Overview

History of Seismology

• 1800s: Cauchy, Possion, Stokes, Rayleigh and others developed the theory of elastic wave propagation, and described the existence of body wave (compressional and shear wave) and surface wave in solid materials.
• 1857: Robert Mallet described the idea that earthquakes radiate seismic waves away from a hypocenter and that they can be located by projecting these waves backward to the source. His work represented the first significant attempt at observational seismology.
• 1889: First teleseismic observation, made in Potsdam for a Japan event.
• 1898: E. Wiechert introduced the first seismometer with viscous damping, capable of producing useful records for the entire duration of an earthquake.
• 1900s: B. B. Galitzen developed the first electromagnetic seismographs.
• 1900: Richard Oldham reported the identification of P, S, and surface waves on seismograms
• 1906: Richard Oldham detected Earth’s core from the absence of direct P and S arrivals at source–receiver distances beyond about 100°.
• 1909: Andrija Mohorovicic found Moho.
• 1907: the first widely used traveltime tables were produced by Zo ̈ppritz
• 1914: Beno Gutenberg published traveltime tableswith core phases
• 1936: Inge Lehmann discovered the solid inner core
• 1940: Harold Jeffreys and K. E. Bullen published the final version of their travel time tables for a large number of seismic phases, which is called JB table.
• 1946: an underwater nuclear explosion near Bikini Atoll led to the first detailed seismic recordings of a nuclear bomb.
• 1949: a Soviet nuclear bomb.
• 1961: the Worldwide Standardized Seismograph Network (WWSSN) was established

Earth’s structure

• Crust: 6 km under the oceans, 30–50 km beneath continents.
• Mantle: 84% of Earth’s volume and 68% of the mass
• Outer Core
• Inner Core