Earthquakes An earthquake is The shaking of the

An earthquake is… • The shaking of the earth’s crust caused by a release

A fault is… • A break in the lithosphere along which movement has occurred.

• Focus: the point at which the rock first breaks and moves in

Seismic Waves • The energy released in an earthquake travels in waves. There are

Primary Waves • Called P waves • Compression waves- squeeze and stretch rock (Push

Secondary Waves • S waves • Side to Side movement. • Can travel only

Surface Waves • Seismic waves that travel along Earth’s Surface • When P and

Measuring Earthquakes • Seismograph: Instrument used to measure an Earthquake • Seismogram: The paper

The S-P Time Interval is the time between the start of the p wave

Locating Earthquakes • Because P waves and S waves travel at different speeds, speeds

Locating Earthquakes • If you know the distance an earthquake occurred from at least

Earthquake Magnitude: strength measured by the amount of released energy • Richter Scale by

Earthquake Hazards • Fire: Causes the most damage in an Earthquake, some utility lines

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Earthquakes

An earthquake is… • The shaking of the earth’s crust caused by a release of energy • Earthquakes can be caused by: – 1. Eruption of a volcano – 2. Collapse of a cavern – 3. Impact of a meteorite – 4. Strain built up along boundaries between plates

A fault is… • A break in the lithosphere along which movement has occurred. Most earthquakes occur in this way. – Friction between plates prevents them from moving, so strain builds up. The rock deforms. Eventually, the strain becomes great enough that the rock moves, and returns to normal shape. This causes an earthquake (elastic rebound theory).

• Focus: the point at which the rock first breaks and moves in an earthquake. Below the surface. • Epicenter: the point on the earth’s surface directly above the focus.

Seismic Waves • The energy released in an earthquake travels in waves. There are three types: – Primary waves (P waves) – Secondary waves (S waves) – Surface waves (Love and Rayleigh)

Primary Waves • Called P waves • Compression waves- squeeze and stretch rock (Push and Pull) • Can travel through any material- solid, liquids, and gases • Travel the fastest

Secondary Waves • S waves • Side to Side movement. • Can travel only through solid material, not liquids or gases • Travel a little more than half the speed of P waves

Surface Waves • Seismic waves that travel along Earth’s Surface • When P and S waves reach the surface, they make Surface waves • There are two types, types Love waves and Rayleigh waves • Cause lots of damage

Measuring Earthquakes • Seismograph: Instrument used to measure an Earthquake • Seismogram: The paper record of the Earthquake data (shaking) is called a seismogram

The S-P Time Interval is the time between the start of the p wave and the s wave.

Locating Earthquakes • Because P waves and S waves travel at different speeds, speeds the difference in their arrival times can be used to determine the DISTANCE away an earthquake occurred.

Locating Earthquakes • If you know the distance an earthquake occurred from at least three different seismic stations, you can determine the location of the epicenter. • Triangulation: Using the S-P time interval data from 3 stations to determine the epicenter

Earthquake Magnitude: strength measured by the amount of released energy • Richter Scale by Charles Richter • Each increase in number represents 10 x an increase in power. • Example: a 4. 0 is ten times stronger than a 3. 0

Earthquake Hazards • Fire: Causes the most damage in an Earthquake, some utility lines and roads get damaged • Liquefaction: When the ground turns to quicksand due to the shaking • Tsunamis: Are caused by underwater earthquakes that make a big wave.