ÖNCEL AKADEMİ: INTRODUCTION TO SEISMOLOGY

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Fault Mechanism

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ÖNCEL AKADEMİ: INTRODUCTION TO SEISMOLOGY

  1. 1. Department of Earth Sciences KFUPM Introduction to Seismology Fault Mechanism Introduction to Seismology-KFUPM Ali Oncel [email_address] http://www.learninggeoscience.net/free/00071/index.html
  2. 2. Previous Lecture <ul><li>Faulting Stresses </li></ul><ul><li>Radiation Patterns </li></ul><ul><li>First Motions and Azimuth </li></ul><ul><li>Compiling Data: Example from 2004 Sumatra Earthquake </li></ul><ul><li>What types of Earthquake Software for solutions of Focal Mechanisms? </li></ul><ul><li>What are the sources of Seismic Data? </li></ul><ul><li>Downloading Seismological Data: Example from IRISH Channel </li></ul><ul><li>Problem in Defining Fault Strike </li></ul><ul><li>What is the Focal Sphere and how it is projected? </li></ul><ul><li>Fault-Plane Solution derived Cross sections of Dip-Slip Faults </li></ul>Introduction to Seismology-KFUPM
  3. 3. What type of faulting? A normal faulting mechanism. Which plane do you think is the fault plane ? A reverse faulting mechanism. Which plane do you think is the fault plane ? Strike-slip faulting. Which strike? Introduction to Seismology-KFUPM
  4. 4. Introduction to Seismology-KFUPM
  5. 5. Introduction to Seismology-KFUPM
  6. 6. <ul><li>Select your area by cursor </li></ul><ul><li>Then, click on button “ submit ” </li></ul><ul><li>Then, click on “ Show Data Set ” </li></ul><ul><li>From Geophysics, select “ CMT Focal Mechanism ” </li></ul><ul><li>Then, Click on “ Submit Data Set ” </li></ul>Select your data of Focal Mechanism via the Interactive Database Introduction to Seismology-KFUPM
  7. 7. Focal Mechanism Map Introduction to Seismology-KFUPM
  8. 8. Now, you can download the map under different options. JPG is easy to download but *.PS is good if making up for picture is needed. Introduction to Seismology-KFUPM Now, just click on the option “JPG” and see the map of focal mechanisms.
  9. 9. Introduction to Seismology-KFUPM
  10. 10. What is CMT? Introduction to Seismology-KFUPM
  11. 11. Homework due March, 28 <ul><li>Through the Interactive Data Module which is explained so far </li></ul><ul><li>http://atlas.geo.cornell.edu/ima.html </li></ul><ul><li>Prepare the focal mechanism map of the area for your term project as file *.jpg, send it to me via e-mail due next lecture. Also, try to provide a discussion about one paragraph on types of the faulting deformation through the region. </li></ul>Introduction to Seismology-KFUPM
  12. 12. Plate Zones <ul><li>Shallow earthquakes at divergent and transform </li></ul><ul><li>boundaries are present; </li></ul><ul><li>b) Shallow, intermediate, and deep earthquakes occur where plates converge. </li></ul>Introduction to Seismology-KFUPM
  13. 13. Large Earthquakes (5 yr) The boundaries of plates are evident from the pattern of earthquake activity. Introduction to Seismology-KFUPM
  14. 14. Active vs. Passive Continental Margins Earthquakes lie mostly along the boundaries of moving plates. Introduction to Seismology-KFUPM Parks and Plates ©2005 Robert J. Lillie
  15. 15. Active vs. Passive Continental Margins Introduction to Seismology-KFUPM The nearest plate boundary to the U. S. East Coast is the Mid-Atlantic Ridge. Parks and Plates ©2005 Robert J. Lillie
  16. 16. Marshak, EARTH (Norton, 2005) Active vs. Passive Continental Margins Parks and Plates ©2005 Robert J. Lillie The U. S. West Coast lies along a convergent plate boundary , and is thus an ACTIVE CONTINENTAL MARGIN . Introduction to Seismology-KFUPM
  17. 17. Active vs. Passive Continental Margins The U. S. East Coast is far from a plate boundary , and is thus a PASSIVE CONTINENTAL MARGIN . Parks and Plates ©2005 Robert J. Lillie Introduction to Seismology-KFUPM Marshak, EARTH (Norton, 2005)
  18. 18. Axis of the oceanic ridge is offset by transform (strike-slip) faults which produce lateral displacement. Ridges and rifts indicate movement . Earthquakes at Mid-Ocean Ridge System Introduction to Seismology-KFUPM
  19. 19. Transcurrent Fault Model <ul><li>Strike-lip earthquakes occur between the ridges and on the fracture zones extending beyond the ridge </li></ul><ul><li>No earthquakes occur on the ridge axes </li></ul><ul><li>For the specific example, earthquake on the transcurrent fault have right-lateral </li></ul>Introduction to Seismology-KFUPM
  20. 20. Transform Fault Model <ul><li>Strike-slip earthquakes occur only between the ridge segments; not on the fracture zones beyond the ridge segments; </li></ul><ul><li>Normal fault earthquakes occur on the ridges axes; </li></ul><ul><li>For the specific example, the strike-slip earthquakes on the transform fault have left-lateral motions. </li></ul>Introduction to Seismology-KFUPM
  21. 21. Introduction to Seismology-KFUPM Fig 7.22 of Lillie
  22. 22. Introduction to Seismology-KFUPM
  23. 23. Introduction to Seismology-KFUPM
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  25. 25. Introduction to Seismology-KFUPM
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  27. 27. Introduction to Seismology-KFUPM

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