What is a Tsunami?
A tsunami is a series of travelling ocean waves of extremely long length and period, generated by disturbances associated with earthquakes occurring below or near the ocean floor.
WHAT CAUSES A TSUNAMI?
- Most tsunamis are generated by shallow focus earthquakes along areas of subduction. Underwater volcanic eruptions and landslides can also generate tsunamis.
- The Suva tsunami in 1953 was caused by massive underwater slumping of sediments during an earthquake.
HAVE THERE BEEN RECENT DESTRUCTIVE TSUNAMIS?
- Yes, there has been at least seven tsunami generated within the Pacific rim resulting from near shore earthquakes, in the ten years from 1975 causing loss of life and property.
HOW FAR CAN A TSUNAMI TRAVEL?
- A large tsunami generated anywhere in the Pacific is capable of causing destruction at long distances. One example is that generated by the 1960 Chilean earthquake.
- This large event (magnitude 9.2) earthquake caused the most destructive Pacific wide tsunami of recent history. n The waves were estimated to be about 20 m high killing 2,000,000 people and injuring 3,000.
- The tsunami wave arrived at Suva 13 hours later and damaged several ships anchored at Walu Bay.It caused 61 deaths in Hawaii, 20 in the Phillippines and 100 more in Japan.
- The waves were estimated to be about 11 m at Hawaii and 6 m at various places in Japan. This shows that the tsunamis generated even at distant locations can be highly destructive.
IS A TSUNAMI LIKELY IN FIJI?
- Fiji being an island nation surrounded by ocean, is particularly vulnerable to tsunamis. However most of Fiji’s coastline is protected by coral reefs and the waves generated by tsunamis outside these reefs lose most of their energy when they break onto the reefs.
- We may not therefore, see gigantic waves on our shores, but we can still suffer considerable damage from smaller waves and flooding. The effect can be greatly enhanced at high tides.
HAVE TSUNAMIS STRUCK FIJI?
- Eleven tsunamis have been recorded in Fiji, of which three were generated within Fiji waters. The most damaging tsunami in Fiji was in 1953. It claimed five lives in Suva and Kadavu and flooded parts of Suva City. The wave heights were estimated to be about 4m and about 5m at Nakasaleka in Kadavu. The tsunami occurred at low tide, and had it occurred at a high tide the damage would have been severe. The tsunami resulted from a massive underwater slumping of sediments caused by an earthquake offshore from Suva. The first of the tsunami waves reached Suva only about three minutes after the earthquake.
- A small tsunami was generated in 1975 by a moderate earthquake in Kadavu Passage and once again, resulted from an underwater landslide.
- This leaves little doubt that a large earthquake can generate another damaging tsunami.
- The 1953 disaster showed that the tsunamis are most dangerous when generated by earthquakes close to you, as you do not get any other warning that a tsunami may have been generated.
CAN YOU BE WARNED OF AN APPROACHING TSUNAMI?
- The Pacific Tsunami Warning Center (PTWC) based in Honolulu, Hawaii and managed by the National Oceanic and Atmospheric Administration of USA issues warnings for the Pacific.
- It is also the center for the International Coordination Group for the Tsunami Warning System in the Pacific. Fiji is the member of this group.
- The warning center has saved a lot of lives since 1952, through timely warnings.
- However, it is not always effective in warning people close to the tsunami source because the tsunami may have already struck coastal areas close to the source before the Center can issue a warning.
HOW CAN YOU BE WARNED?
- This tsunami messages issued by PTWC are relayed through the well-developed communication system of the Fiji Seismology Unit. The unit studies the message and decides whether or not to issue a tsunami warning or not to issue a tsunami warning for Fiji. For a strong earthquake within the Fiji area a tsunami warning pertinent to Fiji immediately; however, the warning may not be issued in time to be useful.
- All tsunami messages will be broadcast on the radio and if a warning is issued then you’re requested to follow the advice given on the radio. Tsunami sirens along the coast will also be activated to alert coastal communities to evacuate.
- Remember if you’re in a coastal area and you feel a strong shaking due to an earthquake, then that may be the only warning you get, before a tsunami strikes, take appropriate action as advised in your Tsunami Safety Rules.
Aerial View of Nasese Foreshore
Officials and international partners
Aerial View of Walu Bay foreshore
TSUNAMI SAFETY RULES?
- Stand by for the tsunami emergency when you hear that a large earthquake has occurred1. Stand by for the tsunami emergency when you hear that a large earthquake has occurred
2. Head for higher ground if you feel a strong earthquake and you’re near the shore. An earthquake in your area is a natural tsunami warning.
3. Stay Out of danger areas until “all clear” is issued by the authorities, because a tsunami is not a single wave, but a series of waves.
4. Nature tsunami warning – any sudden rise or fall of coastal water signals an approaching tsunami.
5. Pay respect to all tsunamis. A small tsunami at one point on the shore can be extremely large few kilometers away.
6. Be prepared for the worst. A tsunami warning will only be issued when a tsunami exists. This means that a tsunami has been observed somewhere and there is no way of knowing what the effect will be on the coastlines of Fiji.
7. All tsunamis are potentially dangerous even though may not damage every coastline that they strike.
8. Keep your distance. Never go down to the shore to watch a tsunami.
9. Warnings apply to you if you live in a coastal area, because sooner of later, a tsunami will visit the coastline close to you.
10. Please cooperate. During a tsunami emergency the emergency organizations such as the Police, the Red Cross and other organizations will try to save your life.