What the Seattle Fault Earthquake Wrought

Ten years ago today at 2pm a powerful M 7.2 earthquake struck along the Seattle fault, causing extensive damage to livelihoods and infrastructure. [4] The estimated loss from the earthquake amounted to roughly $38 billion. [10]  The unfortunate timing of the quake when educational, commercial, and industrial facilities were occupied resulted in a greater number of injuries and causalities than would otherwise would have been expected. [5]

This story is a work of fiction, including all names and quotes, written by WWU DRR students for public education purposes. Site design by Dr. Scott Miles.

The earthquake took the lives of 1,049 people and injured over 17,000 others. [6] Individuals without access to power numbered over 265,000 immediately after the shaking stopped, while individuals without potable water numbered to over 399,000. [7]

The quake severely damaged homes, highways, utilities, and roads. Over 9,000 buildings were completely destroyed and 30,000 other buildings were moderately to extensively damaged. [8] The earthquake generated 13.9 million tons of debris. [9] Violent lateral movement also resulted in secondary impacts, such as fire, liquefaction, landslides, and hazardous material release.

Cost of damage in the Seattle earthquake was similar to the 1994 Northridge earthquake, which balanced out to about $40 billion. However, loss of life was significantly greater in Seattle’s case. While 57 lost their lives in Northridge, over 1000 died in the Seattle earthquake. When the Seattle region last experienced an earthquake in 2001 only one indirect death occurred (from heart attack) and damage was estimated at $2 billion. The 2016 earthquake hit the high bar in both cost and deaths relative to other earthquakes in recent history.

The Seattle Fault earthquake resulted in extensive liquefaction throughout King County. Soil liquefaction describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness as a response to shaking, causing soils to temporarily behave like a liquid. [11] [12] The seismically-induced loss of soil strength can result in ground failure.

Liquefaction induced by the Seattle Fault quake caused extensive damage in areas with a history of fill. Many building and infrastructure foundations in King County were constructed on unconsolidated landfill, detritus, and debris always known to susceptible to liquefaction.

An estimated 35 thousand residents were exposed to the impacts of liquefaction. Related damage was estimated to total around $22 billion. [14]   

Damaged structures types built upon liquefiable soils typically included unreinforced masonry (URM), precast concrete and concrete frame buildings. [16]  Due to lateral movement, many historical buildings, industrial plants, commercial buildings, homes, and infrastructure which predated modern seismic engineering codes sunk into the ground. With the movement of upwelling sediments, structures also leaned and toppled off their foundations. Water ejected from sand boils caused flooding throughout countless neighborhoods around King County.

About 15% (8,029 Acres) of Seattle’s total land experienced liquefaction. [15]  This included the Duwamish river basin, the downtown waterfront, Union Bay, Stadium District, International District, Pioneer Square, and Interbay.

The Interbay neighborhood of Seattle experienced some of the highest amount of liquefaction during the Seattle Fault quake. This was due to the area’s natural history in conjunction with poorly engineered human efforts to transform the soils into developable land.

A century ago, Interbay was home to a wetland characterized by high water content. As the city grew during the early 1900’s, settlers filled the wetlands with debris from massive regarding projects being done around the city. After the soils were “stabilized”, the city laid down a rail line, which attracted many industrial and unsightly warehouses, factories, and back alleys.

Modern day development upon these soils includes major retail stores, such as Whole Foods, PetCo, Staples, as well as hundreds of  small businesses and apaChristchurch_1rtment complexes. Many of these buildings were  rendered unusable as they were destroyed by sinking, breaking, and settlement  of soils.

 The Interbay neighborhood is home to a high concentration of homeless people  who live along the industrial railway that divides Queen Anne and Magnolia.  These populations were displaced due to the extensive damage caused by        liquefaction.

 Soon after the earthquake, Dirk Limetree describes his experience dealing with  the impacts of the hazards.

“I was standing on the corner of Dravus and 15th Avenue when the earthquake struck. I didn’t think the buildings and roads in this area would hold up so poorly. I no longer have my home to come back to. Interbay resembles nothing like it did before the earthquake. All of the buildings are toppled over on their foundations, the train tracks have been thrown off course. The local food distribution center has shut down. I don’t know where to go from here. It’s not just me, either. There are thousands of us with few choices of where to go.”

Several miles away from Interbay, several thousand pipeline failures occurred throughout the Duwamish Valley, the Sammamish Valley, and as far as Renton and Kent. Wastewater treatment pipes and structures were uprooted and destroyed, cutting off access to service to tens of thousands of residents. These floated sewer lines burst, pumps stopped working, and untreated sewage spilled into Lake Washington, Lake Union, the Puget Sound, and Lake Sammamish, as well as other water bodies.

