Posted by Joe Nolan on October 9, 2018
“I fell down into a burning ring of fire, I went down, down, down and the flames went higher.” Johnny Cash was singing about love not the real Ring of Fire’s death and destruction. The Ring of Fire is an area around the Pacific Ocean where most of the world’s earthquakes and volcanic eruptions occur, due to movements of lithospheric plates.
Photo source: USGS https://pubs.usgs.gov/gip/dynamic/fire.html
As shown in the above image, the Ring of Fire includes the entire West Coast of the United States. According to the United States Geological Survey (USGS) data, the 1980 eruption of Mount St. Helens, released 24 megatons of energy, equivalent to 1600 atomic bombs. The blast killed about 57 people, destroyed 200 houses, and was responsible for $3 billion in damage in 2018 dollars.
Many Northwest locals have at least one quake story to share. At magnitude (or mag) 6.8, the 2001 Nisqually earthquake was one of the biggest in recent history. Though nobody died as a direct result of the earthquake, many unreinforced masonry buildings in the greater Seattle area received damage, along with the air-traffic control tower at Sea-Tac airport and the Alaskan Way Viaduct.
Five years earlier, as Charles Nagy was cruising to a 5-2 Cleveland win over the Mariners, the 5.9 mag Duvall earthquake hit, postponing the game while the Kingdome was checked for structural damages.
Though these quake memories are fading, they shouldn’t. The Pacific Northwest Seismic Network, which tracks local seismic activity, shows earthquakes happen about four times a day. In fact, as I write, there’s been a mag 1.0 quake in Mountlake Terrace, a 1.6 mag quake near Graham, and a 4.6 mag quake 191 km west of Port Hardy, Canada — all within the past 24 hours. (Check out the “Most Recent Earthquakes” bar on their website to see where the latest Northwest quakes hit.)
Which areas are most vulnerable to earthquakes and volcanoes?
There are two types of earthquakes of concern in Washington. Subduction Zone or Megathrust Quakes are the biggest danger. These quakes are caused by friction between the North American plate and the San Juan de Fuca plate, which extends from northern California to British Columbia.
A megathrust quake mag 9.0 or more could cause violent and prolonged shaking across Western Washington, including Seattle. However, Seattle risks more danger from an earthquake in the Seattle Fault Zone, which extends east-west through the middle of the city. The last Seattle Fault quake happened over 1,000 years ago, and experts estimate the next one could be as large as mag 7.5.
Washington State is home to five active volcanoes: Mt. Baker, Glacier Peak, Mt. Rainier, Mt. Adams and Mt. St. Helens, with Mt. Rainier posing the biggest threat. While these volcanoes are too far from densely populated areas to pose much of a direct threat from an eruption, ash falls and re-direction of rivers have the potential to cause major disruption and damage statewide.
What kind of risks are we talking about?
Major seismic activity would have a devastating effect on our region, but some types of structures and occupants are at greater risk than others.
- Structures built on unsteady ground: In strong earthquakes, water-saturated soils are shaken so violently that they lose strength, causing structures built on top of these soils to shift or collapse. Within Seattle city limits, about 15% of the total ground area is prone to liquefaction. Understanding soil type and it’s propensity for liquefaction is critical.
In the upcoming weeks, we will share more about the importance of liquefaction in underwriting and rating properties.
- Vulnerable construction types: Seattle has about 819 unreinforced masonry buildings, which don’t fare well in earthquakes. Worse, many of these older brick structures sit on liquefaction-prone soil. Other buildings and homes constructed before 1945 (when building codes were less strict), typically those with brick walls and wood-frame floors and roofs, are more vulnerable as well.
Related: Construction Class Series
- Homes without earthquake insurance: While Washington has the second-highest earthquake risk in the nation, only 11.3% of homeowners have earthquake insurance even though coverage is available, but not required. Western Washington coverage rates are a bit better: Thurston County’s is 18.1% and King County’s 15.7%. The greater the number of uninsured buildings and structures, the slower the region will be able to bounce back from an earthquake.
Related: Earthquakes and Insurance
- Buildings and occupancies prone to secondary impacts: Landslides, tsunamis, ash falls, hazardous materials release, and fires all could become disasters in their own right. Often, more people die from earthquake related fires than building collapse.
- Businesses and residences vulnerable to infrastructure damage:The relatively-small Nisqually earthquake racked up a bill of over $36 million for damage to city buildings, infrastructure, response costs, and repairs to arterial road structures. Given the region’s growth and the resulting new construction, our infrastructure would likely take a much greater financial hit in the event of natural disaster. The Modified Mercalli Intensity scale (MMI) can assist you in understanding the potential damage for your risks. MMI scores are available via PropertyEDGE.
Living in the Ring of Fire poses unavoidable risk. You can address the exposure to your book and customers by understanding these perils. Our PropertyEDGE tool can help you determine your specific risks from earthquakes and other hazards. For more information, contact us anytime.