Seismic site response in the Netherlands: impact of the shallow subsurface composition on earthquake ground motion amplification

Local subsurface compositions can strongly influence the level of amplification of ground motion at the surface during an earthquake. Especially near surface low-velocity sediments overlying stiffer seismic bedrock modify earthquake ground motions in terms of amplitudes and frequency content, the so-called site-response. In the densely populated Netherlands, earthquake site-response is of great concern because it can lead to amplified surface shaking, resulting in significant damage on structures despite the small magnitude earthquakes.

This thesis defines relationships between the subsurface lithological composition and the amplitude of ground shaking. For the Groningen region, we show that the earthquake amplification factors match the vibrations of the background noise, which can therefore be used as a first proxy for site response. This approach is further expanded by using seismic records throughout the Netherlands. Due to the presence of a detailed shallow geological model, an approach is presented to predict earthquake amplification at any location in the Netherlands with sufficient lithologic information. With this resulting site-response zonation map, we can obtain constraints on the seismic hazard and site-response in areas that have limited data availability but have potential risk of seismicity, for example at sites with mining, storage or geothermal activities.