NIWA have not interviewed any witnesses what so ever and indeed suddenly upon receiving azimuth bearings killed off all feedback and communications regarding the event, as if it never happened. Strange behavior from the scientific establishment. The event was too hot to handle so easier to make it go away I suppose. The corroborating evidence is available from multiple sources and that is whats made it too hot to handle. Some things are not meant for public perusal so think the powers that be including the media.

William Hughes-Games said...

Hello Anonymous
I don't understand what you are talking about. Could you be more specific