Using Ambient Vibration Array Techniques for Site Characterization and Seismic Microzonation
Sunday, February 21st to Sunday, February 28th 2010
Thessaloniki, Greece
All aspects of ambient vibrations analysis are reviewed during a eight-day course, read more ...
In recent years, the number of research papers dealing with
ambient vibration analysis methods has increased considerably.
Clearly, the interest in these methods originates from both
the economical attractive cost benefit ratio and the straightforward
data acquisition. Being a non-destructive passive technique, these methods also
complement geotechnical and/or active geophysical methods
within highly populated regions.
Within the EU-SESAME, EU-SISMOVALP and NERIES projects, detailed research have been accomplished to assess the reliability and robustness of ambient vibration analysis techniques for site characterization. Within this context hardware and free-software developments have been carried out to ease the acquisition, processing and interpretation of ambient vibration wave field recordings.
The main findings of these projects however show, that ambient vibration array analysis techniques have to be applied with care.
It requires not only a careful measurement, but especially
the interpretation and the inversion of analysis results need a (self-)critical
review.
The main purpose of this course is thus to achieve the necessary understanding for the problems related to the acquisition and use of these techniques for quantitative information of shear-wave velocity structure. Although opened to any researchers/engineers/students from any country, this course is especially targeted to scientists in charge of accelerometric or seismological networks in the EURO-MED area.
This training course is:
| organised by |
LGIT (Grenoble, France), IGUP (Potsdam, Germany) and ITSAK (Thessaloniki, Greece) |
| presented by |
Marc Wathelet (LGIT), Cécile Cornou (LGIT), Matthias Ohrnberger (UP Potsdam), Bertrand Guillier (LGIT), Alexandros Savvaidis (ITSAK), Héloïse Cadet (ITSAK), Nikos Theodulidis (ITSAK) |
| supported by |
NERIES |
The software development (was) is supported by
NERIES (EU-Project, 2006-2010), SESAME (EU-Project, 2001-2004) , Sismovalp (Interreg IIIB, Alpine Space, 2004-2006), IRD
This is a program which may be subject to slight changes in the future.
| Sunday |
| 09:00-09:30 |
Reception and welcome |
|
| |
- Technical issues and program overview
|
| 09:30-10:30 |
Physical background of ambient vibrations and their use for site microzonation |
Lecture |
| |
- State of the art about the nature of the ambient vibration wave field.
- The linkage between subsurface structure and wave field propagation properties: relationships between site conditions, Rayleigh ellipticity, Airy phase of Love waves and SH transfer function.
- Review of world-wide studies using ambient vibrations.
|
| 10:30-11:30 |
Scientific issues regarding use of ambient noise for site characterization |
Lecture |
| |
- Results from an international benchmark performed within the last ESG2006 Symposium.
|
| 11:30-11:45 |
Coffee break |
| 11:45-12:45 |
Single station measurement, H/V |
Lecture |
| |
- Computation and interpretation of horizontal to vertical spectral ratio technique (H/V)
- Effects of experimental conditions.
|
| 12:45-13:30 |
Introduction to sesarray package |
Exercises |
| |
- Sesarray software philosophy.
- Introduction to general features (figures handling, on-line command tools, data management, etc ...) .
|
|
| 13:30-15:00 |
Lunch break |
| 15:00-15:30 |
Introduction to sesarray package (continued) |
Exercises |
| |
- Sesarray software philosophy.
- Introduction to general features (figures handling, on-line command tools, data management, etc ...) .
|
|
| 15:30-16:30 |
Single station measurement, H/V |
Exercises |
| |
- Geopsy tools for H/V.
- Field data examples.
|
| 16:30-16:45 |
Coffee break |
| 16:45-18:00 |
Single station measurement, H/V (continued) |
Exercises |
| |
- Geopsy tools for H/V.
- Field data examples.
|
| Monday |
| 9:00-11:00 |
Basic array processing concepts (conventional and high-resolution frequency wavenumber, f-k) |
Lecture |
| |
- Overview array processing methods.
- The intuitive shift-and-sum technique in time domain and its transposition into the frequency wavenumber (f-k) domain.
- Discrete
spatial sampling of the continuous seismic wave field (by small groups
of seismic stations - arrays) : concepts of resolution and aliasing.
- Resolution and aliasing of simple linear array layouts and generalisation to bi-dimensional array settings.
- Relation between array geometry and resulting estimation capabilities: rules of thumb and the array response function.
- Background of a widely used method, the high resolution f-k method after Capon (1969).
|
| 11:00-11:15 |
Coffee break |
| 11:15-12:45 |
Array geometry and f-k response |
Exercises |
| |
- Computation of array response with waran_gps software: optimum usage and functionalities.
