Tsunami Monitoring and Warning in Hong Kong
Most tsunamis are generated by submarine earthquakes. Hong Kong has not been seriously affected by any tsunami in recorded history, with the Philippines Islands and Taiwan acting as an almost complete breakwater for such tsunamis in the Pacific. Diffracted sea waves are much weaker and therefore the energy that arrives in Hong Kong has been fairly small.
The Hong Kong Observatory monitors warning messages issued by the Pacific Tsunami Warning Centre (PTWC) and the South China Sea Tsunami Advisory Center (SCSTAC) and keeps a close watch on the sea levels recorded by monitoring stations in the western Pacific, South China Sea and Hong Kong. If necessary, the Observatory will issue a tsunami warning to the public.
Sea level records of nine very minor tsunamis detected in Hong Kong
| Date (Hong Kong Time) |
Origin | Moment magnitude Mw |
Maximum sea level change recorded in Hong Kong (Height above normal tide level) |
|---|---|---|---|
| 1952/11/5 | Kamchatka | 9.0 | 0.15 m |
| 1960/5/24 | Chile | 9.5 | 0.3 m |
| 1985/3/4 | Chile | 7.9 | less than 0.1 m |
| 1988/6/24 | Luzon Strait | 5.7 | 0.3 m |
| 2006/12/26 | Over the sea near Southern Taiwan | 7.1 | less than 0.1 m |
| 2010/2/28 | Chile | 8.8 | less than 0.1 m |
| 2011/3/11 | Over the sea east of Honshu, Japan | 9.0 | 0.2 m |
| 2022/1/16 | Tonga volcano | 5.8 * | around 0.1 m |
| 2024/4/3 | Over the sea east of Hualian, Taiwan | 7.3 | less than 0.1 m |
* A preliminary estimate for this submarine volcanic eruption was calculated by the United States Geological Survey (USGS) using techniques calibrated for earthquakes (USGS, 2022 ).
Tsunami Warning
If a severe earthquake in the South China Sea or the Pacific Ocean is expected to generate a tsunami resulting in a significant tsunami (i.e. a tsunami with a height of 0.5 metre above the normal tide level) in Hong Kong and the estimated time of arrival (ETA) of the tsunami at Hong Kong is within 3 hours, the Observatory will issue a Tsunami Warning to alert members of the public to take precautions.
For significant tsunamis that are not expected to reach Hong Kong in 3 hours, the Hong Kong Observatory would issue a Tsunami Information Bulletin to notify members of the public. In addition, the Observatory would also issue Tsunami Information Bulletins for insignificant tsunamis expected in Hong Kong.
Precautionary Measures
- Stay away from shores, beaches and low-lying coastal areas. If you are there, move inland or to higher grounds. The upper floors of high, multi-storey, reinforced concrete building can provide safe refuge if there is no time to quickly move inland or to higher grounds.
- Do not engage in water sports.
- Vessels should stay away from the shore or shallow waters. If vessels remain moored in typhoon shelters, their moorings should be doubled and all personnel should leave the vessels and head for higher grounds.
- Please observe these precautions until the Observatory cancels the tsunami warning.
- Please stay tuned to the radio or television for further information.