High-resolution reflection seismics applied to detection of groundwater resources in glacial deposits, Sweden

A large proportion of Sweden's ground water resources is contained in sand/gravel glaciofluvial deposits that overlie Precambrian crystalline basement and are covered by clay. The depth to the sand/gravel deposits varies from near-surface to about 100 m and their thickness is generally 10-20 m. Traditionally, due to logistics, short refraction seismic profiles and penetration tests have been used to localize the sand/gravel deposits below the clay and to determine their thickness. However, when the overlying clay deposits are thick or the glacial deposits show significant 2-D structure, refracting waves may not penetrate into the sand/gravel deposits or into the crystalline basement. Reflection seismic methods provide an alternative mapping method and a test profile was acquired over glacial deposits where the structure is well known. Standard processing shows, in general, excellent agreement between the seismic image and the structure determined from penetration tests.