What to do when the next megaquake happens

Most of us have been taught that in an earthquake, we should drop, cover, and hold on. Chris Goldfinger, Professor of Marine Geology and Oregon State University (OSU), challenges this advice in a PBS program that aired on Oct 18, 2022. He suggests your response could vary depending on how much warning you have before the violent shaking starts and what type of building you are in when the quake hits. Continue reading to learn more and watch the 12-minute video. 

Chris Goldfinger offers new perspectives on what to do when a megaquake happens

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Some quakes give early warning
Shallow crustal earthquakes shake violently almost immediately. During these quakes, drop, cover, and hold on is likely your best choice of action to avoid getting injured from projectiles coming off walls and shelves, broken glass from windows, or furniture and appliances tipping over. Leaving a building during violent shaking can be risky. 
Some quakes may give you a bit of warning before the shaking gets destructive. The most violent subduction zone quakes--where one tectonic plate is forced under another--initially produce light pressure waves (P-waves) that travel across the earth faster than the more destructive shaking waves. The further you are from the fault line, the more time you have between feeling the P-waves and the violent shaking waves. In other words, these light P-waves may give you a minute of warning. Depending on the building type and your location near an exit, it may make sense to evacuate immediately if you feel light P-wave shaking. 

Older buildings pose greater risk 
"In Oregon, we're concerned about any building that was built before the mid-1990s," said Erica Fischer, Professor of Structural Engineering at OSU. As Fischer explains, though we started to understand how to build structures in high seismic regions in the 1970s and 1980s, we didn't discover the Cascadia subduction zone until 1988. Excluding wood frame houses, 70 percent of the built infrastructure in West Coast US cities is not up to modern seismic standards, meaning that they may collapse. 

Single family homes are generally safer than larger structures. The greatest risks in single family homes during an earthquake include chimneys, bookshelves, overhead light fixtures that could fall, and porches. Because falling objects are the major concern in homes, ducking and covering might be the safest strategy during an earthquake if you are in a single family home. That said, many homes aren't bolted to their foundation. You may want to invest in seismic retrofitting if you live in a home that was built before the mid-1990s. 
Though Cedar Hills Ready! does not officially recommend any particular businesses, I'll mention a couple of local seismic retrofitting companies as they have kindly participated with our Quake Up! events to provide information and to help you better understand your risks and methods for remediation. These companies include: NW Seismic (www.NWSeismic.com) and EarthquakeTech (www.EarthquakeTech.com). 
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​Non-ductile concrete buildings are rigid and may collapse during the violent shaking of an earthquake. Ductile means that something is pliable, and can be deformed without losing its strength. Concrete is not ductile by nature; it's brittle and can fail in a sudden collapse during an earthquake.
​To meet code, newer concrete buildings are reinforced with rebar and other materials to withstand the side-by-side shaking of a large quake. For example, the Beaverton Public Safety Center, built in 2021, was designed to be the community resource epicenter during an emergency. It is earthquake resistant and built to higher-than-standard seismic resiliency, allowing it to remain fully operational and provide emergency services to the community during a major earthquake or disaster.​

If your house was built before the mid-1990s, you may want to evaluate your home for a seismic upgrade.

Partial collapse of Kaiser-Permanente Building, 1994 Northridge earthquake. (National Information Service for Earthquake Engineering)

Built in 2021, Beaverton's Public Safety Building is earthquake resistant and built to a higher-than-standard seismic resiliency

Unreinforced masonry (URM) buildings are the most dangerous buildings in an earthquake. When side-to-side shaking happens, nothing holds the bricks together so the walls fall apart and the building can collapse.
How can you tell if you are working or living in a URM? The first obvious sign is the presence of "red brick" on the walls. Another common characteristic of a URM brick building is the presence of a header course (see figure). 
If you are living or working in this type of building, you may want to better understand your risks and formulate a plan for how you can protect yourself during an earthquake. Two resources to help include:

• Read about how you can identify URMs on Portland.gov URM webpage. 
• Check out this map that locates Portland's URM buildings. ​

Brick URM showing header and stretcher courses (source FEMA P-774); Click image to go to Portland.gov URM webpage.

Click to open a map with locations for unreinforced masonry buildings in Portland that are likely to collapse in a large quake.

According to Chris Goldfinger, if you are near an exit and start feeling the gentle P-waves of a quake, and you are in a non-ductile concrete building (built before mid-90s) or in a URM, you may have about a minute to evacuate the building before the destructive shaking occurs. If you don't leave the building, duck, cover, and hold on. Check out this video for more details. 

Author

Karen Ronning-Hall, Disaster Preparedness Evangelist, living in beautiful Portland, Oregon, with hubby Bill, daughter Geneva, Bean dog, Thumper kitty, and Terry the turtle.  ​