Non-isostatic effects on crustal thickness: A study using CRUST2.0 in Fennoscandia

The crustal thickness can be determined based on gravimetric–isostatic and seismic models. Modelling crustal thickness by a gravimetric–isostatic model suffers from some problems. The isostatic assumption for compensating the topographic potential is incomplete, as there are other effects which should be considered. Using the isostatic hypothesis for determining the depth of crust causes some disturbing signals, non-isostatic effects, which influence the crustal thickness determination. Isostatic and non-isostatic compensations are the main issues in this paper. We present three methods to overcome the problem due to the disturbing signals, namely the approach by truncating the spherical harmonic approach, determination of non-isostatic correction using a seismic crustal thickness model (e.g., CRUST2.0) and combination of isostatic and seismic models by applying a least-squares adjustment method. The estimated results of the non-isostatic effects varies between −65.2 and 391.8 mGal in Fennoscandia. The root mean squares difference of the crustal thickness obtained from the gravimetric–isostatic model and CRUST2.0 is improved up to six times (from 6.15 to 0.97 km) when the non-isostatic effects are considered.