Reflection seismic measurements across the Granulite Belt of the POLAR Profile in the northern Baltic Shield, Northern Finland

• Reflection seismic measurements were carried out in 1985 on the central part of the POLAR refraction seismic profile in Northern Finland. The survey was planned and executed jointly by the Universities of Helsinki, Uppsala and Hamburg, using digital equipment with a total of 144 channels. By repeating the shots and moving the geophone spreads every day we were able to observe a 42-50 km recording spread. Referred to reflection elements, a line of 84 km total length through the source-receiver midpoints was recorded. We processed the results up to normal moveout-corrected time sections.A number of reflectors dipping 8°-15° to the northeast were recorded in the Lapland Granulite Belt range. These represent a system of sheared granulites which were observed on the surface in the southern part of the profile. From gravity modelling, the bottom of the dipping layers coincides with the lower boundary of the granulites. Between the depths of 22 and 35 km the crust in this area seems to be transparent to seismic signals. This leads to the assumption that the middle part of the crust is characterized by gentle velocity and density gradients. The crust-mantle boundary seems to be a layered Moho with good reflectors lying at depths between 40 and 44 km.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Vattenteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Water Engineering (hsv//eng)

Nyckelord

Vattenteknik

Water Resources Engineering

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ref (ämneskategori)

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