Seismology
Scientific study of earthquakes and elastic wave propagation.
Seismology is the scientific study of earthquakes and the generation and propagation of elastic waves through planetary bodies. It also encompasses the environmental effects of earthquakes, such as tsunamis, and other seismic sources including volcanoes, plate tectonics, glaciers, rivers, oceanic microseisms, and the atmosphere, as well as artificial processes like explosions. A related field, paleoseismology, uses geological methods to infer information about past earthquakes. The motion of the Earth recorded over time by a seismograph is known as a seismogram, and a scientist who works in this field is called a seismologist.
Scholarly interest in earthquakes dates back to antiquity, with early naturalistic explanations proposed by thinkers such as Thales of Miletus, Anaximenes of Miletus, and Aristotle. In 132 CE, Zhang Heng of China’s Han dynasty created the first known seismoscope. During the 17th century, Athanasius Kircher theorized that earthquakes resulted from fire moving within subterranean channels, while Martin Lister and Nicolas Lemery attributed them to chemical explosions inside the Earth. The devastating Lisbon earthquake of 1755 spurred intensified scientific investigation, with John Michell later determining that earthquakes originate within the Earth as waves of movement from shifting rock masses. In the 19th century, Robert Mallet laid the foundation for modern instrumental seismology, coining the term “seismology” and conducting experiments using explosives. The first teleseismic earthquake signal was recorded in 1889, and subsequent work by Fusakichi Omori characterized the decay of aftershock frequency. Emil Wiechert’s theoretical calculations in 1897 suggested a silicate mantle surrounding an iron core. In 1906, Richard Dixon Oldham identified distinct P waves, S waves, and surface waves on seismograms, providing clear evidence for a central core. Andrija Mohorovičić later defined the boundary between the crust and mantle, known as the Mohorovičić discontinuity. Harry Fielding Reid’s elastic rebound theory, developed after the 1906 San Francisco earthquake, remains foundational to tectonic studies. Harold Jeffreys concluded in 1926 that the Earth’s core is liquid, and Inge Lehmann determined in 1937 that a solid inner core exists within it. By the 1960s, these advances culminated in the comprehensive theory of plate tectonics. Seismi
- field
- Earth science
- known_for
- Study of earthquakes, seismic waves, and Earth's interior structure
- father_of_modern_seismology
- Robert Mallet (coined the word 'seismology')
Lore & Background
Scholarly interest in earthquakes dates to antiquity, with early naturalistic explanations from Greek philosophers and the Chinese polymath Zhang Heng. In the 17th century, Athanasius Kircher proposed that earthquakes were caused by fire moving within Earth's channels, while Martin Lister and Nicolas Lemery suggested chemical explosions. The 1755 Lisbon earthquake spurred intensified scientific efforts, with John Michell determining that earthquakes originate within the Earth as waves from shifting rock masses miles below the surface. Robert Mallet later laid the foundation of modern instrumental seismology, coining the term "seismology" and conducting experiments with explosives. The field advanced with the first recorded teleseismic earthquake signal in 1889, and Fusakichi Omori demonstrated that aftershock frequency decays following a mainshock. Emil Wiechert's theoretical work concluded Earth's interior has a silicate mantle surrounding an iron core. Richard Dixon Oldham identified separate P waves, S waves, and surface waves on seismograms, providing clear evidence of a central core. Andrija Mohorovičić discovered the boundary between crust and mantle, defined by a distinct change in seismic wave velocity. Harry Fielding Reid developed the elastic rebound theory after studying the 1906 San Francisco earthquake. Inge Lehmann determined that within Earth's liquid outer core lies a solid inner core. By the 1960s, these findings culminated in the well-established theory of plate tectonics. Seismology also studies tsunamis, volcanic activity, glaciers, rivers, oceanic microseisms, and artificial explosions.
Reader's Guide
By the 1960s, Earth science had synthesized a comprehensive theory of seismic causation and geodetic motions into the well-established framework of plate tectonics. Seismic waves, which are elastic waves propagating through solid or fluid materials, are divided into body waves and surface waves. Body waves include primary (P) waves, which are longitudinal and involve compression and expansion, and secondary (S) waves, which are shear waves. Surface waves travel along interfaces, and normal modes represent a form of standing wave. Controlled-source seismology employs explosions or vibrations for underground exploration. The field also studies environmental effects such as tsunamis, as well as seismic sources from volcanoes, plate tectonics, glaciers, rivers, oceanic microseisms, the atmosphere, and artificial processes like explosions. Paleoseismology uses geology to infer information about past earthquakes. A seismogram, created by a seismograph, records Earth’s motion over time. Seismologists work in basic or applied seismology. Notable historical contributions include the identification of P, S, and surface waves on seismograms, which provided clear evidence of Earth’s central core, and the discovery of the Mohorovičić discontinuity, the boundary between crust and mantle defined by changes in seismic wave velocity. The elastic rebound theory, developed after studying the 1906 San Francisco earthquake, remains foundational for tectonic studies.
Did You Know?
- Robert Mallet coined the word 'seismology' and is considered the 'Father of Seismology'.
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