Geoscience Reference
In-Depth Information
In the last quarter of the 19th century reference to earthquake intensity became
widespread. Let us thus focus on a closer geographical circle: Switzerland and Italy.
Francois Alphonse Forel (1841-1912) proposed a ten-degree scale in 1880 (2 years
after the establishment of the Swiss Seismological Commission in 1878) and plotted
an isoseismal map of the earthquake of December 30, 1879 in the Valais. Albert
Heim (1849-1937) was then the first to use it for the interpretation of an earthquake
(Societe helvetique 1880). In 1881 Forel discussed his scale to gain a more ac-
curate and simplified methodological approach when collecting observational data
(Forel 1881). He proposed his scale to evaluate the seismic events in Switzerland
in 1879/1880. He soon became acquainted with the scale suggested by the Italian
Michele Stefano de Rossi. On the invitation of de Rossi, the two seismologists met,
in order to agree on a single scale for earthquakes occurring on both sides of the
Alps (Forel 1880; Davison 1978).
3
In the following years, Forel and others published yearly reports on seismicity in
Switzerland, and larger earthquakes of the respective year. In 1884 Forel discussed
the collaboration with Rossi and published the joint Rossi-Forel-Scale with ten de-
grees of intensity, designed in 1883 and 'bien adaptee par les sismologistes suisses
et italiens [well adapted by the Swiss and Italian seismologists]' (Forel 1885).
4
This
was the first scale to be widely used internationally, whereas a common feature of all
former scales was that none of them was used by anyone but their authors. In fact,
the Rossi-Forel scale was extended to the United States of America, since Edward
3
“Depuis que cette echelle a ete proposee, j'ai re¸u connaissance d'une echelle analogue etablie
deja en 1875 par M. M.-S. de Rossi, de Rome, et adoptee par les sismologues italiens. Devant
lesdroitsdepriorite evidents de M. de Rossi j'aurais immediatement retir´el'echelle que j'avais
etablie, si nous n'avions re¸u de MM. de Rossi et Gatta la proposition d'etudier en commun une
revision de ces echelles d'intensite, en tenant compte de l'experience des annees ecoulees. Nous
avons accepte avec empressement cette offre; mais le travail de revision est assez long, et nous ne
pourrons l'utiliser que pour le rapport de l'annee prochaine. [After this scale has been proposed, I
learned that an analogous scale has been established in 1875 by Mr. M.-S. de Rossi, from Rome;
the scale being used by Italian seismologists already. As Mr. Rossi has the privilege for having
been the first one to establish the scale, I would have immediately withdrawn mine if there were
not Messrs. Rossi and Gatta to offer to work on a common scale, making use of our experiences
of the past years. We have zealously accepted this offer, even though the revision seems to be
extensive, and we thus can only adapt it next year.]” (Forel, 1881). As a matter of fact, Rossi had
composed his first scale in 1873.
4
Comparision of the Forel and the Rossi-Forel scale; I being the lowest, X the highest intensity
(Forel, 1884).
Echelle Forel 1881
Echelle Rossi-Forel 1883
I/II
I
III
II / III
IV
IV
V
V / VI
VI
VII
VII
VIII
VIII / IX
IX
X
X
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