1. Do we have to take notes?
Yes!

2. Earthquake Measurement (Uh-oh, did you feel something?)
Chapter 7 Section 2-Brigandi

3. Earthquakes are movements or trembling of the ground caused by sudden releases of energy as blocks of rock move.

4. Studying earthquakes to determine location
Seismic waves travel thru rock from the point where the earthquake started. This point is called the focus. Scientists study these waves to find the epicenter of a quake.

6. This point of origin can be on the surface of the earth or as deep as 18 miles below the earth’s surface.

7. Seismic waves travel outward along a fault outward and away from the focus. There are 2 types of waves.
Body waves
Surface waves

8. Body waves travel through a body
Body waves include P and S waves.

9. Earthquake-sensing instruments are called seismometers or seismographs.
Seismometers record P & S wave vibrations as they travel thru the earth
They also record the time that the waves take to reach the seismometer station

11. What do seismometers measure?

12. Scientists use this info to find an earthquake’s epicenter.
The epicenter is the point on the earth’s surface directly above an earthquake’s starting point or focus.
Epicenter

13. The focus is the point inside the earth where the earthquake actually begins

14. Triangulation
The time between the arrival of the P waves and the arrival of the S waves is called lag time.
This tells scientists how far the waves have traveled.

15. Three seismometer stations send their info to each other.
The point where all the circles touch is the epicenter.
This process is called triangulation.

16. What’s the process called?

17. Earthquake Magnitude
The amount of ground motion is measured by the waves it produces by seismograms.
Magnitude is the measure of an earthquake’s strength.

18. Richter Scale The Richter scale measures the ground motion
The Richter scale goes from 0 (weak) to 9 (strong)
The increase of one number means there has been a 10 times increase from the last number
So a number 3 earthquake is ten times as strong as a number 2

19. Richter Scale

20. Moment Magnitude Scale
Richter scales aren’t used anymore
What do you think is used? Right---the Moment Magnitude Scale (bet your parents still think it’s the Richter—ask them!)
Moment Magnitude scale represents a bunch of stuff

21. How much area of the fault moves
The average distance the fault blocks move
And the rigidity of the rocks in the fault zone

22. Earthquake Intensity
This measures the effects of an earthquake at Earth’s surface—what we see after it is over.
The Modified Mercalli scale describes this intensity from 1 – 12 (I-XII)
Level 1 is barely noticeable
Level 12 is total destruction.
Usually the closer you are to the epicenter, the greater the damage

23. What’s the scale called?

25. Measuring Earthquake Intensity
Scientists get data from past earthquakes
This data (info) is used to estimate how much the ground may shake during a future earthquake.

26. The Effects of Earthquakes4

27. Four factors affect the intensity of an earthquake
Size of the earthquake
Distance from the epicenter
Local geology---solid rock doesn’t increase intensity, but loose soil surrounded by water can intensify the ground’s shaking. This is called liquification.
Earthquake-resistant construction: wood and steel are flexible---brick and concrete are not and will break easily

28. These are in countries that do not have good building codes: Mexico, China, thePhillipines, and India

29. Summary – p. 243
________ is a point on the surface directly above where an earthquake_______.
The distance from a seismometer to an epicenter can be determined by using the ___ -____ between P and S waves.
An earthquake’s epicenter can be located by__________>
________ is a measure of an earthquake’s strength.
________ is the effects of an earthquake.
The 4 factors that determine the effects of an earthquake are: magnitude,_____. Local geology, and ________.

30. Answers Epicenter……started Lag time triangulation Magnitude Intensity
Distance from the epicenter…..local construction