Seismic Observatory for Imaging and Monitoring (LOFAR)

Seismic surveying has always been rather expensive. The introduction of a large network of seismic sensors that is part of a wide-area sensor network called LOFAR now makes more cost effective surveying possible. The network will give TU Delft researchers the chance to get images of the subsurface in a completely new way and monitor subsurface changes using time-lapse seismic.



Subsurface images
Over recent years, minor earth tremors and land subsidence have occurred in northern parts of the Netherlands due to gas recovery from the large gas reservoirs present in the area. Better insight into the reasons behind these earth tremors and their relation to gas recovery could help mitigate earth tremors in the future and can be very useful for future exploitation of new gas fields. For this, high quality seismic imaging over long periods is necessary. In order to gain better insight and gather long-term seismic data, researchers at TU Delft have developed a network of underground seismic sensors and a revolutionary method called seismic interferometry. It allows for more cost-effective seismic surveying, as relatively expensive active seismic sensors such as explosions are no longer necessary. In addition, it will help get a better understanding of the deep subsurface. The setting for this new network of underground sensors is located in the Dutch province of Drenthe.

Practical use
The main component of our Seismic Observatory for Imaging and Monitoring project is researching a new technique developed by our Applied Geophysics section, called seismic interferometry. This technique involves making reflection images of the subsurface based on measurements of the naturally occurring acoustic rumblings of the earth. For this, we use our network of sensitive seismic sensors. With the generated live results, we will then investigate the validity of the various computer models we developed at TU Delft.

Furthermore, we focus on gathering long-term data on the subsurface changes (time-lapse seismic). This allows us to monitor the various processes that occur in the subsurface, such as gas recovery or water migration in the shallow subsurface. Eventually time-lapse seismic could be used to monitor the amount of gas inside a reservoir. In close collaboration with the Royal Netherlands Meteorological Institute (KNMI), we also investigate what happens in the subsurface at a depth of 6 to 30 kilometres, using the naturally occurring earth tremors. We aim to gain a better understanding of where and why earthquakes and land subsidence occur and gather knowledge on water migration.

Among several TU Delft staff members, four PhD students are currently involved in this project. We closely collaborate with the National Research School of Integrated Solid Earth Sciences (ISES) in which three Dutch universities participate, and institutes like TNO and KNMI. Our research is part of the much wider LOFAR project, which is based around the revolutionary LOFAR telescope in Drenthe and allows astronomers, geophysicists and agricultural scientists to perform groundbreaking research.

Contact
To learn more about our Seismic Observatory for Imaging and Monitoring project and the related research, please contact Guy Drijkoningen, Faculty of Civil Engineering and Geosciences, Applied Geophysics section.
Telephone: +31 (0)15 278 7846
Email: G.G.Drijkoningen@remove-this.tudelft.nl
Internet: http://www.lofar.org

 

Naam auteur: webredactie
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