Editor's note: The above video from earlier this year details the progress made since the 2001 Nisqually quake.
It will cost an estimated $1.28 billion to seismically retrofit hundreds of earthquake-vulnerable buildings in Seattle, according to the latest report from the city.
The report whittles down the number of unreinforced masonry buildings from the previous estimate of 1,145 to 944. Those buildings are home to approximately 22,050 people.
Typically built of brick or concrete block, the buildings have little in the way of metal reinforcement beyond nails holding the floor boards down. Walls can bulge outward, floors can become disconnected from walls and fall, and parapets can break off. That's concerning for an area where a high-magnitude earthquake is expected to occur sometime in the coming decades.
Though Seattle wouldn't get the worst of the shaking during a magnitude 9 quake along the Cascadia Subduction Zone off Washington's coast, it would still be significant and last for up to five minutes or more. Additionally, one of the biggest faults runs just south of downtown; researchers believe it could produce a magnitude 7 quake.
It would cost an estimated $642,000 to retrofit a three-story, 22,000-square-foot mixed-use building that includes commercial space on the ground floor and 20 residential units above, according to the report. That hypothetical project represents the average building in the city that needs reinforcement.
In 2012, the city established the Unreinforced Masonry Policy Committee tasked with developing recommendations for the Department of Construction and Inspections on a seismic retrofit program. Recommendations were given to the department in 2017, but have yet to be enacted, according to the report. In 2018, the city began work to identify financing and funding options and working on strategies to help property owners who would have difficulty retrofitting buildings.
The report notes that in order for the buildings in the city to be retrofitted, a policy mandating as much will need to be established. Because financial costs will fall largely on private owners that will not receive "significant economic benefits" from retrofits, a successful policy would ease the financial burden, facilitate support and compliance, "and lead to a safer and more resilient Seattle," the report states.