* Earthquakes in and around Japan to which JMA can apply the Earthquake Early Warning technique to promptly and accurately determine the hypocenter and magnitude
|Category||Indication||Estimated maximum tsunami heights||Expected damages and actions to be taken||Quantitative
|Major Tsunami Warning**||Tsunami height is expected to be greater than 3 meters.||over 10 m
10 m5 m
|Huge||Wooden structures are expected to be completely destroyed and/or washed away; anybody exposed will be caught in tsunami currents. Evacuate from coastal or river areas immediately to safer places such as high ground or a tsunami evacuation building.|
|Tsunami Warning||Tsunami height is expected to be up to 3 meters.||3 m||High||Tsunami waves will hit, causing damage to low-lying areas. Buildings will be flooded and anybody exposed will be caught in tsunami currents. Evacuate from coastal or river areas immediately to safer places such as high ground or a tsunami evacuation building.|
|Tsunami Advisory||Tsunami height is expected to be up to 1 meter.||1 m||N/A||Anybody exposed will be caught in strong tsunami currents in the sea. Fish farming facilities will be washed away and small vessels may capsize. Get out of the water and leave coastal areas immediately.|
** Major Tsunami Warnings are issued in the classification of Emergency Warnings.
Detailed information on Emergency Warnings is provided on the Emergency Warning System web page.
|Messages about tsunami||Indication|
(Estimated Tsunami Arrival Time and Height)
|Estimated arrival times* and heights of the tsunami for relevant tsunami forecast regions.* The estimated tsunami arrival time for each tsunami forecast region is the time at which it is expected to hit first in any part of that area. Hence, in some coastal regions, tsunamis may hit after the estimated time.
(High Tide Time and Estimated Tsunami Arrival Time at each place)
|The high tide times and estimated arrival times of the tsunami at selected points.||Tsunami Information (*1)
|Arrival times and heights of the tsunami observed at tide gauges or tsunami meters.|
|Tsunami Information (*2)
(Tsunami Observations at Offshore Gauges)
|Tsunami arrival times and heights observed at offshore gauges, and related tsunami heights along the coast in the corresponding forecast region estimated from offshore observations.|
(*1) Issuance of Tsunami Information based on Tsunami Observations
JMA announces the arrival times and initial movement of the first observed waves in coastal areas, and also provides information on the arrival times and scale of the highest waves observed as of the time of issuance.
As tsunami waves can hit repeatedly and those arriving later may be higher, it is inadvisable to abandon evacuation if the initially observed waves are small. Accordingly, when a Major Tsunami Warning and/or a Tsunami Warning is in effect and observed tsunamis appear much smaller than estimated, JMA uses the phrase "Currently Observing" rather than actual values to keep people aware that higher waves may still approach.
(*2) Issuance of Tsunami Information based on Tsunami Observations at Offshore Gauges
JMA does not provide actual values for observed tsunami heights offshore or estimated maximum tsunami heights for coastal areas
until the thresholds for issuance are reached (in the same way as those for coastal areas) in consideration of the related influence on people's evacuation.
When a Major Tsunami Warning and/or a Tsunami Warning is in effect and estimated tsunami heights for coastal areas are small,
JMA uses the phrase "Currently Observing" for observed heights offshore and "Currently Investigating" for estimated heights in coastal areas to keep people aware that higher waves may still approach.
* For gauges more than 100 km offshore, JMA does not announce the relevant estimated tsunami heights for coastal areas due to the difficulty of determining which tsunami forecast regions waves will reach from offshore gauges. Announcement of tsunami heights observed at such gauges is begun when JMA issues an information bulletin detailing actual values for observed and estimated heights from other offshore gauges closer to the coast. Until this time, the phrase "Currently Observing" is used.
After an earthquake occurs, if no damage is expected, JMA issues Tsunami Forecasts.
|Forecasted sea level changes||Message|
|No tsunami is expected||"No tsunami is expected." (To be included in Earthquake Information.)|
|No damage is expected because sea level changes will be less than 0.2 m, and no special action is needed.|
|Particular attention is needed when fishing, swimming or engaging in other marine activities because tsunami-related sea level changes have been observed and may continue for a while.|