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has been estimated as 6
(Alexandre et al ., 2008 ) . The heavy damage caused by the two
recent M4.6 and 5.3 earthquakes in Liege (Belgium) on 8 November 1983 and in Roermond
(the Netherlands) on 13 April 1992 (De Becker, 1985 ; Plumier et al ., 2005 ; Berz, 1994 )
enhances the need to quantify the possible consequences of the seismic activity in this part
of Europe as the basis for earthquake mitigation strategies and policies of prevention.
An optimum dataset to evaluate the impact of an earthquake would be that for which
specific damage is reported and described for each of the damaged buildings. In Western
Europe, such detailed information has only been collected by the Belgian Federal Calamity
Centre for the localities affected by the destructive earthquake that occurred in Liege
(Belgium) on 8 November 1983. A sufficient dataset should include quantitative damage
information that would allow accurate intensity values to be assigned. Even for recent
earthquakes this kind of data is not necessarily available, resulting sometimes in bad
intensity evaluation.
During the past ten years we have significantly improved our knowledge of the impact of
some damaging past earthquakes in Western Europe by enlarging the historical data archive
and developing the methodologies to identify earthquake traces in historical buildings. In
this chapter, we present and discuss this methodological framework and the impact of
seismic activity on the region from the Lower Rhine area to southern England based
on damage information gathered for seven typical past destructive earthquakes. We also
examine the influence of the sedimentary cover on the intensity of the damage caused by
these earthquakes in the northern part of the study area.
¼
8.2 Seismic activity between the Lower Rhine Embayment and the North Sea
The study area is the most seismically active region of Western and Central Europe to the
north of the Alps ( Figure 8.1 ) . An important part of this activity is concentrated in the
Roer Valley graben, part of the Lower Rhine Embayment that crosses the border region
between Belgium, Germany, and the Netherlands (Hinzen and Oemisch, 2001 ; Camelbeeck
et al ., 2007 ) . Seven earthquakes with M
5.0 have occurred there since 1350, the most
significant had a magnitude M
and affected the region of Duren in Germany on
18 February 1756. More recent strong earthquakes occurred on 14 March 1951, near
Euskirchen in Germany (M
5
¾
=
5.3) and on 13 April 1992 in Roermond, the Netherlands
(M
5.3). Ahorner ( 1975 ) provided a comprehensive seismotectonic study establishing
the relationship between this seismic activity and normal faults in the Roer Valley graben
offsetting Quaternary deposits up to 175 m. Paleoseismic investigations (Camelbeeck and
Meghraoui, 1996 , 1998 ; Vanneste et al ., 1999 , 2001; Meghraoui et al ., 2000 ; Vanneste and
Verbeeck, 2001 ) suggest that coseismic surface ruptures have occurred during earthquakes
with magnitude in the range 6.0-7.0 during the Holocene and late Pleistocene. A synthesis
of these results is given in Camelbeeck et al . ( 2007 ) .
To the west of the graben, seismic activity is also well established in the north of the
Belgian Ardenne and in the Eifel Mountains in Germany. The most significant event of the
whole study region is the M
=
earthquake that occurred in this zone on 18 September
1692, near the city of Verviers (Alexandre et al ., 2008 ) . At the northern limit of the Ardenne,
=
6
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