Tuesday, September 29, 2009

Tsunami Advisory Issued for California and Oregon

As a result of a 8.0 magnitude earthquake that hit the Samoan Islands around 10:48 (Pacific time) this morning NOAA and the USGS issued a Tsunami Warning for the US West Coast…in particular the Coastlines of California and Oregon, with the highest elevated sea-level estimates focused on Port San Luis (CA) and Crescent City (CA).

Southern California is included in the warning areas as well, but the expected raise in sea-level is estimated to much lower.

At this point NOAA is calling for the following (in expected amplitude above sea-level):

San Diego, CA - 15cm
San Pedro, CA - 30cm
Port San Luis, CA - 60cm
San Francisco, CA - 20cm
Cresent City, CA - 65cm
Newport, OR - 15cm
Seaside, OR - 25cm

The initial arrival time is set for about 9:20pm (pacific time) tonight and should continue to push in some energy for several hours afterward…likely into Wednesday morning.

Tsunami Propagation Map - shows the estimated energy pushed out by the earthquake and the subsequent rise in sea-level.

At this point NOAA has issued a Tsunami “advisory” which is below the “warning” level…basically it means that they expect the tsunami wave to be between 0.3 meters and 1 meter…(so 1 to 3-feet). (Hawaii had a “warning” issued earlier but that has been lowered back to the advisory level.)

It is however important to realize that certain topographic features, like bays and harbors can focus and amplify the energy into larger wave crests, which is like why Cresent City and Port San Luis are forecasted to receive larger amounts of energy.

I have had a couple of people email asking me about how this will affect the surf…and in general Tsunamis don’t have any positive effects on the surf. They are not surfable waves…the swell period is much too long, and the actual wave-form when it shoals is more like a series of fast moving tidal swings. Having the tide drain away and then rush back in a relatively short period is definitely not good for surf.

Likely, except in a few cases, we won’t see much actual effects along our coastline…but just to be on the safe side you should avoid low-lying costal areas that are already prone to flooding as well as bays/harbors…at least until they drop the advisory. Hopefully any activity we do see here will be minimal.

Here are some helpful links that you can check out for the latest updates.



Anonymous said...

wave is a wave is a wave?

Anonymous said...

we are all going to die! hahahaha