Warm- UpHave your homework out for me

to check and for several of you to share.

Answer the following questions at the start of today’s notes.

1. Which hypothesis explains the occurrence of an Earthquake?

2. How does this hypothesis suggest and earthquake occurs?

3. What safety measures should you take in the event of a quake?

TOC:90. Measuring Quakes91. Finding an Epicenter92. EQ HWKeywords:• Body waves• P Wave• S Wave• Seismogram• Richter Scale• Moment Magnitude

Measuring Earthquakes

Seismographs measure the waves of energy distributed by the quake.

• Surface waves arrive last and are usually the most intense and destructive.

• Body waves travel through Earth and provide more insight.

Body Waves

P waves:• Compression waves• Alternately expand and

compress material they pass through

• Travel the fastest of all three waves

• Travels parallel to its movement

Body WavesS Waves• Transverse wave• Changes objects volume

temporarily• Travel slower than P waves• Travels at a right angle to

the direction of its movement

• TAKE A SMALL SHEET AND WORK WITH A PARTNER TO COMPLETE THE GRAPH

Locating an Earthquake

• Different speed of waves allows us to locate epicenter

• P Waves travel 1.7 times faster than S Waves

• The longer they travel, the greater the time lapse between them

Reading the Seismogram• Measure the time between

the P Wave ad the S Wave• The amount of seconds

corresponds to a distance based on the graph

• For example: a lag of 2 minutes indicate about a 700 mile distance from the epicenter (SMALL SHEET)

Locating an Earthquake• Station in Atlanta

reports seismic activity• Using the lag between

waves a radius for the location of the epicenter is created.

• How many points exist on the circle?

Locating an Earthquake

• Using another station in Louisiana provides another radius for the epicenter.

• How many points do the two radii have in common?

• What do these points represent?

Locating an Earthquake

• Using a third station pinpoints the Epicenter.

• How many points can all three circles have in common?

• All epicenters are located using 3 Seismic Stations.

• Simulator

Measuring Earthquakes

Earthquakes described by intensity and magnitude

• Intensity is the amount of shaking based on damage

• Magnitude is the measure of the size of the seismic waves released

Which is qualitative?

Moment Magnitude

• Derived from the displacement that occurs along a fault zone

• Most widely used scale because it addresses energy released

• Formula to calculate includes fault surface area, average displacement and rigidity of the rock

QUAKE QUIZ!1. Illustrate a seismogram with a 2.5

minute lag between the first P wave and the first S wave.

2. Use the chart to determine the distance from the epicenter. (Use pg 241 if needed)

3. How many minutes did the P Waves travel before arriving at this location?

4. If the lag were four minutes, does the distance from the epicenter increase or decrease?

5. Illustrate the motion of an S wave. Do these waves cause more or less destruction than P Waves?

Quake Quiz6. What can result from an

earthquake located on the ocean floor?

7. Which is more common on a yearly basis, earthquakes or hurricanes?

8. What branch of science was born out of the 1906 Earthquake?

9. Has a 10.0 Magnitude Earthquake ever been recorded?

10. Where do most US Earthquakes occur?

Bonus….

BONUS

1. Which 3 particles make up soil?2. What is Lansing’s favorite college football

team?

Assignment• Work in groups of 3 to find the

epicenter of an earthquake.• Answer all of the questions as

you proceed through the scenario.

• Coordinates:New York (40 N, 75 W)Seattle (47 N, 122 W)Mexico City (19 N, 100 W)

DO NOT WASTE TIME

Homework:p. 228 1-6

If you group does finish then you may start the HW.