IASPEI Newsletter Feb-Mar2007
Feb-Mar 2007
Visit the IASPEI Web-page: www.iaspei.org
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CONTENTS:
1. IUGG General Assembly in Perugia (Italy) 2007
2. Andrija Mohorovičić (1857–1936) was born 150 years ago
3. International Working Group on Rotational Seismology (IWGoRS)
established
4. News in short
5. Post-doc grants and job opportunities
6. Forthcoming meetings
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. . . . . . . . . .
2. Andrija Mohorovičić (1857–1936) was born 150 years ago
Andrija Mohorovičić, geophysicist of the world
renown and one of the greatest Croatian scientists of all times, was born 150
years ago, on 23 January 1857 in Volosko near Rijeka, Croatia. In 1875 he
enrolled into the Prague University to study mathematics and physics. After
graduation, he taught at high schools in Zagreb and Osijek, and on the Nautical
School in Bakar. In the year 1892 he became director of the Meteorological
Observatory in Zagreb. The following year Mohorovičić obtained the doctorate of
philosophy at the Zagreb University, where he was later elected a titular
associate university professor to teach courses on geophysics and astronomy. He
became the corresponding member of the Academy in 1893, and the full member in
1898. Mohorovičić retired in 1922.
In the beginning of his career, Mohorovičić is engaged in meteorology. His
scientific interests lay in the explanation of various meteorological phenomena
– atmospheric dynamics and observations of rare events (tornado near Novska,
whirlwind near Čazma). He also studied the climate of Zagreb, and the decay of
temperature with height. Without having proper instruments, he builds his own
nephoscope, a camera obscura-like instrument for observation of clouds.
These observations formed the basis for his dissertation. As only recently re-discovered,
Mohorovičić was probably the first to describe atmospheric rotors with the
horizontal axis, which he observed during bora-wind episodes at the northern
Adriatic. Although the paper about it appeared in 1889 in one of the leading
meteorological journals of the time, and was immediately translated into English,
it somehow disappeared from the lists of references in the 1930-ies. The
following citation of his, from 1901, is perhaps the best to illustrate how
clear his visions are: “...The ultimate goal of a meteorologist is to set up
a system of differential equations of the movements of the air, and to obtain as
an integral the general atmospheric circulation, and as particular integrals the
cyclones, anticyclones, tornados, and thunderstorms...”. A perfect
description of today’s weather forecast, at the very beginning of the 20th
century it was even beyond science fiction... Mohorovičić is also recognized for
the unification of the meteorological service in Croatia and Slavonia, and was
the first in Croatia to publish weather forecasts in daily papers.
About the turn of the centuries Mohorovičić's scientific interest turned almost
exclusively to seismology. The reason for this dramatic change is not known –
one can only speculate that intense seismic activity around the Croatian capital
in the late 19th century ignited the spark in his curious mind. The formal
background was also set, as an Earthquake Committee of the Academy was
established in 1880 when Zagreb was devastated by a large earthquake, and
Mohorovičić later became actively involved. He founded the Zagreb seismological
station in 1906, when he installed the Vicentini-Konkoly seismograph in the
basement of the Meteorological Observatory (and on the seismogram number 9 he
recorded the great San Francisco earthquake!). Soon he realized that better
instruments are needed, and purchased the Wiechert horizontal seismographs of 80
and 1000 kg, which became operational in 1908 and 1909. And in his words:
“... with this we are on the level with all the better observatories in Central
Europe...”. The meticulous analyses of recordings of the Kupa Valley
earthquake of 8 October 1909 made by these instruments, together with
seismograms collected from all over Europe, enabled him to prove the existence
of the crust-mantle boundary, which later became known as the Mohorovičić
discontinuity. This unveiling of one of the big secrets of the Earth’s interior
places him among the founding fathers of the modern seismology. It was in line
with how he saw the essence of this young scientific discipline: “... The
goal of seismology is to study the interior of the Earth, and to continue where
the geologist stops, and it has in modern seismographs a sort of binoculars that
enables us to look into the largest of depths...”. This discovery,
recognized as one of the milestones of science in the beginning of the 20th
century, is also the most important scientific contribution ever published in a
Croatian journal. There are also other, less known achievements of his – let’s
only briefly mention his exponential law of velocity increase with depth, an
elegant method of location of epicentres (Mohorovičić’s epicentrals), a method
to determine total friction in mechanical seismographs, a novel seismograph
design (unfortunately never realized), etc. Mohorovičić was also among
the first to recognize the importance of seismic resistant design of buildings.
Indeed, in a series of lectures in the Croatian Society of Engineers and
Architects, as early as 1909 he attempts to “... explain how the Earth
trembles, and how these tremors affect buildings, and draw attention to some
principles that both architects and building contractors should follow...”.
Furthermore: “... In order to study earthquake effects on buildings, we must
first accurately represent the shaking of soil beneath the building, as well as
the forces the shaking exerts, and then we must study how these forces affect
the building as a whole and its individual parts...”. He goes on to analyze
the effects of building resonance, and computes accelerations for various ratios
of the period of dominant shaking and the building eigen-period. Quite ahead of
his time, he sets some of the basic principles of earthquake resistant design,
and warns against erecting heavy buildings on soft and steep slopes, suggests
firm joints between basic building skeleton, the beams and the walls, etc.
He was also the first one to statistically compute expected exposure of
buildings in Zagreb to earthquakes, and tries to persuades entrepreneurs
“...to consider the earthquake hazard and spend more, in order to make buildings
more resistant and safe...”.
Andrija Mohorovičić was a very careful, pedantic and diligent scientist, who
enjoyed to search for explanations of observations in theory, but never favoured
theory over observations. A true erudite, he spoke – besides his mother tongue –
also English, German, Italian and French (in addition to Latin and Greek). He
published about 40 papers, of which he was always the only author. This speaks
not of his vanity, but rather of hard conditions he had to work in, resulting in
a persistent shortage of co-workers. His thoughts and ideas were truly visionary,
often decades before his time (harvesting the wind energy, hail suppression,
Earth and atmosphere models, deep earthquakes, earthquake-resistant design...).
In 1970 one of the craters on the dark side of the Moon was named after him, as
was the asteroid No. 8422 in 1996. Since recently, the crust-mantle boundary on
the Moon as well as on the Mars is also called the Mohorovičić discontinuity.
Andrija Mohorovičić, as only very few Croatian scientists of the international
reputation ever, made his whole career in his homeland, where he is recognized
as the founder of the Zagreb seismological school, the Croatian seismological
and meteorological surveys, and of the public time service. Owing to the
tradition he initiated, University of Zagreb is among the few in the world
awarding a degree in seismology on the undergraduate level. Croatian scientific
community will mark this anniversary by a series of lectures and articles during
the whole 2007, and a postage stamp dedicated to him will be issued in April.
His bust will be erected in front of his house in Volosko. The main event will
be an international meeting with invited speakers (in Zagreb and Opatija,
October 2007) dedicated to Mohorovičić’s scientific legacy and to development of
geophysics since his times.
Marijan Herak and Davorka Herak
Andrija Mohorovičić Geophysical Institute
Department of Geophysics, Faculty of Science
University of Zagreb
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