Seismograph Lets Portola Valley Library Patrons Measure Quakes
By Julia Scott
PORTOLA VALLEY — When you live on the San Andreas fault line, as all Portola Valley residents do, earthquake science is taught in school and geologists lead expeditions through town. It was only a matter of time before residents built their own seismograph to measure tremors under their feet.
It may not look like much, but the seismograph in question — a deceptively simple collection of wire-suspended pendulums, magnets and coils — will be able to sense earthquakes as far away as Chile, provided they affect the tectonic plates that underlie the Bay Area.
In an ironic twist, however, the machine is too sensitive to be able to accurately record a major earthquake happening less than 200 feet away.
“If the San Andreas fault goes off on the Big One, it will saturate it and it won’t be able to measure anything at all. The amplitude of the needle’s movement will exceed the mechanism to record it. Then again, we probably won’t need to be told there’s an earthquake on the San Andreas fault. We’ll know,” joked Ted Driscoll, mayor of Portola Valley.
Driscoll recruited an electrical engineer to help a group of locals build the seismograph, based on an original design and for less than $2,000.
The flat, square machine will take digital readings of earth movement based on the amplitude signals it receives through the tabletop equipment and a thick pipe that extends 14 feet into the ground through the foundation of the new town library. Library patrons will be able to watch the pendulum arms quiver on an axis designed to pick up tremors in Missouri or Melbourne, and library visitors will be able to watch the resulting blips cross a digital screen in real time.
The seismograph will be unveiled at a ribbon-cutting ceremony along with the rest of the library, a new Town Hall and a new community center on Sunday afternoon, marking the end of a $20 million construction project begun just over a year ago.
Portola Valley officials raised the money to move all three buildings 150 feet back from the San Andreas fault line when they realized they were in major danger.
“Where it was lying before, the building would be shredded in half and it was going to fall down. We were convinced we were running a major risk,” explained Driscoll.
Today, sports fields cover the most volatile part of the fault and the new structures are built to withstand almost anything, a big change from the 1948 building codes in effect then they went in.
The new Town Hall is intended not just to survive a major earthquake, but will double as a local emergency-operations center after the worst of the quake is over.
The seismograph was a brainchild of Sheldon Breiner, a well- known local venture capitalist who has founded several companies with his background in geology and computer science.
Tor Lund, an electrical engineer and fellow Portola Valley resident, created a model based on Breiner’s designs and spent the past six months piecing it together with custom-made steel plates and stainless steel screws. He and several friends added lots of extra improvised touches, such as guitar string tighteners to help connect the plates at key places.
The machine was having problems gaining its balance on Thursday, the day Lund and another project engineer attempted to install it on site. Though technically built by amateurs — well-educated amateurs — Lund is confident the seismograph will be able to measure earthquakes on the same order as the fancier machines kept by the U.S. Geological Survey in Menlo Park.
“But right now we’re just trying to get the arms going in the right direction,” he said.
The seismograph won’t be the only high-tech educational tool in the new town library, a “green” building designed to reach the highest possible rating under U.S. Green Building Council LEED standards.
Visitors will also be able to track how much solar power the photovoltaic panels on the roof are feeding into the building at each moment, as well as how much water is being used and conserved.
Staff writer Julia Scott can be reached at 650-348-4340 or at email@example.com.
Originally published by Julia Scott, San Mateo County Times.
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