Post on 23-Dec-2015
BellringerHow does a seismic station determine how far
away an earthquake occurred from that station?
Earthquake SafetyNotes
Earthquake Risk•Earthquakes are most likely at faults
along the boundary between two plates.
•The Pacific Plate and the North American Plate meet along the Pacific coast of the United States.
•The coasts of California, Washington, and Alaska all have a high risk of earthquakes.
Earthquake Risk
•The eastern United States is far from plate boundaries. Only a few big earthquakes have happened in the eastern United States in the past.
•The New Madrid Fault along the Mississippi River on the western border of Tennessee is thought to be a failed rift system from 750 million years ago.
•The South Carolina earthquake zone is from a fault line created during the breakup of Pangea that stays active due to the motion of the N. American Plate.
Tectonic Plate Boundaries
How Earthquakes Cause Damage
•When an earthquake happens, seismic waves cause the ground to shake. The shaking can destroy buildings and break gas and water pipes.
How Earthquakes Cause Damage
•Sometimes the shaking turns soft soil into mud. This is called liquefaction. Liquefaction can make buildings sink into the ground like quicksand.
•Actually, quicksand is a form of liquefaction without the need of an earthquake.
How Earthquakes Cause Damage
•Smaller earthquakes, called aftershocks, can follow a big earthquake. Aftershocks add to the damage done by the big earthquake.
•Aftershocks may strike hours, days, or even months after the primary event.
How Earthquakes Cause Damage
•An earthquake on the ocean floor can cause a huge ocean wave, called a tsunami. Tsunamis can cause a great deal of damage along coasts.
Steps to Earthquake Safety
•If you are indoors when an earthquake hits, you should drop down under a sturdy table or desk. Then you should cover your head and neck with your arms and hold onto the table or desk.
Steps to Earthquake Safety
•If you are outdoors when an earthquake hits, you should move to an open area such as a playground. You should sit on the ground so you will not be thrown to the ground when the earthquake shakes.
Steps to Earthquake Safety
•After an earthquake, you may have no electricity or running water for a while. Stores and roads may also be closed.
•If you live where earthquakes are likely, you should have an earthquake kit. The kit should include canned food, water, and other emergency supplies.
Designing Safer Buildings
•The main danger in earthquakes is falling buildings and objects. To reduce danger, plywood can be added to walls to make buildings stronger. Tall furniture can also be attached to walls.
•Sinking due to liquefaction can be reduced by attaching the building to solid rock beneath the soil.
•Broken pipes can cause fires and flooding. By making piping flexible, the pipes will bend instead of break during an earthquake.
Designing Safer Buildings
•Some high-rise buildings use a technique called base-isolating. In a base-isolated building, springs or rubber pads are placed between the foundation and the bottom of the building, acting like the suspension in a car.
http://www.rubberimpex.com/images/RubberParts/SXRP02/
PrincipleDiagramAntiEarthquakeSeismicIsolationBuildingBaseSupportRubberBearing.gif