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src/ts/lisousi
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==============
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lisousi: Line-source simulation
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-------------------------------
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A program to transform field data to apparently line-source generated
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waveforms in preparation for Cartesian 2D full-waveform inversion.
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Location
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--------
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Repository location:: [src/ts/lisousi](../../../../blob/master/src/ts/lisousi)
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Program description
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-------------------
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### Purpose of lisousi
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Seismic field data is excited by point sources (e.g. hammer blows).
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Full waveform inversion (FWI) approaches which make use of Cartesian 2D
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forward modeling implicitly use a line source to fit the observed data.
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Therefore recorded waveforms must be transformed to simulate equivalent
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line-source generated data prior to application of 2D FWI.
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lisousi offers several single-trace approaches for vertical component and
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radial component data excited by vertical hammer blows or explosions.
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Single-trace approaches can be applied to each seismic trace individually in
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contrast to integral transform approaches, which require data from a complete
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profile. Single-trace approaches have the benefit, that they are independent
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of geophone layout and that they perform reasonably well for data recorded on
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laterally heterogeneous structures. On the downside they must estimate the
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wave number from sample time and receiver offset. They inherently are
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approximations, most of them being derived from the acoustic wave Green's
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function. Nevertheless, they perform surprisingly well on data from
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visco-elastic wave propagation in heterogeneous structures.
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For shallow seismic data we recommend a simple but effective procedure:
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1. scale waveform by r*sqrt(2) (offset times square root of 2)
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2. convolve with 1/sqrt(t) (fractional half integration)
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3. taper samples with 1/sqrt(t)
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Where r is source-to-receiver offset and t is sample time.
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### Features
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- Fourier domain or time domain application of convolution filter (selectable)
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- Selectable scaling optimized for either direct waves, non-dispersive waves,
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or reflected waves
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- Selectable delay of time-domain taper to match source wavelet centroid
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delay
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- Hybrid transformation for cases where near-offset traces suffer from
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delayed taper
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- Ability to read a variety of input formats including !SeismicUn*x and raw
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ASCII (through [libdatrwxx](../../../../blob/master/src/libs/libdatrwxx))
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### Documentation
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* [README](../../../../blob/master/src/ts/lisousi/README)
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* [Summary of options](../../../../blob/master/src/ts/lisousi/usage_text.txt)
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* [Description of options](../../../../blob/master/src/ts/lisousi/help_text.txt)
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* [Theory of operation](../../../../blob/master/src/ts/lisousi/description_text.txt)
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### References
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* T. Forbriger, 2013. lisousi.
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http://www.opentoast.de/Data_analysis_code_lisousi.php
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* T. Forbriger, L. Groos, M. Schäfer, 2014.
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Line-source simulation for shallow-seismic data.
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Part 1: theoretical background.
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Geophys. J. Int., 198(3), 1387-1404.
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[doi: 10.1093/gji/ggu199](http://dx.doi.org/10.1093/gji/ggu199)
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* M. Schäfer, L. Groos, T. Forbriger, T. Bohlen, 2014.
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Line-source simulation for shallow-seismic data.
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Part 2: full-waveform inversion — a synthetic 2-D case study.
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Geophys. J. Int., 198(3), 1405-1418.
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[doi: 10.1093/gji/ggu171](http://dx.doi.org/10.1093/gji/ggu171)
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