By Ulu Aiono
If I think about surviving a tsunami I also think it will happen to somebody else -- not me. But on 2 October 2009 Samoan families and foreign tourists were shocked and shattered by the speed of the tsunami that roared over the reefs, lagoons and low, flat, plains of villages and resorts on the south coast of Upolu island. Drowned. Dead. Missing. Destroyed. Every family, local and tourist, lost something. One local family lost 35 members to drownings and injuries. How do you survive a tsunami.
Can you survive a tsunami?
It depends. You have to get to a location that is out of reach of the tsunami. You can be out of reach by getting to ground that is high enough. You can also be so far inland, on flat terrain, away from the coast, that a tsunami's force will be exhausted before it reaches your location.
In 2004 thousands of Bali citizens and tourists were drowned, or otherwise killed, by a huge tsunami that swamped hundreds of kilometers of Bali's coastline. Nevertheless some tourists and locals survived by running inland, along with wildlife, far enough to escape the full force of the Bali tsunami. Those survivors were lucky. So were some of the Samoa tsunami survivors in October 2009. Some survived despited the tsunami catching them on the flat, coastal, plains of Samoa's Upolu island. They survived by sheer good luck because -- along with those who were killed -- they were caught by the full force of the tsunami and somehow managed to hold onto a tree or object without being fatally injured by tumbling cars, trees, concrete, logs and other flotsam in the roiling waters.
A typical wave of water is like any wave in that it has an amplitude (distance from top of crest to bottom of trough) and a frequency (number of crests passing a fixed point in one second). In normal weather conditions you can count the waves coming onto a beach. Some waves are small. Some waves are big (that is they have a large amplitude). During one minute, sometimes 30 waves will break on the beach. This means the frequency is 30 waves divided by 60 seconds which equals 0.5 waves per second. At other times you might see 60 waves break on a beach -- in one minute. Then the frequency would be 1 wave per second. The greater the frequency the more the number of waves.
A tsunami's destructive force is caused by its extremely low frequency. For example, a tsunami wave that takes three minutes to pass fixed point will have a frequency of 1 wave divided by 180 seconds which equals 1/180 waves per second. That is a very long wave. It contains a lot of water. Tonnes of water. Tsunami observers and survivors call it "a wall of water." In one minute the weight of water passing a fixed point is 160 tonnes if the water is a one meter wide wall of water that is one meter high and moving at 1 kilometer per hour. If the same wall of water is 100 meters wide then 16,00 tonnes of water will land on the beach in one minute. If the wall of water is 100 meters wide and moving at 10 kilometers per hour (not 1 km/hr) then the same 100 meters wide (and 1 meter deep) wall of water will throw 160,000 tonnes of water onto the beach in one minute. That is a lot of water and the associated force will pulverise most things in its path. Also, that much water will roll inland, from the beach, a long way. The faster the tsunami wave travels as it lands on a beach, and the larger its amplitude, and the lower its frequency, the greater the destructive force.
I think you get the picture.
For example in the October 2009 Samoa tsunami many locals and tourists were still recovering from the magnitude 8.0 earthquake that shook the region. Barely ten minutes passed after the start of the quake. One Australian couple, holidaying on the south coast of Samoa's Upolu island had been shaken severely in their resort accommodation. Husband and wife made their way to the resort carpark so as to avoid falling debris during the earthquake. The tsunami caught the couple in the carpark. The husband hung onto his wife. As they tumbled in the roiling waters, the husband caught hold of a tree but lost his grip on his wife. She drowned. In the same tsunami on a tiny island, more of an islet, a few hundred meters off the shore at another resort on Upolu's south coast, a Kiwi school party had scrambled to high ground during the magnitude 8.0 quake. The party watched the tsunami sweep past their island and take all their possessions from the camp site.
A Radio New Zealand crew member described his experience of sudden fear and shock as he got up from a reclining position after watching water drain out of the big lagoon next to his beach-side hut. The crew member yelled "RUN," as he ran for his life away from the beach. Some of the people in other huts were caught. The run to high ground was not easy. There was a lot of vegetation in the way. Later, in the aftermath of the October 2009 tsunami, Samoans and locals on Upolu recounted their shock and grief. One local family lost four generations of members. One Kiwi family lost one child and re-gained two; all had been swept out to sea. Survivors, locals, Samoan police, New Zealand Army and Navy, Australian Army and Navy, worked for weeks to find the dead and drowned.
