New Sensor Promises Assessment of Which Buildings Are Safe After Quake

More than a quarter century ago, the Loma Prieta earthquake tore across the Bay Area landscape. The quake ruptured the Bay Bridge and ripped through buildings, killing 63 people and injuring over 3,000. More than 11,000 homes were destroyed, with over 12,000 people left homeless.

Afterward, city managers scrambled to inspect all the damaged buildings.

As bad as that was, it's far less damage than what could happen to the Bay Area from an earthquake on the Hayward Fault, says David McCallen, a senior scientist with Lawrence Berkeley National Laboratory. The U.S. Geological Survey says the fault, which runs for 70 miles through the middle of the urban East Bay, is "a tectonic time bomb." Scientists have calculated about a 30 percent chance that the Hayward will “break big,” causing a quake of magnitude 6.7 or higher, within 30 years.

“There will be literally hundreds to thousands of buildings that will be impacted by that earthquake,” McCallen said, "and the ability for us to recover from that is going to be a tremendous effort."

McCallen says he has technology that can provide city engineers with a rapid response tool to speed up the evaluation of buildings and help them determine which ones are safe to occupy after a major shaking.

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He’s developed an optical sensor (remember laser pointers?) that can be installed in each floor of a skyscraper, hospital or any other building. The sensors can capture information about their structural integriy and can immediately alert managers about any serious damage.

The sensors send information over the internet or cell networks to emergency response centers, and if all communications are down, they can communicate via satellite phones.  

That means that emergency responders can know in real time which buildings are unsafe. “This technology will give engineers a tremendous leg up in being able to understand whether that building has been damaged,” McCallen said. “They will know immediately, floor-by-floor, the likelihood of that building being damaged.”

Historically, scientists have used an accelerometer to measure how buildings respond to earthquakes. It's a small mechanical vibrating device that measures accelerations in the back-and-forth movement of a building.

But McCallen said the accelerometers cannot measure the vertical displacement of floors inside a building. Plus, they are costly and not widely used.

The sensors allow researchers to measure how two floors move relative to each other, and to detect any stress in the beams and columns of the building.

“This is a whole new paradigm that allows us to measure that drift between floors directly,” McCallen said.

 

While McCallen successfully deployed the sensors using a scale model and a shake table at a laboratory at the University of Nevada, the technology must be tested in an actual earthquake on an actual building.

Over the next few months, he will install sensors at Lawrence Berkeley National Laboratory's Wang Hall, a building close to the Hayward Fault that houses the research institution's supercomputer, called Cori.

While it’s relatively easy to install the sensors in new buildings, finding surfaces in existing buildings can be challenging, as the sensors require a direct line of sight from floor to floor, making a retrofit potentially difficult.

“Once we validate the field performance of these things, then I think we really want to find people that have critical facilities that want to have this technology available,” McCallen said.

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