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Cache displacement in Canterbury NZ 
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Joined: 19 December 09 7:36 pm
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Location: nr Daylesford, VIC
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Post Cache displacement in Canterbury NZ
A little something for a wet Sunday evening while awaiting the tennis or Tour de France :idea:

If you thought finding some caches is hard enough, spare a further thought for Cantabrian (NZ) geocachers. And also visitors like us, heading over to Canterbury and getting in a bit of geocaching while there. We might just find the difficulty rating of some countryside caches should have been ratcheted up a notch or two.

That is because the earthquakes have caused some significant (in geological terms) displacement. For example, the range of lateral displacement along the oft quoted Greendale fault has been measured at up to 5.4m around the centre and tails off to 1.2m at the extremities. So if your GPS doesn't seem to be giving you a good fix on a hide then you may need to roughly double your search radius. In general terms, the Greendale fault is in the Selwyn River area and there are quite a few caches around there.

As for vertical displacement, 1.6m at the W end of the fault to zilch at the Rolleston end. So watch your step ;-)

f.y.i. a significant and difficult task facing the cadastral land management body of any country impacted by such lateral displacement, is realigning (fudging) the displaced areas to the national datum. And inherently in most cases to WGS84.

(Info supplied by our visiting geologist rellie who has been researching the Christchurch quakes - but any gross generalisations, distortions or plain errors are solely mine).

Kenny


03 July 11 7:30 pm
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