Nisqually...10 Years On

Headline from the Seattle Post-Intelligencer, March 1, 2001.

Earthquake occurrences in the past seven days.
(Screen grab from www.usgs.gov)

A quick glance at the USGS' running tally of recent earthquakes in the U.S. (right) reminds us of the country's most tectonically active areas .  It's pretty clear: California and Alaska, followed by several other geographic pockets of notable activity.  For residents of one of those pockets--Seattle and the greater Puget Sound area--the February 28 dateline on the map at right carries special significance.

Today is the 10th anniversary of the magnitude 6.8 Nisqually earthquake, which struck the area at 10:54 a.m. local time on Wednesday, February 28, 2001.  Although it ranks as only the 82nd largest earthquake by magnitude (by my count) in the U.S., it is the third largest on record and the most recent significant quake in Washington state.

The quake originated at a depth of 52 km in the subsurface Juan de Fuca plate, which is subducting under the North American plate in the Cascadia subduction zone.  The epicenter (47.15N 122.72W) was located toward the southern end of Puget Sound, 17.6 km northeast of Olympia, WA and 57.5 km south southwest of Seattle.

Zip code by zip code view of Mercalli Scale intensity of the
earthquake in the Puget Sound region. (map by USGS)

Highway 302 near Olympia, WA following the 2001Nisqually
earthquake. (photo by USGS via Wikipedia)

According to Seattle's Office of Emergency Management website, the Nisqually earthquake caused about $2 billion in damage.  Homes, buildings (including Starbucks HQ), and roadways across the area suffered most, primarily those located near the epicenter and in downtown areas of Seattle such as Pioneer Square.  The Alaskan Way Viaduct, a high-traffic waterfront thoroughfare sustained structural damage, but thankfully did not collapse.  Shaking from the tremor was reported from Oregon to British Columbia, and as far east as western Montana.  Hundreds of injuries and one fatality (attributed to a quake-aggravated heart condition) were also linked to the quake.
 
Although it seems that we have had too many recent reminders worldwide of the devastation that can be caused by large earthquakes, the 2001 Nisqually event brought much-needed attention to the threat posed to the Pacific Northwest.  In the 10 years since, significant efforts have been made to better equip the city for future earthquakes.  These efforts are ongoing and  include helping homeowners retrofit their houses to withstand strong shaking and potentially replacing the Alaskan Way Viaduct.  The biggest seismic threat for the area is thought to be posed by either a massive subduction zone earthquake along the JDF-NA plate boundary, or a shallow earthquake on the local Seattle Fault, which runs beneath the city.


A sampling of additional material and links for the interested reader:

Coverage on the 10th Anniversary

• Seattle Times: Live chat at 12:30 p.m. (Seattle time) on March 1 with Times writer Sandi Doughton, John Vidale, head of the UW Seismology Network and Roger Faris, an instructor for the city of Seattle's earthquake retrofit classes for homeowners; Much more coverage from the Times here.

• Seattle Post-Intelligencer

• University of Washington

Earlier News Coverage

• Seattle Post-Intelligencer: February 28, 2001 and One year anniversary coverage (lots of great figures)
• PBS Online Newhour

A Tunnel to Replace the Alaskan Way Viaduct?

• Seattle Times coverage here and here

Related News Coverage and Opinion

• Science News - April 10, 2009
• Discovery News -  April 9, 2009
• Physorg.com - April 16, 2009
• Discovery News - March 7, 2010
• NY Times - March 27, 2010

Video
From National Geographic via YouTube:


Simulation of an Earthquake of Magnitude 7.0 occurring closer to Seattle than the Nisqually quake - from the Washington state Department of Transporation via YouTube:


Nisqually Earthquake Photo Galleries

• Seattle Times
• Washington state Department of Natural Resources
• The News Tribune

More Information

• Seattle Fault Scenario from the Earthquake Engineering Research Institute
• Tsunami Hazard Map for Elliot Bay area from the Washington state DNR and NOAA
• USGS Nisqually quake pages here and here among others
• Pacific Northwest Seismic Network (PNSN) information about 2001 quake and local earthquake scenarios
• Seattle Office of Emergency Management
• Nisqually Earthquake Information Clearinghouse
• Wikipedia