Earthquakes

Causes of Earthquakes An earthquake is a shaking of Earth’s crust caused by a release of energy Mostly caused by the strain that builds up along faults which are breaks in the lithosphere Strain becomes great enough to overcome friction and land moves

Where do earthquakes happen? (pg ) Earthquakes can happen anywhere that there is stress and strain resulting in a crack (fault) in the Earth’s crust. This most often occurs at plate tectonic boundaries, but they can also occur in the middle of plates that are under a lot of stress.

How often do earthquakes occur? Earthquakes happen everyday around the world, some can’t even be felt

Types of faults (pg531)

Parts of Earthquakes FOCUS: Point at which the first movement occurs during an earthquake –M–Many miles below the Earth’s surface EPICENTER: Point on the Earth’s surface directly above the focus

Body Waves Body waves: Are waves that travel from the focus through the Earth –E–Every Earthquake produces 2 types of body waves P-Waves: Primary Waves (Come First and travel faster) –C–Can travel through solids, liquids and gases S-Waves: Secondary Waves ( Come Second and are slower) –C–Can only travel through solids

Locating and Measuring Earthquakes Seismograph: Detects and records waves produced by earthquakes Seismogram: Record sheet on seismograph – P waves will arrive at the seismograph station first –T–The farther away the earthquake is from the seismograph station the greater the difference in arrival times

Locating the Epicenter Scientists need to know the distances from at least three different stations in order to plot an epicenters location

Why do you need three stations?

Measuring Magnitude of Earthquake Magnitude is the strength of the Earthquake -- ranges 1-10 –Richter Scale: For each increase of 1 whole number represents a 32-fold increase in energy Example: A reading of a 6 on the Richter scale is 32 times stronger than a 5 on the Richter scale

Richter Scale: Related to power or strength

Mercalli Scale The Mercalli scale measures the earthquakes intensity or how much damage it has produced Ranges 1-12

Earthquake Hazards

Tsunamis Fire Flooding Ground displacement Destruction