Structure of the Earth’s Crust in Fennoscandia as Revealed from Refraction and Wide-Angle Reflection Studies

• Main Author: Urmas Luosto
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1996
• Subjects: Key words; crustal structure; Fennoscandia; refraction; wide-angle reflection; Moho-map
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.504.5401; http://www.geophysica.fi/pdf/geophysica_1997_33_1_003_luosto.pdf

The crustal structure in Fennoscandia has been intensively studied by seismic methods over the last one and half decade. The features and differences of the crustal structure are discussed by reviewing examples of velocity models from the seismic profiles for the different regions in Fennoscandia. It is shown that crustal thickness varies from 40 to 65 km in the shield, the thickest values are found in the middle of the shield, in Central Finland. Generally the crust in the shield can be divided into three layers, namely: upper, middle and lower crust. P-wave velocity in the upper crust varies from about 6.0 to 6.4 km/s, in the middle 6.6-6.7 km/s and in the lower one from 7.0 to 7.4 km/s. The sedimentary layer is thin or missing. The ratio of P-wave velocity to S-wave velocity increases with depth from about 1.7 in the upper crust to 1.77 in the lower crust. Outside the shield in the North German Lowland the crust is only 30-35 km thick. Here a layer with a velocity higher than 7.0 km/s is missing, so that the crystalline crust consist only of two layers. The sedimentary layer is of considerable thickness ranging in some areas to a thickness of almost ten kilometres. The Moho contour map has been updated. This map gives a quick view of the general behaviour of crustal thickness variation in the area.