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Earthquakes

Earthquakes. Earthquakes. Usgs.org. Earthquakes. Usgs.org Question: What is the relationship between Earthquakes and Plate boundaries? Stress ( potential energy ) in lithosphere mainly along plate boundaries, is released in form of energy waves (Kinetic energy).

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Earthquakes

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  1. Earthquakes

  2. Earthquakes • Usgs.org

  3. Earthquakes • Usgs.org • Question: • What is the relationship between Earthquakes and Plate boundaries? • Stress ( potential energy ) in lithosphere mainly along plate boundaries, is released in form of energy waves (Kinetic energy). • Ground vibration = Earthquake • Stress: (pressure) force/area • Tension, Compression, & Shear

  4. Types of Stress & Plate Boundaries • Tension pulled apart • Divergent • Compression push together • Convergent • Shear slide past • Transform

  5. Types of Stress & Plate Boundaries 2 1 O C 3 7 O C 4 O O 1 C O 4 O 3 O C 5 O O 2 6 O A B B subducted under A COMPRESSION SHEAR TENSION

  6. Stress & Strain • Depending on type of material • strength/flexibility of the atomic bonds • objects deform differently in response to stress

  7. Stress & Strain • Strain = Deformation due to stress • All objects go thru 3 stages of deformation Elastic Plastic “Ductile” Failure Temporary Permanent Fracture Fold *Fault Earthquakes

  8. Folding & Faulting • Continued Stress after Failure stage • Movement along Fracture plane = Fault plane

  9. Stress & Strain Lab • Define the following terms. • Stress: ______________________________________________________________ • Strain: ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­______________________________________________________________ • Look at the objects. Do not bend or break any of these objects. • Based on your background knowledge infer the following: • 1. Without experimenting, Name different ways you can change the shape of these objects. • ** • * • * • Making sure not to break the objects, Slowly apply the same amount of stress to each • of your objects. Start with the object that you think is the easiest to bend ( strain ). • Apply stress to it and then apply the same amount of stress to the other objects. • Note how each of these objects responded to stress. • 2. Did all objects bend or bend easily? • 3. Explain why. • Observe what happens to each object after the stress is removed. • 4. Did some return to their original shape? Temporary Deformation ( Elastic strain ) • 5. Did some remained deformed? Permanent Deformation ( Plastic strain ) • Now apply enough stress to break ( Fracture ) each object. • 6. Did all objects break using the same/equal amount of stress? • 7. Explain the reason. • 7. Explain what factor(s) affect the rate in which each object deforms ( strains) ? • * • * • 8. Based on its response to stress, which one of these objects resembles most closely to a rock? • *

  10. Fault Diagram

  11. Fault Diagram Footwall Block Hangingwall Block

  12. Types of Faults • Based on Type of Stress and Block Movements • Types of Faults • Types of Stress • Tension, Compression, & Shear • Types of Block Movement • Vertical Horizontal Combination up or down side to side both (up or down AND side to side)

  13. Types of Faults F H • Normal • Tension Stress • Hangingwall block moves down • Vertical movement • Divergent Boundary • Ex. Mid-Ocean Ridges H Pull Pull

  14. Types of Faults 2 1 O C 3 7 O C 4 O O 1 C O 4 O 3 O C 5 O O 2 6 O Normal A B B subducted under A COMPRESSION SHEAR TENSION

  15. Normal Fault H F

  16. Normal Fault

  17. Types of Faults H • Reverse • Compression • Hangingwall goes up • Vertical movement • Convergent boundary • Ex. Andes mountains F H Push Push

  18. Types of Faults 2 1 O C 3 7 O C 4 O O 1 C O 4 O 3 O C 5 O O 2 6 O REVERSE Normal A B B subducted under A COMPRESSION SHEAR TENSION

  19. Reverse Fault F H

  20. Reverse Fault F H

  21. Reverse Fault F H

  22. Reverse Fault

  23. Types of Faults Side • Strike-Slip/Lateral • Shear • Blocks move side to side • Horizontal Movement • Transform Boundary • Ex. San Andreas fault Side

  24. Types of Faults 2 1 O C 3 7 O C 4 O O 1 C O 4 O 3 O C 5 O O 2 6 O REVERSE STRIKE - SLIP Normal A B B subducted under A COMPRESSION SHEAR TENSION

  25. Types of Faults L • Strike-Slip/Lateral fault • Right Lateral • Left Lateral R

  26. San Andreas Fault • Strike-Slip /Lateral Right Lateral

  27. Strike-Slip Fault Left Lateral Right Lateral

  28. L R L

  29. Types of Faults • Combination/ Oblique-Slip • Shear combined with Compression or Tension • side to side and up or down • Horizontal and Vertical

  30. Fault Block Models Type of Fault Type of Stress Tectonic Boundary Example Location

  31. Types of Faults Review • Based on Type of Stress and Block Movements • Types of Faults • Types of Faults Review

  32. Earthquakes • Continued stress • Build up of ( potential energy) due to frictional lock • Release of energy (kinetic) due to a slippage along the fault plane • Seismic waves travel thru rocks ~ Earthquakes

  33. Earthquakes • Seismic waves • Cause ground vibration = Earthquake

  34. EPICENTER SEISMIC WAVES FOCUS FAULT PLANE

  35. Seismic Waves • Energy released from Focus • Types of Seismic Waves. • Based on Velocity & type of Stress and Strain • 1. Body Waves ~ Travel thru interior of earth • 2. Surface Waves ~ Travel on the surface of crust

  36. Seismic Waves • 1. Body waves ~ Travel thru interior • Primary P-waves • First arrivals 5 -15 Km/s • Compressional waves compression & tension • Solid & Liquid • Secondary S-waves • 4 – 7 Km/s • Shearing waves side to side/up & down • Solids only P- wave P- wave P- wave S- wave S- wave

  37. P-S waves and the Shadow Zone • Indications of a liquid outer core

  38. Seismic Waves • 2. Surface waves ~ Travel on the surface of crust • Last arrivals / L - waves • 6 Km/s • most damaging • Rayleigh waves • retrograde rolling motion • Love waves • Shearing ~ side to side & up and down

  39. Earthquake Measurement • Ancient Chinese Seismograph 132 A.D.

  40. Earthquake Measurement • 1. Mercalli Intensity Scale • Evaluation of intensity/amount of damage • Scale l to XII • least most • Intensity Contour lines • Epicenter Mercalli Lab

  41. Earthquake Measurement • 2. Richter Magnitude Scale • mathematical measurement • amount of energy released/strength • Scale 1 - 10 Magnitude & Frequency • Higher Magnitude • Lower Frequency

  42. Earthquake Search Labs • Virtual Earthquakes

  43. Earthquake Hazards A • Magnitude • Depth of Focus deep vs. shallow • Distance from Epicenter • Location Active plate boundaries B

  44. Earthquake Hazards • Type of Foundation/Ground material • Solid Rock Loose Soil • Less damage More damage

  45. Earthquake Hazards • Liquefaction ~Water saturation of ground material • L2 L3 • Tsunamis ~Seismic sea waves • caused by underwater earthquakes • T1T2T3 • NOAA 2004 Tsunami Simulation • Evidence of ancient Tsunami in Australia originated in Hawaii

  46. Earthquake Hazards • Structural Design ~ Flexible foundation S1

  47. Earthquake Hazards • Population density ~ city vs. rural • Time of event ~ • workday vs. weekend • day or night • Duration of event ~ seconds to minutes • After shocks ~ weaker quakes after the main event • destruction of weakened structures

  48. Seismic Risk Map

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