- Building experience on how modifications in array layout affect the theoretical array performances.
|
| 12:45-13:30 |
Conventional and high-resolution f-k processing |
Exercises |
| |
- Application of the conventional and high-resolution f-k algorithms to estimate the dispersion curves from noise synthetics.
|
| 13:30-15:00 |
Lunch break |
| 15:00-16:30 |
Conventional and high-resolution f-k processing (continued) |
Exercises |
| |
- Application of the conventional and high-resolution f-k algorithms to estimate the dispersion curves from noise synthetics.
|
| 16:30-16:45 |
Coffee break |
| 16.45-18.00 |
Conventional and high-resolution f-k processing (continued) |
Exercise |
| |
- Application of the conventional and high-resolution f-k algorithms to estimate the dispersion curves from noise synthetics.
|
| Tuesday |
| 9:00-10:30 |
Spatial autocorrelation method (SPAC) |
Lecture |
| |
- Background of the spatial autocorrelation technique (SPAC) introduced by Aki (1957).
|
| 10:30-10:45 |
Coffee break |
| 10:45-13:30 |
Spatial autocorrelation method (SPAC) |
Exercise |
| |
- Application of the method to the synthetic data set, previously mentioned.
- Comparison with FK estimates: advantages and limitations of each approach.
|
| 13:30-15:00 |
Lunch break |
| 15:00-17:00 |
Active surface waves techniques (SASW, MASW) and passive linear array technique |
Lecture and exercise |
| |
- The SASW, MASW and passive linear array techniques: theory, acquisition, processing and resolution limits.
- Application of MASW to real data set.
|
| 16:30-16:45 |
Coffee break |
| 16:45-18:00 |
Active surface waves techniques (SASW, MASW) and passive linear array technique |
Exercise |
| |
- Application of MASW to real data set.
|
| Wednesday |
| 9:00-11:00 |
Dispersion curve inversion |
Lecture |
| |
- Short introduction to the fundamentals of inversion theory.
- Direct search methods based on a random sampling, and particularly the Neighbourhood algorithm.
- Specific issues solved for the inversion dispersion curves: robustness of the
forward computation, non-uniqueness of the final solution.
|
| 11:00-11:15 |
Coffee break |
| 11:15-13:30 |
Dispersion curve inversion |
Exercises |
| |
- Introduction to dinver software
- Inversion of theoretical dispersion curve in order to identify critical issues.
- Model parameterisation and parameter range (vP, vS), a natural way to introduce prior information and to reduce the non-uniqueness.
|
| 13:30-15:00 |
Lunch break |
| 15:00-17:00 |
Preparation of the field experiment |
Tutorial |
| |
- Presentation of the WARAN (wireless array network) equipment.
- Presentation of the active seismic equipment.
|
| Thursday |
| 8:00-18:00 |
Field experiment |
Field |
| |
- Field experiment in Thessaloniki (noise array and MASW).
|
| 21:00-... |
Workshop Diner |
| Friday |
| 9:00-11:00 |
Dispersion (autocorrelation) curve inversion |
Exercises |
| |
- Inversion of synthetic dispersion and autocorrelation curves.
- Influence of the frequency range used for inversion.
- Influence of prior information for reducing non-uniqueness.
|
| 11:00-11:15 |
Coffee break |
| 11:15-13:30 ... |
Dispersion (autocorrelation) curve inversion |
Exercises |
| |
- Integrating to a single dispersion curve (autocorrelation curve) dispersion curves (autocorrelation curves) obtained through different processing.
- Handling shear-wave profiles: extraction of usefull engineering parameters (e.g. Vs30).
|
| 13:30-15:00 |
Lunch break |
| 15:00-16:30 |
Processing field data. |
Exercises |
| |
- Analysis of the signals recorded on the field with f-k, high-resolution f-k, SPAC and MASW techniques.
|
| 16:30-16:45 |
Coffee break |
| 16:45-18:00 |
Processing field data. |
Exercises |
| |
- Analysis of the signals recorded on the field with f-k, high-resolution f-k, SPAC and MASW techniques.
|
| Saturday |
| 9:00-11:00 |
Processing field data. |
Exercises |
| |
- Combining results of arrays dispersion/autocorrelation curves estimated by the different arrays.
- Comparison with dispersion/autocorrelation curves obtained in previous measurements .
|
| 11:00-11:15 |
Coffee break |
| 11:15-13:30 |
Processing field data. |
Exercises |
| |
- Decision on the usable frequency range for the inversion target.
- Inversion of dispersion/autocorrelation curve in order to derive velocity model.
|
| 13:30-15:00 |
Lunch break |
| 15:00-16:45 |
Processing field data |
Exercises |
| |
- Inversion of dispersion/autocorrelation curve in order to derive velocity model.
|
| 16:45-17:00 |
Coffee break |
| 17:00-18:30 ... |
Processing field data |
Exercises |
| |
- Extraction of velocity models and Vs30.
|
| Sunday |
| 9:00-11:00 |
Discussion of results from data sets |
Moderated discussion |
| |
- Comparison of the individual results obtained during the inversion.
