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'Hidden' earthquake faults underlay Peninsula

Original post made on Feb 25, 2011

The San Andreas fault might be the iconic expression of the shifting tectonic plates sliding deep beneath Bay Area residents' feet, but numerous faults run up and down the Peninsula, some with a potential shaking power that has not been evident in what geologists consider "historical times" -- since 1776.

Read the full story here Web Link posted Friday, February 25, 2011, 10:52 AM

Comments (14)

Posted by Lives-In-A-Quake-Zone
a resident of Another Palo Alto neighborhood
on Feb 25, 2011 at 11:50 am

This is an interesting article. The USGS also has a lot of material on earthquakes on their Menlo Science Center web site:

Web Link

There are a number of troubling questions, though. For instance, what does a homeowner (or a potential homeowner) do with this kind of information/data?

or ..

Even if the USGS could predict earthquakes, what should the residents, local, county and state governments do to take advantage of foreknowledge of a pending earthquake?

Increasing the effectiveness of building standards/codes in earthquake-prone areas seems to be something that "government" should be doing. Hopefully, "government" is inspecting/rating all large structures for their ability to withstand seismic events.

It's nice that this information is available, but it's not clear that we (as a society) know what to do with it.

Posted by look it up yourself
a resident of Adobe-Meadow
on Feb 25, 2011 at 12:06 pm

Don't blame you real estate agent. Look up the earthquake zones yourself. Lots and lots of tax money goes to create these maps and make the available to the public. Besides, the latest maps are probably a lot more accurate than what your agent may have known in 1967. The area between Foothill Expressway and the Pacific Ocean is laced with fault lines. And the area between Hwy 101 and the bay has lots of semi-stable landfill.

Posted by look it up yourself
a resident of Adobe-Meadow
on Feb 25, 2011 at 12:11 pm

What can you do with the information? Talk to an engineer and stabilize and reinforce your own house without having the government nanny you. And talk to your insurance agent to get the coverage appropriate for your situation. Owners of large buildings are probably already doing this.

Posted by Lives-In-A-Quake-Zone
a resident of Another Palo Alto neighborhood
on Feb 25, 2011 at 12:27 pm

> The area between Foothill Expressway and the Pacific Ocean is
> laced with fault lines. And the area between Hwy 101 and the
> bay has lots of semi-stable landfill.

So it should be zoned as "unstable..due to being earthquake prone" and residential construction disallowed?

> Look up the earthquake zones yourself

Hmmm .. most people can't read a simple road map. What are these sorts supposed to make of a seismic activity/fault zone map?

Posted by get a grip when it's shaking
a resident of Professorville
on Feb 25, 2011 at 12:49 pm

Sue and Sara, please consult the online USGS fault maps for your edification. The Monta Vista fault in not "right near her house".
It's on the west side of 280, above Eastbrook and slices across Magdalena (it's the reason the San Antonio Hills are there from the uplifting thrust of eons ago. Ms. Siegel' Briarwood home is almost 2 miles east of the Monta Vista fault trace.
Sensationalism in media outlets only confuses people. Complacency sets in when the big one doesn't hit. Christchurch New Zealand was hit by a Thrust fault near the surface, but they were prepared because of the Sept. 2010 quake.
Yes, be prepared, reinforce your house with Simpson strong tie straps above and below, reinforce your brick chimney, have a fully stocked first aid kit, portable radio, flashlights, plenty of extra batteries, 3 days of drinking water, some propane for cooking and sterilizing water on your outdoor grill, $200. cash in the house as ATM's, Credit card machines may be down if power goes out. Inside, make sure water heater is well strapped, heavy bookcases and tall cabinets are secured to the wall with L brackets. Outside, make sure you have a gas meter shut off wrench ($10 at OSH)strapped near the gas meter,
Emergency communicatin plan, have a text (not cell) plan to reach loved ones. Cell towers will be overwhelmed with panicked folks. Texting is more reliable. Keep it short, have a rendevous point if possible, but don't gab with "OMG, DID YOU FEEL IT?, I'M SO FREAKED"
Keep the cell lines free for really important communication links to confirm safety of loved ones.

Posted by homeowner
a resident of Another Palo Alto neighborhood
on Feb 25, 2011 at 1:42 pm

If you know this info, it must be disclosed in writing to any prospective buyers. A lot of stuff must be disclosed -- it is NOT "buyer beware" when it comes to residential real estate.

