1. J. Louie 2/24/2005 Refraction Microtremor for Shallow Shear Velocity in California Urban Basins John Louie, Nevada Seismological Lab UNR students: J. B. Scott, T. Rasmussen, W. Thelen, M. Clark Collaborators: S. Pullammanappallil & B. Honjas, Optim LLC W. J. Stephenson, R. A. Williams, & J. K. Odum, USGS Support from: IRIS-PASSCAL Instrument Center at NMT  More details at www.seismo.unr.edu/hazsurv John Louie, Nevada Seismological Lab UNR students: J. B. Scott, T. Rasmussen, W. Thelen, M. Clark Collaborators: S. Pullammanappallil & B. Honjas, Optim LLC W. J. Stephenson, R. A. Williams, & J. K. Odum, USGS Support from: IRIS-PASSCAL Instrument Center at NMT  More details at www.seismo.unr.edu/hazsurv

2. J. Louie 2/24/2005 ReMi measures Rayleigh dispersion with linear refraction arrays (paper by Louie, April 2001 BSSA). Refraction Microtremor for Shallow Shear Velocity 100-m depth resolution Initial funding from SCEC, UNR, VUW, Optim LLC

3. J. Louie 2/24/2005 What if energy arrives transverse to the linear array? Refraction Microtremor for Shallow Shear Velocity Initial funding from SCEC, UNR, VUW, Optim LLC

4. J. Louie 2/24/2005 Majority of energy piles up close to the minimum- velocity envelope. Refraction Microtremor for Shallow Shear Velocity Initial funding from SCEC, UNR, VUW, Optim LLC

5. J. Louie 2/24/2005 Fieldwork is quick and simple; best results in cities. Refraction Microtremor for Shallow Shear Velocity Initial funding from SCEC, UNR, VUW, Optim LLC

6. J. Louie 2/24/2005 Low-frequencies, 1-20 Hz, so bad geophone plants still work. Refraction Microtremor for Shallow Shear Velocity Initial funding from SCEC, UNR, VUW, Optim LLC

7. J. Louie 2/24/2005 Fieldwork is quick and simple; best results in cities. Refraction Microtremor for Shallow Shear Velocity Initial funding from SCEC, UNR, VUW, Optim LLC

8. J. Louie 2/24/2005 Fieldwork is quick and simple; best results in cities. Refraction Microtremor for Shallow Shear Velocity Initial funding from SCEC, UNR, VUW, Optim LLC

9. J. Louie 2/24/2005 ReMi has classified hard and soft sites around the world by measuring V 30, average shear velocity to 30 m depth. Refraction Microtremor for Shallow Shear Velocity

10. J. Louie 2/24/2005 Four deep suspension logs in Santa Clara Valley Collaboration with Stephenson, Williams, Odum (USGS), and Pullammanappallil (Optim) Refraction, MASW, and ReMi at each hole ReMi-Borehole Comparison

11. J. Louie 2/24/2005 No surface method can match log details. ReMi-Borehole Comparison

12. J. Louie 2/24/2005 Depth-averaged velocities are a good match. But CCOC’s LVZ is a problem. ReMi-Borehole Comparison

13. J. Louie 2/24/2005 Joyner et al. (1981) quarter-wavelength spectra similar at important frequencies. ReMi-Borehole Comparison

14. J. Louie 2/24/2005 We Follow Field’s (2001) Amplification-Mapping Strategy Two Inputs for Microzonation: V 30 and Basin Depth (Z 1.5 ?)

15. J. Louie 2/24/2005 July 2003 San Gabriel Valley & Los Angeles Shallow Shear-Velocity Transects B-C C-D D D-E Transect mapped on NEHRP hazard class map by Wills, from SCEC Phase 3 Report Supported by USGS, NEHRP ERP and IRIS-PASSCAL

16. J. Louie 2/24/2005 Los Angeles Transect  Approximately 60 km in length  Followed San Gabriel River Bike Path  20 m takeout interval, 300 m array, recorded for 30 min  4 teams, 3 people each, 4.5 days  120 IRIS/PASSCAL “Texan” single-channel recorders mated to a vertical 4.5-Hz geophone Supported by USGS, NEHRP ERP and IRIS-PASSCAL

17. J. Louie 2/24/2005 Los Angeles Transect: Levee Effects  V 30 levee: 245 m/s  V 30 non-levee: 241 m/s

18. J. Louie 2/24/2005 Los Angeles Transect: V30 Results

19. J. Louie 2/24/2005 Boreholes in Open-File Reports  Four within 1 km of transect  Also an incomplete posting at ROSRINE, Pico Rivera 2

20. J. Louie 2/24/2005 Rosrine/USGS Pico Rivera 2  Good correlation with transect below 8 m depth.

21. J. Louie 2/24/2005 Los Angeles Transect: V30 Results

22. J. Louie 2/24/2005 Los Angeles Transect: Full Results

23. J. Louie 2/24/2005 Measured V 30 vs Wills et al. (2000)  Average measurements within ranges for classes B- C, D, and D-E  N. San Gabriel Val. Measurements average above predicted C-D range  60 new C-D data points B B-C C C-D D D-E E

24. J. Louie 2/24/2005 V 30 vs Geologic Unit  Large V 30 variation inside each unit  Large V 30 variation between units

25. J. Louie 2/24/2005 V 30 vs Soil Type  In general, large V 30 variation within units  Units 2 and 5 may be NEHRP D  Large V 30 variation between units

26. J. Louie 2/24/2005 V 30 vs Riverbank Elevation  Fast, bouldery alluvium at higher elevations on River’s alluvial fan

27. J. Louie 2/24/2005 Spatial Statistics on V 30  Line in log-log spectrum means fractal  V30 less predictable as distance from measurement increases  “Noise Floor”- minimum variance reached at 700 m separation  Incorporate fractal dimension into PSHA? Noise Floor

28. J. Louie 2/24/2005SummarySummary  ReMi allows rapid seismic shaking-hazard classification, as required by IBC2000.  Long ReMi transects can geophysically characterize spatial variations in shaking hazard.  Mapped soil and geologic units do not reliably predict the measured V 30.  210 Measurements in LA match predictions, add to class C-D data, and quantify spatial variance.  ReMi allows rapid seismic shaking-hazard classification, as required by IBC2000.  Long ReMi transects can geophysically characterize spatial variations in shaking hazard.  Mapped soil and geologic units do not reliably predict the measured V 30.  210 Measurements in LA match predictions, add to class C-D data, and quantify spatial variance.

29. J. Louie 2/24/2005 Most of Strip, Downtown; south side of Basin only 79 sites total 1145 well logs & geologic mapping Las Vegas Transect

30. J. Louie 2/24/2005 Some correlation to faulting, soil type? Las Vegas Transect

31. J. Louie 2/24/2005 Geologic Info to Predict V s NSL, July ‘03, sponsored by LLNL  Can soil maps predict V s ?

32. J. Louie 2/24/2005 How to Extrapolate Shallow V s  Correlate transect measurements against Soil Map.  Correlate 75 Vs values against stratigraphic model. Soil Stratigraphy

33. J. Louie 2/24/2005 How to Extrapolate Shallow V s  Predictions are good where there are many measurements.

34. J. Louie 2/24/2005 How to Extrapolate Shallow V s  Predictions are not good where there only sparse measurements.  Soil map predictions are not conservative.  Stratigraphic model predictions are, at least, conservative.