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ABSTRACT: Andrija Mohorovičić was a prominent Croatian scientist in the field of seismology and meteorology at the end of the nineteenth and in the early twentieth century. He was born on 23 January 1857 in Volosko near Opatija, and died on 18 December 1936. Mohorovičić was at first active as the meteorologist, but at the turn of the centuries his scientific interest turns exclusively to seismology. He initiated the scientific study of earthquakes in Croatia, and equipped the Zagreb observatory with the best instruments (Wiechert seismographs) of his time. Studying the seismograms of the earthquake that occurred on 8 October 1909 in the Pokupsko region (Croatia), Mohorovičić was able to prove the existence of the boundary layer – Mohorovičić discontinuity – between the Earth's crust and the mantle, thus establishing himself as one of the greatest and most renowned scientists of all times. His studies of the Pokupsko earthquake also yielded the procedure of unique location of earthquake focus and the analytical expression for the increase of elastic wave velocity with depth (Mohorovičić's law). Based on theoretical considerations, Mohorovičić also predicted the shape of deep-focus earthquakes. Mohorovičić's other contributions are also important (Mohorovičić's epicentrals, Mohorovičić's seismograph, Mohorovičić's travel-time curves (hodochrones)). He worked actively until the late 1920-ies.

Andrija Mohorovičić was a prominent Croatian scientist in the field of seismology and meteorology at the end of the nineteenth and in the early twentieth century.
He was born on 23 January 1857 in Volosko near Opatija, where he attended the elementary school. He continued the education in the grammar school in Rijeka. By the age of 15 he spoke fluent Italian, English and French, followed by German, Czech, Latin and ancient Greek. In 1875 he enrolled in the department of mathematics and physics at the Faculty of Philosophy in Prague. After graduating, Mohorovičić was appointed teacher at the grammar school in Zagreb (1879–1880) and then in the secondary school in Osijek. On 1 November 1882 he began to teach at the Nautical School in Bakar, where he remained for 9 years. In 1883 he married Silvija Vernić, who gave birth to three sons. In 1891 he was transferred to the secondary school in Zagreb at his own request, and on 1 January 1892 became the director of the Meteorological Observatory. In 1893 Andrija Mohorovičić was awarded the doctorate of philosophy at the Zagreb University. Soon afterwards he was habilitated as the private docent, and in 1910 became the 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. As early as 1893 he had become an associate member, and in 1898 a full member of the Yugoslav Academy of Sciences and Arts in Zagreb. At the end of 1921 he retired. He died on 18 December 1936 and was buried at the Mirogoj Cemetery in Zagreb.
The period spent at 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.
After becoming the head of the Meteorological Observatory in Zagreb (1892) he gave a scientific interpretation of some meteorological phenomena. In 1901 Mohorovičić was appointed head of the complete meteorological service of Croatia and Slavonia, which he raised to a European level in personnel and equipment. Gradually, he extended the activities of the observatory to other fields of geophysics: seismology, geomagnetism and gravity.
In March 1892 Mohorovičić began the astronomical observation of stars passing through the local meridian to establish the accurate time. At the beginning of April 1893 he founded a network of stations for thunderstorm observation, and in 1899 he set-up hail-defense stations in the Jaska District. A. Mohorovičić also showed interest in extraordinary meteorological phenomena like the tornado near Novska in 1892, and the whirlwind near Čazma in 1898. He studied the climate in Zagreb, and in his last paper in meteorology (1901) he discussed the decrease in atmospheric temperature with height.
After the turn of the century Mohorovičić's scientific interest focused exclusively on the problems of seismology. The Wiechert seismographs installed at the Zagreb observatory by him in 1908 and 1909 soon became his chief scientific concern. He did not have long to wait for the seismographs to record two strong events – the Messina earthquake of 20 December 1908, and the Pokupsko (Kupa Valley) one of 8 October 1909. Mohorovičić was engrossed by both events. Extensive destruction in Messina prompted him to theoretical consideration of buildings' behavior during earthquakes. Analyzing the seismograms of the Pokupsko earthquake, he advanced insight into the spreading of elastic seismic waves through the Earth's interior. In these studies he was the first to establish the existence of the surface of velocity discontinuity that separates the crust of the Earth from the mantle and which was named the Mohorovičić Discontinuity in his honor. Soon afterwards, scientists confirmed the existence of this discontinuity under all the continents and oceans. His studies of the Pokupsko earthquake also yielded the procedure of unique location of earthquake focus and the analytical expression for the increase of elastic wave velocity with depth (Mohorovičić's law). Based on theoretical considerations, Mohorovičić also predicted the shape of deep-focus earthquakes, which was confirmed by Wadati in 1928. Mohorovičić's other contributions are also important (Mohorovičić's epicentrals, Mohorovičić's seismograph, Mohorovičić's travel-time curves (hodochrones)).
Many of the Mohorovičić's thoughts and ideas were truly visionary. 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 19 December 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. Doctor Mohorovičić raised the meteorological observatory in Zagreb from modest beginnings to a completely equipped modern institute that enjoyed world renown, especially in seismic measurements. He also organized the meteorological service in Croatia and Slavonia. At the beginning of his scientific career Doctor Mohorovičić devoted most of his energy to meteorology, but he had most success in the field of seismology and he founded the so-called Zagreb School of world recognition in this field of science."

