Town Square

On Deadline: Could a quake/tsunami hit Palo Alto, East Palo Alto, Menlo Park? You bet

Original post made by Jay Thorwaldson, editor emeritus, on Mar 18, 2011

In the shadow of the double-whammy disaster in Japan (assuming nuclear meltdown doesn't make it a triple) the inevitable question is: Can it happen here?

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Posted by Anon.
a resident of Crescent Park
on Mar 20, 2011 at 2:09 am

We can never rule anything out, but in terms of a surge pushing all the way down to the bay due to a tsunami ... I'm a little skeptical.

The reason I am skeptical is that if said giant tsunami is not high enough to go over the mountains that protect us the only surge that will be able to push a volume of water into the bay would be the golden gate.

Assuming it is a pulse of water ... a wave that surges in and then washes out ... only a certain amount of water would be able to pass through the golden gate ... even if it was 30 or 40 or even more feet high, how much actual volume of water would make it into the bay, and as it levels out how much would it fill the bay as far south.

I think a reasonable calculation could be made if one had the numbers of how high the wave is for how long and has fast it washes out. I question if the results would be anything like a 55 inch rise in sea level ... because that would be a steady state phenomenon, where a tidal wave would be wash of water in and out depending on the volume and frequency of the wave it is questionably whether that wave would push significantly all the way to the end of the bay.

Obviously if the tidal wave was big enough and lasted long enough it would fill the whole bay. I'd love to see if someone has done a simulation using values of the maximum measured rise and fall of sea level over the maximum time of the wave and apply that to a rush of water through the golden gate.

All things being equal I would much rather be here than in say New Your City/Manhattan which is the exact opposite of our configuration. Of course we could get the huge earthquake we CA is supposed to fall into the ocean like Atlantis, and we can never plan for something like that.

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Posted by Giraffe
a resident of Duveneck/St. Francis
on Mar 21, 2011 at 12:32 am

The headline of this article claims that a tsunami could hit Palo Alto. The body of the article talks about the pumping out of ground water, global warming, problems with San Francisquito Creek, 100 year floods, ... However, the body of the article doesn't even contain the word 'tsunami'! I wish the author had chosen a more suitable headline - he apparently is capitalizing on current events to talk about real problems, but it seems that a tsunami in Palo Alto is not one of them.

For actual information about tsunamis in the bay, see
Web Link. While this report only mentions the south bay in passing, it appears that even with their worst case scenario (a 9.2 in the Aleutians, not on the Hayward fault), the water level in Palo Alto would only rise a few inches.

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Posted by Astounded!
a resident of Another Palo Alto neighborhood
on Mar 21, 2011 at 9:20 am

Good lord! The author of this article has demonstrated little, or no, knowledge of the mechanics of tsunamis. With the USGS so close, one would have thought that someone writing on this topic would at least have tried to talk to a geologist, or someone familiar with tsunamis, before committing this much time to something that is not substantiated with fact.

Oddly, everything written here (more of a memory dump of problems surrounding San Francisquito Creek than anything else) is true--just not applicable to the topic in the headline.

(And this is supposed to pass as quality "journalism".)

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Posted by How will we know?
a resident of Southgate
on Mar 21, 2011 at 6:05 pm

The area that flooded in 1998 was ALL creek flooding. It was a much smaller area than the tidal flood zone. IF a "perfect storm" hit then a tidal flood might run the entire north/south length of Palo Alto, a bit east of Middlefield Road. Homeowners in the tidal flood plain know where the line is because of mandatory FEMA flood insurance.

Why is it that almost all Palo Alto discussion of flooding deals with San Francisco Creek and omits the tidal flood risks? Granted, creek flooding is more likey to happen than tidal flooding, but creek flooding has a much lower risk for catastrophic loss of life and massive property damage.

In the event of a levee breech or a tsunami, how will residents know about the rising waters? If it happens during the school day, how will PAUSD know to evacuate kids at Duvaneck, Ohlone and Palo Verde? If it happens at night, how will residents know to evacuate?

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Posted by PA mom
a resident of Green Acres
on Mar 22, 2011 at 11:35 am

That's a good question. We have a telephone alert system, but do we have a siren alert system to give citizens instant notice that they had better get emergency alert info quick (and will they know where)?

In the event of a disaster, do not expect outside help. The schools should have plans.

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Posted by PA mom
a resident of Green Acres
on Mar 22, 2011 at 11:41 am

Additionally, aren't some of the homes on the south/east side of town in a dam inundation zone (certainly los altos is over here)? What's that all about?

There is a shallow fault running right under Gunn HS that a lot of residents don't know about, capable of at least as large a quake as hit Christchurch recently. Confirmed by USGS.

Almost as bad as not making plans for things we know could go wrong as you have pointed out, is hubris that ends up in poor planning and the completely preventable post-disaster refrain: "we never expected anything so severe".

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Posted by Gordon
a resident of Greater Miranda
on Mar 22, 2011 at 10:37 pm

The BIG one hit Japan. No one predicted a 9.0 quake followed by a 30' high tsunami which combined to create a third major catastrophe in the making, a nuclear meltdown with wide spread radiation contamination.

An earthquake-created wrenching of the earth under or near our Bay could create a tsunami-like wall of water wiping out all low lying structures all around the Bay. USGS can create the scenario for you with some authority.

The dike systems protecting communities bordering the Bay will NOT get the job done when the really BIG ONE hits.

The Redwood City Saltworks proposal — the joint venture of Cargill and developer DMB Associates — will likely be going back to the drawing board on its plans for thousands of homes and millions of square feet of commercial buildings on 1,436 acres of salt flats, much of it below the level of the Bay in normal times. No insurance company in its right mind will be writing insurance there.

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Posted by Why not?
a resident of Professorville
on Mar 22, 2011 at 11:44 pm

Seems like it would be very profitable for an insurance company to collect lots of premiums dollars to insure homes in a flood zone. After many years of doing this, if THE BIG ONE hit, they won't have to pay out very much. The CA Insurance Commissioner will let them donate to his favorite charity instead. The Insurance Commissioner during the Northridge Quake did that and then retired in Hawaii!

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Posted by Crescent Park Dad
a resident of Crescent Park
on Mar 23, 2011 at 7:10 pm

USGS has published tsunami impact maps for the Bay Area. The assumption is a catastrophic earthquake in the Aleutian Islands. From what I can remember, I don't think the PA airport gets wet...

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Posted by Waves
a resident of Crescent Park
on Mar 24, 2011 at 7:20 pm

I think Crescent Park Dad is correct. Here is the doc he might be referring to : Web Link, written by scientists from UCLA and Humboldt State for the The California State Lands Commission, in 2006.

The report says that the Alaskan quake in 1964 created a wave at the Presidio of 7', peak to trough. At Hunter's Point, the wave was reduced 50%, ie, to 3.5' and at the southern end of the bay, it was reduced to 10%, about 18". I suppose if it happened at a high tide, and the water was moving fast, it _might_ get the airport wet, but I really have no idea if that would happen or not.

I was surprised to learn that there is an 8' low tide -> high tide difference in the Palo Alto baylands. It is interesting to stand on the boat dock there while the tide is running - it reminded me of the tsunami hitting the Santa Cruz boat harbor.