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A brief history of seismology

A brief history of seismology. Early 1800’s – theoretical development of elastic wave propagation (Cauchy, Poisson, Stokes, Rayleigh, etc)– knew about body waves and surface waves long before observed

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A brief history of seismology

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  1. A brief history of seismology • Early 1800’s – 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)

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

  3. 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

  4. Raypaths for P and S demonstrating the core shadow

  5. Example of travel time curves

  6. 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 • 1960’s computers, ISC started in 1964 – vast improvement in location ability – see plate boundaries • 1960 Chile eq (M=9.5) – free oscillations • 1960—1980 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

  7. Shear velocity -- +-1% isovelocity surfaces Includes S and SS cluster analysis data

  8. Seismometers on the moon 1969--1972

  9. Continuously excited oscillations of the sun observed by looking at doppler shift of spectral lines -- helioseismology

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

  11. 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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