Definition and History
Seismology is the branch of Geophysics which studies the land tremors and Earth's inner structures, using the seismic waves generated by earthquakes (natural sources) and explosions (artificial sources).
Seismology
Over the ages, many people have made use of legends to explain the violent earthquakes which periodically devastated the regions where they lived.
The Hindu mythology imagined the Earth to be supported by eight powerful elephants and explained the seismic shock as being a consequence of the movement which they produced. The ancient Japanese believed that the earthquakes were caused by Namazu, a gigantic mythical fish that lived in the mud below the Earth's surface.
Biblical reports as the fall of Jericho Walls, about 1100 B.C, or the destruction of the cities of Sodom and Gomorrah could have been, in fact, associated to the occurrence of earthquakes in those places.
The Chinese had an important role in the history of seismology: they were the first ones to elaborate a seismic catalog and to construct a device to detect earthquakes. The description of the most important earthquakes occurred in China and dates from 3000 years ago, and the professor Cheng Heng (Historical Personages) built his seismoscope in 132 a.D.
At the end of the 19th century, seismographs with a greater level of sensitivity and trustworthiness began to appear, making the implementation of a great number of stations all around the world possible. It was in 04/18/1889, for the first time, that a distant earthquake was registered. It occurred in Japan and was recorded by the Postdam Observatory, in Germany.
In the 60's, Seismology enjoyed a new wave of progress with the implantation, by the United States, of a large worldwide seismographic network called World-Wide Standardized Network (WWSSN). Early in the following decade, there were 120 of these stations scattered around 60 countries. In Brasília, the station number 61 was constructed in 1972. In spite of WWSSN's having been implemented for the sake, in part, of military purposes (detection of nuclear explosions carried out by the old Soviet Union), it has brought remarkable advances for the Geosciences, Seismology especially. This network of standardized seismographs, with extensive geographic distribution and high detectability, has allowed for more accurate calculations of the seismic parameters, something fundamental for the establishment of the Plate Tectonics' Theory.