Andrija Mohorovicic

Andrija MohorovicicAndrija Mohorovicic was born in 1857 in Volosca and died in 1936. He studied in Prague and later taught for nine years at the Nautical School in Bakar. In 1892 was appointed director of the Meteorological Observatory in Zagreb. After a few years he taught at the University of Zagreb, and towards the end of the 19th century, he was a distinguished member of the Academy of Sciences in Zagreb. At the beginning of his scientific career he devoted much of his energy to meteorology, but had significantly more success in the field of seismology and founded the so-called “School of Zagreb,” which gained worldwide recognition in this field of science.

According to Mohorovicic’s theory, the seismic waves created by earthquakes at shallow depth, spread through the Earth’s interior. With his researches he discovered a discontinuity of speed that separates the crust from the mantle below. Later, scientists confirmed the correctness of Mohorovicic’s theory, and they recognized the existence of this discontinuity in all the continents and oceans. This theory was named, in honour of Mohorovicic, ” the Mohorovicic Discontinuity.”

His theories were later expanded, identifying the epicentres of earthquakes with sophisticated scientific instruments called seismographs. Over time, the abbreviated term “Moho” was used to identify both the Mohorovicic’s name and his theory of discontinuity. Scientists have speculated as the years go by about the composition and the main characteristics of the Earth’s surface. In 1909, Andrija Mohorovicic was able to show that these phenomena were caused by areas of diverse density between the rocks of the crust and the mantle.

Nowadays Andrija Mohorovicic is considered one of the founders of the modern seismology in the world. He also modernized the meteorological observatory in Zagreb making it a modern institution, fully equipped, which now enjoys a worldwide reputation. He also organized a new weather service in Croatia and Slovenia. Thanks to Andrija Mohorovicic, the new seismology employs delicate instruments to measure seismic swarms and the intensity of the shocks.

The experimental discovery that an earthquake could be registered by a delicate pendulum at great distances from the focus marks the first step in the new science. It is undoubtedly to Mohorovicic’s vigorous personality that we owe the application of this fact to the study of earthquakes. Comparative data were thus obtained, and rapidly led to an increased knowledge of the properties of the earth. We must appreciate the important work of Andrija Mohorovicic, because earthquakes do not directly pose danger to people but the effect of ground shaking can be devastating for buildings where people can be crushed and buried under the rubble.

Another major hazard is flooding due to the breaking of dams or levees along a river. If there is an earthquake under the ocean there is the risk of a tsunami or a “seiche,” a small tsunami, that occurs on lakes shaken by the earthquake. Finally there is the high risk of the fire caused by ruptured gas lines or power lines that can spark blazes.

It may really be claimed that during the close of the nineteenth and the beginning of the twentieth century seismologists, among whom the name of Mohorovicic stands pre-eminent, have succeeded in dragging the study of earthquakes from the region of ignorance and superstition and in making it a quantitative science proceeding on the principles of physical philosophy.

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