Earthquake risk continues to propel this program and emphasize its urgency.
Immediately after the 2001 Nisqually earthquake, WSDOT made $3.5 million in earthquake repairs to keep the viaduct safe and functional and began semiannual earthquake inspections to closely monitor cracks, structural movement and foundation integrity. |
Crews check for structural damage during the semiannual inspection. |
Below is a summary of all inspections and their findings since 2001.
| Inspection Date |
Inspection Results / Actions |
| March 2008 |
The section of the viaduct between Columbia Street and Yesler Way settled another 3/8ths of an inch, bringing the total amount of settlement to approximately five-and-a-half inches. Columns continue to settle incrementally in this area, where repairs are nearly complete to strengthen several column foundations. No new structural damage was caused by the additional settlement. View photos of this inspection and the public tour we held during inspection weekend. |
| January 2008 |
The quarterly inspection reveals that the Alaskan Way Viaduct settled approximately 1/8 of an inch where foundation strengthening work is taking place between Columbia Street and Yesler Way. No new structural damage was caused by the additional settlement. |
| October 2007 |
No additional settlement and no new structural damage are detected for the section of the viaduct between Columbia Street and Yelser Way. Work begins to strengthen four column foundations in this area. |
| June 2007 |
Analysis of the Alaskan Way Viaduct visual inspection results indicates additional settlement. The viaduct has settled an additional ¼ of an inch to a total of approximately five inches. The settlement continues to occur in the same area between Columbia Street and Yesler Way. |
| March 2007 |
Analysis of the Alaskan Way Viaduct inspection results indicate no additional settlement. Due to half an inch of settlement at two piers found during the two previous inspections, WSDOT will move forward with repairs between Columbia Street and Yesler Way. |
| October 2006 |
Analysis of the Alaskan Way Viaduct inspection results indicate a small amount of settlement has occurred on the viaduct. An area that WSDOT has been monitoring has settled an additional 1/4 of an inch. This area has settled a total of 4 3/4 inches since we began measuring in 2001. |
| March 2006 |
Analysis of the Alaskan Way Viaduct inspection results indicate a small amount of settlement has occurred on the viaduct. An area that WSDOT has been monitoring has settled an additional 3/8 of an inch. This area has settled a total of 4 1/2 inches since we began measuring in 2001. |
| October 2005 |
Analysis of the Alaskan Way Viaduct inspection results from October indicate that no new settlement has occurred on the viaduct. A crack that WSDOT has been monitoring has grown from 4 mm to 7 mm. WSDOT engineers repaired the crack (pdf 107 kb) in November 2005. |
| March 2005 |
Two columns across from Colman Ferry Terminal between Columbia Street and Yesler Way settled 0.25 inches
View the inspection results (pdf 19 kb). |
| September 2004 |
No measurable settlement. |
| March 2004 |
No measurable settlement across from Colman Ferry Terminal. Very minimal settlement in south sections (near Washington Street). |
| October 2003 |
Viaduct section across from Colman Ferry Terminal settles an additional 1.0-1.2 inches (east and west sides) since March 2003 inspection. Continued minimal settlement in south viaduct sections (near Washington Street). |
| March 2003 |
Crews discover viaduct section across from Colman Ferry Terminal has settled 0.5 inches on the east side and 2.0 inches on the west side since last inspection. Continued minimal settlement in south viaduct sections (near Washington Street). |
| November 2002 |
Crews discover viaduct section across from Colman Ferry Terminal has settled 0.5 inches on the east side and 1.2 inches on west side. Minimal settlement—fractions of an inch, found in south viaduct sections (near Washington Street). |
| February - April 2001 |
WSDOT makes $3.5 million in post-Nisqually earthquake repairs. |
Additional Earthquake, Volcano and Tsunami Resources
The United States Geological Survey Web site is an excellent source of Washington earthquake information. It includes maps outlining Washington State seismicity, seismic hazard areas and faultlines as well as detailed earthquake and tsunami histories, factsheets and studies.
The Pacific Northwest Seismograph Network, based out of the University of Washington's Earth and Space Science department, catalogs all the latest local seismic and volcano activity. It also includes helpful info on earthquake hazards and types as well as preparedness and safety tips.
The Earthquakes Canada Web site is another good source of information for earthquakes in British Columbia and Western Washington.