• Startseite

• Institut

• Einleitung

• OnSITE - On-line seismic imaging for tunnel seismic exploration

• Finite-Difference Seismic Wave Simulation

• Seismic Prediction Ahead of Boreholes

• Inversion of Surface Waves

Time-Domain Full Waveform Tomography

For better parameter estimation, both in active source and earthquake seismology, we need to exploit the richness of broad-band, three-component waveforms and we need more powerful imaging methods to integrate and jointly interpret the multi-component data sets from seismic experiments. Of particular interest is the detection and characterization of different scales in the crust, which are diagnostic for the physical,  chemical, and geological processes that cause them.  Also the estimation of independent elastic parameters that characterize different properties of the subsurface is of high importance. Meeting the challenge of multi-scale and multi-parameter imaging requires to gather seismic waveforms with high spatial density. Full waveform tomography (FWT) is a powerful method for multi-scale and multi-parameter imaging. It is an inverse method that accounts for the full waveform of seismograms recorded over a broad range of frequencies and apertures. In contrast to migration, FWT seeks to find the  true parameter field by directly solving the partial differential viscoelastic wave equations.  FWT allows for a mapping of very large to small-scale structures where the latter can be smaller than the seismic wavelength, hence providing a tremendous improvement of resolution compared with traveltime tomography.

Although first implementation in the 1980's were conducted in the time-domain, the frequency-domain version of waveform tomography developed in the 1990's (e.g. Pratt and Worthington, 1990) has now emerged as an efficient imaging tool, capable
of being used on a production basis for large-scale 2D problems.  The main advantage of the frequency-domain approach is the possibility of starting the inversion at low frequencies (large scale structures) and then moving to higher frequency components
(smaller scales), hereby realizing a multi-scale approach. This frequency selection also helps to mitigate the non-linearity of the inverse problem. However, the time-domain approach should not be neglected because it seems to be better adapted to modern cluster type computers.

Work group

Thomas Bohlen
Daniel Köhn
Andre Kurzmann
Nhi Xuan Ngyen

Funding

The methodological developments are financially supported by  Verbundnetz Gas AG (Leipzig), and the Technical University Bergakademie Freiberg.

References

Pratt, R.G., and Worthington, M.H., 1990, Inverse theory applied to multi-source cross-hole tomography. Part I:
Acoustic wave equation method, Geophysical Prospecting, 38, 287-310.

Wiebke Suhr, 2007, Acoustic full waveform inversion for transmission and reflection geometry, diploma thesis, Kiel University (pdf)