Lithosphere down to depths ~ 30 kilometers

The shaping of the living surface of the Netherlands is genetically linked to tectonic processes occurring at depths greater than 5-10 km. These processes lead to subsidence and uplift of the surface itself, to the state of stress in the near surface, and to the occurrence of potentially damaging earthquakes and are intimately linked to structures inherited during the earlier geological assembly of the Netherlands lithosphere. Little is known of the actual structure and composition of the crust and upper mantle beneath the Netherlands. A key question for the specific case of the northern part of the Netherlands is:

• Is there a relationship between the faults as observed in the first few kilometers to those in the deeper structure?

Answering this question will be major step forward in the understanding of the physical processes that affect the surface contours of the northern part of the country. So what is needed is denser 3D information of the crust. The permanent areal sensor array of LOFAR may be expected to do this. As sources for seismic waves the small earth tremors induced by the gas extraction can be used. Currently, the KNMI has some stations active in the north, with the aim to locate and characterize the earthquakes. These stations are very sparse and are not aimed at obtaining information of the deeper crust. The LOFAR-project goals are therefore

• Design and construct a seismic network such that 3D information of the deeper subsurface of the North of the Netherlands can be obtained.

Once this network is built, the 3D structure of the North of the Netherlands will be obtained after the deployment of this network