Nisqually Earthquake 2002, Washington

1st General Meeting held March 1, 2001
Location: University of Washington, Moore Hall, Seattle, WA

WARNING: Provisional Report, Subject to Revision

Approximately 100 people filled the small classroom at Moore Hall on the University of Washington campus.

Topics Discussed

Overview seismolgical report:

• A maximum 20% horizontal acceleration was measured,
• Up to 10 mm of horizontal displacment resulted
• Normal faulting earthquake trending to the northeast, caused by tensional stresses in the Juan de Fuca North America plate.

Geotechnical:

• Capitol Lake: Liquefaction and landslides
• Maple Valley: 0.17 horizontal acceleration

Bridges:

• Initially 30 bridges closed. After examination only 3 remained closed

Socio-economic impacts:

• 1 death
• 272 injuries, 4 critical
• $1 to 2 billion dollars and rising

Lifelines:

• 20 pipeline failures, far less than in earthquakes of similar magnitude quakes
• Communications were overloaded,
• Water systems did well,
• Wastewater had minor problems,
• Some problems with highways and bridges,
• Railroad (BNSF) had a problem at the Narrows in Tacoma,
• Ferry dock—failure (operational?),
• Airports:
  • SeaTac—Glass blown out of the control tower,
  • Boeing Field—much liquefaction, glass broken in control tower

Notes from the Geotechnical/Seismological breakout session

Questions to be Answered

• What needs to be seen?
• What has been seen?
• What needs to be revisited?
• Where do we go tomorrow?

Summary of damage reports

Capitol Lake:
visited by many
Liquefaction, landslide, and lateral spreads
Shifted railroad abutment

Port of Seattle:
visited by many

Terminal 5:
- Fresh ground cracks at the north end (1/2" wide by 20' long)

APL property:
- Sand boils
- Cracks 1-2" wide and 300'-400' long (possible vertical movement of up to 1")

Pier:
- 2"-3" pier settlement near bridge (south end)
- Movement of pier relative to base in asphalt (signs of shaking)

Terminal 18:
- Similar to terminal 5, also a sinkhole.

Terminal 25 and 30:
- Cracking and sand boils (20' diameter)

West Marginal Way:
Not much to be seen in the way of damage

South of Spokane St.:
Cracks and sand boils

Hydraulic fill north of Myrtle Edwards:
An improved area, no damage, cranes operating

Port of Olympia:
Sand boils/cranes operational

Port of Tacoma:
Puyallup River levees—no problems
Asarco embankment—will be revisited

Nisqually Delta:
Some sand boils, only minor ground cracks, some in perimeter dike of fish hatchery

Puyallup River Valley:
nothing obvious

Kent—Auburn Valley:
Minor cracking in Renton (S&W)

Lower Duwamish:

Boeing Field—Extensive liquefaction on east side - 300' long zones; 9" of settlement, cracks, sink hole reported 4' wide by 6' deep on north end of runway. West side, less liquefaction, few scattered sand boils, ground cracking, joint separation. Someone should map sand boils with relationship to old buried river meanders.

16th Ave. South and East:

Marginal Way: A handful of 2 cm cracks
Seattle Chocolates: 1st Ave South and Holgate—Sand boils
Coleman Dock: 2" of settlement over approximately 100' adjacent to pile supported section
Pioneer Square: Settlement of approximately 1 ½" all the way to Jackson, cracking

West Seattle:
Landslides on private property, involving 5 backyards with slopes of 35-40 degrees, cracks at the top of the slope (11" vertical and 8" horizontal)

Olympia:
Landslide on Martin Way, 25' wide by 350' in length (vertical displacement to 10')

Tumwater—Crosby & Mottman:
Aztec wall 9'-12' high about 100' long with a 3:1 slope above—revisit

Sunset Lake—Tumwater:
4' vertical and 5' horizontal
Gas line breaks, mobile homes shifted, sand boils

North Creek—Woodinville:
Not much seen

Woodinville—Bothell:
A couple inches of settlement at a motel; 6" vertical and 4" lateral

Highway 101 near Mud Bay:
A draw filled with material over a length of 100 meters (a flow slide). Meeting near end. Will hold another meeting tomorrow night.