the impacts of the cascadia subduction zone earthquake on...

Dr. Althea Rizzo Oregon Military Department Office Of Emergency Management

The Impacts of the Cascadia Subduction Zone Earthquake on Oregon

What are the geologic hazards in Oregon?

Earthquakes

Tsunami

Volcanos

Earthquakes

•Earthquakes occur when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake.

Tsunami

•Tsunamis are generated when geologic events cause large, rapid movements in the sea floor that displace the water column above.

•The Pacific Coast is at risk both from locally and distantly generated tsunamis.

Why earthquakes? 100 years ago

German geophysicist Alfred Wegener • Theory of Continental Drift

• Landmasses of Earth fit together • Evidence of fossils on opposite sides of

the ocean

1960s - Plate Tectonics

What are earthquakes?

Earthquake = fault rupture

Rupture causes sudden release of strain energy

Shock radiates out from

rupture as seismic waves

Producing the shaking we

experience as the earthquake

Deep / Intraplate

• Deep quakes are usually less than M7.5.

• The 2001 Nisqually, Washington quake (M6.8).

• Damaging deep earthquakes occur every 10-30 years.

• The seismic energy disperses over a much larger area. Damage is usually less than in a similar sized shallow quake.

• Few, if any, aftershocks occur.

• No tsunami expected, although landslides could trigger local tsunamis.

Shallow / Crustal

Aftershocks are common and may cause further disruption.

No tsunami expected, although there could be a local tsunami from landslides.

Shallow / Crustal

• Strong shaking is generally 20-60 seconds, although it could be longer in localized areas.

• Shallow quakes are usually less than magnitude (M) 7.4.

Shallow / crustal

• (Incomplete) List of magnitude 4.0 or larger earthquakes in Oregon

• 1873 6.3 SSW of Coos Bay, OR

• 1930 5.0 WNW of Salem, OR

• 1936 6.1 SSE of Walla Walla, WA (felt in OR)

• 1941 5.0 S of Portland, OR

• 1957 5.0 S of Tillamook, OR

• 1965 4.3 ENE of Baker, OR

• 1968 4.6 WNW of Adel, OR

• 2009 4.1 WNW of Grants Pass, OR

Hazard -- Shallow / Crustal

Map showing earthquakes in last 48 hours

Small shallow earthquakes are recorded every day in Cascadia; damaging quakes occur every few decades.

http://www.pnsn.org/req2/

Shallow / Crustal

• Most crustal quakes are shallow, Klamath Falls (6.0) and Scotts Mills (M5.6) in 1993.

• Damage can be very heavy in the area of the epicenter and along the fault.

Subduction Zone

Ok, back to Cascadia

What is the Cascadia Subduction Zone?

Know your Cascadia Subduction Zone

600 miles long, from northern California to British Columbia

Capable of producing very large earthquakes (M9+) that impact a wide area

Similar in size and impact to the 2004 Sumatra earthquake

Can produce devastating tsunamis

37% chance of a mega-thrust earthquake in the next 50 years *

Last Cascadia Subduction Zone earthquake occurred in 1700

When will the next one occur?

• We just don’t know

Average recurrence: • 240 years (south of Cape Blanco)

• 5-600 years (entire length)

• 190-1,200 years between EQ

Mw ~9 500 yrs

Mw 8.5-8.8 430 yrs

Mw 8.5-8.3 320 yrs

Mw 7.6-8.4 240 yrs

(Modified from Goldfinger et al. (in press) by adding magnitude estimates and some labels)

Recurrence

21 3 11 8

Cascadia = Strong Shaking and Tsunami

• Strong Ground Shaking

• >8.0 Mw

• >2 min. shaking

• Tsunami

• within 15 to 25 minutes

What happens during a Cascadia Subduction Zone earthquake?

Strong ground shaking

2010 Haiti earthquake 2011 Tohoku earthquake

1993 Molalla High School

Shaking intensity – CSZ in Lake Oswego

Source: http://www.oregongeology.org/hazvu

Strong

Very Strong

Severe

Compared to Japan 2011 EQ

2004 Sumatra

Coastal subsidence

People evacuate with small boats down a road flooded by the tsunami waves in the city of Ishinomaki in Miyagi prefecture_JIJI PRESS_AFP_Getty Images

Coastal coseismic subsidence

Cartoon of crustal deformation due to fault locking between earthquakes (top) and during an earthquake (bottom) Figure from Leonard et al 2003.

Coseismic subsidence

Maps of GPS horizontal velocities (left) and the combined GPS vertical velocities with tide and leveling uplift rates (right). Vertical rates colored according to their magnitude. Warm colors indicate uplift. (Gina Schmalzle)

Landslides in Ferndale, WA

Landslides

2010 Taiwan

Japan

Astoria

http://www.oregongeology.org/sub/slido/

Landslides in Jackson County

http://www.oregongeology.org/sub/slido/

Liquefaction

1964 Alaska

2011 Christchurch

1964 Niigata Liquefaction

Source: unknown

Liquefaction

Source: http://www.oregongeology.org/hazvu

Tsunami

Tsunami

2004 Indonesian tsunami 2011 Tohoku tsunami

Tsunami

Local – Caused by a subduction zone earthquake near the Oregon shore

Distant – Caused by a subduction zone earthquake far away from the Oregon shore

Tsunami

Distant Tsunami • Arrives 4 + hours after the earthquake • Lower damage and flooding than local

tsunamis • National Tsunami Warning System can warn

you • Warning and Advisory require protective

action • National Tsunami Warning Center • http://wcatwc.arh.noaa.gov/

hrs

Tsunami Evacuation Maps

Tsunami Inundation Maps

Tsunami Evacuation Modeling

•How long does it take to get out of the bad zone?

