By Emily Keller-O'Donnell
August 13, 2023
As the start of the upcoming school year approaches, many students in Washington State will be attending K-12 public schools that may be unsafe in a major earthquake. However, following years of modernization efforts and millions of dollars spent on renovations and reconstruction to enable school buildings to better withstand a major tremor, information about the seismic readiness of school buildings remains difficult to obtain. Although some school districts provide information about seismic upgrades completed for individual school buildings, there is no publicly available state database providing information for all schools.
Construction projects to upgrade or replace school buildings are often announced on school district websites, but seismic information about older school buildings that are not in line for upgrades is harder to find. The $3.4 million School Seismic Safety Project provided risk assessment reports for a portion of Washington school districts following geological and engineering assessments of 274 schools from 2017-2021, but more than 1,700 additional public schools were not included.
The Washington Office of Superintendent of Public Instruction (OSPI) maintains a database that includes seismic risk ratings from low to very high for some school buildings, but the data is complicated to interpret and not publicly available (the data was obtained for this article via a public records request). Buildings are assessed based on factors such as proximity to faults, building age, construction type, soil density and whether there has been any subsequent retrofitting. As data collection is ongoing, campus risk assessments are provided for only about one third of the 1,992 schools listed in the data, including 278 schools that are assessed as having high or very high seismic risks. Some information has not been updated to reflect building closures or other changes.
The Washington State Department of Natural Resources lists 20 potential seismic events that could strike the state. The last major earthquake to hit the region was the 6.8 magnitude Nisqually quake in 2001, which occurred at night, when school children were not in class.
The Cascadia Subduction Zone, located offshore in the Pacific Ocean, is estimated to produce megathrust earthquakes of 9.0 magnitude or higher about once every 400-600 years. The last known megathrust earthquake along this fault occurred in the year 1700. Some scientists have estimated that there is a 37 percent chance of a megathrust earthquake of 7.1 magnitude or higher along this fault line in the next 50 years.
The Seattle Fault can produce earthquakes of up to 7.5 magnitude in the center of the city anywhere from 200-15,000 years apart. The last known quake along this fault line, which runs horizontally across the city, was 1,100 years ago. In the earthquake scenario pictured below, Seattle and surrounding areas in western King County are predicted to experience ground shaking of 7.0-9.0 Modified Mercalli Intensity (MMI), a localized measurement that is distinct from earthquake magnitudes along a fault line. Many schools would face a double threat from an earthquake and possible resulting tsunami from Puget Sound.
About one in five Washington State public schools are located in King County, which has 523 schools. This area includes the Seattle School District, the largest school district in the state, with an estimated 55,000 students.
Seismic risks at Washington schools vary according to proximity to fault lines and geologic conditions such as soil conditions, in addition to construction type and other building factors. Newer buildings typically have a much lower seismic risk level than older buildings, particularly those that were constructed before 1975. Retrofitting work can reduce the risk level for older buildings.
Construction type and year built have a significant impact on a building's seismic risk level. In 2018, the state created a URM Dashboard, providing an inventory of unreinforced masonry (URM) buildings, often built before the 1940s, which are considered one of the most dangerous types of buildings in an earthquake. At a cost of $200,000, the study identified 1,176 confirmed URM buildings across the state, including 34 public schools and 42 private schools. But many school names are omitted from the dashboard, leaving users to search listed addresses to identify the included schools. In December 2021, the Seattle City Council passed a resolution to establish a framework for a mandatory retrofit ordinance for all of the URMs in the city. There are no retrofit ordinances for the state.
In the Office of Superintendent of Public Instruction's database, one in twelve schools shows at least one URM construction type listed: URM bearing walls, or concrete or steel frames with URM infill walls. URM buildings are often identifiable via an alternating brick pattern with a narrow brick width every 5-6 rows. But the presence of URMs does not tell the whole story, as a wide range of factors affect a building's current seismic risk level.
A comparison of two schools below illustrates the complexity of trying to understand risk levels at individual schools based on currently available data.
The Github page for this project is available here.
Garfield High School
Concord International Elementary School
These two Seattle schools are both listed as confirmed unreinforced masonry buildings in the Washington URM Dashboard.
Concord was built in 1913 and retrofitted in 2000.
Garfield was built in 1923 and retrofitted in 2006.
(Retrofit data provided by the City of Seattle).
Only Concord shows a characteristic URM brick pattern from photos retrieved online.
But Concord has a "low" overall earthquake risk, while Garfield has a "very high" risk, according to OSPI data. The construction type listed for the highest risk building areas in both schools is concrete shear walls, not URM construction.
Concord photo: July 2008, by Joe Mabel, Wikimedia Commons. Garfield photo: July 2017 @ 2023 Google.