- General discussion of experience gained during this complete test.
|
| 11:00-11:15 |
Coffee break |
| 11:15-13:30 |
Course summary |
Discussion |
| |
- Summary
of the various steps involved for the task of ambient vibration array and MASW
analysis and site characterisation by the inversion of one-dimensional
earth models. Recall of the advantages and limitations of using ambient vibrations to site characterisation.
|
| 13:30-15:00 |
Lunch break |
| 15:00-... |
Departure of Participants |
Open discussion |
- Aki, K. (1957). Space and time spectra of stationary stochastic waves, with special reference to microtremors, Bull. Earthq. Res. Inst. 35, 415-456.
- Bard, P.-Y. (1999). Microtremor measurements: a tool for site effect estimation?, State-of-the-art paper, 2nd International Symposium on the Efects of Surface Geology on Seismic Motion, Yokohama,
Balkema, 3, 1251--1279.
- Bettig, B., P.-Y. Bard, F. Scherbaum, J. Riepl,
F. Cotton, C. Cornou and D. Hatzfeld (2001). Analysis of dense array
noise measurements using the modified spatial auto-correlation method
(SPAC). Application to the Grenoble area., Bolletino di Geofisica Teorica ed Applicata 42, 281-304.
- Capon, J. (1969). High-resolution frequency-wavenumber spectrum analysis, Proc. IEEE 57, 1408-1418.
- Sambridge, M. (1999a). Geophysical inversion with a neighbourhood algorithm: I. Searching a parameter space, Geophys. J. Int. 138, 479-494.
- Sambridge, M. (1999b). Geophysical inversion with a neighbourhood algorithm: II. Appraising the ensemble, Geophys. J. Int. 138, 727-746.
- Tokimatsu, K. (1997). Geotechnical site characterization using surface waves, In Proc. 1st Intl. Conf. Earthquake Geotechnical Engineering, Ishihara (ed), Balkema, 1333-1368.
- Cornou, C., M. Ohrnberger, D. M. Boore, K. Kudo, P.-Y. Bard (2006). Using ambient noise array techniques for site characterisation: results from an international benchmark, in Proc. 3rd Int. Symp. on the Effects of Surface Geology on Seismic Motion, Grenoble, 29 August - 01 September, 2006, Bard, P.Y., Chaljub, E., Cornou, C., Cotton, F. and Guéguen, P. Editors, LCPC Editions, paper NBT. pdf
- Wathelet, M., D. Jongmans, M. Ohrnberger, and S. Bonnefoy-Claudet (2008). Array performances for ambient vibrations on a shallow structure and consequences over Vs inversion, Journal of Seismology , 12(1) , 1-19. pdf
- Wathelet M. (2008). An improved neighborhood algorithm: Parameter conditions and dynamic scaling, Geophysical Research Letters , 35(9) , 26-30.pdf
All deliverables and reports of the SESAME project are available here (especially, D18.06, D19.06, D24.13 may be of interest).
This course aims to transfer and promote scientific and technical achievements of NERIES-JRA4 "Geotechnical Site Characterization" on a wide European and global scale. Although opened to any researchers/engineers/students from any country, this course is especially targeted to scientists in charge of accelerometric or seismological networks in the EURO-MED area. The official language is english.
Online registration is open until January 22nd 2010. If the number of applicants is larger than 30, the organisers reserve their rights to select the participants who will be informed by January 25th. For selection, priority will be given to strong motion operators in broader EURO-MED area.
The course will take place in Mediterraneen Palace hotel, Thessaloniki, Greece. The registration fee is fixed to 1000 euros per participant. These fees include a single room reservation with buffet breakfast for eight nights (from 20/02/2010 to 28/02/2010). The organizers will cover all expenses related to tuition, training, support material, field experiment, workshop diner, coffee breaks during the course.
Special conditions:
- Participants are requested to attend the course with their own laptop, if possible. In such a case they are requested to indicate in the online registration their operating system (windows/linux/mac, etc.).
- A limited number of financial support may be available upon request to participants from developing countries.
| Cécile Cornou |
cecile dot cornou at obs dot ujf-grenoble dot fr |
| Nikos Theodulidis |
ntheo at itsak dot gr |
| Alexandros Savvaidis |
alekos at itsak dot gr |
| Marc Wathelet |
marc dot wathelet at ujf-grenoble dot fr |
| Matthias Ohrnberger |
mao at geo dot uni-potsdam dot de |
| Bertrand Guillier |
bertrand dot guillier at obs dot ujf-grenoble dot fr |
| Héloïse Cadet |
kdhelo at gmail dot com |
Here you can find the program of last editions and all photos taken during these courses:
- Grenoble, November 2005: program, photos (thanks to Sylvette Bonnefoy, Mehmet Ergin, Fabrizio Cara and Carlo Cauzzi).
- Berlin, April 2006: program
- Caracas, October 2006: program, photos (thanks to Victor Rocabado).
- Algiers, July 2007: program
- Bangalore, November 2007: program
- Istanbul, May 2008: program
- Thessaloniki, December 2008 program
