Faults and Earthquakes - Earthquake Engineering for Structural Design - page 199

New Madrid
zone
Charleston
Zone
Figure 6.18 Earthquake distribution for Eastern USA (after Hinze et al, 1988)
The average recurrence is an earthquake of 4.7 every 10 years and an earthquake of
5.6 every 100 years (Ukearthquakes, 2008).
Belgium is the territory which provides examples of the high vulnerability of the
stable continental interiors. It demonstrated the necessity to better understanding
the seismic activity and the potential of important earthquakes in the intraplate
areas. The main earthquakes in this area occur in the bordering region between
Belgium, the Netherlands and Germany, often called the “Lower Rhine
Embaymant” (Fig. 6.20). A part of it, the Roer (Rur) rift system appears as the
most active area with several earthquakes with magnitudes larger than M 5.0. In
these areas a series of grabens and rifts exist (Berg, 1994, Schafer and Siehl, 2002,
BGHRC, 2003). The Rhine Valley rift system forms a NW-oriented fault between
the parallel Upper Rhine and Central North Sea grabens. The earthquake
epicenters from 1350 to 2004 in this region, plotted in Figure 6.21, show that many
events exceed magnitude M 5.0; the strongest known seismic event occurred in
1692, being appreciated having a magnitude M 6.3 (Camelbeek, 2005). In the near
region of Liege, the known activity is less important, but the earthquake of 1983,
with a magnitude M 4.7 caused important damage in the city. The recent studies
suggest that the magnitude could approach M 7.0.