Seismic monitoring network for induced seismicity in the Netherlands

The seismic monitoring network in the Netherlands consists of a dense network of shallow borehole arrays (200 m depth) and surface accelerometers in the Groningen region and a sparser network in the rest of the country. The dense network in Groningen is targeted at induced seismicity due to gas extraction. Other sources of induced seismicity include mining activities like salt mining, subsurface gas storage and geothermal energy. The Dutch ambitions for geothermal energy are high. Hundreds of systems need to be installed in the coming decades. Monitoring of potential induced seismicity is one of the risk measures. The monitoring network is currently being assessed for detection of induced seismicity for a magnitude of completeness of ML = 1.5. This threshold is met for a large part of the country, except for the middle and southwestern part. The network will be upgraded to fill the gaps. The densification of the network allows for lower uncertainty in hypocenter determination. In order to achieve this, a detailed 3D nationwide seismic velocity model and new location methods will be developed and applied. In addition, the borehole vertical arrays will be used more effectively in the seismic analysis.