Lesson 1: Geological Faults

• • crack in the Earth's crust that allows blocks of rock to move relative to each other
• Introduction

  • fractures in the Earth's crust where rocks have dipped past each other
  • due to tectonic forces and can occur at various angles and directions of slip
  • studying faults helps us understand seismic activities, predict earthquakes, and explore natural resources
• Normal Faults

  • occur when the crust is extended and one block of rock drops down relative to the other
  • characterized by a steeply inclined fault angle (<45 degrees)
  • typically form in regions experiencing tensional stress (divergent)
• Reverse Faults

  • occur where two blocks of the Earth's crust are pushed together
  • typically form in regions experiencing compressional stress (convergent)
  • inclined more than 45 degrees
• Strike-slip Faults

  • characterized by horizontal movement along the fault line
  • form due to shear stress
  • typically vertical or near-vertical
  • either right-lateral (dextral) or left-lateral (sinistral)
• High-angle Faults

  • greater than 45 degrees - steep inclined angle
  • normal or reverse faults
• Low-angle Faults

  • less than 45 degrees
  • thrust faults
  • also have steep but in the opposite slip direction
• Horizontal

  • occurs parallel to the Earth's surface
  • classifies strike-slip faults
• Vertical

  • occurs perpendicular to the Earth's surface
  • classifies normal and reverse faults