11:45 〜 12:00
[S01-4-06] Investigation of deep sedimentary and crustal structures with passive seismic methods
Passive ambient-vibration measurements are well established to investigate the uppermost shear-wave velocity structure, usually limited to few hundred meters depth. Tomographic methods based on earthquake recordings are widely used for the study of the deeper crust, at depths of the order of several kilometers. We plan to fill the gap between both depth ranges using passive array measurements. The study area is the Swiss foreland.
From a geological perspective, the Swiss foreland mainly consists of quaternary deposits on top of Molasse and Mesozoic deposits of variable thickness ranging from about 1 to 5 km above the crystalline basement. The goals of our measurements are the identification of the main impedance contrasts in the subsurface, their comparison with a-priori information and the computation of local shear-wave velocity profiles. In order to investigate different depth ranges, several array configurations of increasing size were deployed, ranging from small scale of about 10 m to very large scale up to 10 km of inter-station distance.
We will present the results of first array measurements in the Molasse basin in northern Switzerland. Three arrays of different size have been deployed. The recorded data were processed using different techniques. The H/V and ellipticity curves for all single stations were computed, while the array processing yielded Rayleigh and Love wave dispersion curves in a wide frequency range. We used different methods, including three-component high-resolution FK, SPAC and Wavefield Decomposition (WaveDec). The final step of the analysis is the joint inversion of all available data and the definition of shear-wave velocity profiles including their regional variations. We discuss the applicability and resolution power of seismic passive methods to the investigation of shallow and deep structures.
From a geological perspective, the Swiss foreland mainly consists of quaternary deposits on top of Molasse and Mesozoic deposits of variable thickness ranging from about 1 to 5 km above the crystalline basement. The goals of our measurements are the identification of the main impedance contrasts in the subsurface, their comparison with a-priori information and the computation of local shear-wave velocity profiles. In order to investigate different depth ranges, several array configurations of increasing size were deployed, ranging from small scale of about 10 m to very large scale up to 10 km of inter-station distance.
We will present the results of first array measurements in the Molasse basin in northern Switzerland. Three arrays of different size have been deployed. The recorded data were processed using different techniques. The H/V and ellipticity curves for all single stations were computed, while the array processing yielded Rayleigh and Love wave dispersion curves in a wide frequency range. We used different methods, including three-component high-resolution FK, SPAC and Wavefield Decomposition (WaveDec). The final step of the analysis is the joint inversion of all available data and the definition of shear-wave velocity profiles including their regional variations. We discuss the applicability and resolution power of seismic passive methods to the investigation of shallow and deep structures.