1. Do Now – In Notebooks 1. What is an earthquake? 2. What kind of stress acts on a normal fault? Does the crust lengthen or shorten? 3. What is the difference between the focus and epicenter of an earthquake?

2. Measuring Earthquakes How are earthquakes measured?

3. Seismology  The study of earthquake waves is called Seismology  Earthquake waves can be detected at great distances by Seismometers  A seismometer’s record is known as a Seismogram

5. Time-Travel Curves  Years of data collection has led to time-travel curves  The curves tell the time an S- and P-wave takes to reach a certain distance  P-waves arrive first  The difference between waves on a seismogram determines the distance from the epicenter

6. Time-Travel Curves

7. Locating Earthquakes  Epicenters are located by the separation between S- and P- waves on a seismogram  Cannot use one location to map epicenter  Need to use three or more seismic stations  Time can be measured in same way

8. Magnitude and Intensity  The amount of energy released during an earthquake is known as its magnitude  The amount of damage done by an earthquake is known as intensity  Three scales measuring intensity/magnitude  Richter Scale  Moment Magnitude Scale  Modified Mercalli Scale

9. Do Now – In Notebooks  What is the difference between an earthquake’s magnitude and intensity?  What is the amplitude of a curve?  You will need:  Notebooks  Southern California Earthquake Packet  Pencil  Calculator (See me if you need one)

10. MAGNITUDE AND INTENSITY How are earthquakes measured?

11. Richter Scale - Magnitude  The Richter Scale is based on the largest waves generated by the quake  Each number on the scale is an increase of 10  Ex: 8 is 10x larger than 7, 100x larger than 6

12. Moment Magnitude Scale  The Moment Magnitude Scale includes:  Size of fault rupture  Amount of movement along fault  Rocks’ stiffness  Uses more data than Richter Scale – More accurate

13. Modified Mercalli Scale - Intensity  The Modified Mercalli Scale assesses damage from a quake

14. Factors affecting Intensity  Depth of Focus  Distance from Epicenter