Category: Meteorology

Q

asked by Rafael Baez, San Juan, Puerto Rico and Sandy Sanders

A

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USC Tsunami expert and surfer Jose Borrero takes it on the head:



QUESTION #1



Ok, the answer: what happens to the boat in the earthquake or with the tsunami wave?



I have only read accounts of ships at sea that were sailing over a region when an earthquake goes off. The captains reported that they felt as if the ship had hit rocks even though they were in many hundreds (or thousands) of feet of water. They also reported a violent shaking or a booming. The reason is that some of the energy radiated from the earthquake are in the form of compression waves, kind of like sound waves (look in your old high school science textbooks). The compression waves hit the bottom of the boat and bounce off, causing the abrupt shaking.



Now say you are far from the earthquake, but a tsunami was generated and you are hit by the tsunami waves while at anchor. The result is that the boat will be at the mercy of the currents and the rise and fall of the sea level. The boat may hit bottom and be left high and dry, or be floated up until the limit of the anchor chain is reached. If strong currents and waves come, the boat will basically be at the mercy of the rising an falling sea level.



The safest place for a ship during a tsunami is in deep water, the deeper the better -- 150 ft of water should be sufficient.



QUESTION #2





Yeah, you know I've thought about that a lot. I mean a lot. There are a bunch of surf spots (many I've surfed) that are in tsunami prone areas.



Anyone remember what happened at g-land in June of 1994? An earthquake, which went off south of Java, generated a tsunami which swept through the camp and washed all the sleeping surfers deep into the jungle (it happened at night). The people in the village nearby were not so lucky, some 200 were killed as a result of the tsunami.



Other places where we surf and there is a good likelihood of tsunamis?



Mainland Mexico -- the 1985 earthquake that wiped out Mexico City, also had a tsunami. The quake originated offshore of Mexico near Caleta de Campos, which is near a really good left hand point break which I won't dare mention here.



Nicaragua -- September 1992, the town in front of JJ's surfcamp at Popoyo was totally wiped out and some 300 Nicaraguans were killed (BTW, it's totally rebuilt now and filled with houses again, tsunami bait for the next one...)



Peru -- has a 500-year history of tsunamis from Arica to the border with Ecuador. Pisco has been WIPED OUT by tsunamis at least 4 times in the last 500 years.



Chile -- site of the biggest earthquake and tsunami besides the one that happened last week



Nor-Cal -- the Cascadia subduction zone runs from Mendocino to British

Columbia, it can make earthquakes and tsunamis BIGGER than what happened in Sumatra!



So what would you do??????



You're out surfing, the waves are good, the sun is shining then BOOOOOOOM a rumble comes from distance you see dust rising from the land as the palm trees are shaking violently back and forth, the sea around you erupts in white foamy shock-waves. After a minute or so it's over, deadly silent. The waves suddenly aren't breaking so good, there are weird currents and surges. What do you do?



Ok, here's what I'd do. If I'm at a beachbreak, close to shore, and there are some nice hills on land, I'd paddle like hell for the beach, fire up my truck and drive up the hill (or run!) You may have a few minutes before the tsunami hits with a vengeance. If I'm on a deepwater reef or a big pointbreak or an outer reef, I'd probably paddle for the horizon. If I tried to go into shore and the current wouldn't let me in, I'd turn around and paddle for the horizon -- at least you have a flotation device!



Many people are killed by tsunamis when they are hit by floating debris or smashed into buildings or walls. If you are far enough offshore, there is nothing being tossed around that can kill you. Also if you are a good surfer, you can (hopefully) handle yourself in heavy water, and you definitely have a better chance than some random tourist on the beach. But if you paddle for the horizon,

remember you better wait a while -- like a few hours -- before trying to get back in. Tsunamis can last for a while.



There are some good lessons to be learned by survivors of past tsunamis. The USGS has put out a great pamphlet called "Surviving a Tsunami: Lessons from Chile, Hawaii, and Japan" you can down load it here. Check out page 14, "Climb on to something that floats" !