Seismology
Seismology (from the
Greek seismos = earthquake and
logos = word) is the scientific study of
earthquakes and the movement of waves through the
Earth. The field also includes studies of variants such as
seaquakes, as well as causes such as
volcanoes and
tectonic plates. A related field is
paleoseismology.
Earthquakes, and other earth movements, produce different types of
seismic waves. These waves travel through rock, and provide an effective way to "see" events and structures deep in the Earth.
One of the earliest important discoveries was that the
outer core of the Earth is
liquid.
Pressure waves pass through the core.
Transverse or
shear waves that shake side-to-side require rigid material so they do not pass through the core.
Seismic waves produced by
explosions have been used to map
salt domes and other
petroleum-bearing
rocks,
geological faults, rock types, and long-buried giant
meteor craters. For example, the
Chicxulub impactor, which is believed to have killed the
dinosaurs, was localized to Central America by analyzing ejecta in the cretaceous boundary, and then physically proven to exist using seismic maps from
oil exploration.
Using
seismic tomography with earthquake waves, the interior of the Earth has been completely mapped to a resolution of several hundred kilometers. This process has enabled scientists to identify convection cells,
mantle plumes and other large features of the inner Earth.
Seismographs also effectively discover unusual, otherwise unobserved phenomena such as large meteors striking uninhabited ocean, or underground nuclear tests. Ocean meteor strikes as large as ten kilotons of TNT, (equivalent to about 4.2 × 10
13 J of effective explosive force) have been reported.
One of the first attempts at the scientific study of earthquakes followed the
1755 Lisbon earthquake.
:''Main article:
Earthquake predictionMost seismologists do not believe that a system to provide timely warnings for individual earthquakes has yet been developed, and some believe that such a system would be effectively impossible. More general forecasts, however, are routinely used to establish seismic hazard. Such forecasts estimate the probability of an earthquake of a particular size affecting a particular location within a particular time span.
Various attempts have been made by seismologists and others to create effective systems for precise earthquake predictions, including the
VAN method. Such methods have yet to be generally accepted in the seismology community.
*
Gutenberg, Beno*
Kanamori, Hiroo*
Lehmann, Inge*
Mercalli, Giuseppe*
Milne, John*
Mohorovičić, Andrija*
Oldham, Richard Dixon*
Sebastião de Melo, Marquis of Pombal*
Richter, Charles Francis*
Papazachos, Vassilis*
Varotsos, Panayotis*
Catastrophe modeling*
Earthquake*
Geophysics*
Plate tectonics*
Reflection seismology*
Seismometer*
Volcanology*
The IRIS Consortium
