Shear wave velocity structure estimation using surface waves of different wavelengths Petr Kolínský Department of Seismology Institute of Rock Structure and Mechanics Academy of Sciences of the Czech Republic and Department of Geophysics Faculty of Mathematics and Physics Charles University in Prague New Knowledge and Measurements in Seismology, Engineering Geophysics and Geotechnics – OVA ’06 Ostrava, 17. a 18. dubna 2007

surface waves

frequency-time analysis – basics multi-channel filtering Gaussian filters constant relative resolution filtering optimal filtration instantaneous period estimation compilation of the dispersion curve using primary, secondary,... local maxima

frequency-time analysis frequency - time representation using the Fourier Transform multi-channel filtering = the inverse FT for different central frequencies is a spectrum of the original signal is the Gaussian filter (weighting function) we obtain a set of filtered spectra

frequency-time analysis example of Gaussian filters

frequency-time analysis classical depiction of spectrogram amplitude frequency time group velocity - scale diagram period diagram

frequency-time analysis group velocity epicentral distance arrival time of energy maximum

frequency-time analysis example of several nearly monochromatic filtered signals example of truncating the filtered signals how to provide a proper truncating?

frequency-time analysis how the filtered seismogram is summed using the truncated filtered signals

frequency-time analysis filtered seismogram

inversion problem Isometric Method (IM) was recently developed at Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic, by Jiri Malek isometric algorithm connects the advantages of several commonly used methods, see: “Tarantola, A.: Inverse Problem Theory, Elsevier Science B.V, Amsterdam, 1987” IM is a fast algorithm, which was developed for solving weakly non- linear inverse problems with many parameters

forward problem forward problem is solved during almost all iterations of the inversion the dispersion curves are computed by matrix method presented in: “Proskuryakova, T. A., Novotny, O. and Voronina, E. V.: Studies of the Earth Structure by the Surface Wave Method (Central Europe), Nauka, Moscow, 1981 (in Russian)” It uses modified Thomson – Haskell matrices for Love waves program for computing the forward problem was developed at the Department of Geophysics, Faculty of Mathematics and Physics, Charles University, Prague, by Oldřich Novotný

SVAL - program The source code is written in PASCAL using Delphi environment (Borland, version 7.0). The code emerges as a result of translation of other codes from FORTRAN language (Kolínský, Novotný). Then it was compiled together with code written in Delphi (Málek). It is possible to distribute and execute the SVAL program using one *.exe file (3 MB).

results velocity models and inversion scattering measured and inverted dispersion curves

shallow seismic measurement Date2004 June Magnitudevery small :-) event location14.15 E N (Karlštejn) Depthsurface origin time13:15:12 UTC Sourcehammer beating a metal plate epicentral distance50 m StationKarlštejn station location14.15 E N SeismometerSM 6 – 4 Hz

quarry blast Date2003 June 05 Magnitudenot estimated event location E N (Horní Rozmyšl) Depthsurface origin time17:49: UTC Sourcequarry blast epicentral distance km StationKynžvart KYNZ station location E N SeismometerLenartz 3-D 5\,s \\

Aegean Sea Earthquake Date2005 October 20 Magnitude5.9 event location26.75 E N (Aegean Sea) Depth10 km origin time21:40:04.09 UTC Sourcenatural tectonic earthquake epicentral distance km StationHáje HAJ station location E N SeismometerGuralp 30

South Iran Date2005 November 17 Magnitude6.0 event location E N (South Iran) Depth10 km origin time10:22:19 UTC Sourcenatural tectonic earthquake epicentral distance km StationNečtiny NEC station location E N SeismometerGuralp 30 s

Kuril Islands Date2007 January 13 Magnitude8.2 event location E N (Kuril Islands) Depth12 km origin time04:23:20.2 UTC Sourcenatural tectonic earthquake epicentral distance km StationPanská Ves PVCC station location E N SeismometerSTS s

Resultant shear velocity profiles Normal view log view

conclusion