Seismographs%20By%20Danielle%20Stroup

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SeismographsBy Danielle Stroup
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Definition

• Record zigzag trace
• Detect earthquakes all over the globe
• Time, location, and magnitude
• Goal to accurately record motion

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History

• Chinese and Egyptians
• Devices allowed marbles to fall
• 132 AD Chinese scientist Chang Heng invented
  seismoscope
• Invention called a dragon jar

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Seismograph Advances

• Modern seismograph invented in the 1800s
• 1855 Luigi Palmeri of Italy
• Recorded time, intensity, and duration for the
  first time of small earthquakes
• 1880 JA Ewing invents pendulum seismograph
• HO Wood and J Anderson mass suspended by torsion

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Mathematical Theory

• 1841 Earliest mathematical theory by Forbes
• Considered only simple non-oscillatory ground
  displacements
• 1877 Response of a seismograph to arbitrary,
  periodic, ground motion written in Japan had
  little influence on the development of
  seismographs

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Theory

• Tilting was neglected in the early development of
  the seismograph.
• Forced damped harmonic-oscillator seismographs
  were presented by Perry, Ayrton, and Lippmann
• Had little effect on the construction of
  seismographs
• 1890's the importance of tilt was much debated
• 1900 become convinced that the effect of tilting
  could usually be neglected.

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Improvements

• Press-Ewing seismograph
• Records long period waves
• Widely used around the world
• Press-Ewing pendulum seismograph uses the Milne
  pendulum

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Seismographs

• Compact, light weight, battery operated
• Performs self-tests
• Very detailed computer vibration analysis
• Utilized four channels for signals

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Blasting seismograph

• Monitor, record, analyze, display, and print
  ground vibration and airblast
• Measures seismic wave
• Data from blast events represented
• Displayed on a liquid crystal display (LCD)

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Components

• Attached to seismograph to collect data
• Vibration sensor (geophone) three sensors
• Vibration sensor has internal weight that when
  moved, creates a voltage
• Measures absolute velocity
• Microphone to measure airblast

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Data

• Shows peak particle velocity, displacement, and
  the frequency of movement
• Require different standards and limits depend on
  the type of structures
• Technology is increasingly utilized
• Sensors are placed very close to the blast

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Conclusion

• Instruments have been used for over eighteen
  hundred years
• From seismoscopes to seismographs suitable for
  detailed studies of earth motion