There is an interesting article "Imagining an Alaska-generated tsunami hitting Los Angeles" about a new USGS study of a hypothetical tsunami from an earthquake in Alaska hitting California.

I haven't had a chance to look at the new report this article is based on, but it looks interesting. You can find the original report at "The SAFRR (Science Application for Risk Reduction) Tsunami Scenario".

Sobering, and thoughtful material. I quickly jumped to the portions of the report that dealt with my local area - the authors went into a lot of detail. Interestingly, they did not attempt to deal with damage that would occur to any of the facilities or resources within Channel Islands National Park, just offshore. While trivial in terms of the overall damage total, the tsunami would profoundly affect the Park.

All this could be worse than any cryoseism...All in all, it would be appreciated if you Alaskans could just hold it down and keep quiet...

Somewhere along that path, with considerably less lead time, is Vancouver Island and the City of Vancouver.

I can't tell if this event is more powerful than previously expected events (the .pdf download hangs; apparently it's popular).

I do pay attention to the tsunami evac. routes when I travel down there. However, if Alaska sends a Big One while I am on vacation, I shall be most put out. (Where is that emoticon that has lasers for eyes?)

OT, the quote that "The narrative of an event that has not yet happened is an unusual product for scientists" is curious to say the least. I can think of at least one multi-decade-long global screaming match that might fit this description.

I tend to agree with Doug. Cities in Washington and Oregon are probably at considerably more risk. Not only do they have the risk from an Alaskan tsunami, but also from the fault lines off the coast of Oregon as well (generating a local tsunami from the ocean along the Oregon coastline). In California, the place that normally sees real problems is Crescent City - due to the unusual way that incoming waves are amplified (in height) when they come into the bay there.

But there's no doubt that So. Cal could suffer some expensive damage. I think it's likely that we are going to see some pretty serious activity - seismic or tsunami. And quite probably in our own lifetimes. But was we've said many times - no-one can tell when.

cheers,
Pete

Pete & Doug,

I think you may be misunderstanding the purpose of this scenario. Risks associated with earthquakes might be broken into several broad categories.

First there is the immediate local damage and distruction associated with the earthquake itself. In North America, think of San Francisco in 1906, Anchorage in 1964, or Northridge in 1994. These can occur and cause damage anywhere, not just along the coast. The most severe damage is generally within a couple of hundred kilometers of the actual earthquake. In areas with a history of such earthquakes, the hazard is generally well known and understood by both the population and emergency planners.

In coastal areas, a local earthquake can also create a tsunami and cause severe damage along the nearby coast. Warning time is very short, perhaps only 15-25 minutes, and tsunami damage will be added to that initially caused by the earthquake. Historical examples in N America would be Seward, Kodiak, Valdez, Old Chenaga, and other Alaskan communities after the 1964 quake. Coastal communities in Oregon, Washington, and British Columbia are at great risk of a tsunami after a major quake along the Cascadia Subduction Zone. That risk has not been well understood in the past, but is beginning to be widely publicized by the USGS and other agencies.

The third type of hazard is a tsunami from a distant earthquake hitting the West Coast of North America. This would be a situation where there is no local earthquake to get peoples attention, but there might be as much as 4 hours of warning of the approach of the tsunami. This is a very different sort of problem. While a few local areas on the west coast (eg. Crescent City, CA) have suffered from these kinds of events, the hazard is not as well recognized as it should be by many emergency planners and most of the population as a whole. That is the problem this scenario is meant to emphasize.

While this publication focuses on the effects on Los Angeles (which is after all the largest population center on the West Coast), I think it is really meant as a template for any area on the coast. Also, the report dicusses the wide spread economic effects of damage to the ports of Los Angeles and Long Beach. The economic impact would extend far beyond coastal California! (Other major west coast ports such as Seattle and San Francisco are not as likely to be damaged by a tsunami from a far distant earthquake.)

For example, last night I was browsing through Chapter J, "Emergency Management Response to a Warning-Level Alaska-Source Tsunami Impacting California". It is an interesting look at the problems emergency management officials would face if given 4 hours warning of an approaching tsunami. How do you get the word out? How do you best use that warning time to mitigate the effects on the port? Distant tsunamis can consist of several waves, over a period of hours, and the first wave is not always the largest. How do you keep people from returning to the coast after the first wave has come and gone?
Not simple problems.

In 1812 there was a significant earthquake with its epicenter in the Santa Barbara Channel somewhere near Santa Rosa and Santa Cruz Islands. It sent a quick tsunami up to the very doorstep of the Santa Barbara Mission. Legend has it that the earthquake caused the Chumash to abandon Santa Rosa Island and seek shelter on the mainland under the care of the benevolent Franciscan fathers. There are impressive scars on Santa Rosa Island from this event quite obvious today.

That quake has been in the news recently because of series of mag 2 to 3 quakes in the area - precursors to a larger event? No one knows.

Local planners have taken some steps - modelling and preparing evacuation routes for a 3 meter tsunami on our coast. Signs are up indicating the location of tsunami zones, indicating that one should seek high ground. My home is 200 feet above MSL so i feel pretty good.

We had plenty of warning (eight hours or so)for the 2011 Japanese event, although it still caused significant damage in the local harbor. i was on Santa Rosa Island at the time, right along the south coast, when the wave arrived. We noticed absolutely nothing out of the ordinary. Coastal and sea bottom configuration are everything in determining tsunami effects...

PS. If people go to the coast to see the tsunami and get a thrill, just remember that you can't stop Darwin. To their credit, the local authorities do try....