Tsunami Damage to Infrastructureand the consequence for a small coastal community

Harry YehOregon State University

The 2004 Indian Ocean Tsunamiand

The Previous (smaller) Tsunamis

The 2004 Indian Ocean Tsunami (Mw 9.2): Lhoknga

Photo by Jose Borerro

5 m

Trubean, the 1992 Flores Tsunami (Ms 7.5)

The 2004 Indian Ocean Tsunami (Mw 9.2)

Vedaranniyan, India

The 1992 Nicaragua Tsunami(Mw 7.6)

El Popoyo

The 2004 Indian Ocean Tsunami (Mw 9.2)

Photo by Jose Borerro

Banda Aceh

The 1993 OkushiriTsunami, Japan (Ms 7.2)

Aonae

• Individual tsunami effects on the coastalareas were similar to the previous tsunamievents.

• What makes the 26 December 2004 eventdistinct is the extent of the affected area.

2004 Indian Ocean Tsunami

Well engineered reinforced concrete structures were often survived

Banda AcehNicobar Islands

Mega Tsunamis: ground shaking may last along time, more than several minutes.

Therefore, the ground at low-elevation may beliquefied much more than anticipated – This isa lesson learned from the 2010 Chile Tsunami:more from Professor Scott Ashford

The duration of high-frequency energy radiation is about 500 sec.The rupture length is about 1200 km. (Ni, Kanamori, Helmberger, 2005)

Seismic Data of the 2004 Indian Ocean Tsunami

(Ammon, et al., 2005)

Rupture Process of the 2004 Indian Ocean Tsunami

Damage to Bridges

April 1, 1946 Aleutian Tsunami

The earlier tsunami attackwashed away one sectionof the bridge

Hilo, Hawaii, 1946

Nagappattinam, India: 2004

A bridge jammed up with boats

Scour Damage of the Bridge

Kalpakkom, India, 2004

Impacts to Service Water Lines

Failure of a sewage line due to scour

Kalpakkom, India, 2004

Flood due to Severe Subsidence

Coastal Subsidence: Nicobar IslandsThe 2004 Indian Ocean Tsunami

Salt (Sea) Water Effects

Indira Point, Great NicobarThe 2004 Indian Ocean Tsunami

Discolored Vegetation

Impacts of “Salt (sea) Water”

Kovalam,India: The 2004 Indian Ocean Tsunami

Sediment and Boulder Transport

Tsunami Sediment Deposits

Playa El Coco, Nicaragua, 1992

Playa El Coco, Nicaragua, 1992

Tsunami Sediment Deposits

Boulder Deposits

Trubean, Flores, 1992

Impacts to Topological Features

Return-Flow Channel Incision

DevanaanpattinamIndia, 2004

Sri Lanka, Kalutara Beach, 2004

Return-Flow Channel Incision

Tsunami ScourFoundation FailureMomentary Liquefaction

The 2004 Indian Ocean Tsunami:Chennai

Roads

Tsunami Scour Problems

Scour Formation: 2004 Indian Ocean Tsunami

Runup height 4.1 mScour depth 1.5 m

Sri Lanka: photo by Patrick LynettScour depth ≈ 2.0 m

Devanaanpattinam

Foundation Failure: the 1993 Okushiri Tsunami

Scour depth: 4 m

Capsized breakwater due tofoundation failure at AonaePort, Japan

Scour Formation

Kesen-numa, Japan: the 1960 Chile Tsunami

Scour hole more than 8 m deep at the entrance to the port.

After Takahashi et al. (1992)

Scour Formation

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• The maximum scour depth in the onshore area is less than 3 m.• Pore-pressure driven scour does not occur farther inland than x = –300 m.• The maximum scour depth is found to be 6.2 m deep at 450 m offshore

Offshore

Spatial Variation of Scour Depth

α = 1/250.Maximum runup height 4.6 mRunup/drawdown process 16 min.

1

2

3

4

5

Quay-wall collapse

Momentary Liquefaction

Konakano, Japan: the 1960 Chilean Tsunami.

Tsunamis Often Induced Fire

1993 Okushiri Tsunami, Japan

Summary• Difference between a mega tsunami and other significant

tsunami.• Reinforced concrete structures are often survived.• Mega Tsunamis: ground shaking may last a long time, more

than several minutes → liquefaction problems.• Bridge damage and failure.• Ground subsidence.• Salt water intrusion and its effects.• Sediment and boulder transport.• Impacts to geo-morphology.• Tsunami Scour, Foundation Failure, and Momentary

Liquefaction• Fire and wind generation

A Small Coastal Community in Southern Oregon

Demographic Information

• Population 2,000

• 900 males and 1100 females

• Median resident age: 45 years

• Population density: 800 peopleper square mile

Hypothetical Cascadia Rupture

Goldfinger and others (2008)

• A large earthquake of Mw 8.5strikes the southern Oregon andthe northern California coasts --it’s a rupture of the Cascadia.

• Happened during a winter day;therefore, no satellite imageinformation would betransmitted, and very limitedairborne reconnaissance wouldbe possible .

• Ground shake lasts 2 minutes.Some liquefaction and landslideare likely.

• Recall that, when the magnitude of theearthquake is sufficiently large (say > 7.5),individual tsunami effects on the coastalareas were similar regardless its magnitude.

• What makes it distinct is the extent of theaffected area, and the duration of groundshake.

Hypothetical Tsunami Effects

Hypothetical Tsunami Effects

• The first tsunami arrives 20minutes after the earthquake.

• Maximum runup height ~ 20 m (60ft): This estimate might be a littlehigh, but possible, considering theeffect of the river outflow that maycause tsunami focusing.

• There will be 5 significant tsunamiattacks in 90 minutes.

• The red line represents theestimated inundation area.

Hypothetical Tsunami Effects

• The entire area will be subsided by2 m (6 ft).

• The largest subsidence of 6 m (20ft) at the harbor.

• A series of tsunamis propagatealong the river up to 20 km (12.5miles) from the mouth.

• Immediately after the event, say 6hours later, they found 50 peopledead and 100 people missing.

Hypothetical Tsunami Effects

• Completely wipe out wood-framebuildings located west of the mainroad (HWY 101); many of thebuildings east of the main road arealso damaged heavily.

• Coastal sediments are deposited inthe areas up to El. 17 m (56 ft).Significant scours are resulted inthe area up to El. 5 m (16 ft).

• Because of the sediment (deposit)blockage and the severesubsidence, the river will beflooded to the south.

Hydro Information

Ecological impacts due to “salt (sea) water” intrusion may becomean issue.Ground water will become brackish and not suitable to drink.

Location Map

• Highway 101 would bedamaged both north andsouth of the city: numerouslandslides.

• In the case of the Mw 8.5event, the affected areawould be from Florence, ORto Crescent City, CA.

• A possible access to thecoast from the inland wouldbe HWY 199 via NorthernCalifornia.

Bridge over the River

Will the bridge fail?

Probably not, but it won’tbe passable, because ofthe severe subsidence andliquefaction effects.

Scenario

• Only possible communication would be satellitephones.

• No port or airport runways can be used.