20 years after Northridge earthquake, technology advances improve safety

Friday marks the 20th anniversary of the deadly Northridge earthquake in Southern California that shook Los Angeles residents from their sleep, caused freeways to crumble and flattened buildings on its way to claiming at least 57 lives. It was the last deadly quake to strike a U.S. metropolitan region.

Twenty years later, area residents have turned to technological advances in the hopes of lessening the damage of the next massive quake. 

The U.S. Geological Society is developing an early warning system that sends alerts to cell phones and computers with up to a minute of warning before the quake hits. 

"If you can detect that earthquake very quickly, you can warn people before the strongest shaking arrives at their location," says USGS geophysicist Doug Givens.

The system relies on 400 solar-powered sensors set up along California's fault lines. But scientists say they still need 400 more to improve the accuracy. 

The system links with public transportation systems to increase safety. It is already set up with the San Francisco train system, and the trains will automatically slow down during a quake.

Construction crews are also busy bolting home foundations to reinforcements, which they say could be the difference between houses standing and houses collapsing.

The shaking during the 1994 magnitude-6.7 quake lasted 10 seconds and was felt from San Diego to Las Vegas. More than 9,000 people were injured. Counting heart attacks, the death toll stood at 72, according to a 1995 study.

As for damage, 82,000 residential and commercial buildings were damaged or destroyed, including many apartment complexes with ground-floor parking. Some 200 steel-frame buildings suffered significant cracking. Seven freeway bridges collapsed and 212 others were damaged. The quake sparked fires, and affected communication, water and power systems, causing $20 billion to $25 billion in damages.

Experts say there is a 99 percent chance that next massive quake will hit the state sometime over the next 30 years.