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zones. He thus erroneously classified several of the mountain regions (e.g., the zone
westward of the epicenter region between Aosta, Sitten and Zermatt in his map) as
being of low intensity. This flaw might be a result of a lack of experience when de-
signing seismic maps for the Alpine region, where the bulk of population inhabited
the bottoms of mountain valleys.
The second isoseismal map of the 1855 Visp event (Fig. 5), published by Volger
two years later (Volger 1858) seems to be outlined with greatest care and attention.
The author used the detailed data collecting campaign and plotted the isoseismal
lines according to the classification (intensity/damage scale) from 0 (strongest ef-
fects) to 6 (limit of perceptibility). Whereas the first map showed a distinction of
five degrees only, this latter one showed six different intensity degrees. Volger con-
sidered all individual reports - sometimes contradictory for one region - which
resulted in numerous 'islands' of higher intensity in fields of lower ones. Such a
regional exactness in following the reported information for individual localities
(mostly distributed non-regularly in mountain valleys) produced a rather compli-
cated pattern of isoseismal lines, from which the general shape of the shaken region
is difficult to be read. In this respect the simple and more generalized first map by
Petermann (Fig. 6) seems to be more instructive.
The high level of the maps shows that the cartographic representation of the
macroseismic field was undoubtedly proposed and constructed by Petermann. The
mode of expression of the distribution of the macroseismic effects in the maps is
completely different: whereas in the preliminary map (Fig. 6) Petermann applied
five tones of the same color, in the final map (Fig. 5) isolines dividing regions of
different degree of macroseismic effects were used.
Volger defined degrees of his 'intensity scale' in the legend of his macroseismic
map as follows:
(0) in the hatched zone
...
the whole settlements were ruined
(1) in the zone limited by line 1
...
the most important parts of buildings
collapsed
(2) in the zone limited by line 2
...
numerous walls cracked, smaller parts
of buildings collapsed
(3) in the zone limited by line 3
...
chimneys toppled, numerous traces of
minor damage occurred
(4) in the zone limited by line 4
...
tremors to be felt strongly
(5) in the zone limited by line 5
...
ground movements to be observed
(6) entire zone limited by line 6
...
from which observations - of any
kind - were reported.
Even though Volger never used the term 'macroseismic intensity', he obviously
succeeded in creating one of the first applicable macroseismic scales based on the
observation of damage, the behavior of objects and the perception of the people,
i.e. upon principles that are applied in all later intensity scales developed up to the
present (Kozak and Vanek 2006).
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