Over the last decades, 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 usually adopted in microzoning activities within highly populated regions.

Within the EU-SESAME, EU-SISMOVALP, EU-NERIES, EU-EPOS and EU-SERA projects, detailed research have been accomplished to assess both the reliability and robustness of ambient vibration analysis techniques for extracting soil dynamic properties (site characterization). Within this context hardware and open-source software developments have been carried out to ease the acquisition, processing and interpretation of ambient vibration 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 starting assumptions, the interpretation and the inversion of analysis results need a (self-)critical review.

The main purpose of this training course is thus to achieve the necessary understanding of the problems related to the acquisition and use of these techniques based on ambient vibration analysis. The final goal of such techniques is the quantitative assessments of shear-wave velocity structure.

The course is divided in two parts:

• an introduction to ambient vibration processing and Geopsy usage (6 days)
• an expert workshop dealing with advanced processing techniques (1.5 days)

This course is targeted to students, engineers and researchers. Little or no experience with ambient vibrations and/or Geopsy software is required to attend the first six days. The second part of the course (Saturday afternoon and Sunday) will gather several experts from broad scientific horizons. All participants of the first part are also invited to attend.

Contributions

This training course is:

organised by	ISTerre (Grenoble, France), INGV (L'Aquila, Italy), Institute of Earth and Environmental Science (Potsdam, Germany)
presented by	Cécile Cornou, Giuseppe Di Giulio, Bertrand Guillier, Matthias Ohrnberger and Marc Wathelet

The open-source software development of Geopsy package is (was) supported by NERIES (EU-Project, 2006-2010), SESAME (EU-Project, 2001-2004) , Sismovalp (Interreg IIIB, Alpine Space, 2004-2006), EPOS-IP (EU-Project), SERA (EU-project), and IRD

Course outline

This is a program which may be subject to slight changes in the future.

Monday 4th March
09:00-09:30	Reception and welcome
	Technical issues and program overview
09:30-10:30	Physical background of ambient vibrations	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.
10:30-11:15	Scientific issues regarding use of ambient noise for site-characterization	Lecture
	Results from an international benchmark performed within the last ESG2006 Symposium. INTERPACIFIC results. Current scientific or practical questions to be addressed.
11:15-11:30	Coffee break
11:30-12:30	Introduction to Geopsy software package	Exercise
	Geopsy package philosophy. Introduction to general features (figures handling, on-line command tools, data management, etc ...).
12:30-14:00	Lunch break
14:00-16:00	Single-station measurement, H/V	Exercises
	Computation and interpretation of horizontal to vertical spectral ratio technique (H/V) - (Rayleigh wave ellipticity versus diffuse wave field). Effect of experimental conditions Geopsy tools for H/V Field data examples
16:00-16:15	Coffee break
16:15-18:00	Single-station measurement, H/V (continued)	Exercises
	Geopsy tools for H/V Field data examples
Tuesday 5th March
9:00-10:45	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 theoretical array response function. gpfksimulator for showing possible problems/bias Background of a widely used method, the high resolution f-k method after Capon (1969).
10:45-11:00	Coffee break
10:45-12:30	Array geometry and f-k response	Exercises
	Computation of array response with warangps software: optimum usage and functionalities. Building experience on how modifications in array layout affect the theoretical array performances.
12:30-14:00	Lunch break
14:00-16:00	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.
16:00-16:15	Coffee break
16:15-18:00	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.
Wednesday 6th March
8:30-9:45	L'Aquila region from a seismic risk perspective	Lecture
	Geological structures, historical seismicity, building vulnerability Available data sets for L'Aquila region and recent 2016-2017 seismicity in central italy (very briefly)
9:45-10:00	Coffee break
10:00-13:00	Field work	Exercises
	Setting up a small-aperture 2D array
12:30-14:00	Lunch break
14:00-16:00	Spatial autocorrelation method (SPAC)	Lecture
	Background of the spatial autocorrelation technique (SPAC) introduced by Aki (1957). MSPAC / ESAC / Two stations SPAC / Long-term Cross-Correlation
16:00-16:15	Coffee break
16:15-18:30	Spatial autocorrelation method (SPAC)	Exercises
	Application of the method to the synthetic data set, previously mentioned. Comparison with FK estimates: advantages and limitations of each approach.
19:00-...	Workshop Dinner
Thursday 7th March
09:00-10:45	Processing field data	Exercises
	Analysis of the signals recorded on the field: H/V / Ellipticity / f-k, high-resolution f-k, SPAC
10:45-11:00	Coffee break
11:00-12:30	Processing field data (continued)	Exercises
	Analysis of the signals recorded on the field: H/V / Ellipticity / f-k, high-resolution f-k, SPAC
12:30-14:00	Lunch break
14:00-16:00	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. Combining Rayleigh dispersion curves with other observable: elliptiicty peak, ellipticity curves and Love dispersion curves
16:00-16:15	Coffee break
16:15-18:00	Dispersion curve inversion	Exercises
	Introduction to dinver software Inversion of a 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.
Friday 8th March
9:00-12:30	Continuing analysis and Inversion on Field data	Exercises
	Inversion of dispersion curves found in previous exercises. Handling shear-wave profiles: extraction of useful engineering parameters (e.g. Vs30).
12:30-14:00	Lunch break
14:00-16:00	Continuing analysis and Inversion on Field data	Exercises
	Handling shear-wave profiles: extraction of useful engineering parameters (e.g. Vs30, SH response).
16:00-16:15	Coffee break
16:00-17:30	Discussion of results from data sets	Modarated discussion
	Comparison of the individual results obtained during the inversion. General discussion of experience gained during this complete test.
Saturday 9th March
09:00-12:30	Course summary.	Discussion
	Summary of the various steps involved for the task of ambient vibration array 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.
12:30-14:00	Lunch break
14:00-18:00	Advanced techniques for better site caracterizations	Workshop
	H/V inversion (diffuse wavefield, Rayleigh ellipticiy) [Detailed program under preparation] Francisco Sanchez-Sesma (UNAM, Mexico) Bérénice Froment (IRSN, France) Agostiny Lontsi (ETH, Switzerland) Manuel Hobiger (ETH, Switzerland)
Sunday 10th March
09:00-12:00	Advanced techniques for better site caracterizations	Workshop
	Three-component array methods (Rayleigh, Love, ellipticity) [Detailed program under preparation] Marc Wathelet (ISTerre, France) Maurizio Vassallo (INGV, Italy) Bertrand Guillier (ISTerre, France)
12:30-14:00	Lunch break
14:00-18:00	Advanced techniques for better site caracterizations	Workshop
	Inversion (joint inversion, bayesien approaches, uncertainties) [Detailed program under preparation] Paolo Bergamo (ETH, Switzerland) Manuel Hobiger (ETH, Switzerland)

