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Using Ambient Vibration Techniques for Site Characterization, Seismic Microzonation and Buildings

Monday, September 19th to Sunday, September 25th 2016
Beirut, Lebanon

All aspects of ambient vibrations analysis are reviewed during a seven-day course, read more ...

ul  ndu  usj  auf  cnrs  rumarre  jeai 
ird  uga  ieu  isterre

Over the last decade, 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 extracting soil (site characterization) and building dynamic properties. Within this context open-source hardware and 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 of the problems related to the acquisition and use of these techniques for quantitative assessments of shear-wave velocity structures and building dynamic properties. This course is targeted to students, engineers and researchers.

Contributions

This training course is:

organised by ISTerre (Grenoble, France), NDU (Louaize, Lebanon), LU (Beirut Lebanon)
presented by Marc Wathelet (IRD-ISTerre), Cécile Cornou (IRD-ISTerre), Bertrand Guillier (IRD-ISTerre), Christelle Salameh (NDU-ISTerre), Jacques Harb (NDU), Dalia Youssef Abdel-Massih (LU), Yara Maalouf (NDU).

The software development (was) is supported by NERIES (EU-Project, 2006-2010), SESAME (EU-Project, 2001-2004) , Sismovalp (Interreg IIIB, Alpine Space, 2004-2006), EPOS-IP (EU-Project), IRD

Course outline

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

Monday
09:00-09:30 Course opening ceremony  
 
  • Technical issues and program overview
09:30-10:45 Principles of seismic wave propagation Lecture
 
  • Focus on surface waves properties.
  • The linkage between subsurface structure and wave field propagation properties: relationships between site conditions, Rayleigh ellipticity, dispersion curves of surface waves and SH transfer function
10:45-11:00 Coffee break
11:00-12:30 Signal processing basics Lecture
 
  • A/D sampling problem, instrument transfer function.
  • Spectral analysis, Fast Fourier Transform, Power Spectrum.
12:30-14:00 Lunch break
14:00-15:30 Introduction to Geopsy software package I Exercise
 
  • Presentation of Geopsy.org modules
  • Using graphics concept in Geopsy.org software package
  • Plotting graphics, importing and exporting layers, makeups, etc.
15:30-15:45 Coffee break
16:00-17:30 Introduction to Geopsy software package II Exercises
 
  • Starting Geopsy, opening existing & storing databases
  • Import and export of signals, waveform tools (filter, FFT, ...)
  • Views, editing and manipulating header entries, sorting, grouping, importing coordinates
 
Tuesday
9:00-10:30 Ambient vibration wavefield Lecture
 
  • State of the art about the nature of the ambient vibration wave field.
  • Review of world-wide studies using ambient vibrations for site characterization and buildings.
10:30-10:45 Coffee break
10:45-12:30 Single-station ambient vibration method for extracting soil and building dynamic properties Lectures
 
  • Computation and interpretation of horizontal to vertical spectral ratio technique (H/V)
  • Effects of experimental conditions, recommendations for field measurements
  • Computation and interpretation of ambient noise measurements for buildings: resonance frequencies, damping, modal shape
12:30-14:00 Lunch break
14:00-15:30 Single station measurement, H/V Exercises
 
  • Geopsy tools for H/V.
  • Field data examples.
15:30-15:45 Coffee break
16:15-18:00 Extracting building dynamic properties Exercises
 
  • Geopsy tools for buildings
  • Field data examples (resonance frequencies, damping, modal shape).
Wednesday
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 the array response function.
  • Background of a widely used method, the high resolution f-k method after Capon (1969).
10:45-11:00 Coffee break
11:00-12:30 Conventional and high-resolution f-k processing Exercises
 
  • Building experience on how modifications in array layout affect the measurable wavelength range.
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.
16:00-16:15 Coffee break
16:15-17:45 Active surface waves technique (MASW) Lecture and exercises
 
  • The SASW, MASW and passive linear array techniques: theory, acquisition, processing and resolution limits.
  • Demonstration of MASW application
Thursday
08:30-09:00 Lebanon from a seismic risk perspective Lecture
 
  • Geological structures
  • Historical seismicity
  • Building vulnerability
09:15-10:45 Preparation of the field experiment Lecture
 
  • Presentation of WARAN (wireless array network) equipment.
  • Presentation of the active seismic equipment.
11:00-18:00 Field experiment Field
 
  • Field experiment in Byblos downtown (noise array, MASW and building measurement) and lunch boxes !.
19:00-... Workshop Dinner
Friday
9:00-10:45 Spatial autocorrelation method (SPAC) Lecture and Exercises
 
  • Background of the spatial autocorrelation technique (SPAC) introduced by Aki (1957).
  • Application and comparison with FK estimates: advantages and limitations of each approach
10:45-11:00 Coffee break
11:00-12:30 Dispersion curve inversion Lecture
 
  • Short introduction to the fundamentals of inversion theory.
  • Direct and global 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.
12:30-14:00 Lunch break
14:00-15:45 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).
  • Discussion of inversion results: what do we get ?
  • Handling shear-wave profiles: extraction of usefull engineering parameters (e.g. Vs30).
15:45-16:00 Lunch break
16:00-17:30 Processing field data. Exercises
 
  • Analysis of the signals recorded on the field with H/V and MASW techniques.
Saturday
09:00-10:45 Processing field data. Exercises
 
  • Analysis of the signals recorded on the field with f-k, high-resolution f-k, SPAC techniques.
10:45-11:00 Lunch break
11:00-12:30 Processing field data. Exercises
 
  • Analysis of the signals recorded on the field with f-k, high-resolution f-k, SPAC techniques.
  • Combining dispersion estimates from passive and active techniques.
12:30-14:00 Lunch break
14:00-15:45 Processing field data. Exercises
 
  • Decision on the usable frequency range for the inversion target.
  • Inversion of the dispersion curve
15:45-16:00 Coffee break
16:00-18:00 Processing field data. Exercises
 
  • Extraction of engineering parameters (e.g. Vs30).
  • Comparison of the individual results obtained during the inversion.
  • General discussion of experience gained during this complete test.
  • 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.
Sunday
09:00-12:00 Entertainment and open discussion
 
  • Open discussion on the scientific and technical problems encountered by participants.
  • Visit of the Jeita cave.

Suggested readings

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 June 15th 2016. If the number of applicants is larger than 20, the organizers reserve their rights to select the participants who will be informed by June 22nd.

The course will take place at NDU, Louaize, Lebanon. The registration fee is fixed to 800 USD per participant. The fees include all expenses related to tuition, training, support material, field experiment, workshop dinner, lunches and coffee breaks during the course.

A limited number of grants are available to support the registration fee and/or travel expenses of selected participants, with priority given to students working in a developing country.

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-elcapitan) during the online registration.

A list of suggested accommodations will be available soon.

Contacts

Cécile Cornou cecile dot cornou at univ-grenoble-alpes dot fr
Bertrand Guillier Bertrand dot Guillier at ird dot fr
Marc Wathelet marc dot wathelet at univ-grenoble-alpes dot fr
Jacques Harb jharb at ndu dot edu dot lb
Dalia Youssef Abdel-Massih Dalia.Abdelmassih at ul dot edu dot lb

Archives

Here you can find the program of last editions and all photos taken during these courses: