A brief history of seismology History – continued History-continued History – continued

A brief history of seismology History - continued History-continued History - continued www.phwiki.com

A brief history of seismology History – continued History-continued History – continued

Komando, Kim, Host;Producer has reference to this Academic Journal, PHwiki organized this Journal A brief history of seismology Early 1800’s – theoretical development of elastic wave propagation (Cauchy, Poisson, Stokes, Rayleigh, etc)– knew about body waves in addition to surface waves long be as long as e observed 1857 Mallett, Naples – concept that earthquakes radiate seismic waves (though he assumed that all sources were explosions in addition to only radiated P waves) 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)

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History-continued Recording earthquakes at various ranges led to velocity structure Oldham (1900) identifed P in addition to S in addition to 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

Raypaths as long as P in addition to S demonstrating the core shadow Example of travel time curves

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 as long as 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

Shear velocity – +-1% isovelocity surfaces Includes S in addition to SS cluster analysis data

Seismometers on the moon 1969-1972

Continuously excited oscillations of the sun observed by looking at doppler shift of spectral lines – helioseismology 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)

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

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