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SWAN (Surface waves analysis)                  

 

 

 

Software for MASW/Re.Mi. seismic data analys

SWAN is a new software package to analyse and processing data acquired with the methods:
 MASW-SASW(REfraction MIcrotremors)
 REMI (REfraction MIcrotremors)

The MASW(active) method is used to reconstruct the velocity profile of the S waves in the shallow subsurface, while the REMI (passive) technique allows to reach greater depths; both seismic survey types are less expensive and faster than alternative direct or indirect methods used in geotechnical engineering.

SWAN
can be used at different levels, without compromising the quality of results, and is a powerful tool both for research-type analyses in seismic methods and for professionals that need fast and reliable interpretations.

Main features of the software are:
 Analysis of 2-dimensional sections of the ground using multi-shot  data obtained  by rolling-along the receivers array.
 Graphic interface studied to simplify the 
   Parameters setting to defines the synthetic model for the inversion in interactive mode 
   Picking option directly on the spectrum graph to extract the dispersion curve
   Editing of the experimental dispersion curve
 
Computational algorithms complete, fast and  efficient:
   computation of the  FK, FV and FX spectra
   several windowing options (boxcar, hamming, hanning, blackman, bartlett, etc.)
   parameter estimation of the synthetic model of the ground up to 30 layers
   control of the main parameters during the automatic inversion process (tolerance on errors and fit, noise level settings)
 Export of images in several graphic file formats.

The processing flow of the raw data follows these steps: 
 Pre-processing:
   Clean-up of signal from noise events and ambient sources
   Assembly of virtual arrays, to overcome the limitations on geophones available in site
 Spectral analysis, through FFT, of the  seismogram obtained, through mathematical tools user selectable
 Extraction (manual or automatic) of the experimental dispersion curve with display in the frequency domain
 Generation of a dispersion curve based on a synthetic model of the ground, through the characterization, of the thickness of each layer, of the velocity of S waves and of P waves
 Inversion of the synthetic model in interactive mode, or automatic (with options to reconstruct or constrain the S waves velocities or the layer thicknesses)
 After the processing the value of the parameter Vs30 is calculated, to classify the site according to the design and engineering standards and regulations.



 Download SWAN DEMO

Scientific bases of our algorithms:

Rix, G.J. and Lai, C.G.
Model-Based Uncertainty in Surface Wave Inversion
Proceedings, GeoCongress 2006, “
Geotechnical Engineering in the Information Technology Age, Atlanta, February 26-March 1, 2006. Paper Reference No. 11904.

Lai C.G., Wilmanski K. (Editors)
Surface Waves in Geomechanics: Direct and Inverse Modeling for Soils and Rocks, CISM Lecture Notes No. 481, CISM-Springer Verlag, pp. 385, ISBN: 3-211-27740-4. CD with software programs for surface wave analysis is included.

Lai, C.G.
Chapter 3 – Surface Waves in Dissipative Media: Forward and Inverse Modelling” in Surface Waves in Geomechanics: Direct and Inverse Modeling for Soils and Rocks. Edited by C.G. Lai and K. Wilmanski, CISM Lecture Notes Vol. No. 481, Springer-Verlag, pp. 385, October 2005. ISBN: 3-211-27740-4. CD with software programs for surface wave analysis is included.

Rix, G.J.
Chapter 3 – Near-Surface Site Characterization Using Surface Waves” in Surface Waves in Geomechanics: Direct and Inverse Modeling for Soils and Rocks. Edited by C.G. Lai and K. Wilmanski, CISM Lecture Notes Vol. No. 481, Springer-Verlag, pp. 385, October 2005. ISBN: 3-211-27740-4. CD with software programs for surface wave analysis is included.

Lai, C.G., Foti, S., Rix, G.J.
Propagation of Data Uncertainty in Surface Wave Inversion
Journal of Environmental and Engineering Geophysics, 10(2), pp. 219-228, July 2005.

Lai, C.G., Rix, G.J., Foti, S., Roma, V.
Simultaneous Measurement and Inversion of Surface Wave Dispersion and Attenuation Curves
Soil Dynamics and Earthquake Engineering, Vol. 22, No. 9-12, pp. 923-930, October-December 2002.

Rix, G.J., Lai, C.G., Spang, A.W.
In Situ Measurements of Damping Ratio Using Surface Waves
Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 126, No.5, pp. 472-480, May 2000.

Lai, C.G., Foti, S., Godio, A., Rix, G.J., Sambuelli, L., Socco, V.
Geotechnical Site Characterization Using Geophysical Techniques
Italian Geotechnical Journal, RIG, Special Publication, No.3, pp. 99-118, September 2000, Specialty Panel of 20
th Italian National Conference on Geotechnics, Parma, Italy, September 22-25, 1999 (in Italian).

Lai, C.G.
Spectral Analysis of Surface Waves – Active Methods – Technical Recommendations
Italian Geotechnical Journal, RIG, No.4, pp. 201-212. December 2000.

Lai, C.G., Rix, G.J.
Inversion of Multi-Mode Effective Dispersion Curves
Proceedings, 2
nd International Symposium on Pre-Failure Deformation Characteristics of Geomaterials, IS Torino 99, Torino, Italy, September 26-29, 1999, Vol. I, pp. 411-418.

Lai, C.G., Rix, G.J.
Simultaneous Inversion of Rayleigh Phase Velocity and Attenuation for Near- Surface Site Characterization
Contract Report prepared for the National Science Foundation under Grant No. CMS-9402358, and the U.S. Geological Survey, Department of Interior, Award No. 1434-95-G-2634, Report No. GIT-CEE/GEO-98-2, July, 1998, pp. 258.

Strobbia, C.
Surface wave methods: acquisition, processing and inversion,
Ph.D. Thesis, Politecnico di Torino, Italy, 2003

 

 
 

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