Suggested readings

• 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, and 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.
• 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.
• Wathelet M. (2008). An improved neighborhood algorithm: Parameter conditions and dynamic scaling, Geophysical Research Letters, 35(9), 26-30.
• Wathelet, M., Guillier, B., Cornou, C., Roux, P., and Ohrnberger, M. (2018). Rayleigh wave three-component beamforming: signed ellipticity assessment from high-resolution frequency-wavenumber processing of am- bient vibration arrays, Geophysical Journal International, 215(1), 507-523.

All deliverables and reports of the SESAME project are available here (especially, D18.06, D19.06, D24.13 may be of interest).

Registration and Fees

This course aims at transfering and promoting scientific and technical achievements of current and past research projects. This course is targeted to students, engineers and scientists with a background in signal processing for geophysical/seismological applications. The official language is English.

Online registration is open until January 14^th 2019. If the number of applicants is larger than 20, the organizers reserve their rights to select the participants who will be informed by January 16^th.

The course will take place at L'Aquila, Italy (Via Michele Jacobucci 4, Sala Ipogea, Consiglio Regionale dell'Abruzzo, Abruzzo). The registration fee is fixed to 700 euros per participant. The fees can be paid by bank transfer. The fees include all expenses related to tuition, training, support material, field experiment, workshop dinner, lunches and coffee breaks during the course. They do not include accommodation.

Participants are requested to attend the course with their own laptop, if possible. In such a case they are requested to indicate their operating system (windows/linux/mac) during the online registration.

The attendance to the advanced workshop is free of charge. If you want to register only to the advanced workshop you have to register on SERA workshop website

A list of suggested accommodations will be available soon.

Contacts

Cécile Cornou	cecile dot cornou at univ-grenoble-alpes dot fr
Giuseppe Di Giulio	giuseppe dot digiulio at ingv dot it
Matthias Ohrnberger	matthias dot ohrnberger at geo dot uni-potsdam dot de
Bertrand Guillier	Bertrand dot Guillier at ird dot fr
Marc Wathelet	marc dot wathelet at univ-grenoble-alpes dot fr

Archives

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
• Thessaloniki, February 2010 program
• Las Vegas, February 2012 program
• Grenoble, February 2014 program
• Beirut, September 2016 program