1. The surface profiles in Grenoble area determined by the MASW measurements Seiji Tsuno, Cecile Cornou, Pierre-Yves Bard (LGIT) QSHA meeting, 1/Juin/2007, Nice

2. Today’s presentation Procedure of the MASW measurements in Grenoble area and those analyses Inversion of Rayleigh wave to S-wave velocity profiles Wave-length of Rayleigh in Grenoble area (combining between our results and the results by BRGM) Distribution maps of surface velocities and engineering bedrock (combining between our results and the results by BRGM) On higher modes obtained by the MASW method Estimation of damping factors on surface

3. MASW measurements and the analyses

4. Concept of MASW method

5. Measurement sites ILL MONSIEUR G15 STADE RAILWAY MSPORT G12 KAWASE2 KAWASE1 IMPOT CASERNE BASTILE CAMPUS TAILLAT FORAGE G03 ROCK Belledonne G10 ROCK Vercors G17 ROCK Bastile G18 H/V Seismic station MASW by BRGM

6. Outline of Measurement Site LongitudeLatitudeDateIntervalSamplingOff-set distanceMass Campus5.77269445.19837922/1/20072m4000Hz0, 5, 10, 15, 20m3, 5kg Taillat5.78998945.19418423/1/20073m1000Hz0, 10, 20m5kg G035.80845.21723/1/20072m1000Hz0, 10, 33m3, 5kg Forage5.82145.20926/1/20073m1000Hz0, 10, 20, 40, 60m5kg Caserne5.72545.18430/1/20072m1000Hz0, 10, 20m5kg Kawase15.72232645.17696329/1/20073m1000Hz0, 10,20m5kg Impot5.70576345.17721825/1/20072m1000Hz0, 10m5kg Ill5.69550745.2079129/1/20073m1000Hz0, 10, 20, 40m5kg Kawase25.72038445.16218225/1/20073m1000Hz0, 10, 20, 30m5kg G125.75095545.15416525/1/20072m1000Hz0, 10, 20, 30m5kg Msport5.72788645.14416731/1/20073m1000Hz0, 20m5kg Railway5.70741745.15035431/1/20073m1000Hz0, 20m5kg G185.67617545.22504724/1/20072m1000Hz0, 10m5kg Monsieur5.68327745.2003824/1/20073m1000Hz0, 10, 15, 20, 40m5kg G155.68641245.19518724/1/20072m1000Hz0, 10, 20, 40m5kg Stade5.69345.16525/1/20073m1000Hz0,10, 20m5kg Bastille5.72545.231/1/20071, 4m4000Hz0m3, 5kg G175.63245.1671/2/20071m4000Hz0, 20m3kg G105.8545.1981/2/20071m4000Hz0, 20, 40m3kg * Except Kawase1, we made hammer shots at both sites. * At Bastille in Chartreuse, at G17 in Vercors, at G10 in Belledonne, we also made the measurements of MASW on horizontal waves.

7. Process of analysis  Normalization (for the distance between a shot point and receivers)  High resolusion method (Capon)  Using the records integrated  Stacking (in time domain)  Multi-offset (in frequency domain) HR BFM Offset- 40m Offset- 0m Does the excitation of modes depend on the condition of shot points ? (and on the wave-length ?) Recording  Sampling 1000Hz (4000Hz in rock site)  Array length of 46 or 69m – interval 2 or 3m (23 and/or 92m in rock site)  4.5Hz (Vertical sensors)  14Hz (Horizontal sensors in rock site)

8. Dispersion curve - north-east basin Campus Taillat G03 Forage 1 st higher mode ? Fundamental mode PV = 100m/s

9. Dispersion curve - centre ville Caserne Kawase1 Impot Ill PV = 200m/s

10. Dispersion curve - south of Grenoble Kawase2 G12 Msport Railway PV = 250m/s

11. Dispersion curve - west of Grenoble G18 Monsieur G15 Stade PV = 100m/s

12. Dispersion curve - Rock sites Bastille G17 G10 2000m/s 1000m/s 2000m/s Array response - Array length 24m

13. Dispersion curve of Love wave - Rock sites Bastille G17 G10 1200m/s500m/s 1400m/s Array response - Array length 24m

14. Comparison with dispersion curves determined by microtremors Campus Forage Taillat Array response

15. Inversion of Rayleigh wave to S-wave velocity profiles

16. Inversion  Genetic algorithm after Yamanaka and Ishida (1995)  Target of fundamental mode of Rayleigh wave  Adopting of 3 or 4 layers  5 trials with different random numbers  Selection of minimum misfit result GA

