Presentation on theme: "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."— Presentation transcript:
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
http://environment.nationalgeographic.com/e nvironment/natural-disasters/earthquake- profile.html http://environment.nationalgeographic.com/e nvironment/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.
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.
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/