Tuesday, January 11, 2011

Moho for Mohorovičić discontinuity, named after Yugoslavian/Croatian seismologist A. Mohorovičić

Andrija Mohorovičić was born in 1857 inVolosko, an Istrian village on the Adrian Coast. In 1910 he became a university professor in Zagreb, teaching astronomy and geophysics [1]. By studying the spreading behavior of seismic waves registered during earthquakes, he found a velocity discontinuity for those waves. This discovery lead to the conclusion that a boundary exists inside the earth, which separates the crust from the mantle. The boundary became known as Mohorovičić Discontinuity, or Moho for short.

Here is how L. Don and Florence Leet introduce this discontinuity in my favorite booklet on the early history and science of seismology [2]:

When rocks that transmit earthquake waves at one speed lie on rocks that transmit them at a different speed, the boundary where the rocks meet at is called a “discontinuity.” The boundary discovered by Mohorovicic has been named after him, the Mohorovicic discontinuity.” Since this is quite a mouthful, it is usually referred to simply as the Moho.” The layer above the Moho is called the earth's crust” and the layer below it the earth's mantle.”

Indeed, Mohorovičić is difficult to say, spell and mark up. Moho is a much easier term. Moho also sounds somewhat Hawaiian, underlining its wave and quake association.

: earthquakes, seismology, boundaries within earth, Croatia

References and recommended reading
Andrija MohorovičićProminent Istrians [www.istrianet.org/istria/illustri/mohorovicic]
[2] L. Don and Florence Leet:
EarthquakeDiscoveries in Seismology. Dell Publishing Co., Inc, 750 Third Avenue, New York, N. Y. , 10017, USA, 1964; page 83.

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