1.Intro to geology 2.Plate tectonics 3.Minerals 4.Rocks 5.Igneous rocks 6.Volcanism 7.Weathering & erosion 8.Sediments and Sedimentary rocks 9.Metamorphic rocks 10.Rock record and Geologic time 11.Rock deformation 19. Earthquakes 20. Evolution of continents 21. Exploring Earth’s Interior 17. Earth beneath the ocean, shorelines 12. Mass wasting 13. Hydrologic cycle and Groundwater 14. Streams 15. Deserts & winds 16. Glaciers, Ice Ages 18. Landscapes 22. Energy and Mineral Resources 23. Earth’s environment, Global Change, Human Impacts Where are we? Dynamic motions External factors Resources

CHAPTER 19 Earthquakes 1)Some recent Earthquakes 2)What is an Earthquake 3)Seismology 4)Locating an Earthquake 5)Earthquake intensity and magnitude 6)Earthquake and plate tectonics 7)Earthquake destruction

Earthquakes : Study questions  Know the definition of an earthquake and how it is related to fault movement  Foreshocks, aftershocks, elastic rebound  What is the difference between earthquake focus and epicenter?  Know the three different kinds of seismic waves, and their characteristic motion, and properties of propagation.  How is an earthquake epicenter located?  Earthquake depth and how they are related to different kinds of plate boundaries and increasing distance from a subduction zone.  Know the Richter magnitude scale and what each unit means with respect to increase in wave amplitude and energy.  Which factors contribute to the destruction caused by earthquakes?

2) What is an earthquake? Earthquake Earthquake – vibration of earth, often caused by slippage along a fault Earthquake focus - fault slip location Fault - crack in Earth where slip occurs Epicenter – point on earth’s surface directly above focus From: Tarbuck/Lutgens: Earth

Fault definition: a fracture where displacement has occurred: rocks on either side of fault have moved relative to each other. Remember from Ch. 11: Rock deformation

2) What is an earthquake? elastic rebound - plates are continually moving & fault is stuck - crust starts deforming (stores elastic energy) - fault breaks, releases elastic energy, rock “snaps back” fault Fig

2) What is an earthquake? aftershocks small earthquakes that follow an initial earthquake in same vicinity foreshocks small earthquakes that sometimes precede a large one by few days See Fig. 19.3

3) Seismology seismology - the study of earthquake “waves”, earthquakes, Earth ancient Chinese seismograph instrument to record seismic waves seismic waves seismogram - recording of ground shaking from seismographs

3) Seismology Types of seismic waves “body waves” P-waves (“P” for primary) S-waves (“S” for secondary) Expansion/compression: push/pull motion Shear: side-to-side motion “surface waves” travel on Earth’s surface travel in Earth’s interior Figure Story 19.5

3) Seismology Types of seismic waves S-wave Surface-wave Motion produced by the different wave types P-wave

4) Locating an earthquake P-waves & S-wave travel at different speeds 1. Measure time between P and S wave on seismogram 2. Use travel-time graph to get distance to epicenter 3. Draw circle on a map with radius of that distance 4. Three or more circles should intersect at EQ! Recipe: fastest

4) Locating an earthquake 1. Measure time between P and S wave on seismogram 2. Use travel-time graph to get distance to epicenter 3. Draw circle on a map with radius of that distance 4. Three or more circles should intersect at EQ! See Fig. 9.16

5) Earthquake Intensity and magnitude l Richter Magnitude l Moment Magnitude  Richter magnitude - concept introduced by Charles Richter in 1935  Amplitude of the largest seismic wave recorded (P, S, or surface) and distance  Note: Logarithmic scale  Related to physical properties of faulting  Proportional to seismic energy released  Proportional to area of fault break Fig. 19.7

5) Earthquake Intensity and magnitude l Large Earthquakes occur less frequently than smaller ones! Fig. 19.8

5) Earthquake Intensity and magnitude

6) Earthquake and plate tectonics l recall: fault types (from Ch. 11) See Fig

See Fig and Shallow: Normal faulting, transform faulting, thrust (=reverse) fault Intermediate+ Deep: subduction zones 6) Earthquake and plate tectonics

7) Earthquake destruction l important factors: Intensity & duration of shaking Soil type (soft? hard rock?) Building design l other effects: LiquifactionTsunamis

7) Earthquake destruction l important factors: Intensity & duration of shaking Soil type (soft? hard rock?) Building design l other effects: LiquifactionTsunamis Seismic hazard map (see Fig )

7) Earthquake destruction l important factors: Intensity & duration of shaking Soil type (soft? hard rock?) Building design l other effects: LiquifactionTsunamis Fig

Earthquakes : A few sample MC What does the elastic rebound theory describe? A. the build-up and release of stress during an earthquake B. the fluctuations in groundwater prior to an earthquake C. the formation of mountain ranges by successive earthquakes D. the uplift of the crust in response to erosion

Earthquakes : A few sample MC What causes the up-and-down wiggles on the seismogram? A. electromagnetic pulses B. ground vibrations C. tsunami waves D. variations in air pressure

Earthquakes : A few sample MC Which of the following correctly lists the order in which seismic waves arrive at a seismograph station? A. P waves  surface waves  S waves B. P waves  S waves  surface waves C. S waves  P waves  surface waves D. surface waves  P waves  S waves

Earthquakes : A few sample MC An earthquake’s Richter magnitude is based on ______. A. the amount of energy released during an earthquake B. the amount of ground movement caused by seismic waves C. the distance between the earthquake and the seismograph station D. the observed effects on people and structures

Earthquakes : A few sample MC The ground motion during a Richter magnitude 8 earthquake is ______ times greater than the ground motion during a Richter magnitude 6 earthquake. A. 2 B. 10 C. 100 D. 1000

Earthquakes : A few sample MC How many seismograph stations are needed to locate the epicenter of an earthquake? A. 1 B. 2 C. 3 D. 4

Earthquakes : A few sample MC Shallow earthquakes, less than 20 km deep, are associated with ___________. A. convergent plate boundaries B. divergent plate boundaries C. transform plate boundaries D. all of the above