Comment on the Seismic Method Depth-Recursive Tomography on Grid (DRTG)

Hrubcová, P., Środa, P., Vavryčuk, V., Babuška, V., Grad, M.

Surveys in Geophysics

34 (4), 2013, 521-529, 10.1007/s10712-013-9228-0

The Comment addresses three papers published recently in Surveys in Geophysics. These papers are related, using the same seismic tomography approach (Depth-Recursive Tomography on Grid - DRTG) developed by the same first author and deal with modelling of seismic refraction crustal data in the Bohemian Massif and their geological interpretation. The comment shows essential deficiencies of the DRTG approach. Three synthetic tests disclose that the ray coverage at deeper parts of the models drops dramatically and such a ray coverage is not sufficient to reliably recover the structure. Thus, the application of DRTG tomography overestimates the data constraints in large parts of the model, which result in unconstrained velocity anomalies at depths below ~8 km. For these reasons, the velocity models derived from DRTG tomography and their geological interpretations cannot be accepted.