Tsunami Damage to Infrastructure - ORWARN Tsunami Damage To...• Individual tsunami effects on the...
Transcript of Tsunami Damage to Infrastructure - ORWARN Tsunami Damage To...• Individual tsunami effects on the...
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.