Earthquakes Glossary

  1. Aftershocks
    The series of smaller earthquakes that follow a major earthquake.
  2. Arrival time
    The instant at which an earthquake wave appears at a seismograph station.
  3. Body waves
    Seismic waves that pass through the interior of the Earth.
  4. Compressional waves
    Waves in which particles of material move back and forth parallel to the direction in which the wave itself moves.
  5. Displacement (or offset)
    The amount of movement or slip across a fault plane.
  6. Earthquake
    A vibration caused by the sudden breaking or frictional sliding of rock in the Earth.
  7. Earthquake engineering
    The design of buildings that can withstand shaking.
  8. Earthquake zoning
    The determination of where land is relatively stable and where it might collapse because of seismicity.
  9. Elastic-rebound theory
    An explanation for how energy is spread during an earthquake. As plates on opposite sides of a fault are subjected to force and shift, they accumulate energy and slowly deform until their internal strength is exceeded. At that time, a sudden movement occurs along the fault, releasing the accumulated energy, and the rocks snap back to their original undeformed shape.
  10. Epicentre
    The point on the surface of the Earth directly above the focus of an Earthquake.
  11. Fault
    A fracture on which one body of rock slides past another.
  12. Fault creep
    Gradual movement along a fault that occurs in the absence of an earthquake.
  13. Fault scarp
    A small step on the ground surface where one side of a fault has moved vertically with respect to the other.
  14. Fault trace (or line)
    The intersection between a fault and the ground surface.
  15. Focus (hypocentre)
    The location where a fault slips during an earthquake.
  16. Foreshocks
    The series of smaller earthquakes that precede a major earthquake.
  17. Induced seismicity
    Seismic events caused by the actions of people (e.g. filling a reservoir that lies over a fault with water).
  18. Intraplate earthquakes
    Earthquakes that occur away from plate boundaries.
  19. L-waves (Love waves)
    Surface seismic waves that cause the ground to ripple back and forth, creating a snake-like movement.
  20. Liquefaction
    The abrupt loss of strength of a wet sediment (either sand or clay) in response to ground shaking.
  21. Mercalli intensity scale
    An earthquake characterisation scale based on the amount of damage that the earthquake causes.
  22. Magnitude
    A number that indicates the relative size of an earthquake, as determined by measuring the maximum amplitude of ground motion recorded by a seismograph.
  23. P-waves
    Compressional seismic waves that move through the body of the Earth.
  24. R-waves (Rayleigh waves)
    Surface seismic waves that cause the ground to ripple up and down, like water waves in a pond.
  25. Recurrence interval
    The average time between successive geologic events.
  26. Resonance
    This occurs when each new wave arrives at just the right time to add more energy to a system.
  27. Richter scale
    A scale that defines earthquakes on the basis of the amplitude of the largest ground motion recorded on a seismogram.
  28. S-waves
    Seismic shear waves that pass through the body of the Earth.
  29. Seiche
    Rhythmic movement in a body of water caused by ground motion.
  30. Seismic belts (zones)
    The relatively narrow strips of crust on Earth under which most earthquakes occur.
  31. Seismic gap
    A potentially dangerous area where a known active fault has not slipped for a long time.
  32. Seismic waves
    Waves of energy emitted at the focus of an earthquake.
  33. Seismogram
    The record of an earthquake produced by a seismograph.
  34. Seismograph (seismometer)
    An instrument that can record the ground motion from an earthquake.
  35. Shear waves
    Seismic waves in which particles of material move back and forth perpendicular to the direction in which the wave itself moves.
  36. Stick-slip behaviour
    Stop-start movement along a fault plane caused by friction, which prevents movement until stress builds up sufficiently.
  37. Surface waves
    Seismic waves that travel along the Earth's surface.
  38. Travel-time curve
    A graph that plots the time since an earthquake began on the vertical axis, and the distance to the epicentre on the horizontal axis.
  39. Tsunami
    A large wave along the sea surface triggered by an earthquake or large submarine slump.
  40. Wadati-Benioff zone
    A sloping band of seismicity defined by intermediate and deep-focus earthquakes that occur in the downgoing slab of a convergent plate boundary.
Card Set
Earthquakes Glossary
Adapted from 'Earth: Portrait of a planet'. Marshak, 2005, W. W. Norton & Company, Inc.