A massive earthquake magnitude 9.0 occurred at 14.46 JST (05.46 UTC) on Friday 11th March 2011 with the epicentre situated approx. 70km east of the Oshika Peninsula of Tohoku. The earthquake was the largest ever ti strike Japan and triggered a tsunami with waves of up to 40.5m and travelling inland up to 10km.
The datum was lowered in 1986 by 3mm. On the original diagram this was not applied to the RLR factor.
Documentation added 2014-03-13
The GPS benchmark information has been downloaded from the SONEL website. GPS benchmark P109 is 13.618m above RLR.
Geographical Survey Institute Kitasato -1 Tsukuba-shi Ibaraki-ken 305