Andrija Mohorovic 1857-1936
Andrija Mohorovic was born on 23 January 1857 in Volosko, a coastal Istrian village near Opatija, where his father, also named Andrija, was a blacksmith making anchors. The younger Andrew himself loved the sea and he married a captain's daugher, Silvija Verni. Together, they had four sons. seismologist born in Volosko 1857
Andrija Jr. obtained his elementary education in his home town, continued his study in the gymnasium of a neighboring town, Rijeka, and received his higher education in mathematics and physics at the Faculty of Philosophy in Prague in 1875. There, one of his professors was the famous physicist Ernst Mach. At the age of 15 the junior Mohorovičić knew Italian, English and French and later he learned German, Latin and Ancient Greek.
His career began with a teaching post in the Zagreb gymnasium (1879-1880) and then secondary school in Osijek. On November 1, 1882 he began to teach at the Nautical School in Bakar, near Rijeka, where he remained for nine years. Work in the Nautical School in Bakar was crucial for the beginning of Andrija Mohorovičić's scientific work. This is where he first came into direct contact with meteorology, which he taught at the Nautical School, and which absorbed him to such a degree that he founded a meteorological station in Bakar in 1887.
He started to make systematic observations and measurements, constructing instruments of his own design to measure the horizontal and vertical velocity of the clouds. He was meticulous in his daily work. Much later, in 1907, in his "Instructions for the observation of precipitation in Croatia and Slavonia", he wrote: "Anyone not used to performing his work conscientiously, should not be involved in observing precipitations". He was one of the founding fathers of the Society for Assisting the Poor and Worthy Students of the Royal Nautical School in Bakar.
At his own request in 1891, he was transferred to the secondary school in Zagreb. On January 1, 1892 he became the head of the Meteorological Observatory on Gric in Zagreb, where he continued to work in the meteorological observatory, establishing a service to all of Croatia, all the while simultaneously teaching geophysics and astronomy at the university.
Among the extraordinary meteorological phenomena that he observed was the tornado in Novska on March 31, 1892 that took 13-ton railway carriage with 50 passengers and threw it at a distance of 30 metres. He also observed the vijor (whirlwind) near Bazma in 1898, and studied the climate in Zagreb, and in his last paper in meteorology (1901) discussed the decrease in atmospheric temperature with height.
The accumulated date of his obvservations of clouds represented a basis for his doctoral thesis "On the observation of clouds, and the daily and annual cloud period in Bakar" presented to the University of Zagreb and which gained him his degree as doctor of philosophy in 1893.
In March 1892 Mohorovičić began the astronomical observation of stars passing through the Gric meridian to establish the precise time. At the beginning of April 1893 he established a network of stations for following thunder storms, and in 1899 he founded hail-defence stations in the Jaska District. At the beginning of 1899 he started a project for research into and harnessing of the energy of the bura in the karst region, because "...this would be so beneficial for our barren littoral".
In 1893 he became corresponding member, and in 1898 full member of what was then the Yugoslav Academy of Sciences and Arts in Zagreb. In 1901 he was appointed head of the complete meteorological service of Croatia and Slavonia, which he raised to a European level in personnel and equipment. And finally, he gradually extended the activities of the observatory to other fields of geophysics: seismology, geomagnetism and gravitation, switching his main interest toward seismology. He acquired a few seismographs that were installed before the occurrence on October 8, 1909 of the Pokuplje (Kupa Valley) earthquake with its epicentre 39 km southeast of Zagreb.
Soon after going to Zagreb, he was habilitated as private docent (?), and in 1910 became titular associate university professor. From 1893 to 1917-18 he taught subjects in the fields of geophysics and astronomy at the Faculty of Philosophy in Zagreb.
He advanced insight into the spreading of seismic waves of earthquakes with shallow depths through the Earth. He discovered that when an earthquake occurs two waves, longitudinal and transverse, that propogate through the soil with different velocities. When seismic waves strike, the boundary between different types of material, they are reflected and refracted, just as light is when it strikes a glass block. Their arrival times at the locations of the seismological observatories are registered and following the traditions of seismologists available data are freely distributed to their colleagues. Analyzing the data of seismographs from a dozen stations, Mohorovičić showed that the Earth consists of a surface layer above an internal core.
From the calculations he was able to estimate the thickness of the upper layer as 54 km (nowadays, it is known that it varies between a few kilometers at the bottom of the oceans to about 70 km. under the highest mountains). In these studies he was the first in the world to establish, on the basis of seismic waves, a surface of velocity discontinuity that separates the crust of the Earth from the mantle and which was named the Mohorovičić Discontinuity, also known as the Moho, in his honour.
Mohorovičić discontinuity (the Moho)
The boundary between the crust and the mantle in the earth. This is a depth where seismic waves change velocity and there is also a change in chemical composition. Named after Andrija Mohorovičić, the Istrian seismologist who discovered it. The boundary is between 25 and 60 km deep beneath the continents and between 5 and 8 km deep beneath the ocean floor.
On the heels of Andrija's discovery, scientists confirmed the existence of this discontinuity under all the continents and oceans. Mohorovičić's thoughts and ideas were truly visionary and came to expression many years later (the effects of earthquakes on buildings, harnessing the energy of the bura, models of the Earth, deep-focus earthquakes, hail defence, locating earthquake epicentres, seismographs, etc.).
He retired at the end of 1921, and died on December 18, 1936 and was buried at the Mirogoj Cemetery in Zagreb. The well-known Swedish seismologist M. Bath included Andrija Mohorovičić among the 13 most outstanding seismological researchers in the period from 1900 to 1936.
On December 19, 1936, a day after the death of Andrija Mohorovičić, the Zagreb paper Novosti published the following article: "The scientist Professor Andrija Mohorovičić, member of the Yugoslav Academy of Sciences and Arts, one of the founders of modern seismology, has died. He was a well-known and respected figure in Zagreb, and his scientific work in the field of seismology gained him world recognition. He is today considered one of the founders of modern seismology in the world."
In 1970 a large crater (77 km in diameter) on the far (dark) side of the moon was named in his honour.
•Skoko, Dragutin, "Andrija Mohorovicic", U.S.G.S., v36 (January 2000), p. 1-2.
•University of Zagreb, Department of Geophysics, Faculty of Science - Dragutin Skoko and Marijan Herak, Andrija Mohorovičić
•Norwegian Physical Society - Andrija Mohorovičić
•Earthquake glossary - Moho
•Billich portrait - http://www.Billich.info