Why do I bring this up? Because for the past two months there has been a rumor circulating on the internet that a tsunami will happen on July 22. The basic premise behind the claim is that the combined gravitational pull of the Sun and Moon pulling on the Earth's tectonic plates during the July 22 lunar eclipse will cause a major quake. The author of the tsunami hoax (as it's being called) took some NASA data of the eclipse path across the Pacific and compared where it crossed tectonic plate margins. Based on when the maximum eclipse would pass over the area (and factoring in an arbitrary 1 hour lag time), the person assumed an underwater earthquake would be triggered and therefore a tsunami too.
While researchers have and continue to investigate any (weak, if any) relationship earthquakes have with the tides, the scientific consensus is that great earthquakes cannot be triggered by the very weak tidal forces imposed on them, even when these forces are at their maximum during eclipses. (Tiny earthquakes may sometimes correlate with the tides, but those are never dangerous and certainly not tsunamigenic.) The July 22 prediction is simply speculation and is NOT based on science. This type of hoax preys upon people's fears and spreads unnecessary and perhaps even dangerous false alarm.
I can't tell you how many emails I've fielded from concerned people asking about this - probably about one per day on average for two months. In all cases, I've told the emailer that the rumor cannot be true, and there is no way to determine when the next quake will strike. All we can do is act quickly and appropriately once it does. This hoax has gotten so prevalent that NOAA even released a short statement today:
NOAA's Tsunami Warning Centers in Hawaii and Alaska operate 24 hours a day monitoring seismic and water level data for potential tsunamis. According to the scientists on duty, none of the predictions about July 22 should be taken seriously. There is no correlation between earthquakes and eclipses and there is no scientific reason for a big earthquake or a tsunami to occur preferentially in July.
However, anyone living near the coast should learn as much as tsunamis as possible and be prepared. In particular, you should know the natural warning signs and take action to go inland to a higher elevation if you are near the beach and the following occurs: (1) you feel an earthquake -- the ground starts shaking and it is hard to stand up, (2) the water recedes from the shoreline exposing the ocean floor, and (3) you hear a loud roar coming from the ocean. For additional information please visit the following websites: International Tsunami Information Center, Snopes.
The Snopes site does a pretty good job at refuting the claims made in the supposed tsunami prediction. Also, remember that tsunamis aren't weather either!
July 10 Update: Check out the Earth Observatory of Singapore for a really good debunking of this hoax.
July 20 Update: The hysteria has gotten so bad in Sri Lanka, that their Meteorology Department issued a statement earlier today denying any truth to the hoax.