Earthquake Hazards

I. Landslides

- can be caused by earthquake hundreds of miles away

Three main types:

1. Fall - usually from a cliff

2. Slip - i.e. slump

3. Flow - i.e. avalanche

* Loess - wind blown sediment deposits

Earthquake Hazards

I. Landslides

- 1995 landslide in La Conchita, California

- 2005 landslide in La Conchita, California

Earthquake Hazards

II. Liquefaction

* the fluidization of fairly solid ground

Three main types:

* 1. Flow - saturated sediments move horizontally (often toward lower elevations)

Earthquake Hazards

II. Liquefaction

*2. Fountaining - geyser of water and sand created by heavy layer of rock on saturated sand.

Earthquake Hazards

II. Liquefaction*3. Flotation - saturated sand on the surface becomes liquefied. Objects could float or sink.

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II. Liquefaction- can cause major structural damage.

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II. Liquefaction- Susceptibility of SF Bay area to liquefaction

Earthquake Hazards

III. Floods

Four main types:* 1. Impoundment Flood - landslide blocks river’s flow, causing water to rise upstream.

Non-lethal. Plenty of time to evacuate. Mostly property damage.

Quake Lake

Earthquake Hazards

III. Floods

2. Damburst Flood - contents of lake are released downstream due to damage to dam or levee

Very lethal! May result after impoundment flood.

Earthquake Hazards

III. Floods

* 3. Displacement Flood - Water is forced out of a lake or river by a landslide or large-scale surface deformation.

Earthquake Hazards

III. Floods

* 4. Transgression Flood - Coastal land sinks during earthquake and ocean/lake/river water moves in.

This type is permanent.

Earthquake Hazards

IV. Great Waves

* A. Tsunamis - extremely large waves that can travel across entire oceans and cause great destruction.

Earthquake Hazards

IV. Great Waves

A. Tsunamis- What causes a tsunami?

- Violent shaking or surface deformation creates a shallow wave that covers a large area.

- Ships at sea will not feel it.- May move up to a couple hundred miles per hour in open ocean.

- As it nears land, the front edge of the wave slows down, but the back remains fast. Along with a shallow shore, this causes the wave to increase in height.

- Sometimes, hundreds of feet high.

Earthquake Hazards

IV. Great Waves

A. Tsunamis

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IV. Great Waves

A. Tsunamis

- Are they very destructive?

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IV. Great Waves

A. Tsunamis

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IV. Great Waves

*B. Seiche - sloshing of water back and forth in a lake or enclosed harbor.

- usually minimal damage / only reaches a few yards high.

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IV. Great Waves

* C. Bore - single crest of water rushing along a river, often upstream.

- can smash or overturn boats

- example - Mississippi River, 1811-1812

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IV. Great Waves* D. Displacement Wave - great wave caused by displacement of water, due to landslide or underwater ground deformation.

- example - Lituya Bay, Alaska - landslide pushed water 1720 ft. up opposite shore.

- occurs in lakes or enclosed harbors.

Earthquake Hazards

V. Structure Failure

- even in recent years, 1000’s killed due to lack of building codes.

- causes the most loss of life

- China, Mexico, Armenia, and Turkey have all lost over 15,000 in single quakes in the past 25 years due to poorly built structures.

- When looking at susceptibility to earthquakes, we need to consider three aspects:

Earthquake Hazards

V. Structure Failure* A. Foundation

- Structures built on solid rock stand up better than structures built on sand or loose sediment.

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V. Structure Failure* B. Materials

- People build with what they have. Historically, it has been adobe, wood, or stone.

- Wood has much more necessary flexibility.

- Which is the most earthquake resistant?

* Which is the least earthquake resistant?

* Adobe - 100,000’s killed in China due to adobe building collapses.

- Today, we use steel. It is extremely strong but will also bend slightly. Often used to reinforce concrete.

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V. Structure Failure* C. Design

- Most buildings constructed to resist vertical forces, not horizontal forces.

* 1. Resonance - If an earthquake shakes the ground at the same frequency of the building, the building itself will amplify the shaking and literally shake itself apart.

- Two big problems?

- Mexico City, 1985 - 98% of all collapsed buildings in the downtown area were between 6 and 18 stories high. Very few of the shorter or taller buildings collapsed.

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V. Structure FailureC. Design

- Structure failure in Mexico City, 1985.

Earthquake Hazards

V. Structure FailureC. Design

* 2. Outside ornaments or facade can fall off.

- Two big problems?

Earthquake Hazards

VI. Fire- Sometimes an earthquake can cause a fire so enormous that the earthquake itself is the lesser of the two evils.

- Lisbon (1755), San Francisco (1906), Tokyo (1923).

- How does an earthquake cause such disastrous fires?- historically, extensive use of wood in buildings and open flames for cooking.- broken gas lines and electrical lines- destruction of firefighting equipment and water lines- large number of separate fires that grow into one enormous fire- flammability of household items (couches, beds)

Earthquake Hazards

VI. Fire

What is this and how did it kill 40,000 people?