January 23, 1857: Andrija Mohorovi?i? is born
Andrija Mohorovi?i? (1857-1936)
Scientific activity: Meteorology, Seismology
Known for: Mohorovi?i? discontinuity
Croatian meteorologist and geophysicist who discovered the boundary between the Earth’s crust and mantle - a boundary subsequently named the Mohorovi?i? discontinuity.
As early as 1908 Mohorovi?i? had succeeded in acquiring new and improved seismographic equipment for the Zagreb observatory, making it one of the most advanced in Europe, and on October 8 of the following year the station recorded a destructive earthquake in the Kulpa Valley. From these readings and those of other stations, Mohorovi?i? observed that certain seismic waves arrived at detecting stations sooner than anticipated, and he deduced that the earthquake was centred in an outer layer of Earth - since called its crust - and that the fast waves had traveled through an inner layer - the mantle. Between them lay what was later named the Mohorovi?i? discontinuity.
Much later observations by more sophisticated instruments confirmed his discovery. Often referred to as simply the Moho, this crust - mantle interface lies at a depth of about 35 km on continents and about 7 km beneath the oceanic crust. Modern instruments have determined that seismic-wave velocity rapidly increases to more than 8 km per second at this boundary.
Mohorovi?i? later discovered a technique for locating earthquake epicentres and calculated the travel time of seismic waves. He was an early advocate of earthquake-resistant construction.
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Article: “Mohorovi?i?, Andrija”. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD
Picture: Andrija Mohorovi?i?. Reproduced from Croatian Academy of Sciences and Arts website.
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