Cascadia Subduction Zone Earthquakes

A Magnitude 9.0 Earthquake Scenario

The Cascadia Region Earthquake Workgroup (CREW)

Acknowledgments• Xxx• Xxx• Xxx

The Northwest’s Earthquake Hazard

Different sources & types of earthquakes• Shallow/crustal• Deep (Nisqually M.6.8

in 2001)• Subduction zone

Photo by Eric Stahung, Seattle M

unicipal Archives

The Cascadia Subduction Zone

700 miles long (1,130 km)

Last great rupture: 1700

500-year average recurrence

Odds within next 50 years: 1 in 10

Explorer, Juan de Fuca, and Gorda Plates forced under the North American Plate

Image Source: Oregon Department of Geology and Mineral Industries

Cascadia Earthquake Scenario

Magnitude 9.0 Felt region-wide Shaking felt for 3–6

minutes Shaking intensities

greatest along coast & where local conditions amplify seismic waves

Image Source: U

SGS

Expect a Large Tsunami

JAPAN’S KITAKAMI RIVER BEFORE M9.0 QUAKE & TSUNAMI ON MARCH 11, 2011

KITAKAMI RIVER AFTER QUAKE & TSUNAMI (MARCH 14, 2011)

Image Source: NASA Earth Observatory

Expect Damaging Aftershocks

Earthquake Aftershocks (M6 +)

M9.2, Prince William Sound, Alaska, 1964

11 within first day

M9.1, Aceh-Andaman, Sumatra, 2004

13 within first 4 days

M8.8, Maule, Chile, 2010

21 within first 2 months

M9.0, Tohoku, Japan, 2011

59 within first 3 months

Image Source: USGS

If the Earthquake Happens Tomorrow

Earthquake-related losses estimated using Hazus

For Cascadia M9.0: • Injuries: 30,000 +• Fatalities: 10,000 +• Economic losses:

$70 + billionPhoto Source: NOAA/NGDC, Shunichi Koshimura

Expected Impacts Essential InfrastructureBuildings

Communities on the CoastThe East Side & Beyond

Photo Source: CERA, Ross Becker

Transportation Networks (Bridges, Roads, and Rail Lines)

FACTORS THAT AFFECT PERFORMANCE: Proximity to coast Age of structure Type of ground (e.g.

sediment, fill, existing landslides)

Lack of redundancy

EXAMPLES OF POTENTIAL IMPACTS: 19 bridges on Oregon’s

Interstate 5 heavily damaged 56 of 135 bridges on U.S.

Hwy 101 in Oregon collapse Rail service disrupted due to

bridge damage near Portland, Olympia, and Seattle

Ports, Shipping Channels, and Airports

Greatest damage on coast No tsunami at Seattle,

Portland, or Vancouver (BC), but damage from shaking & strong currents

Columbia and Willamette shipping channels blocked

Slight to moderate damage to airports along I-5; fuel shortages likely

Photo Source: Geotechnical Extreme Events Reconnaissance (GEER)

Electricity, Natural Gas, Liquid Fuel

Western areas: Widespread

power outages Loss of natural

gas service Liquid fuel

shortages (also in some eastern areas)

Photo by Jim Henderson

Water Systems

Interruption of water supply

Lengthy restoration/ repair times

Fire hazard (downed power lines, broken gas pipes)

Photo Source: National Archives and Records Administration, H.D. Chadwick

Communications

Landline & wireless services disrupted:• Broken cables• Equipment failures and structural damage• Power outages • Jamming

Major undersea transpacific cables severed

Interdependence of Infrastructure

Landslides and damaged bridges can prevent crews from reaching downed power lines and broken pipes.

Communications systems, water-treatment plants, and hospitals can operate on back-up power supplies only for a few days.

Damaged fuel pipelines and terminals may limit fuel supplies for generators and vehicles.

Photo Source: University of Washington, Nisqually Earthquake Clearinghouse

What Will Happen to Buildings?

