The impact of the earthquake activity in Western Europe from the historical and architectural heritage records - Intraplate Earthquakes - page 214

Egen, drew up a macroseismic map applying an intensity scale (Gisler et al ., 2008 ) . For
that purpose, Egen used a scale he invented himself (Egen, 1828 ) . We have synthesized and
critically assessed the information provided by this and other contemporaneous scientific
studies and newspapers of the LowCountries. To improve our knowledge of the damage and
earthquake effects in its epicentral area, we also undertook a systematic survey of the official,
private, and religious historical sources of this region. All these original witness accounts,
as well as a description of their historical sources, are available at http://seismologie.be/
cup2014.html .
8.5.6.1 Analysis of historical data
Based on some of the reports about the earthquake, it is possible to classify the effects of the
1828 earthquake as well as to approximate the intensity values on the EMS-98macroseismic
scale for the different affected localities (Grunthal et al ., 1998 ) .
The descriptions of damage indicate that in the epicentral area houses experienced
moderate to extensive damage. For many localities situated in the epicentral area, the
descriptions concentrate on the amount of damage to chimneys or cracks in the walls, and
do not mention the collapse or complete destruction of houses, as was the case, for example,
for the 1692 Verviers earthquake, which happened in the north of the Belgian Ardenne
(Alexandre et al ., 2008 ) , discussed in the next section. This suggests that unreinforced
masonry buildings presenting grades of damage 2 and 3 (moderate to extensive) may have
been widespread in these cities. As already mentioned, Belgian traditional houses of this
epoch were mainly unreinforced masonry buildings, which can be classified as vulnerability
classes ranging from A to B. Hence, if buildings were classified as vulnerability A, the
corresponding intensity should have reached values of VII. On the other hand, if they had
vulnerability B, the intensity could have been one order of magnitude higher (VIII). In either
scenario, few buildings should have presented damage states equal to or greater than 4,
which agrees with the damage observations. Some reports suggest that damage grade 4 could
have been attributed to some of the building stock of Heron, Lens-Saint-Remy, and Petit-
Hallet. In these cases, it would thus be realistic to consider that the affected buildings were
of vulnerability class A; therefore we assessed a maximal intensity of VII in these localities.
In view of the local reports, we have also attributed intensity VII to the following
localities: Berloz, Crehen, Gelinden, Heron, Jauche, Lens-Saint-Remy, Marilles, Petit-
Hallet, Tienen, Waremme, and the nearby villages of Longchamps, Froidebise, andWalquin
( Figure 8.5 a ).
We also associated a possible intensity range of VI-VII with the localities for which at
least one report mentioned that many houses may have lost their chimneys or were cracked
or damaged. This is the case for Andenne and Bilzen. Intensity values of VI-VII have also
been assessed for the village of Grand-Hallet. For this locality, there is no report on the
damage caused by the 1828 earthquake to the houses, but the repair costs of the church are
close to those paid for the church of Berloz, suggesting significant damage.
For other localities situated in the epicentral area of this earthquake or at its periph-
ery, damage is mentioned, but it appears as quantitatively less important. We assessed,
nevertheless, intensity VI for those where a certain number of chimneys collapsed. This