260 events in the Netherlands, Belgium and Germany from 1750 - 2007 are used in this study. The magnitude of the events ranges from 2.5 to 6.0, the depth from 5 - 20 kilometres.

To analyse the influence of the different input parameters and to explore the ranges of the output of the hazard analysis, a logic tree approach is used. The input parameters of this approach are:

• Seismic zonation:
1. Old KNMI 1996 zones
2. Zonation used by Hinzen (Bensberg, GE)
3. Zonation used by Leynaud (Liege, B)
• Attenuation relation:
1. Ambraseys 1996
2. Campbell 1997, 2003
3. Berge-Thierry 2003
4. Dost 2003
• Magnitude-Frequency relation:
1. Same b-value for all sources
2. Difference b-value in and outside Roer Valley Graben
• Maximum magnitude
1. Ml = 6.4
2. Different Ml - Mw conversions
3. Including paleoseismicity: Mw = 6.1-6.6 (vd Berg et al. 2002)

The magnitude of the events in the Netherlands is determined in Ml, but in the hazard analysis Mw will be used. The relation between Ml and Mw for the southern part of the Netherlands is determined based on 20 events for which both Ml and Mw is calculated.

In a simulation of 2000 experiments the a- and b-values and the maximum magnitude were determined. The simulation calculates the best fit of a truncated exponential function to the data. In each experiment the data were randomly perturbed. The outcome shows the distribution of the parameters.

• a = 2.66±0.14
• b = 0.77±0.03
• Mmax = 6.2±0.2

We are aiming at an in-depth variability analysis to determine the hazard uncertainties and the major factors influencing these uncertainties. In addition to updating the hazard map a main goal of this study is to compare our results with the hazard studies done in Belgium and Germany and to achieve a well fitting map at the borders of the countries. This last issue is important for a relevant application of the Eurocode 8 in the border regions. The map shows the seismic hazard in the Netherlands by tectonic earthquakes with a return period of 475 years. This means that in the red areas an intensity VII can be reached ones every 475 years, or with a probability of 10% in 50 years. For the areas with intensity lower than V, there are not enough data to specify in more detail. The hazard due to induced earthquakes in the northern part of the Netherlands is not included in this map. The intensities are according to the European Macroseismic Scale (EMS).

• I - Not felt, even under the most favorable circumstances.
• II - Scarcely felt. Vibration is felt only by individual people at rest in houses, especially on upper floors of buildings.
• III - Weak. The vibration is weak and is felt indoors by a few people. People at rest feel a swaying or light trembling.
• IV - Largely observed. The earthquake is felt indoors by many people, outdoors by very few. A few people are awakened. The level of vibration is not frightening. Windows, doors and dishes rattle. Hanging objects swing.
• V - Strong. The earthquake is felt indoors by most, outdoors by few. Many sleeping people awake. A few run outdoors. Buildings tremble throughout. Hanging objects swing considerably. China and glasses clatter together. The vibration is strong. Topheavy objects topple over. Doors and windows swing open or shut.
• VI - Slightly damaging. Felt by most indoors and by many outdoors. Many people in buildings are frightened and run outdoors. Small objects fall. Slight damage to many ordinary buildings; for example, fine cracks in plaster and small pieces of plaster fall.
• VII - Damaging. Most people are frightened and run outdoors. Furniture is shifted and objects fall from shelves in large numbers. Many ordinary buildings suffer moderate damage: small cracks in walls; partial collapse of chimneys.