Posted by narnia
a resident of Menlo Park
on Feb 25, 2011 at 2:57 pm

Certainly some precautions make sense, but Professorville speaks as if all live in single family housing (YOUR outdoor grill he/she says). The truth is that for many multiple units buildings /townhouses of which there are a huge number in the area, for renters and owners alike there is little they can do to reinforce a building for practical reasons. The renter needs the landlord to do it and the condo owners need others to agree to do it. Even the gas shut off valves are off the limits in large buildings. For short term visitors even those aware of the danger some things cannot be done. Sensible guidelines are issued only for single family units. Those guidelines should be made into law for medium to large multiple units building.

Posted by Lives-In-A-Quake-Zone
a resident of Another Palo Alto neighborhood
on Feb 25, 2011 at 4:34 pm

> Keep the cell lines free for really important communication
> links to confirm safety of loved ones.

Laptops/Netbooks/etc. should be configured with Skype, or some sort of similar telephony software (google has a free outbound service at this time). This means buy a headset, and maybe setting up an outbound account with a few dollars balance. WiFi hot spots will be up where electricity and telephone service is up, so people could make telephone calls via VoIP in these hot spots-taking some pressure off cell phone service.

Posted by B-Obama
a resident of Atherton
on Feb 26, 2011 at 8:40 am

Don't expect FEMA to rebuild your house if it is damaged in a quake either. Many people are under the misconception if a major quake hits the area and is declared a disaster zone that FEMA will pay to have your house rebuilt. They will not. They will only assist with living expenses and might offer low interest lows to rebuild your house. Only earthquake insurance will pay to rebuild your house. Yes I am an insurance agent. Just want to clear this myth and misconception many people have. Oh and don't forget if you have children brace all your tall, large or heavy furniture to the wall to prevent injury if they fall over in a quake or minor trembler.

Posted by Local Observer
a resident of Los Altos
on Feb 26, 2011 at 9:40 pm

Another serious issue is liquefaction. Think what happened to the Marina in San Francisco during Loma Prieta; the Marina was some 70+ miles from the epicenter and had massive damage. My home was much closer to the epicenter and only some knick-knacks fell from a shelf and were damaged (and easy to repair).

I did some research earlier this week about this issue and found some interesting new websites with maps, one of which may make Palo Alto residents' spines tingle (see below URL aka web link).

I don't know if there's a message size limit here, so I'll keep this short and point only to top-level URLs from which you can easily find the PDF maps.


Web Link

Second, again from the USGS, "Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region, California". Start at this URL:

Web Link

And now the spine-tingly ones, from the California Department of Conservation dated February 2009 (i.e., current). Start at this URL:

Web Link

The two most important files for Palo Altans are from the California Geological Society, Seimic Hazard Zones, Palo Alto Quadrangle, PDF map here:

Web Link 6.9MB

and the 70-page report "SEISMIC HAZARD ZONE REPORT FOR THE PALO ALTO 7.5-MINUTE QUADRANGLE, SAN MATEO AND SANTA CLARA COUNTIES, CALIFORNIA" accompanying the map which is available here:

Web Link 7.3MB

Posted by Jocelyn Dong
editor of the Palo Alto Weekly
on Feb 28, 2011 at 11:00 am

Jocelyn Dong is a registered user.

A reader has asked for the link to the interactive USGS map that was printed on page 16 of the Feb. 25 edition of the Weekly (and also included in the online article, above).

Here's the URL for the Quaternary Faults Web Mapping Application: Web Link

Posted by Steve
a resident of Menlo Park
on Feb 28, 2011 at 12:46 pm

Here's link to a guide to earthquake preparation that USGS, Red Cross, FEMA, and other agencies put out a few years ago. It describes the earthquake hazards in the Bay Area and what both homeowners and renters need to do to be prepared.
Web Link
Hard copies of this publication are sometimes available at Home Depot and Orchard Supply. They're always available at the map counter at USGS in Menlo Park.

Posted by george
a resident of Charleston Gardens
on Feb 28, 2011 at 1:14 pm

There is a wealth of information on the following web site:
concerning what to do to prepare for an earthquake.

Posted by Faulty Info..
a resident of Midtown
on Feb 28, 2011 at 4:00 pm

Both the owner selling the house/lot and the person planning to buy the lot/home should be told about facts of the land by the realtor. But I'm not sure just what a realtor is truly responsible re: the structural parts of the house, the ground, etc.
Anyone know exactly how it should work?

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