[Tagging] Accuracy of survey

John Willis johnw at mac.com
Wed Dec 31 23:32:39 UTC 2014


It was over 5 meters in some places along the coast, but only a very small part. Under the ocean, it was 25m. 

Most of japan stayed put, but the northern section along the coast was stretched a bit wider, but the coast sank about 1m, so with coastal flooding, japan didn't get that much bigger. There was no uniform movement so you'll get a different number depending on what number you like (largest, average for Ojika peninsula, average for North Japan, etc) 

Anyway you slice it, The Pacific Ocean is a bit smaller now. 

So Northern Japanese mountains, roads, and farms all have fractionally different dimensions and altitudes now.

Everyone talks about the big one, but there were thousands of aftershocks, and a hundred or so very large ones, including ones inland that caused 1m tall fissures, gaps, and trenches to open up all over north japan, severing roads and buildings.  All of them have different elevations now and slightly different road alignments. The release of pressure from the big one allowed all of the smaller inland faults to start moving again. 

Here's a pdf (full of pictures) of a 6.6 a month later that caused 1m uplift and offset in Fukushima. 
http://www.geerassociation.org/GEER_Post%20EQ%20Reports/Tohoku_Japan_2011/QR4_Preliminary%20Observations%20of%20Surface%20Fault%20Rupture_06.06.11.pdf

At the small peninsula closest to the earthquake, Ojika-hanto, the parking lot across the street from the shoreline is the new shoreline. I visited in July 2011. This is completely due to the lowering of the seabed from the quake. 
https://www.flickr.com/photos/javbw/11091302756/in/set-72157638113676925
The sidewalk is visible(left), but the unclassified road to the far left and the old shoreline, is completely underwater now, as is the pier. 

While realigning the coastline is possible, they will be surveying for a decade or so just to figure out everything that moved. 

Javbw 

Sent from my iPad

> On Dec 31, 2014, at 9:36 PM, Mateusz Konieczny <matkoniecz at gmail.com> wrote:
> 
> According to http://www.dw.de/quake-shifted-japan-by-over-two-meters/a-14909967 it was 2,4 m.
> 
> 2014-12-30 22:22 GMT+01:00 Rainer F├╝genstein <rfu at oudeis.org>:
>> 
>> W> Ultimate 'accuracy'? You do realise that the tectonic plates are moving?
>> 
>> btw: as a result of the Mar.2011 earthquake, japan has moved by at
>> least 5m. how did OSM react?
>> 
>> 
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