17. S-wave vel. profiles - north-east basin

18. S-wave vel. profiles - centre ville

19. S-wave vel. profiles - south of Grenoble

20. S-wave vel. profiles - west of Grenoble

21. S-wave velocity profiles - Rock sites

22. Comparison of Love wave dispersion Love Wave Rayleigh Wave

23. Wave-length of Rayleigh in Grenoble area

24. Dispersion of Rayleigh waves - Sedimentary basin - Measurement by LGIT Measurement by BRGM

25. Wave length of Rayleigh waves - Sedimentary basin - Measurement by LGIT Measurement by BRGM

26. Dispersion and Wave-length of Rayleigh waves - Rock site - Dispersion curve Wave-length

27. Dispersion and Wave-length of Love waves - Rock site - Dispersion curve Wave-length

28. Dispersion and Wave-length of Rayleigh waves - Microtremors - Dispersion curve Wave-length

29. Comparison of wave-lengh of observation with ESG model Wave-length Vs 400m/s

30. Distribution maps of surface velocity and engineering bedrock in Grenoble area

31. Distribution of surface velocity of Rayleigh wave Bedrock map in Grenoble basin

32. Distribution of surface velocity of Rayleigh wave - comparison of dif. WL On surface At WL 20m At WL 50m

33. Distribution of surface velocity of Rayleigh wave -2 Distribution of surface velocity of Rayleigh wave - (m/s)

34. Observation map in Grenoble area ILL -221 MONSIEUR -118 G15 -124 STADE -149 RAILWAY -256 MSPORT -327 G12 -232 KAWASE2 -312 KAWASE1 -243 IMPOT -237 CASERNE -220 BASTILE -218 CAMPUS -116 TAILLAT -160 FORAGE -102 G03 -113 ROCK Belledonne G10 -217 ROCK Vercors G17 -145 ROCK Bastile -218 G18 -146 Unit – m/sec 253 86 177 113 188 151 262 146 207 276 167 115 119 136 142 86 172 130 184 127 117 115 133 177 174 133

35. Depth of engineering bedrock (Vs 400 - 500m/s) Bedrock map in Grenoble basin Distribution of surface velocity of Rayleigh wave - (m/s)

36. Higher mode - Can we use the dispersion of higher mode to invert for S-wave velocity profiles ?

37. Comparison of theoretical dispersions with observations Phase velocity - Taillat Phase velocity – G03 Power spectra (G03 and Taillat)

38. Dispersion curve in Forage (borehole site) Phase velocityF-K spectra Power spectra

39. Estimation of damping factors - Examples -

40. Waveform inversion using recordings of the MASW measurment (at Forage) Comparison of theoretical waveforms (red line) calculated by DWM with observation recording (black line) generated by hammer hit Q = 15Q = 50 (Frequency independent model) Propagation

41. Ricker wavelet used in DWM (Forage) F-K spectra Source (Ricker wavelet 0.03s)

42. Waveform inversion using recordings of the MASW measurment (at G03) Comparison of theoretical waveforms (red line) calculated by DWM with observation recording (black line) generated by hammer hit Q = 15Q = 50 (Frequency independent model) Propagation

43. Ricker wavelet used in DWM (G03) F-K spectra Source (Ricker wavelet 0.03s)

44. Conclusion We determined the surface profiles in Grenoble area by the MASW method. Also, we made the distribution map of the engineering bedrock (Vs 400-500m/s) in Grenoble area. The dispersions of Rayleigh waves obtained by the MASW method are in agreement with those by microtremors. The S-wave velocity of 400-500m/sec is entirely appeared in Grenoble basin. On the other hand, the surface velocities higher than Vs 400m/s are quite various. Especially in the middle-west of Grenoble basin, the soft sediment (Vs < 400m/s) is deeply covered. We determined the S-wave velocity (Vs > 2km/sec) in rock sites. The wave-length of Rayleigh waves in Grenoble area observed by this study is slightly different from the previous model (ESG model). We proposed the estimation method on quality factors of surface layers using the waveforms excited by the hammer shot.

