So is the risk of an tsunami so low there that it is considered safe to have fully loaded oiltankers idle off the coast, or would this be not a problem for those tankers?
The way tsunamis affect different locations is quite interesting! The wave length (distance between two peaks/troughs) at sea can be hundreds of kilometers long, a tsunami could pass under your tiny boat while out at sea and you wouldn't even notice it. It's only as they approach land that the shallow depths force the wavelength to shorten, forming the giant waves we usually associate with tsunamis.
So i looked at this map http://www.charts.noaa.gov/OnLineViewer/11323.shtml and the water depth seems to be about 60 feet if i'm doing it right, i don't know if this is considered safe in such cases or how long they would take to reach a safe depth. Guess it just makes me uncomfortable to have them idle there fully loaded to make a better buck.
I don't think there's ever been a Tsunami in Galveston Bay. Now hurricanes... Like another poster said, they're safer out there than closer in, and having them inside the actual Galveston bay would be incredibly dangerous due to congestion.
About 66 million years ago there was probably quite the Tsunami in Galveston Bay. Courtesy of the Chicxulub impactor.
But you might be right, I'm not really sure what the landmasses looked like so long ago. Also I don't think the place was actually named "Galveston Bay" at the time. :)
For big ships, idling off the coast is exactly where you want them during inclement weather. They're big enough that waves aren't really an issue - it's getting battered against land that's the problem.
[1] http://www2.scholastic.com/content/images/articles/sn_ts/sn_...
[2] https://en.wikipedia.org/wiki/Tsunami