Abstract
In this study, we present a new Moho depth model in Fennoscandia and its surroundings. The model is tailored from data sets of XGM2019e gravitationl field, Earth2014 topography and seismic crustal model CRUST1.0 using the Vening Meinesz-Moritz model based on isostatic theory to a resolution of 1° × 1°. To that end, the refined Bouguer gravity disturbance is determined by reducing the observed field for gravity effect of topography, density heterogeneities related to bathymetry, ice, sediments, and other crustal components. Moreover, stripping of non-isostatic effects of gravity signals from mass anomalies below the crust due to crustal thickening/thinning, thermal expansion of the mantle, Delayed Glacial Isostatic Adjustment (DGIA), i.e., the effect of future GIA, and plate flexure has also been performed. As Fennoscandia is a key area for GIA research, we particularly investigate the DGIA effect on the gravity disturbance and gravimetric Moho depth determination in this area. One may ask whether the DGIA effect is sufficiently well removed in the application of the general non-isostatic effects in such an area, and to answer this question, the Moho depth is determined both with and without specific removal of the DGIA effect prior to non-isostatic effect and Moho depth determinations. The numerical results yield that the RMS difference of the Moho depth from our model HVMD19 vs. the seismic CRUST19 and GRAD09 models are 3.8/4.2 km and 3.7/4.0 km when the above strategy for removing the DGIA effect is/is not applied, respectively, and the mean value differences are 1.2/1.4 km and 0.98/1.4 km, respectively. Hence, our study shows that the specific correction for the DGIA effect on gravity disturbance is slightly significant, resulting in individual changes in the gravimetric Moho depth up to − 1.3 km towards the seismic results. On the other hand, our study shows large discrepancies between gravimetric and seismic Moho models along the Norwegian coastline, which might be due to uncompensated non-isostatic effects caused by tectonic motions.
Highlights
Geoscientists frequently use three sources of information to investigate the Earth’s interior structure
The first set is understood as direct evidence from rock samples by drilling projects, the second set includes the records of seismic waves, which are generated, for example, by earthquakes, explosions, volcanoes and other natural or anthropic sources, and the third set of information is the gravity field models generated through modern satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE) and Gravity field and steady state Ocean Circulation Explorer (GOCE), which can provide global and homogeneous coverage of data
STD standard deviation of the estimated quantities over the study area, dgXFGAM2019e free-air gravity disturbance, dgTBIS Bouguer gravity disturbance corrected for topography, bathymetry, ice thickness and sediment basins, dgNIE gravity disturbances corrected for non-isostatic effects (NIEs), dgTRBISN1 refined Bouguer gravity disturbance corrected for the stripping corrections structures and NIEs without removal of the Delayed Glacial Isostatic Adjustment (DGIA) effect, dgDGIA DGIA effect on gravity, dgTBBISN similar to dgTRBISN1 but with the NIEs determined with application of the special correction for the density heterogeneities related to bathymetry, ice, sediments, and other crustal components by applying stripping corrections) and corrected for NIEs
Summary
Geoscientists frequently use three sources of information to investigate the Earth’s interior structure. The first set is understood as direct evidence from rock samples by drilling projects, the second set includes the records of seismic waves, which are generated, for example, by earthquakes, explosions, volcanoes and other natural or anthropic sources, and the third set of information is the gravity field models generated through modern satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE) and Gravity field and steady state Ocean Circulation Explorer (GOCE), which can provide global and homogeneous coverage of data. In case of the seismic method, Moho is identified by the travel time of the seismic wave reflected at the Moho boundary, whereas in the gravimetric method, gravity data are used under a certain isostatic hypothesis, which assumes isostatic equilibrium of the crust on the dense underlying mantle (e.g., Abrehdary 2016). Due to the high cost seismic data acquisition and lack of global
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