Seismology

Seismology ( /saɪzˈmɒlədʒi/; from Ancient Greek σεισμός (seismós) meaning 'earthquake' and -λογία (-logía) meaning 'study of') is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic, atmospheric, and artificial processes such as explosions. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of earth motion as a function of time is called a seismogram. A seismologist is a scientist who does research in seismology. Seismology ( /saɪzˈmɒlədʒi/; from Ancient Greek σεισμός (seismós) meaning 'earthquake' and -λογία (-logía) meaning 'study of') is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic, atmospheric, and artificial processes such as explosions. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of earth motion as a function of time is called a seismogram. A seismologist is a scientist who does research in seismology. Scholarly interest in earthquakes can be traced back to antiquity. Early speculations on the natural causes of earthquakes were included in the writings of Thales of Miletus (c. 585 BCE), Anaximenes of Miletus (c. 550 BCE), Aristotle (c. 340 BCE) and Zhang Heng (132 CE). In 132 CE, Zhang Heng of China's Han dynasty designed the first known seismoscope. In the 17th century, Athanasius Kircher argued that earthquakes were caused by the movement of fire within a system of channels inside the Earth. Martin Lister (1638 to 1712) and Nicolas Lemery (1645 to 1715) proposed that earthquakes were caused by chemical explosions within the earth. The Lisbon earthquake of 1755, coinciding with the general flowering of science in Europe, set in motion intensified scientific attempts to understand the behaviour and causation of earthquakes. The earliest responses include work by John Bevis (1757) and John Michell (1761). Michell determined that earthquakes originate within the Earth and were waves of movement caused by 'shifting masses of rock miles below the surface'. From 1857, Robert Mallet laid the foundation of instrumental seismology and carried out seismological experiments using explosives. He is also responsible for coining the word 'seismology'. In 1897, Emil Wiechert's theoretical calculations led him to conclude that the Earth's interior consists of a mantle of silicates, surrounding a core of iron. In 1906 Richard Dixon Oldham identified the separate arrival of P-waves, S-waves and surface waves on seismograms and found the first clear evidence that the Earth has a central core. In 1910, after studying the April 1906 San Francisco earthquake, Harry Fielding Reid put forward the 'elastic rebound theory' which remains the foundation for modern tectonic studies. The development of this theory depended on the considerable progress of earlier independent streams of work on the behaviour of elastic materials and in mathematics.