Crustal velocity structure under the RUKSA seismic array (Karelia, Russia)

Introduction

Figure 1

[2] Observations with the small aperture RUKSA array (Figure 1) were carried out in 1999 in the Petrozavodsk region (Karelia, Russia) within the framework of the SVEKALAPKO international experiment [Bock, 2001]. Small aperture seismic arrays (sometimes referred to as seismic antennas) have been widely used since the 1980s as an effective tool for the location of seismic events of various origins, primarily, for the monitoring of the Non-Proliferation Treaty. Data of seismic antennas are also effectively used for the study of seismic noise properties and seismic wave scattering, as well as for the recording and identification of local seismic events. One of the immediate tasks involved in the analysis of array records is the determination of the structure of the medium in the area of the temporary array site and, in particular, the construction of a 1-D velocity model of the crust and the upper mantle. The method of the receiver function [Langston, 1979; Vinnik, 1977; Vinnik and Kosarev, 1981] developed for the analysis of three-component seismic records is effective for the detection of main interfaces or zones of higher velocity gradients but fails to reliably determine absolute values of velocities in model layers. The inverse problem of the velocity structure determination from a known receiver function can be solved by invoking additional information on the parameters to be determined [Ammon, 1990; Kosarev et al., 1987]. To reduce the ambiguity of the inversion, Julia et al. [2000] performed joint inversion of the receiver function and group velocities of Rayleigh waves in the Arabia region. Using joint inversion of P and S wave receiver functions, Vinnik et al. [2004] constructed a 3-D model of the crust and upper mantle (down to 150 km) under the Tien Shan. Residuals of P and S traveltimes were included in the inversion in (L. P. Vinnik et al., in press, 2006). In the present paper, Ps traveltimes from the 410- and 660-km boundaries and Rayleigh phase velocities are used as additional optimization constraints.