[time-nuts] Freestanding mast

[jimlux]

Steve Rooke wrote:
> Well, Steve has been experiencing a LOT of after-shocks, some of which
> are still big enough to move things around and I found I had to grab
> hold of my cup of tea to stop it shaking onto the floor last night. In
> fact these after-shocks are still opening up new cracks in roads and
> causing buildings to fall.
> 
> As for my height position, I have run a few surveys but I'm getting
> varying readings and I wonder if the after-shocks are messing up the
> survey results. The latest one which was during a fairly stable period
> was 6.8 MSL.
> 
> The mast could have sunk a bit or even this whole area could have done
> as I live on reclaimed marsh-land. My Mothers 3 year old house looks
> like it has sunk a bit at one and and risen at the other, ie. it looks
> like it has tipped slightly as her house is built on a concrete
> pontoon.

You could easily have a displacement of a meter or more..

The  (M7+) Landers earthquake here in Southern California a few years 
back had a lateral displacement of 10 meters or so and vertical 
displacements of a meter.

If there's any soil subsidence, that would also account for a lot

http://all-geo.org/highlyallochthonous/2010/09/tectonics-of-the-m7-earthquake-near-christchurch-new-zealand/

has a nifty picture: the classic aerial shot of a hedgerow/treeline with 
obvious displacement (about halfway down the page)
"New Zealand geologists have already identified a 13km fault trace with 
3-4 m of right lateral, strike-slip offset, and variable vertical 
movement of up to 1 m. "


Also there was this in a page linked from the above:
Deformation

Portable GPS instruments are planned to be deployed on September 6 
(Monday) to re-occupy GPS 40 - 50 sites in the region looking for 
changes. GNS scientists will be joined by colleagues from Land 
Information New Zealand (LINZ).

A preliminary estimate of the McQueen's Valley (MQZG) co-seismic 
displacement is 135 mm at about 300 degrees azimuth. This permanent 
receiver is located on Banks Peninsula. This result is consistent with a 
magnitude 7.1 earthquake on a vertical strike-slip fault at the location 
where the geologists have found surface rupture, but it is only one 
point and it would be consistent with many other scenarios as well. We 
can expect displacements of 200+ mm at a number of the temporary GPS 
stations we are planning to visit, and there is one station in 
particular that may be within a few kilometres of the surface rupture 
and thus have a much higher displacement.






> 
> It wouldn't surprise me if they adjust the height of MSL but I would
> have thought they would have moved it the other way in an attempt to
> forestall fears of the effects of Global Warming.
> 
> Regards from Quake City,
> Steve
>