ONAHAMA

Documentation - date unknown

Gauge re-sited 1/7/77

Documentation added 1991-06-11

Onahama 642/041 RLR(1965) is 9.0m below Attached BM

Documentation added 1993-07-12

Positive secular trend reverses into a negative one during the 1970s.

Documentation added 2012-02-21

A massive earthquake of magnitude 9.0 occurred on Friday 11th March 2011 with the epicentre approx. 70km east of the Oshika Peninsula of Tohoku. It was the most powerful known earthquake to hit Japan and triggered a tsunami with waves up to 40.5m and travelling up to 10km inland. It looks as if the earthquake badly damaged the tide gauge at Onahama as there is a jump and then it stops working in July 2011. Data following the earthquake has been flagged.

Documentation added 2013-02-04

There have over the years been a number of different benchmarks because of space restrictions not all are included on the RLR diagram. Where two or more benchmarks have the same name the later are suffixed. Throughout the RLR factor has remained the same.

Documentation added 2022-04-05

Following review of data affected by the Tōhoku earthquake of 2011, all data has been flagged as good as GSI have recommenced levelling at the site. The station flag has been set to indicate the record needs to be treated with care, but the data appears to accurately reflect the earthquake's ongoing effect on local relative sea level.