Geology 1 MT2: EQs

  1. earthquake
    the sudden slip on a fault (release of elastic energy) and the resulting ground shaking and radiated seismic energy caused by the slip
  2. hypocenter (focus)
    • the first point on a fault that moves in an EQ
    • the EQ originated at the hypocenter
  3. epicenter
    the point on the earth's surface that is directly above the hypocenter
  4. rupture area
    the portion of a fault that slips in an EQ
  5. surface trace
    where the fault breaks the earth's surface
  6. blind fault
    a fault that does not break the earth's surface
  7. elastic rebound theory
    • 1. stresses (force/area) are applied to a fault
    • 2. strain (deformation) accumulates in the vicinity of friction-locked faults
    • 3. strain accumulation reaches a threshold and fault slips suddenly
    • 4. rupture (slip) continues over some portion of the fault
  8. 2 types of seismic waves
    • body waves - move through the earth's interior
    • surface waves - through earth's surface
  9. 2 types of body waves
    • p-wave: (primary wave)
    • the first wave to arrive following an EQ
    • propogate by alternately compressing/expanding material
    • can move through solids, liquids, gases

    • s-wave: (secondary wave)
    • shear wave
    • can only move through solids
  10. 2 types of surface waves
    Love wave: horizontal shearing of the earth's surface

    Rayleigh wave: "rolling" of the earth's surface
  11. calculating the distance to an EQ
    depends on the time gap b/t p-waves and s-wave arrivals (∆ t)

    • ∆ t = ts - tp
    • [ts= s-wave arrival time, tp= p-wave arrival time]

    D= (Vp x Vs) / (Vp - Vs) x ∆ t
  12. what is Richter magnitude based on?
    the amplitude of the largest s-wave
  13. 4 steps to find Richter magnitude:
    • Find distance
    • Measure amplitude and find log
    • Find log A0 from graph
    • Find difference: ML= logA - logA0
  14. A fault that has both horizontal and vertical offset
    oblique fault
  15. Fault that moves without an EQ
    fault creep
Card Set
Geology 1 MT2: EQs
Geology 1 MT2: EQs