45. Individual dispersion (Sedimental basin)

46. Campus Phase velocityF-K spectra Wave-length = 57.6m Wave-length = 45.5m

47. Taillat Phase velocityF-K spectra Wave-length = 66.5m Wave-length = 84.7m

48. G03 Phase velocityF-K spectra Wave-length = 65.7m Wave-length = 95.8m

49. Forage Phase velocityF-K spectra Wave-length = 53.4m Wave-length = 26.6m

50. Caserne Phase velocityF-K spectra Wave-length = 25.7m Wave-length = 43.8m

51. Kawase1 Phase velocityF-K spectra Wave-length = 33.4m Wave-length = 23.9m

52. Impot Phase velocityF-K spectra Wave-length = 44.5m Wave-length = 48.8m

53. Ill Phase velocityF-K spectra Wave-length = 22.3m Wave-length = 81.1m

54. Kawase2 Phase velocityF-K spectra Wave-length = 44.3m Wave-length = 41.1m

55. G12 Phase velocityF-K spectra Wave-length = 46.5m Wave-length = 83.2m

56. Msport Phase velocityF-K spectra Wave-length = 47.4m Wave-length = 52.7m

57. Railway Phase velocityF-K spectra Wave-length = 69.4m Wave-length = 62.5m

58. G18 Phase velocityF-K spectra Wave-length = 45.5m Wave-length = 43.3m

59. Monsieur Phase velocityF-K spectra Wave-length = 41.2m Wave-length = 39.9m

60. G15 Phase velocityF-K spectra Wave-length = 33.8m Wave-length = 30.1m

61. Stade Phase velocityF-K spectra Wave-length = 35.8m Wave-length = 71.4m

62. Higher mode dispersion -1

63. Higher mode dispersion -2

64. Higher mode dispersion -3

65. F-K Power spectra -1

66. F-K Power spectra -2

67. F-K Power spectra -3

68. Individual dispersion (Rock sites)

69. Bastile - Rayleigh wave Phase velocityF-K spectra Wave-length = 20.7m Wave-length = 92.9m

70. G17 - Rayleigh wave Phase velocityF-K spectra Wave-length = 32m Wave-length = 94.2m

71. G10 - Rayleigh wave Phase velocityF-K spectra Wave-length = 34.9m Wave-length = 101.5m

72. Bastile - Love wave Phase velocityF-K spectra Wave-length = 29.4m Wave-length = 120.4m

73. G17 - Love wave Phase velocityF-K spectra Wave-length = 31.3m Wave-length = 53.4m

74. G10 - Love wave Phase velocityF-K spectra Wave-length = 19.3m Wave-length = 113.2m

75. Higher mode and Love wave dispersion Love Wave Rayleigh Wave

76. F-K Power spectra - R. and L. Love Wave Rayleigh Wave

77. Next step Estimation of S-wave velocity structures at measurement sites Categorization of surface structures in Grenoble Basin Comparison of the geological data Detecting of common minimum velocity layer in Grenoble - for 3D simulation For this purpose, do we need to take into account the results of array microtremors ? Do we need to make more MASW measurements in Grenoble basin, for detail categorization on surface structures ? Comparison these results with the proposed model Confirmation of the estimated shallow structures by using earthquake recordings (which recordings do we select ?) We would estimate the damping factor on surface by applying the waveform inversion with the discrete wave-number method. We include the higher mode and/or Love wave dispersion, to invert the S-wave velocity structures.

78. Inversion We have three steps to invert the basin structures. With the dispersion of Rayleigh wave estimated by MASW method Taking account of the dispersion estimated by Array Microtermors → To determine deeper structures Including of Higher modes and/or the dispersion of Love wave → To determine structures in detail

79. Measurement errors Time errorDistance error

80. Spectral inversion using earthquake recording