So, can you survive a tsunami. It depends. If the tsunami catches you by surprise then your survival chances are limited. Even if you are, somewhat, prepared but the vegetation and other obstacles are difficult for you to pass then your chances are limited. On the other hand, you can get lucky. Some locals were caught by the Samoan tsunami and got lucky. One woman, tossed about in the waters, caught hold of pole in the ground. She survived. And old man caught hold of a palm tree and survived. Others were not so fortunate.
Can you survive a tsunami?
It depends. You have to get to a location that is out of reach of the tsunami. You can be out of reach by getting to ground that is high enough. You can also be so far inland, on flat terrain, away from the coast, that a tsunami's force will be exhausted before it reaches your location.
In 2004 thousands of Bali citizens and tourists were drowned, or otherwise killed, by a huge tsunami that swamped hundreds of kilometers of Bali's coastline. Nevertheless some tourists and locals survived by running inland, along with wildlife, far enough to escape the full force of the Bali tsunami. Those survivors were lucky. So were some of the Samoa tsunami survivors in October 2009. Some survived despited the tsunami catching them on the flat, coastal, plains of Samoa's Upolu island. They survived by sheer good luck because -- along with those who were killed -- they were caught by the full force of the tsunami and somehow managed to hold onto a tree or object without being fatally injured by tumbling cars, trees, concrete, logs and other flotsam in the roiling waters.
A typical wave of water is like any wave in that it has an amplitude (distance from top of crest to bottom of trough) and a frequency (number of crests passing a fixed point in one second). In normal weather conditions you can count the waves coming onto a beach. Some waves are small. Some waves are big (that is they have a large amplitude). During one minute, sometimes 30 waves will break on the beach. This means the frequency is 30 waves divided by 60 seconds which equals 0.5 waves per second. At other times you might see 60 waves break on a beach -- in one minute. Then the frequency would be 1 wave per second. The greater the frequency the more the number of waves.
A tsunami's destructive force is caused by its extremely low frequency. For example, a tsunami wave that takes three minutes to pass fixed point will have a frequency of 1 wave divided by 180 seconds which equals 1/180 waves per second. That is a very long wave. It contains a lot of water. Tonnes of water. Tsunami observers and survivors call it "a wall of water." In one minute the weight of water passing a fixed point is 160 tonnes if the water is a one meter wide wall of water that is one meter high and moving at 1 kilometer per hour. If the same wall of water is 100 meters wide then 16,00 tonnes of water will land on the beach in one minute. If the wall of water is 100 meters wide and moving at 10 kilometers per hour (not 1 km/hr) then the same 100 meters wide (and 1 meter deep) wall of water will throw 160,000 tonnes of water onto the beach in one minute. That is a lot of water and the associated force will pulverise most things in its path. Also, that much water will roll inland, from the beach, a long way. The faster the tsunami wave travels as it lands on a beach, and the larger its amplitude, and the lower its frequency, the greater the destructive force.
I think you get the picture.
For example in the October 2009 Samoa tsunami many locals and tourists were still recovering from the magnitude 8.0 earthquake that shook the region. Barely ten minutes passed after the start of the quake. One Australian couple, holidaying on the south coast of Samoa's Upolu island had been shaken severely in their resort accommodation. Husband and wife made their way to the resort carpark so as to avoid falling debris during the earthquake. The tsunami caught the couple in the carpark. The husband hung onto his wife. As they tumbled in the roiling waters, the husband caught hold of a tree but lost his grip on his wife. She drowned. In the same tsunami on a tiny island, more of an islet, a few hundred meters off the shore at another resort on Upolu's south coast, a Kiwi school party had scrambled to high ground during the magnitude 8.0 quake. The party watched the tsunami sweep past their island and take all their possessions from the camp site.
A Radio New Zealand crew member described his experience of sudden fear and shock as he got up from a reclining position after watching water drain out of the big lagoon next to his beach-side hut. The crew member yelled "RUN," as he ran for his life away from the beach. Some of the people in other huts were caught. The run to high ground was not easy. There was a lot of vegetation in the way. Later, in the aftermath of the October 2009 tsunami, Samoans and locals on Upolu recounted their shock and grief. One local family lost four generations of members. One Kiwi family lost one child and re-gained two; all had been swept out to sea. Survivors, locals, Samoan police, New Zealand Army and Navy, Australian Army and Navy, worked for weeks to find the dead and drowned.
So, can you survive a tsunami. It depends. If the tsunami catches you by surprise then your survival chances are limited. Even if you are, somewhat, prepared but the vegetation and other obstacles are difficult for you to pass then your chances are limited. On the other hand, you can get lucky. Some locals were caught by the Samoan tsunami and got lucky. One woman, tossed about in the waters, caught hold of pole in the ground. She survived. And old man caught hold of a palm tree and survived. Others were not so fortunate.
