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It should be noted that the classification degrees used in Petermann's preliminary
map are slightly different from those applied in the final macroseismic map. The
zones of different tone of color in Fig. 6 are defined as follows:
Zone 1
...
of the strongest movements, where whole buildings, churches, etc.
collapsed. It is denoted by the darkest tone of brown
Zone 2
...
where large parts of buildings were damaged
Zone 3
...
where shaking caused small damage but in general the earthquake
appeared as strong
Zone 4
...
where individual small damage to buildings was mentioned
Zone 5
...
where tremors were undoubtedly felt. It is denoted by the palest tone
of brown.
A comparison of the macroseismic classification at the corresponding sites in both
maps is given in Kozak and Vanek (2006). The highest degrees of both scales were
defined by construction damage, while only limits of the smallest effects considered
human responses. Both scales were fully based on classification of damage to con-
structions, and no ground effects were taken into consideration, even though rock
falls and ground fractures and cracks occurred in the region (Fig. 4).
Despite these weak spots, both the preliminary Petermann map and the enhanced
map of Volger's intensity classifications can be seen as an important step forward,
namely a more detailed damage-to-construction-classification, which became even
more important in later macroseismic scales. The distortion of the damage scale
appeared partly due to Volger's possible overestimation of many reports coming
from the densely inhabited regions of Baden, Zurich and Winterthur, where the level
of damage reports did not correspond to actual degree of damage in this area; Volger
apparently attributed his earthquake-effect class 3 (instead of class 4) to numerous
such localities. It should be taken into account that a more detailed definition of
Volger's categories - in general - was not possible due to his neglect of different
types of construction, considered in later macroseismic intensity scales (Kozak and
Va n ek 2006).
6Impacts
It is now very interesting to follow the thread of the impact and reception of
Volger's ideas and inputs. Four years after the issue of Volger's monograph, Robert
Mallet, a practical engineer, presented a coherent system of macroseismic earth-
quake investigation of the December 16, 1857, Basilicata (central Italy) earthquake
(Mallet 1862). No direct evidence has been found that Mallet knew and made use
of Volger's construction of isoseismal lines; however, Mallet - in 1862 - evidently
used almost identical methods for the construction of isoseismals, as Volger did four
years earlier.
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