On Deadline: Could a quake/tsunami hit Palo Alto, East Palo Alto, Menlo Park? You bet | March 18, 2011 | Palo Alto Weekly | Palo Alto Online |

Palo Alto Weekly

Spectrum - March 18, 2011

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

by Jay Thorwaldson

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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Former Weekly Editor Jay Thorwaldson can be e-mailed at jthorwaldson@paweekly.com.

Comments

Posted by Sethro, a resident of another community
on Mar 18, 2011 at 3:09 pm

It's a point well taken to take earthquake planning seriously and have appropriate supplies (including cash on hand). I'm glad I did when Loma Prieta struck. Earthquakes aren't just a possibility here, they are a matter of inevitability.
On the topic of a tsunami being generated inside the bay itself, there is a very, very slim chance. Tsunamis are a result of a land mass displacing water. They can be generated by an earthquake from a subduction fault but not from the slip/strike faults in the bay area. It's the wrong type of movement to generate large waves. The only way a tsunami could be generated inside the bay would be from a large landslide into the bay (as had happened at Lake Tahoe).
A tsunami could enter the Bay through the Golden Gate but the direction of travel would be towards the East Bay, not the South Bay. It would take a very large wave (30 feet or more) to have any significant flooding impact in the Palo Alto area.
Or so I've been told by USGS earthquake scientists based in Menlo Park.


Posted by Anon., a resident of Crescent Park
on Mar 20, 2011 at 1:11 pm

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.


Posted by Anon, a resident of Another Palo Alto neighborhood
on Mar 20, 2011 at 6:03 pm

Anon from Crescent Park:

Remember that the wavelength of a tsunami is much, much longer than a wind driven wave, and, the amount of energy involved is vastly larger. A 30-foot wind-driven wave has enough energy to kill someone (e.g. at Maverick's recently), but, if you look at the videos of the recent tsunami in Japan, you will realize that a 30-foot tsunami has many orders of magnitude more energy.


Posted by Anon., a resident of Crescent Park
on Mar 20, 2011 at 6:55 pm

> Anon, a resident of Another Palo Alto neighborhood

I realize a tidal wave has a lot of energy, but only a relatively small segment of that wave can get into the bay, so it gets dispersed, like radiation in the air from Fukushima such that it will spread out in all directions. I'd like to know if anyone can simulate this?

For instance integrate the surge of water to get a volume and then distribute that around the bay and see if evenly distributed how high the tide would be? It would be ugly to see the ballpark floating down to the south bay but maybe we could float it over and ground it on the PA airport! ;-)

For sure heaven help anyone on Alcatraz.


Posted by Orwell, a resident of another community
on Mar 21, 2011 at 9:55 am

Think and worry EARTHQUAKE before you get shingles talking tsunami.
IF a tusnami hits Palo Alto, it would most certainly come after an iron meteor being on target on the Stanford admissions office.


Posted by WilliamR, a resident of Fairmeadow
on Mar 22, 2011 at 9:48 pm

The Army Corps of Engineers has a large-scale model of San Francisco Bay at their facility in Sausalito. They use it for studying tidal movements and currents, so they are probably researching how a tsunami surge through the Golden Gate would affect the rest of the Bay. (Google 'San Francisco Bay Model' for more information and the times it is open to the public.)


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