1. Earthquakes

2. What is an Earthquake?
A vibration of the Earth’s surface that follows a release of energy in the Earth’s crust

3. What causes an Earthquake?
The Earth’s outer surface is broken up into tectonic plates
These plates constantly move away from, towards, or past each other
An EQ occurs when the stresses caused by these plate movements are released

4. EQ Prone Areas?
Most of the World’s EQ’s are on the circum-Pacific seismic belt known as the “Ring of Fire”
95% of all EQ’s happen at active plate boundaries

5. Popular ones? Japan California Philippines Indonesia NZ Alaska Mexico
Chile

6. EQ Terminology
The following words will help understand when reading or listening:
Focus
Epicenter
Intensity

7. Focus
The energy released in all directions from EQ’s originate from their source: FOCUS (where they started)
The energy released is known as waves that travel quickly through the Earth’s crust
As distance from the focus increases, the strength of the waves decreases

9. Epicenter
The Epicenter is the location directly above the Focus of the EQ

10. Intensity A measure of the effects of the EQ at a particular local
Dependent on the following:
Strength of EQ (magnitude)
Distance from Epicenter
Nature of surface materials
Building design
Many EQ’s occur in oceanic areas or at great focal depths and are either not felt, or their intensities do not reflect their true strength

12. The Usual Around the world every year this happens:
900,000 - <3.0 Magnitude EQ’s (potentially perceptible)
56,000 - <6.0 Magnitude EQ’s (Destructive)
Magnitude EQ’s (Major! Serious Damage)
>8.0 Magnitude (Total destruction at epicenter)

13. Besides the shaking:
The biggest reason for EQ’s destruction is usually the shaking of the ground….what else comes with them is sometimes worse!
Fires
Landslides
Liquefaction of ground

14. Fires
When the ground shakes and cracks, gas lines, water lines, electric lines are damaged most of the time (underground usually)

15. Fires Some times, the most destructive….an easy fix if water is on…
San Francisco, 1906: The estimation was 8.3 on the Richter scale, but worse than the shaking itself, the earthquake caused fires that burned out of control for three days. Two thirds of the city burned down, and totally wiped out the downtown business district. Tens of thousands of people lost their homes and fled the city and an estimated 3000 people died.

16. Landslides
Depending on surface material and landscape of what “is being shaken”

17. Biggest in History…
Mt St Helens (Cascade Region) Peru 1970: 66,000 dead

18. Liquefaction
When soil loses strength and stiffness in response to an applied stress, usually an EQ or other sudden change in stress condition, causing it to behave like a liquid.

19. Ex’s of Liquefaction Alaska 1964
Mexico City 1985 : rests on the ancient lakebed of Lake Texcoco, which is a large basin filled with liquefiable sand and ground water. In the Mexico City earthquake of 1985, the wet sand beneath tall buildings liquefied and most of the 10,000 people who died were in buildings that collapsed as their foundations sank into liquefied sand.

22. The Biggest and Baddest!
DESKTOP!