Southern California Earthquake Preparedness

Southern California Earthquake Preparedness

Mexico’s Early Warning Earthquake system worked in the 7.1 earthquake this week, giving 20 seconds warning for a quake that was 70 miles from Mexico City. Further cities got up to a minute of warning. Mexico City had just practiced a response drill where evacuating buildings is the proper response, considering their old brick buildings. It undoubtedly saved many lives. A map of Mexico City in the NY Times showed 62 collapsed buildings. Mexico City is built on an old lake bed covered by sediments, with many buildings not supported on pillars on rocks. Shaking from an earthquake is also increased on this type of soil.

Update:  Several of the buildings that fell in Mexico City were concrete, but had columns that were steel bound by only single horizontal squares.  The concrete just falls apart upon shaking.  They should have had another set of squares inside them at 45 degree angles, and cross beams on the outside.  Los Angeles has 1,500 such old concrete buildings, and in 2015 passed a law to retrofit such buildings in 25 years.

The Los Angeles Basin, Huntington Beach, part of Irvine, and other areas are also build on soft soil that may suffer from liquefaction in an earthquake. Our high tech, aerospace, world leading university, wealthy Southern California area still does not have an earthquake early warning system, despite efforts over many years by Cal Tech’s Lucy Jones to develop and get funding for such a system. Last year, California and Gov. Brown passed a bill not allowing California to fund such a system. Trump’s budgets for 2017 and 2018 had cut out funds for such a system. Fortunately, the House has passed putting the system in the budget, and the Senate and President Trump had agreed on a continuation budget until December. But the system needs creation funds, and yearly funding.

Southern California is primarily threatened by the San Andreas fault, which expects an 8 plus earthquake every hundred and fifty years, and it has been that long since the last big earthquake on it. The Newport-Inglewood fault running near the coast had a 6.4 quake in 1933 in Long Beach, killing 115, and collapsing schools. There are many faults parallel to the coast and the San Andreas, and a lot of crossing faults. The Northridge quake in 1994 was a 6.7 and caused $13-$44 billion in damages. Despite being in the San Fernando Valley, it shook the Los Angeles Basin on its soft soil.

Other countries’ early warning systems were developed only after severely deadly earthquakes: Mexico lost 9,500; Japan more than 5,000; Taiwan more than 2,000; Turkey 17,000; and China 70,000. Do we have to wait for such a tragedy?

The overall project will cost only $38 million to build and $16 million to run.  On the scale of losses in an earthquake of lives or property damage, this is very small.  The House appropriations subcommittee overseeing the Department of the Interior, which includes the USGS, has approved on July 12 the continuation of an $10.2 million per year current budget.  This is included in the FY18 Interior Appropriations bill.  $23 million has already been invested by the federal government.

The system will shut down major natural gas pipelines, the Metro trains, airports, hospitals, oil refineries, and provide warnings to schools and universities.  It can give a minutes warning for a quake on the San Andreas fault originating on the Salton Sea.

California suffers from old buildings with parking spaces on the ground floor, with upper floors supported only on posts. A 2016 survey of such buildings in the LA area released by the LA Times, found 13,500. More than 3,200 buildings in the San Fernando Valley had 75,000 units. There are 55 buildings with more than 100 units, more than half in the valley. These are called soft-storied buildings, or ding-bats. Under a new law, owners are required to retro-fit such units within 7 years of being notified. The earthquake upgrades are often just X beam bracing of the ground floor walls and spaces between parking spaces. Estimated costs can be as high as $130,000 per building.

I hope the two Mexican earthquakes serve to speed up the retrofit processes for both soft buildings and old concrete buildings at least in response to tenant and insurance company pressures. I hope they also get the earthquake early warning system funded, and can speed it up also.

 

 

About Dennis SILVERMAN

I am a retired Professor of Physics and Astronomy at U C Irvine. For a decade I have been active in learning about energy and the environment, and in lecturing and attending classes at the Osher Lifelong Learning Institute (OLLI) at UC Irvine.
This entry was posted in Earthquakes. Bookmark the permalink.

Leave a Reply