Most important papers by Andrija Mohorovičić:
 

• Mohorovičić A. (1908): Epicenters of earthquakes in Croatia and Slavonia (Epicentra potresa u Hrvatskoj i Slavoniji). Godišnje izvješće Zagrebačkog meteorološkog opservatorija za godinu 1906. Part IV. Introduction (Uvod) 15-19. In Croatian.
• Mohorovičić A. (1910): Earthquake of 8 October 1909 (Potres od 8. X 1909; Das Beben vom 8. X. 1909.). Yearly report of the Zagreb meteorological observatory for the year 1909 (Godišnje izvješće zagrebačkog meteorološkog opservatorija za godinu 1909), Zagreb, 63 pp. Reprint edition: Školska knjiga, Zagreb, 1977 (in Croatian and German); English translation : Geofizika, 9, 3-55 (1992).
• Mohorovičić A. (1911): The effects of earthquakes on buildings (Djelovanje potresa na zgrade). Vijesti hrv. društva inž. i arh., Zagreb (in Croatian).
• Mohorovičić A. (1913): Developments in seismology in the last fifty years (Razvoj seizmologije posljednjih pedeset godina). Ljetopis JAZU, 27, Zagreb (in Croatian).
• Mohorovičić A. (1914): Hodograph der normalen P-Wellen fur eine mittlere Herdtiefe. Beilage zu den Seismischen Aufzeichnungen. Kr. zem. zavod za meteorologiju i geodinamiku, Zagreb. Litographed.
• Mohorovičić A. (1915): Hodograph of the first longitudinal earthquake waves (emersio undarum primarum) (Hodograf prvih longitudinalnih valova potresa (emersio undarum primarum)). Rad JAZU 204,1-20.
• Mohorovičić A. (1914); Hodograph der ersten longitudinalen Wellen eines Bebens (emersio undarum primarum). Bulletin des travaux de 1'Academie Yougoslave des Sciences et des Beaux-arts, Classe des sciences mathematiques et naturelles 2,139-157.
• Mohorovičić A. (1915): New phases in the onset of an earthquake (Nove faze u slici početka potresa). Rad JAZU 208, 89-109.
• Mohorovičić A. (1915): Neue Phasen im Anfange des Bildes eines Bebens. Bulletin des travaux de 1'Academie Yougoslave des Sciences et des Beaux-arts, Classe des sciences mathématiques et naturelles 4, 65-86.
• Mohorovičić A. (1915): Zu dem mittelitalienischen Beben vom 13. Jänner 1915. 2. Beilage zu den Seismischen Aufzeichnungen. Kr. zem. zavod za meteorologiju i geodinamiku, Zagreb, 5 pp. Litographed.
• Mohorovičić A. (1915): Zur Frage der Emergenzgeschwindigkeit. 1. Beilage zu den Seismischen Aufzeichnungen. Kr. zem. zavod za meteorologiju i geodinamiku, Zagreb, 4 pp. Litographed.
• Mohorovičić A. (1916): Die Bestimmung des Epizentrums eines Nahbebens. Gerlands Beitrage zur Geophysik 14,199-205.
• Mohorovičić A. (1916): Vorlaufige Mitteilung uber das Beben vom 12. III. 1916. Berichte uber seismische Aufzeichnungen. Kr. zem. zavod za meteorologiju i geodinamiku, Zagreb. No pagination
• Mohorovičić A. (1917): Principles and construction of a seismograph, and a proposal for construction of a new seismograph for recording of horizontal component of ground motion (Principi konstrukcije sismografa i prijedlog za konstrukciju nova sismografa za horizontalne komponente gibanja zemlje). Rad JAZU 217, 114-150 (in Croatian).
• Mohorovičić A. (1918): Prinzipien fur die Konstruktion eines neuen Seismographen. Bulletin des travaux de 1'Academie Yougoslave des Sciences et des Beaux-arts, Classe des sciences mathematiques et naturelles 9/10, 6-20.
• Mohorovičić A., Mohorovičić S. (1922): Hodographs of the longitudinal and transversal earthquake waves (undae primae et undae secundae) (Hodografi longitudinalnih i transversalnih valova potresa (undae primae et undae secundae)). Part 1. Hodographs. Written by A. Mohorovičić. Rad JAZU 226, 94-190 (in Croatian).
• Mohorovičić A. (1923): Hodographen der longitudinalen und transversalen Wellen eines Bebens (undae primae et undae secundae). 1. Hodographen. Bulletin des travaux de 1'Académie Yougoslave des Sciences et des Beaux-arts, Classe des sciences mathematiques et naturelles 15/18, 1-16.
• Mohorovičić A. (1924): A critical review of the seismic instruments used today and of the organisation of seismic service. Bulletin of Seismological Society of America I, 38-59.
• Mohorovičić A. (1925): Hodographes des ondes normales P et S soulignees (Pn, P*, S*) et des deux premieres reflexions pour les profondeurs de 1'hypocentre de 0, 25, 45, 57 kms. UGGI, Section de Seismologie, A. Travaux Scientifique 3, Paris,1-60.
• Mohorovičić A. (1926): Zur Frage der wahren Empfindlichkeit eines Seismographen. Gerlands Beitrage zur Geophysik 15, 201-214.