Seismic tomography of the upper mantle beneath the north-eastern Bohemian Massif (central Europe)

We present a 3-D velocity model of the upper mantle beneath the northern and eastern parts of the Bohemian Massif (BM) based on data from passive seismic experiment BOHEMA II (May 2004–June 2005) consisted of 35 temporary stations complemented by data of permanent observatories. The resulting tomographic model, with a variance reduction of 84%, shows relatively small velocity variations, both in size and in amplitude. A small-size high velocity perturbation in the eastern part of the model can be related to the complex structure beneath the Sudetes/Moravo-Silesian unit contact. Similarly to results from the BOHEMA I experiment in the western BM, the presented model from BOHEMA II data confirms the north-southward thickening of the lithosphere. Though in the upper mantle the low perturbations prevail, some inconsistencies among the isotropic velocity perturbation model, Sp receiver function inferences and anisotropic models of the mantle lithosphere domains indicate that both the topography of the lithosphere–asthenosphere boundary and internal velocity structure of the upper mantle beneath the BM can be complex. We tested two regularization techniques: truncated singular value decomposition and damped least square method, results of which lead us to prefer the damped least square method. The truncated singular value decomposition seems to be more sensitive to uneven ray geometry.

► BOHEMA II tomography does not indicate any vast velocity variations in the upper mantle beneath the NE Bohemian Massif. ► We prefer the damped least square regularization because the later seems to be more sensitive to uneven ray geometry.