Beat the Wave

Earthquake Far Away

You won’t feel the ground shake

4+ hours before waves arrive

Limited Inundation

Distant Tsunami

•Beaches

•Harbors

•Rivers, Inlets

•Other low-lying areas

Distant Tsunami

Tsunami Alert Messages National Tsunami Warning Center

Alert Level Threat Action

Information Statement

Minor waves at most No action suggested

Watch Danger level not yet known Stay alert for more info

Advisory Strong currents likely Stay away from the shore

Warning Inundating waves possible Full evacuation suggested

Distant Tsunami

Mass Notification

Systems

NOAA Alert Radio

Sirens TV/Radio

Social Media

Distant Tsunami Notification

Evacuation Before a Distant Tsunami

• WHO: Only those in the

distant tsunami zone

• HOW: Probably by car

• WHERE: ???

Re-entry After a Distant Tsunami

•Cancellation Message

•Re-enter with Caution

•Damage

•Harbors

•Beaches

• Low-lying areas

•Roads, Bridges

•Clean up

Local Tsunami • Arrives minutes after the earthquake

• Much higher waves

• Much further inland penetration

• NOAA Tsunami Warning System ineffective

• Earthquake = Only Warning

• NO OFFICIAL WARNING!

• Self Evacuation required

What Tohoku teaches us about Cascadia

Probability versus Possibility

• Planning assumptions led to inadequate mitigation

• (Probable) Response planning was based on a recurrence of the 1896 Meiji Sanriku or 1960 Chile tsunamis.

• (Possible) 869 Jogan earthquake and tsunami

• significantly larger

• viewed as an “outlier,” a 1,000-year event that was low probability.

• The planning scenario supposedly depicted a high-probability “100 year event.”

Assumptions have human impact

• 22,600 persons killed or missing nationwide

• 15,500 confirmed deaths

• 92.4% drowning

• 107,000 buildings collapsed, and another 111,000 partially collapsed

• BUT ….

• 6.5 million people live within 200 miles of rupture zone

Initial earthquake magnitude estimations feeds previous assumptions

• Earthquake initially estimated at 7.9M

• Tsunami warnings issued based on this false information

• Subsequently, magnitude was raised to 8.9, then 9.0

• Earthquake damage caused power and telecommunication outages which prevented people from getting updated tsunami warnings

Factors affecting survival of tsunami

•geography and topography

•distance to high ground

•pre-disaster land use

Physical factors

Factors affecting survival of tsunami

• time of the event

• limited mobility

• caregiving behavior

• inaccurate conclusions drawn from past tsunami experiences

• instinct to protect property

Human factors

Survival factors: disaster preparedness

•Regularly practiced drills

• Saw other people evacuating

Recommendations

• Harden infrastructure

• Clear wayfinding

• Practice, practice, practice

Enhance tsunami evacuation routes where high ground available

Build vertical evacuation refuges where high ground is not available.

Embed tsunami information in ambient built environment

R. Wilson

Japanese emergency response challenges.

• Scale of the tsunami disaster

• Infrastructure damage prevented early reporting of damage and response needs.

• Access to satellite telephones was limited and inadequate to fill the communications gap.

• Highway and rail lines along the coast were destroyed, and access from the major highways to the west was blocked in many places by road damage and landslides.

• Marine access from the Pacific Ocean side of Iwate, Miyagi, and Fukushima prefectures was blocked on the first day by continuing tsunami action, and later by damaged dock facilities and floating debris.

• Fuel for vehicles and equipment was not available due to loss of power and damage to facilities.

Responders as victims

• Many jurisdictions lost political and response personnel,

• Facilities destroyed.

• Otsuchi

• Lost mayor, seven senior staff, and 31 other municipal employees in the tsunami.

• Minamisanriku

• Emergency operations and tsunami warning center was destroyed. 10 staff members survived by clinging to antennas on the roof.

Recommendations: Ensure Critical Continuity

• Relocate critical facilities out of inundation zone

• Retrofit critical facilities

• Prohibit building new critical facilities in inundations zone

• Ensure future construction of critical facilities meet the most robust standards

Emergency Shelter and Housing

•About 470,000 evacuees required shelter

• Local governments are responsible for post-disaster care and sheltering with assistance provided by the national government

Challenges to sheltering

• Dependent on local government officials, undamaged facilities, and logistic support.

• Pre-designated shelters destroyed.

• In some areas, food and water were not delivered for up to three days.

• Sheltering - mix of planned and ad hoc

In-place sheltering

• People with places to stay with family or friends or staying in their own homes

• Barrier to information and services as those living in shelters.

• Impacted lifeline services and other amenities

Recommendations

• Robust sheltering planning

• Bring the message home

• Personal preparedness

• Neighborhood prep

• Community prep

Aftershocks

www.scec.org/scecvdo

Aftershocks

• 3 aftershocks > 7Mw within 40 minutes

• Aftershock area

• 500 km x 200 km

• More than 9,500 aftershocks as of March 2012

Great Japan Earthquake

Contact Information

Geological Hazard Program Coordinator

Althea Rizzo (503) 378-2911 ext.

22237 Althea.rizzo@state.or.us