1. Earthquake Introduction
12/14/15

2. Earthquake Key Terms Earthquake “Seismos” Seismology Seismologist
Sudden, violent shaking of the ground due to movement of tectonic plates
“Seismos”
Greek word meaning to shake
Seismology
Study of earthquakes
Seismologist
Scientist that studies earthquakes
Seismic waves
Waves of energy that travel through Earth during an earthquake
Seismograph
Instrument used to record earthquakes
Produces seismograms

3. What Causes Earthquakes? (Myths)
Ancient Greeks thought strong winds blowing through lots of underground caverns caused earthquakes
Up to 17th century people thought large, restless creatures underneath the surface caused earthquakes

4. What Actually Causes Earthquakes
Most earthquakes take place near tectonic plates
Convergent: strong e-quakes, deep in Earth’s crust
Divergent: weak, shallow (near surface of Earth’s crust)
Transform: moderate, shallow
Movement of plates results in rock deformation

5. Deformation of Rocks Plastic Deformation Elastic Deformation
Does NOT lead to earthquakes
Rock layers fold like clay
After pressure from plates is released, rocks stay in folded shape
Does lead to earthquakes
Rocks bend and stretch like rubber bands
Elastic Rebound occurs when pressure is released
Rock snaps back to original shape

6. Seismic Waves Two main types
Body Waves: travel through the Earth
Surface Waves: travel at Earth’s surface (obviously)
Waves travel at different speeds and move material they travel through differently

7. Three Unique Waves P – Waves: S – Waves: Surface Waves (or L – Waves):
Primary (arrive first, travel fastest)
Pressure (squeeze and stretch rock layers)
Can travel through solids, liquids, gases
S – Waves:
Secondary (arrive second, travel slower)
Shear (swing side to side)
Can only travel through solids
Surface Waves (or L – Waves):
Slower than Body Waves (P & S Waves)
Travel along top of Earth’s crust
Move ground in circular motion (like a roller coaster)
Most destructive (damage) seismic wave