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1、Earthquakes,The rupture and sudden movement of rocks along a fault.,6.1 Earthquakes and Plate Boundaries,A fault is a fracture surface along which rocks can slip. Majority of earthquakes occur in Earths crust. Part of the energy released from earthquakes spreads as complex waves.,Elastic Strain Ener

2、gy,Elastic strain is the energy stored as a material changes in shape.,6.1 Earthquakes and Plate Boundaries,When rocks can no longer change shapethe fault breaks and slips, causing earthquakes.,Elastic Strain Energy (cont.),6.1 Earthquakes and Plate Boundaries,Focus,The focus is the location on the

3、fault where an earthquake begins.,6.1 Earthquakes and Plate Boundaries,The closer the focus is to the surface, the stronger the shaking will be.,Epicenter,The point on Earths surface directly above the earthquakes focus.,6.2 Earthquakes and Seismic Waves,Fault Zones,Plate boundaries are usually made

4、 of multiple faults called zones that are 40200 km wide.,6.1 Earthquakes and Plate Boundaries,Plate Boundaries and Earthquakes,Lithospheric plates interact at different plate boundaries and produce earthquakes.,6.1 Earthquakes and Plate Boundaries,Earthquake size and depth and fault type depend on t

5、he type of plate boundary.,Plate Boundaries and Earthquakes (cont.),6.1 Earthquakes and Plate Boundaries,Earthquakes Away from Plate Boundaries,6.1 Earthquakes and Plate Boundaries,Earthquakes Away from Plate Boundaries (cont.),6.1 Earthquakes and Plate Boundaries,New Madris Earthquakes of 1911,Mill

6、ions of years ago, a long zone of intense faulting was formed when the crust began to pull apart, but did not break completely. Today, the crust is being compressed, or squeezed together. (p. 246),,Lesson 1 Review,Strike-slip faults occur at what type of plate boundary? Aconvergent plate boundary Bt

7、ransform plate boundary Cdivergent plate boundary Dsubduction plate boundary,6.1 Earthquakes and Plate Boundaries,,Lesson 1 Review,The focus of an earthquake is ____. Awhere an earthquake is first felt on the surface of Earth Bwhere an earthquake dissipates Cwhere the fault and a plate meet Dwhere a

8、n earthquake begins,6.1 Earthquakes and Plate Boundaries,,Lesson 1 Review,Which boundary is associated with earthquakes that occur at relatively shallow depths and are small in size? Adivergent plate boundary Bconvergent plate boundary Ctransform plate boundary Dsubduction plate boundary,6.1 Earthqu

9、akes and Plate Boundaries,seismic wave epicenter primary wave secondary wave,6.2 Earthquakes and Seismic Waves,Seismic Wave,Waves move outwardfrom the focus in alldirections. 3 main types of seismic waves.,Waves of energy that are produced at the focus of an earthquake.,6.2 Earthquakes and Seismic W

10、aves,1. Primary Waves (P-waves),6.2 Earthquakes and Seismic Waves,2. Secondary Waves (S-waves),6.2 Earthquakes and Seismic Waves,3. Surface Waves,6.2 Earthquakes and Seismic Waves,Earthquake (p.252),6.1 Earthquakes and Plate Boundaries,,Lesson 2 Review,Surface waves cause rock particles to move with

11、 a(n) _____. Aside-to-side motion Brolling motion Cup-and-down and side-to-side motion Dside-to-side and rolling motion,6.2 Earthquakes and Seismic Waves,,Lesson 2 Review,What is a characteristic of P-waves? AThey cause rock particles to vibrate perpendicular to the direction that waves travel. BThe

12、y cause rock particles to vibrate in the same direction that waves travel. CThey only travel through solids. DThey are the slowest seismic wave.,6.2 Earthquakes and Seismic Waves,,Lesson 2 Review,Which type of wave causes the most destruction at Earths surface? AP-wave BS-wave Csurface wave Dcombina

13、tion of P-wave and surface wave,6.2 Earthquakes and Seismic Waves,6.3Measuring Earthquakes,seismograph seismogram,Measuring Earthquakes,Scientists determine size of earthquakes by measuring how much the rock slips along the fault.,They also analyze the heights of the seismic waves, which indicate ho

14、w much energy is released by an earthquake.,6.3 Measuring Earthquakes,Seismograph,Records size, direction, and the movement time of ground,6.3 Measuring Earthquakes,Records the arrival times of the P- and S-waves,Seismogram,Record of the seismic waves,6.3 Measuring Earthquakes,Used to calculate the

15、size and locations of earthquakes,Reading a Seismogram,Wave heights indicate the amount of ground motion for each type of wave.,Difference between the arrival times of P-waves and S-waves determines the distance of the seismograph from the epicenter. (p.260),6.3 Measuring Earthquakes,Locating an Epi

16、center,Triangulation is used to locate the epicenter.,This method is based on the speeds of the seismic waves. At least three seismographs must record the distances.,6.3 Measuring Earthquakes,1. Find the arrival time differences.,6.3 Measuring Earthquakes,2. Find the difference from the epicenter.,6

17、.3 Measuring Earthquakes,3. Plot the distance on a map. (p. 263),6.3 Measuring Earthquakes,Measuring Earthquake Size,Magnitude measures the amount of energy released by an earthquake.,Determined by the buildup of elastic strain energy in the crust, at place where rupture occurs Magnitude scale is ba

18、sed on record of height of ground motion and ranges from 09. Richter Magnitude Scale,6.3 Measuring Earthquakes,Moment Magnitude Scale,Used today because it is a more accurate scale for measuring earthquake size.,Based on the amount of energy released during an earthquake.,6.3 Measuring Earthquakes,E

19、arthquake Intensity,Intensity values vary and depend on the distance from the epicenter and the local geology.,6.3 Measuring Earthquakes,Usually, the maximum intensity is found near the epicenter. (p. 264),,Lesson 3 Review,What information should be known in order to determine the epicenter? Aarriva

20、l time of P-waves and surface waves at two seismograph stations Barrival time of P- and S-waves at two seismograph stations Carrival time of P- and S-waves at three seismograph stations Darrival time of P-waves and surface waves at three seismograph stations,6.3 Measuring Earthquakes,,Lesson 3 Revie

21、w,Triangulation is used to determine an earthquakes ____. AP-waves BS-waves Cepicenter Dmagnitude,6.3 Measuring Earthquakes,,Lesson 3 Review,What two factors influence intensity values? Apopulation and distance from the epicenter Bdistance from the epicenter and distance from the ocean Cpopulation a

22、nd local geology Dlocal geology and distance from the epicenter,6.3 Measuring Earthquakes,Predicting Earthquakes,At this time, geologists cannot predict earthquakes. Geologists can, however, determine the seismic risk by locating active faults and where past earthquakes have occurred. Geologists create seismic risk maps. (p.274),6.3 Measuring Earthquakes,Avoiding Earthquake Hazards,6.4 Earthquake Hazards and Safety,End of Resources,