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Earth Systems 3209

Earth Systems 3209. Reference: Chapters 4, 15, 16, 19; Appendix A & B. Unit: 4 The Forces Within Earth. Unit 4: Topic 4.1. Terminology Associated with Seismic Activity. Focus on . . .

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Earth Systems 3209

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  1. Earth Systems 3209 Reference: Chapters 4, 15, 16, 19; Appendix A & B Unit: 4The Forces Within Earth

  2. Unit 4: Topic 4.1 Terminology Associated with Seismic Activity Focus on . . . • defining the following terms; seismology, earthquake, seismic wave, foreshock, aftershock, seismograph, seismogram, focus and epicentre.

  3. Terminology Associated with Earthquakes • When an earthquake occurs, the elastic energy is released and sends out vibrations that travelthroughout the Earth. These vibrations are called seismic waves. The study of how seismicwaves behave within Earth is called seismology. • Earthquake - is the vibration of Earth produced by the sudden, rapid release of energy. Usually along faults. • Main causes of earthquakes include: • Moving magma • Elastic rebound • Movement along faults

  4. Foreshock and Aftershock • Foreshock • a minor earthquake preceding a greater one which originate at or near the same location. • Aftershock • small earthquake or tremor that follows a major earthquake.

  5. Earth’sSurface Fault Plane Earthquake Focus and Epicenter • A fault is the plane or zone of fracture separating two blocks that are abruptly displaced during an earthquake. • The focus is the point at depth, usually in a fault zone, where the displacement and sudden release of elastic energy originates. It marks the initial release of energy associated with the earthquake. • The epicenter is the point on the surface directly above the focus. Epicenter Focus

  6. Seismograph and Seismogram • Earthquakes generate seismic waves which can be detected with a sensitive instrument called a seismograph. • How a seismograph works: • Free weight is freely suspended from a support that is attached to bedrock. • When earthquake occurs, inertia keeps the weight motionless while rock and supports vibrate.

  7. Seismograph and Seismogram • A seismogram is a graph output by a seismograph. It is a record of the ground motion at a measuring station. • Used to locate the epicenter of an earthquake. • These paper records are important when seismologist wants to locate the position of the epicenter of an earthquake. • P-waves, S-waves, and Surface waves are all recorded on the seismogram as seen below:

  8. Example 1: Which branch of Earth Sciences would study the properties of earthquake waves? (A) geomorphology (B) meteorology (C) seismology (D) volcanology

  9. Example 2: In the diagram below, where is the epicentre of the earthquake located? A B C (D) D

  10. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Question: Which of the following instruments can help locate how far away an earthquake occurred? (A) seismograph (C) tilt meter (B) magnometer (D) seismogram Which is the point of origin of an earthquake? (A) epicentre (C) epicycle (B) fault (D) focus

  11. Solutions . . . Question: Which of the following instruments can help locate how far away an earthquake occurred? (A) seismograph (C) tilt meter (B) magnometer (D) seismogram Which is the point of origin of an earthquake? (A) epicentre (C) epicycle (B) fault (D) focus

  12. Summary . . . Overview of Points covered: • Common terminology include; • Seismology • Earthquake • Seismograph • Seismogram • Focus • Epicenter • Foreshock • Aftershock

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