The 2011 off the Pacific coast of Tohoku Earthquake on 11th March 2011 largely sank the ground level and caused damages to sea embankments and drainage facilities of the Pacific coast of Tohoku region and northern part of Kanto region. This has enhanced the risk of the submergence and flood in these regions, especially during the spring tide, when the flood tide level becomes higher than usual.
Therefore, JMA has called special attention to the tide level by issuing storm surge advisories to these regions as necessary even at tide levels lower than predefined advisory criteria, and by giving tidal information during the spring tide.
After that, the details of the ground sink and submergence have been revealed and the reintegration of sea embankments and drainage facilities is going on. Under these conditions, after consultation with relevant local authorities, JMA will tentatively set lowered criteria for storm surge warnings and advisories in the earthquake affected area (Iwate, Miyagi, Fukushima and Ibaraki prefectures) from 26 July 2011.
These tentative criteria will enable JMA to issue storm surge warnings or advisories more adequately, taking into account the ground sink, for the higher spring tide in autumn and storm surges caused by typhoons.
Tentative criteria for storm surge warnings and advisories will change along with the progress of reintegration of sea embankments and drainage facilities.
During the spring tide, JMA issues tidal information as necessary for the region where the ground level largely sank as before.