6.9-magnitude quake rocked California 35 years ago. Now experts ask, ‘did you feel it?’

More than three decades ago, a powerful jolt shook the Northern California area for 20 seconds and “ ended decades of tranquility in the San Francisco Bay region.”

The 6.9 Loma Prieta earthquake, which “severely shook the San Francisco and Monterey Bay regions” just after 5 p.m. on Oct. 17, 1989, was the strongest to hit the area since the 7.9 Great San Francisco earthquake of 1906, according to the United States Geological Survey.

The quake, also known as the World Series Earthquake, caused an estimated $6 billion in property damage, left 63 people dead and injured more than 3,700, according to USGS. Parts of three bridges, including the San Francisco–Oakland Bay Bridge, collapsed.

Loretta Eskenazi was trapped on the Bay Bridge that day, she recounted in an essay published by Mission Local.

“I began to run. I breathed hot auto exhaust as I weaved in and out of the abandoned cars as others now came out of their stupor and decided to move it,” Eskenazi wrote. “Yes, this was, indeed, reality. We were awake. This was really happening.”

And now, the U.S. Geological Survey is asking people who also remember that day 35 years ago to fill out the agency’s “Did you feel it?” report.

“While 1989 was (a) long time ago, we still see the value of collecting the population’s input from their experience at the time,” Earthquake Science Center Director Christine Goulet said in an Oct. 8 news release. “This will support better knowledge and preparedness plans.”

Created a decade after the quake, the “Did you feel it?” system helps inform experts about earthquakes’ effects, as well as helps their forecasting of future events, emergency responses and building codes, the agency said. People can retroactively file a report in English, Spanish or Chinese.

As of Oct. 10, the “ Did You Feel It? ” questionnaire had just over 12,500 responses for the Loma Prieta earthquake.

With such a wide region impacted by the quake, USGS said additional reports will help create a map of the shaking with “finer detail,” including in every neighborhood.

“This type of data collected from the public helps us better understand the impact of past and future earthquakes,” Goulet said.

To fill out a report, visit USGS .

What to know about earthquakes

Magnitude measures the energy released at the source of the earthquake, the U.S. Geological Survey says. It replaces the old Richter scale.

Quakes between 2.5 and 5.4 magnitude are often felt but rarely cause much damage, according to Michigan Tech. Quakes below 2.5 magnitude are seldom felt by most people.

Earthquakes’ sudden , rapid shaking can cause fires, tsunamis, landslides or avalanches. They can happen anywhere, but they’re most common in Alaska, California, Hawaii, Oregon, Puerto Rico and Washington, according to the Department of Homeland Security.

If an earthquake strikes, it’s best to protect yourself right away. Here are tips from experts:

• If you’re in a car : Pull over and stop. Set your parking brake.

• If you’re in bed: Turn face-down and cover your head with a pillow.

• If you’re outdoors: Stay away from buildings. Don’t go inside.

• If you’re inside: Stay and don’t run outdoors. Stay away from doorways.

The best way to protect yourself during an earthquake is to drop, cover and hold on, officials say.

“Wherever you are, drop down to your hands and knees and hold onto something sturdy,” officials say. “If you’re using a wheelchair or walker with a seat, make sure your wheels are locked and remain seated until the shaking stops.”

Be sure to cover your head and neck with your arms, and crawl under a sturdy table if possible. If no shelter is available, crawl to an interior wall away from windows.

Once under a table, officials say you should hold on with one hand and be ready to move with it.

“There can be serious hazards after an earthquake, such as damage to the building, leaking gas and water lines, or downed power lines,” officials say. “Expect aftershocks to follow the main shock of an earthquake. Be ready to Drop, Cover, and Hold On if you feel an aftershock.”

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