Earthquakes occur when the faults suddenly move, or the magma divides into the crust. When earthquakes occur, they send seismic waves through the Earth. The seismographs are the instruments used to record seismic waves. The simplest ones contain a weight and a pen connected to a spring. The seismograph is screwed to the ground, so during an earthquake, it moves with the ground, while the weight and the pen remain practically still, due to inertia. The pen moves through a rotating paper roll that records the seismic waves. This is known as the seismogram and is used to understand earthquakes. Seismologists study this activity.
During an earthquake, seismic waves arrive first at the closest seismograph and later at the farthest. This information is used to locate the earthquake. In this way, through seismology, the tremors produced by the displacements of the lithospheric plates – the rigid outer part of the Earth, consisting of the crust and upper mantle – can be evaluated, and the propagation of the waves can be studied.
Thanks to seismology, earthquakes began to be classified depending on their Intensity, defined on the discrete Mercalli scale, and then on Magnitude by means of the popular Richter scale. There are in many countries worldwide, organizations and institutions that are dedicated to the study of seismology to record all types of information, analyze it, store it, and conduct studies on this type of movement.
History
The seismology goes back to ancient times. The first speculations about earthquakes were made by Thales of Miletus, Aristotle and Zhang Heng who designed the first seismoscope in 132 BC. There were many theories regarding the origin of earthquakes, from the movement of fire within the Earth to a series of explosions inside her. In the year 1761, John Mitchell determined that earthquakes were waves of movement caused by rocks that moved up to thousands of kilometers below the Earth. Robert Mallet, in the year 1857 founded instrumental seismology, and in 1906, Richard Dixon identified and separated P waves and S waves in seismograms. Today, professionals like Giuliano Panza are leading the industry. Panza is a famous seismologist who served as a professor at the University of Trieste, Italy. He is renowned for the many contributions he’s made to the field of seismology and his studies on the interior structure of the Earth. Within the framework of a very large international co-operation, Giuliano Panza has formulated quite a revolutionary model for the lithosphere-asthenosphere system in the European area, which predicts the existence of almost aseismic lithospheric roots. These roots are located in correspondence with most of the orogenic belts, and interrupt the low velocity channel in the asthenosphere (the layer of the Earth’s mantle below the lithosphere in which there is relatively low resistance to plastic flow, and convection is thought to occur), identified for the first time by Beno Gutenberg, in 1948. It is not surprising that Panza received the Beno Gutenberg medal from EGU for his fundamental contributions to the dynamics of the lithosphere-asthenosphere system, the construction of synthetic seismograms, and the statistical aspects of seismicity on a global scale.
What is seismology for?
Seismology helps us to make studies regarding earthquakes that happen on earth. It is a science created to observe the different vibrations that occur naturally in the Earth, and has been useful in understanding how tectonic plates work, the internal structure that the earth possesses, the understanding and the origin of the earthquakes, and the way the Earth releases energy giving rise to seismic hazard. Seismological methods are now used to investigate the interiors of the Moon and Mars as well.
