Earthquake

Chapter 3 Lesson 4

Earthquake

• An Earthquake is a sudden movement in the Earth’s crust.

• The rock on both sides of a fault is pushed and pulled by forces in the crust.

• When layers of rock that are stuck together suddenly slip, an earthquake occurs.

Earthquake

• The focus, is the place where the slipping begins in an earthquake.

• Waves of energy ripple out from the focus, and spread out from directly above the focus.

• That point is the earthquake’s epicenter. • The point that waves of the earthquake

radiate outward like the ripples in a pond when a stone is thrown in. Epicenter

Earthquake

Earthquake

• http://environment.nationalgeographic.com/environment/natural-disasters/earthquake-profile.html

• Earthquakes happen along the boundaries of tectonic plates because the pressure from the movement of the plates pushes on nearby faults.

Earthquakes

Earthquake

• Seismometers is an instrument that detects and measures waves produced by an earthquake.

• Earthquakes produce three different kinds of waves: Primary waves, Secondary waves, and Surface waves.

Earthquake

• Primary waves move the fastest, they pass through both the solid and liquid layers of Earth.

• Secondary waves travel about half as fast as primary waves, and move only through solid layers. Secondary waves move up and down.

• Surface waves are the slowest. These waves cause the most damage.

Earthquake

• Seismometers are able to help pinpoint the location of an earthquake.

• The difference in time between the arrival of Primary and Secondary waves, at a seismometer station, gives the distance to the epicenter of the quake.

• Scientists need information from three stations to pinpoint the epicenter of an earthquake. (Three stations build a triangle)

Earthquake

• Triangulation: the process of determining the location of a point by measuring angles to it from known points. Geometry!

• Magnitude: is the measure of the amount of energy released by an earthquake.

• Richter Scale, and Mercalli Scale are used to measure earthquakes.

Earthquake

Earthquake

Earthquake

• Aftershocks are sometimes felt after the main earthquake

• Aftershocks are earthquakes with lesser magnitudes.

• Tsunamis are huge waves caused when an earthquake occurs beneath the water and the land is pushed quickly upward.

Earthquake

• People can take steps to reduce the damage caused by shaking during and earthquake.

• People can be warned about a future earthquake.

• People can seek a safe place and be aware of the surrounding dangers during an earthquake.

Earthquake

• Damage to buildings is reduced by placing layers of rubber and steel between a building and its foundation.

• These layers cushion up-and-down motion but still allow the building to more from side to side as the ground moves.

• http://www.earthquakeprotection.com/