The earthquake induced the ignition of approximately 300 fires around the county within the first ten minutes after shaking stopped. The presence of aftershocks, the shifting of damaged structures, spilled chemicals, the leaking of natural gas, and residents’ turning utilities off and on ignited fires across Edmonds, Sammamish, Downtown Seattle, Ballard, Queen Anne, and Georgetown. Breaks in water mains impeded access to water to fight fires; about 5,000 leaks and bursts were identified. The fire damage was valued at nearly half a billion dollars and it displaced about 6,000 people.

Widespread landslides were another secondary hazard produced by the Seattle Fault quake. Because of uncharacteristically high amounts of rainfall leading up to the quake, soils were already saturated and more prone to failure. It is estimated that 30,000 landslides occurred throughout the county. The tremors induced catastrophic shallow ground failure off of steep hills along the bluffs of Queen Anne, Magnolia, Capitol Hill, Beacon Hill, West Seattle, North Beach, Rainier Valley, and the Central District. Landslides in other areas of King County, east of Seattle, were less abundant away from the lake and coastal bluffs. Most of the landslides in these areas impacted roadways, homes, and businesses.

Jessica Goodrich, a Seattle native, owns a home on one of Seattle’s Magnolia bluff. Her home was one of the few structures remaining along the hillside after the Seattle Fault earthquake.

She described that, “I knew this entire area is at risk for falling into the ocean,” she said. “The houses were built before the city had steep slope regulations. In spite of this, my home has been extensively retrofitted with piles that anchors my home to the hillside. The city recently implemented a new drainage system to keep the slopes from becoming saturated.“

One third of the landslides triggered were located in areas that were not predicted to fail in landslide hazard maps available before the earthquake.

Karen Shorefire, a graduate student in geology at the University of Washington stated, “We found that many of the landslides triggered in the earthquake were not in areas defined as prone to landslides prior to the quake. People frequently claim that knowledge of slope instability is very mature, but this illustrates that there must be a concerted effort conduct further research into seismically induced landslide hazard in King County. Having the ability to accurately identify landslide prone areas could save the lives of hundreds, maybe thousands of people in the future.”

The Seattle Fault earthquake caused extensive, short term and long term damage to King County, including the Seattle area. Violent shaking not only destroyed thousands of structures and roads, but also initiated several other secondary hazards, such as landslides, fires, liquefaction, and tsunamis. King County’s recovery will be an ongoing, daily process for years to come. The earthquake inspired a sense of urgency to better understand future earthquake impacts. Efforts to study the nature of earthquakes, vulnerable human populations, and antiquated and outdated structures have skyrocketed.

1. Anderson, M. L.; Dragovich, J. D.; Blakely, R. J.; Wells, R.; Brocher, T. M. (2008), Where Does the Seattle Fault End? Structural Links and Kinematic Implications [Abstract #T23B-2022] (abstract #T23B-2022), American Geophysical Union Fall Meeting 2008

2. Blakely, R. J.; Wells, R. E.; Weaver, C. S.; Johnson, S. Y. (February 2002), “Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data”,

3. Karlin, R. E.; Holmes, M.; Abella, S. E. B.; Sylvester, R. (February 2004), “Holocene landslides and a 3500-year record of Pacific Northwest earthquakes from sediments in Lake Washington”, Geological Society of America Bulletin 116 (1–2): 94–108, Bibcode:2004GSAB..116…94K, doi:10.1130/B25158.1

4. Troost, K. G.; Booth, D. B. (May 22, 2004), Geology of Seattle: City of Seattle Field Trip, Seattle-Area Geologic Mapping Project Department of Earth and Space Sciences University of Washington

5, 6, 7. HAZUS (2011) Earthquake Event Report. Washington Department of Natural Resources

8, 9, 10, 14,15. FEMA, HAZUS (2011) Understanding Earthquake Hazards in Washington State. Modeling a Magnitude 7.2 Earthquake on the Seattle Fault Zone in Central Puget Sound. Department of Natural Resources

11. Yamamuro, J. A.; Lade V. P. (1997) Static Liquefaction of Very Loose Sands. Canadian Geotechnical Journal, 43(6): 905-917

12. Ishihara, K. (1971) Liquefaction of Subsurface Soils During Earthquakes. Department of Civil Engineering, Tokyo.

13. Which Soils are Liquefaction Susceptible?. Central Washington University. (2009_. Web. 22 Feb 2015.

16. Tetra Tech. (2014) Regional Hazard Mitigation Plan Update Volume 1: Planning-Area-Wide-Elements. King County Office of Emergency Management