Be Geo-Hazard Smart: Aware & Prepared

If you attended the "Be Geo-Hazard Smart: Aware & Prepared," on Sunday, Feb 25th, you likely came away with a much better understanding of the local earthquake hazards in the Beaverton and Portland area, and what to do to protect your family and home. We had two speakers: Aaron Fox, a noted geologist and top-notch emergency manager, and Rick Eilers, President of Prepared Northwest, Inc. This article highlights some of the key learnings and provides links for you to continue learning about geo-hazards and residential seismic retrofits.

Aaron Fox, our first speaker, a geologist and emergency manager, generously shares his expertise to a full house

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Local Geo Hazards

In his hour-long presentation, Aaron Fox described various types of earthquakes and fault lines in the Pacific Northwest. His agenda included these topics:

• Geology of the Tualatin Valley
• Probable Tualatin Valley Scenarios
• Earthquake Effects
• What about My Neighborhood
• Be Prepared

Tualatin Valley Scenarios
Based on data from the 2018 DOGAMI study, Aaron described the impact of two probable earthquake scenarios: the Cascadia Subduction Zone Quake verses the Portland Hills Fault.  
     The Portland Hills fault zone is the largest shallow fault that cuts beneath Portland, Oregon. It stretches from Oregon City to Scappoose.  While the amount of energy released by a Portland Hills quake (Mw 6.8) will be less than a Cascadia Subduction Zone quake (Mw 9.0), geologists estimate that a quake along the Portland Hills fault zone will result in more casualties and damages to buildings in Washington County due to the proximity to the epicenter. Estimates include casualties in the range of 3,200 - 15,800 people and a 19% to 29% building loss ration for Washington County. 
    Aaron said that the Cascadia Subduction Zone quake has a higher probability of happening than a quake from the Portland Hills fault. The ground motion will be longer in duration, shaking for minutes rather than seconds. Estimates include casualties in the range of 1,000 to 8,000 people and a 8% to 14% building loss ratio for Washington County. 

Click image to open the Dogami Fact Sheet

Click to find the free downloadable book from Oregon State University

Earthquake Effects
Aaron described what happens during and after an earthquake, showing examples of landslides,  fires, flooding, and liquefaction. For example, this dramatic video of soil liquefaction in Japan shows what might happen during an earthquake in the Pacific Northwest. Many areas in Beaverton and Portland metro areas are at moderate to high risk for liquefaction. ​

What About My Neighborhood? Free Geo-Hazard Tools
     How do you know what the specific risks are for your home or business? Aaron mentioned several free online tools you can use to research where you spend the most time. For example, Oregon HazVu, a Statewide Geo-Hazards Viewer, is an interactive tool provided by the Oregon Department of Geology and Mineral Industries (DOGAMI). You enter an address and choose the types of hazards you want to visualize. In the image below, for instance, the pink areas show that much of Beaverton and Portland are at moderate  to very high risk for liquefaction. The blue lines on the map show local fault lines. ​

Click the image to open Oregon HazVu, a Statewide Geo-Hazards Viewer. Enter an address and specify the hazards you want to visualize. This example shows that Beaverton and Portland are at high risk for liquefaction.

Science and Engineering Links
Aaron provided additional links with free tools for mapping your risks. His list included:  

• Statewide Geo-Hazards Viewer (HazVu) 
• Statewide Landslide Information Database for Oregon (SLIDO)
• SeismiCat online seismic risk assessment tool
• Oregon Hazard Exploer for Lifelines Program (O-HELP) from Oregon State University (OSU)
• FEMA 547 Seismic Retrofitting, Whole Building Design Guide

Preparedness Links
 Aaron emphasized the importance of getting prepared for an earthquake and other disasters. He provided the following links to help you take the next steps:

• Get an early warning with ShakeAlert in Oregon
•  Get the facts by reading the DOGAMI Fact Sheet
• Be 2-Weeks Ready from Oregon Emergency Management (OEM)
• Build a two-bucket emergency toilet, described by RDPO Emergency Toilet Program
• Learn ​"How to Prepare Your Kids for the Cascadia Quake" by PDX Parent
• Read the Free Digital book: "Living with Earthquakes in the NW: A Survivor's Guide" by Robert S. Yeats​

Retrofitting Your Home

Our second speaker, Rick Eilers, President of Prepared Northwest, Inc., described and answered questions about residential seismic retrofits. He explained that if your house was built before 1986, it may be more vulnerable to earthquake damage. You can strengthen your home by making sure the wood portion of the house is connected to the concrete foundation with anchor bolts as required by current state building codes. These connections help move the forces generated from an earthquake through the house walls to the foundation, thus reducing the chance that the house will fall off the foundation during an earthquake.

Our second speaker, Rick Eilers, described considerations for home retrofits

Oregon Code Updates in 1986
     In 1986, Oregon adopted a statewide building code for 1- and 2- family homes. This code required the wood structure of the house be attached to the foundation using ½" diameter bolts every 6 feet. If your house was built in 1986 or later, you should already have these bolts. If your house was built before 1986, you should consider a seismic upgrade to protect your house and your family's safety.​

Benefits and limitations of Seismic Upgrades
     According to Rick, the biggest benefit of a seismic upgrade is that it reduces the chance that your home will fall off its foundation. If your house falls off its foundation, it will be condemned and you won't be able to live in it. In an extended disaster from an earthquake, being able to live safely in your home as a shelter can make a big difference in your survival and could also significantly shorten the time it takes for your family to recover. 
     Rick also described the limitations: a seismic upgrade won't protect your home from all damage during an earthquake. For example,  seismic upgrades won't prevent damage or harm caused by items falling off walls and out of cabinets or furniture and appliances moving during an earthquake. The risk and damage from moving objects within a home can be substantial, so in addition to a seismic upgrade, he suggested that you take some simple steps to earthquake-proof your home, such as strapping down your hot water heater, installing cabinet latching devices, and securing photos and pictures to studs using closed-loop picture hangers. ​

Acknowledgements

Thank you to both of our knowledgeable speakers and Neighbors Ready! volunteers that made this event possible! Thank you to our guests and neighbors who showed up to listen and learn. 

Author

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