This document provides an overview of topics in seismology, including measuring earthquake faults, fault parameters, focal mechanisms, and waveform modeling. It discusses different types of faults like normal faults, reverse faults, and strike-slip faults. It also covers plotting fault planes based on strike and dip, determining fault types from beach ball representations, and using waveform modeling to better resolve earthquake source parameters and focal mechanisms when first motion data is insufficient.

1. Solid Earth Geophysics Ali Oncel [email_address] Department of Earth Sciences KFUPM Today’s class: Seismology Measuring the Interior Reading: Fowler Chapter 4

2. Earthquake Faults PP. 215-17 of Stein and Wysession, 2003

3. Earthquake Fault Parameters PP. 218 of Stein and Wysession, 2003

4. Directivity of Slip Motion PP. 219 of Stein and Wysession, 2003

5. Earthquake Focal Mechanisms PP. 226 of Stein and Wysession, 2003

9. what type of earthquake along what fault orientation is this? Ambiguity: • which is fault plane ? • which is auxiliary plane ? can be either: • right-lateral on EW fault • left-lateral on NS fault 2 Minutes

10. Thrust faults (b): focal mechanism same for both use geological setting to determine most reasonable shaded: compressional (a): W dipping fault (c): E dipping fault also Anderson’s theory : thrusts dip < 45° http://www.seismo.unr.edu/ftp/pub/louie/class/plate/seismology.html

11. Normal faults shaded: compressional (a): W dipping fault (c): E dipping fault (b): focal mechanism same for both use geological setting to determine most reasonable

12. Beach Ball Representation of Typical Faults Fig. 4.2.14 of Stein and Wysession, 2003 Bolt, 1978

13. 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?

14. Fournier and Petit, 2007, JSG www.lgs.jussieu.fr/tectonique/tectonique2/vie_du_labo/pdf/oblique_rifting_JSG_ 2007 .pdf

15. World Stress Map Different colors correspond to different methods of measurement maximum horizontal stress

16. Plotting Planes -1: Strike & Dip Fig. 4.2.10 of Stein and Wysession, 2003

17. To plot a plane striking N45E and dipping 60E, rotate the stereonet (or tracing paper above it) so that the strike is at the top and the dip can be measured along the equator. After plotting the appropriate meridian, rotate the net back to the geographic orientation with north at the top. Plotting Planes : Strike & Dip Strike = N45°E, Dip = 60°, Rake = 70° Fig. 4.2.11 of Stein and Wysession, 2003

18. WAVEFORM MODELING S&W 4.3-11