Performance depends on:• Proximity to coast• Type of soil• Age (building code)• Type of structure

(e.g. wood-frame) Utility connections

may break Tall structures may

resonatePhoto Source: University of Washington, Nisqually Earthquake Clearinghouse

URMs & Other Hazardous Buildings

Notoriously poor performance (URMs, tilt-ups, etc.)

Safety hazard URMs are

numerous:• Portland: approx.

1,800• Seattle: approx.

1,000

Photo Source: University of Washington, Nisqually Earthquake Clearinghouse

Nonstructural Damage

At-risk components include: • Chimneys• Suspended ceilings• Fire sprinkler systems• Elevators• Partition walls• Air handling units• Hot water tanks

Unsecured inventoryPhot

o So

urce

: CER

A, R

oss

Beck

er

Critical Facilities

Widespread damage (coast & some western areas)

Restoration times variable (months–years)

Nonstructural damage Photo by Joe Mabel

Pacific Coast & Strait of Juan de Fuca

Coastal subsidence Strong ground

shaking Tsunami flooding• Within 15–20 minutes• Multiple waves• Variable wave heights▪ Ocean Shores, WA:

16–20 ft (5–6 m)▪ Northern CA: 26+ ft

(8+ m)Image Source: Washington State Department of Natural Resources

Tsunami Inundation Zones

Immediate evacuation Intense shaking + wave

impact, debris, scouring Hard hit:• Eureka & Crescent City, CA• Seaside & Warrenton, OR• Moclips to mouth of

Columbia River, WA• Port Alberni, BC

Image Source: NOAA/NGDC, Shunichi Koshimura

Earthquake & Tsunami Refugees

Refugees likely (coast + some western areas)

Sheltering in place

Seasonal issues Challenges for

low-income groupsPhoto Source: FEMA, Walt Jennings

The East Side & Beyond

EAST SIDE

Hydrogeologic impacts Staging for emergency

response Influx of hospital patients Transfer of administrative

functions to backup sites Economic impacts (e.g.

disruption of supply chain)

FURTHER AFIELD

Disruption of communications• Severing of undersea

transpacific cables• Rerouting

Possible damage from ocean-crossing tsunami (Pacific coastal areas)

Preparing for the Big One

Key First Steps: Studying & assessing the hazard

Assessing the risk

Image Source: W

ashington State Departm

ent of Natural Resources

Raising Awareness

On-going public education of officials, businesses, families, and individuals• CREW • Local and state emergency management and

scientific agencies

National programs• FEMA’s www.ready.gov• USGS’s Earthquake Hazards Program• National Weather Service: Tsunami ReadyTM program

Resilience Planning & Mitigation

Publication of state-wide resilience plans (WA & OR)

Sector-specific assessment, planning, and mitigation

Image Source: Washington State Department of Transportation

Engineering & Building Codes

STEPS FORWARD: Seismic designs for building

& retrofitting are well-tested • Base isolation & other

techniques• Basic life-safety retrofitting

Assessments of building stock (e.g school buildings) to prioritize upgrades

CHALLENGES: Only post-1990s seismic

standards address sub-duction quakes

Older buildings are not designed for big quakes

Current code addresses life-safety only

Grading ordinances are lacking

Earthquake Early Warning Systems

What they do: Detect the first, smaller

seismic waves Provide a few seconds

to a few minutes of warning before arrival of damaging waves

Time to: Drop, cover, & hold on Shut off gas mains Open fire station doors Slow freeway traffic Clear traffic from

hazardous structures (bridges, viaducts)

Preparing for Tsunamis

Map inundation zones Educate population Post signs along

evacuation routes Model evacuations Develop vertical

evacuation where needed

Asses & strengthen evacuation routes

Next Steps Forward

Invest in research, assessment, planning, and mitigation

Implement recommendations Adopt latest building codes Develop personal response plans,

maintain emergency supply kits, reduce risks at home & at work

Image Source: O

SU Active Tectonics and Seafloor M

apping Lab