1. 8.3 Destruction from Earthquakes
Damage to structures depends on …
Intensity and duration of vibrations.
Nature of the material on which the structure is built.
Design of the structure.
Building Design
How a Building Collapses with shaking
How a Building Survives Shaking

2. Peru BEFORE 1970 Earthquake.
Peru AFTER 1970 Earthquake.

3. LIQUEFACTION Liquefaction Lab
*Take a plastic cup, carefully cut off the bottom of it, and place it upside-down in a pie plate
*Hold the cup in place and carefully pour fine sand (beach sand works well) into the upside-down cup until it is about � of the way full
*Put a mass of some sort on the surface of the sand
*Pour water into the pie plate (outside of the cup) while still holding the cup firmly in place
*Tap on the side of the cup, but be sure to hold the cup in place
*Watch as the mass falls through the sand as if through liquid
*This is what sometimes occurs during earthquakes and is known as liquefaction
LIQUEFACTION

4. Liquifaction = when otherwise stable soil becomes weak and liquid-like beneath buildings.

5. TSUNAMI Incorrectly called Tidal Waves. Occurs when…
Earthquake displaces ocean floor vertically along a fault.
Vibration of a quake sets off an underwater landslide.
Travels at
mph!

6. Once formed, a tsunami resembles ripples in a pond.

7. At landfall. In the open ocean… At about 5500 meters depth.
At 900 meters depth.
At 20 meters depth.
At landfall.

8. Pg 230 Figure 11

9. After a large tsunami hit Hawaii, the Tsunami Warning System was developed for the Pacific.
Similar systems have been adopted throughout much of the world.

10. Turkey
Tsunami
(52:53)

11. EARTHQUAKES CAUSE LANDSLIDES
Damage isn’t limited to shaking and waves!
Sumatra land slide killed 10 people.
Ireland
Union Pacific Railway, Seattle WA

12. Ground subsidence = sinking of the ground
That sinking feeling…
Ground subsidence = sinking of the ground
It looks like a flood.
It feels like a flood.
But the water didn’t rise.
School in Alaska
The GROUND SUNK!
Alaska Earthquake March 27, The village of Portage, at the head of Turnagain Arm of Cook Inlet, is now flooded at high tide as a result of 6 feet of tectonic subsidence during the earthquake

13. EARTHQUAKES CAUSE FIRES
Japan
Gas line on fire.

14. Why do we need to predict Earthquakes?

15. So far short term predictions have NOT been successful.
Can we predict Earthquakes in the short-term to provide early warning systems?
Scientists measure…
uplift
subsidence
strain on rocks near active faults
water levels and pressure in wells
radon gas emissions
small changes in electromagnetic properties of rocks
So far short term predictions have NOT been successful.

16. So far long term predictions have NOT been successful…
Can we predict Earthquakes in the long-term to provide probabilities that a certain magnitude of earthquake will occur within years?
Based on the idea that earthquakes are cyclic (they occur in a somewhat regular cycle).
As soon as an earthquake occurs (and releases the pressure) the pressure begins to build again.
Scientists study the history of the earthquakes looking for patterns.
Scientists study SEISMIC GAPS (areas along a fault where there has not been activity for a long time.)
So far long term predictions have NOT been successful…
but we’ll keep trying.