Earthquakes  Earthquakes:  the shaking and trembling that results from the movement of rock beneath Earth’s surface  See simulation below:  Terashake Terashake

Caused by STRESS  Stress:  a force that acts on rock to change its shape or volume

1. Shearing  pushes a mass of rock in two opposite directions  Causes rock to break and slip apart or to change its shape  See simulation below: 

2. Tension  Pulls on the crust  Stretching rock so that it becomes thinner in the middle  See simulation below: 

3. Compression  Squeezes rocks until it folds or breaks  Compresses rock like a giant trash compacter  See simulation below: 

What is a Fault?  A break in Earth’s crust  Slabs of crust slip past each other  Occurs along a plate boundary  Forces of plates: compress, pull, or shear the crust so it breaks

Types of Faults  Normal- caused by tension  Reverse- caused by compression  Strike-slip -caused by shearing Fault Movements See simulation below:

Mountain Building  From faulting  Two normal faults  From folding  Anticline - forms an arch  Syncline - forms a bowl  Plateau - large area of flat land  From vertical fault

Earthquake Terminology  Focus  Point beneath Earth’s surface where rock that is under stress breaks, triggering an earthquake  Epicenter  Point on the surface directly above the focus

Seismic Waves  P Waves  First waves to arrive  Compress and expand the ground like an accordion  Can travel through solids and liquids

Seismic Waves  S Waves  Vibrate from side to side as well as up and down  Only move through solids, not liquids

Seismic Waves  Surface waves  Move slower than P and S waves  They produce the most severe ground movements  Some roll like ocean waves  Others shake from side to side Wave Movements See simulation below:

Detecting Seismic Waves  Seismograph  Records and measures the vibrations of seismic waves

Measuring Earthquakes  Magnitude - measurement of earthquake strength based on seismic waves and movement along faults  Mercalli Scale - rate earthquakes according to their intensity  How affect people buildings, people and land surface  Richter Scale - rating of the size of seismic waves as measured by a particular type of seismograph  Moment Magnitude Scale - estimates the total energy released by an earthquake