Inversion of travel times obtained during active seismic refraction experiments CELEBRATION 2000, ALP 2002 and SUDETES 2003

Abstract

A series of kinematic inversions based on robust non-linear optimization approach were performed using travel time data from a series of seismic refraction experiments: . These experiments were performed in Central Europe from 2000 were processed in this study. The goal of this work was to find seismic velocity models yielding travel times consistent with observed data.Optimum 2D inhomogeneous isotropic P-wave velocity models were computed. We have developed and used a specialized two-step inverse procedure. In the first "parametric" step, the velocity model contains interfaces whose shapes are defined by a number of parameters. The velocity along each interface is supposed to be constant but may be different along the upper and lower side of the interface. Linear vertical interpolation is used for points in between interfaces. All parameters are searched for using robust non-linear optimization (Differential Evolution algorithm). Rays are continuously traced by the bending technique. In the second "tomographic" step, smallscale velocity perturbations are introduced in a dense grid covering the currently obtained velocity model. Rays are fixed in this step. Final velocity models yield travel time residuals comparable to typical picking errors (RMS ~ 0.1 s).As a result, depth-velocity cross-sections of P waves along all processed profiles are obtained. The depth range of the models is 35 -50 km, the velocity varies in the range 3.5 -8.2 km/s. Lowest velocities are detected in near-surface depth sections crossing sedimentary formations. The middle crust is generally more homogeneous and has typical P wave velocity around 6 km/s. Surprisingly the lower crust is less homogeneous and the computed velocity is in the range 6.5 -7.5 km/s. The MOHO is detected in the depth 30 -45 km.

Crustal structures beneath the Saxonian Granulite Massif, the České středohoří and the Doupovské hory Mts. based on the depth-recursive tomography

“…9 shows the results of the previous interpretations by Růžek et al (2007) and Grad et al (2008) derived from their final S01 models. Although the comparison of these models just for one x-coordinate may not be representative on the whole, the sweeping out of the LVZ in both previous models can be inferred.…”

“…Růžek et al (2007) developed a special two-step inverse procedure for inverting the refracted Pg, Pn and reflected Pm phases. They derived velocity models down to the Moho along eight refraction profiles from recent seismic experiments in the Bohemian Massif.…”

“…They derived velocity models down to the Moho along eight refraction profiles from recent seismic experiments in the Bohemian Massif. Based on their error analyses, Růžek et al (2007) considered the S04 and other obtained models reliable down to a 15 km depth, where only the velocity anomalies exceeding 5 % can be reliably detected.…”

Linearization of the Sobolev and Babeyko's formulae for transformation of P-wave velocity to density in the Carpathian-Pannonian Basin region

“…In the Carpathian-Pannonian region it has been observed that this P-wave velocity interval is valid for the whole crust (e.g. Grad et al, 2006;Hrubcová et al, 2005;Růžek et al, 2006;Środa et al, 2006 ).…”

Depth-Recursive Tomography Along the Eger Rift Using the S01 Profile Refraction Data: Tested at the KTB Super Drilling Hole, Structural Interpretation Supported by Magnetic, Gravity and Petrophysical Data

“…Růžek et al (2007) applied a special two-step tomography along the eight seismic profiles whose seismic data were obtained during the CELEBRATION 2000, ALP 2002experiments (Brückl et al 2003Grad et al 2003). The SUDETES 2003 profile S01 is oriented along the Eger Rift in the SW-NE direction (Fig.…”