Posted by: rosyroadsadventures | August 11, 2011

Tsunami Alert

N 18° 20.5′ W 64° 42.8′

Coral Bay, St. John

Well, that was interesting! We are anchored here in Coral Bay and the Tsunami Warning System went off this morning.

After the sirens stopped, a voice came over a loudspeaker directing everyone to evacuate to higher ground. After a brief moment of panic – they have lots of minor earthquakes in the region – I went online to check the seismic activity sites. Nothing there, and no info on the marine radio. Found an article on a local news forum mentioning a planned test today of the first phase of the Tsunami Siren Warning System that was recently installed throughout the VI. They repeated the message, then played a different message that told everyone except for emergency personnel to stay off the roads. Later they played a message stating this was a drill. The whole exercise took about an hour. Thank goodness for internet access to information.

After reading up a bit on the subject, I found that geophysicists consider the Caribbean basin to be a major tsunami hazard area. There are large faults around the area including the Puerto Rican trench, the deepest location in the Atlantic Ocean, where the North American plate and the Caribbean plate merge. The area is capable of generating tsunamis of 40 feet or higher, which was experienced here in 1867. A significant tsunami has been recorded in the Caribbean about every 50 years. The last large one was in 1946 when over 1800 people were killed by a tsunami generated off the coast of the Dominican Republic.

If you are on land, the obvious advice is to quickly move to higher ground. On a boat, the advice is that if you are at sea, stay at sea and move to deeper water if possible, since tsunami waves are usually imperceptible there. In a harbor, it gets a little trickier to evaluate the best plan. One must consider the existing weather and sea conditions as well as the ocean floor topography, and how much time is available before the tsunami hits.

On the Mar Azul, we are still discussing those scenarios and how we would have handled this morning’s alert had it been the real thing. Bob is leaning toward Option A: continue to read his book and hope for the best, since if it’s The Big One it’s probably too late to either dinghy to shore or head out to sea; or possibly Option B: stay at sea all the time to avoid any tsunami risk; or Option C: spend time worrying about hurricanes because they are a greater threat. I’m liking the option of immediately hauling up the anchor and heading out, since we could be in 100 foot depths within 30 minutes and 500 foot depths within an hour.

This gives you some idea that decision making aboard can be most interesting at times. Any other advice out there? Of course in many of our destinations we won’t have to make any decision at all since they don’t have tsunami warning systems.

This is our first experience in Coral Bay on the southeast side of St. John. There are probably about seventy boats anchored here that appear to belong to local residents. Almost all are sailboats – so different than in Puerto Rico. Only a few are occupied, and there is very little activity in the harbor. They don’t seem to get charter boat traffic here. There is a town dinghy dock and a neat little settlement ashore with several restaurants and shops. It has been quiet and peaceful– other than the tsunami siren.

Coral Bay, St. John, US Virgin Islands

Ashore, Coral Bay



  1. Wow!

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