A brief history of seismology

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A brief history of seismology

• Early 1800s theoretical development of elastic
  wave propagation (Cauchy, Poisson, Stokes,
  Rayleigh, etc) knew about body waves and surface
  waves long before observed
• 1857 Mallett, Naples concept that earthquakes
  radiate seismic waves (though he assumed that all
  sources were explosions and only radiated P waves)

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History -- continued

• First time-recording seismometer (Cecchi, 1875)
• Deployments of seismometers in Japan by Milne et
  al. in 1880s
• First teleseism recorded in 1889
• 1896 first seismometer in US (at Lick
  observatory)
• 1898 first damped seismometer (Wiechert)
• Early 1900s electromagnetic sensing (Galitzin)

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History--continued

• Recording earthquakes at various ranges led to
  velocity structure
• Oldham (1900) identifed P and S and surface waves
• Oldham (1906) identified the core shadow
• Mohorovicic (1909) identified crust-mantle
  boundary
• Travel time tables (Zoppritz 1907, Gutenberg,
  1914 (radius of the core), JB

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Raypaths for P and S demonstrating the core shadow
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Example of travel time curves
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History continued

• 1928 Wadati identifies existence of deep
  earthquakes Wadati-Benioff zones (still not
  understood how deep earthquakes happen)
• Nuclear tests (1946 Bikini atoll, 1949 first
  Russian test) later go underground lots of
  bucks for seismology
• 1961 WWSSN
• 1960s computers, ISC started in 1964 vast
  improvement in location ability see plate
  boundaries
• 1960 Chile eq (M9.5) free oscillations
• 19601980 Geophysical inverse theory developed
  largely to look at Earth structure 1D structure
  including mantle discontinuities firmly
  established.
• 1984 beginning of IRIS easy access to data
• 1990 seismic tomography, imaging the 3D
  structure

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Shear velocity -- -1 isovelocity surfaces
Includes S and SS cluster analysis data
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Seismometers on the moon 1969--1972
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Continuously excited oscillations of the sun
observed by looking at doppler shift of spectral
lines -- helioseismology
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History -- continued

• Reid develops elastic rebound theory after 1906
  earthquake
• 1923 Nakano develops double-couple model of the
  seismic source (controversial until the 60s!)
• 1935 development of Richter magnitude scale
  (better estimate of size is moment developed by
  Aki in 1966)

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Image of slip surface outlines 1300-km-long
earthquake, lasting for about 8 minutes This
could be produced for future events within 20 to
30 minutes of the earthquake start time
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