Satish Pullammanappallil and Bill Honjas. Optim LLC, Reno, Nevada, USA. John N. Louie. J. Andrew Siemens. Siemens & Associates, Bend, Oregon, USA

Size: px

Start display at page:

Download "Satish Pullammanappallil and Bill Honjas. Optim LLC, Reno, Nevada, USA. John N. Louie. J. Andrew Siemens. Siemens & Associates, Bend, Oregon, USA"

Bonnie Baldwin
8 years ago
Views:

1 Comparative Study of the Refraction Microtremor (ReMi) Method: Using Seismic noise and standard P-wave refraction equipment for deriving 1-D S-wave profiles Satish Pullammanappallil and Bill Honjas Optim LLC, Reno, Nevada, USA John N. Louie University of Nevada Seismological Laboratory, Reno, Nevada, USA J. Andrew Siemens Siemens & Associates, Bend, Oregon, USA Hidetoshi Miura Terra Corporation, Tokyo, Japan 6 th SEG-J International Symposium, Tokyo, Japan

John N. Louie University of Nevada Seismological Laboratory, Reno, Nevada, USA J.

2 2003 Optim LLC Refraction Microtremor Technique Based on two fundamental ideas Standard refraction equipment deployed similar to a shallow P-wave refraction survey to record ambient noise (microtremor) 4.5 to 14 Hz (or higher) vertical geophones depending on application. Depth of penetration is inversely proportional to natural frequency of geophones used. Slowness-frequency (p-f) transformation of the recorded microtremor Separate Rayleigh waves from other seismic arrivals and allow identifying true phase velocity against apparent velocities SeisOpt ReMi

Depth of penetration is inversely proportional to natural frequency of geophones used.

3 Why SeisOpt ReMi 2003 Optim LLC Disadvantages of commonly used methods Drilling and logging S-wave velocities (such as OYO logger) Expensive & time consuming Permitting required Physical restrictions Surface methods SASW & MASW Expensive & time consuming Specialized recording equipment required Artificial seismic source required Advantages of using SeisOpt ReMi Data acquisition and analysis takes about three hours No physical restrictions beyond required 100 m to 200 m line deployment space, minimal permitting Data can be acquired along roads, in buildings & at active construction sites No specialized recording equipment required Standard refraction seismograph & refraction P-wave geophones No artificial seismic source Uses ambient noise: Quiet site not required Can be used offshore as effectively as on-shore

$specialized recording equipment required Standard refraction seismograph & refraction P-wave geophones No artificial seismic source Uses ambient noise: Quiet site not required Can be used offshore as$

4 SeisOpt ReMi Method 2003 Optim LLC Acquire seconds microtremor data along a linear array. Array length depends on depth of investigation recommended minimum length 100m. Crooked line geometry can be handled. Step 1: p-τ transformation or the Slant Stack operation (Thorson and Claerbout, 1985) of the vertical particle velocity A(p=p0+ldp, τ=kdt) = Σ A(x=jdx, t=idt = τ+px) Surface Waves Data Courtesy of Terracon, Las Vegas, NV, USA Step 2: Fourier transformation: p-τ to p-f domain (McMechan and Yedlin, 1981) F A (p,f = mdf) = Σ A(p,τ=kdt)ei2π m df kdt

Step 1: p-τ transformation or the Slant Stack operation (Thorson and Claerbout, 1985) of the vertical particle velocity A(p=p0+ldp, τ=kdt) =

5 Lower limit of the apparent phase velocities can be recognized as the true phase velocities (Louie, 2001) SeisOpt ReMi Method 2003 Optim LLC Step 3: Velocity Spectral Analysis (Louie, 2001): Power spectrum S A (p,f ) = F A* (p,f) F A (p,f) S A ( p,f ) = [S A (p,f)] p>=0 + [S A (-p,f)] p<0 : S total ( p,f ) = Σ S (p,f)] A n Dispersion Picks

Analysis (Louie, 2001): Power spectrum S A (p,f ) = F A* (p,f) F A (p,f) S A ( p,f )

6 SeisOpt ReMi Method 2003 Optim LLC Step 4: Interactive Forward Velocity Modeling Avoids ambiguities associated with inversion, while providing the user with ability to include constraints while modeling

7 2003 Optim LLC Case Study: Oregon State University Geotechnical Engineering Field Research Test Site Hz geophones with 10 ft spacing deployed along a linear array p-f Image

Research Test Site 36 10-Hz geophones with

8 36 10-Hz geophones with 10 ft spacing deployed along a linear array Case Study: Oregon State University Geotechnical Engineering Field Research Test Site 2003 Optim LLC Depth, ft Vs, ft/s -100 Shear-Wave Velocity, ft/s

Engineering Field Research Test Site 2003 Optim LLC 0 300 800

9 2003 Optim LLC Case Study: Oregon State University Geotechnical Engineering Field Research Test Site Shear-wave profile from ReMi overlain on refraction velocity model from

$ReMi overlain on refraction velocity model$

10 Comparison of SeisOpt ReMi with SCPT at OSU Case Study: Oregon State University Geotechnical Engineering Field Research Test Site 2003 Optim LLC Depth, ft Shear-Wave Velocity, ft/s Seismic Cone Penetration Test (SCPT) Circa 1997

-40-50 -60-70 -80-90 -100 300 500 700 900 1100 1300 1500 1700 1900 2100 2300

11 Comparison of SASW with SCPT at OSU Case Study: Oregon State University Geotechnical Engineering Field Research Test Site Optim LLC Depth, ft Profile from SCPT measuremen t ReMi Analysis S eptember Spectral Analysis of Surface Waves (S AS W) Geocon Northwest Circa Shear-Wave Velocity, ft/s

12 Case Study: Wickiup Dam, Deschutes National Forest, Oregon Optim LLC Depth, ft Grout Treatment Zone -100 Cross-Hole Pre-Grout ReMi, V30=673 ft/s -120 Post-Grout ReMi, V30=827 ft/s Shear-Wave Velocity, ft/s Comparison of Cross-hole and SeisOpt ReMi at Wickiup

Zone -100 Cross-Hole-99-01 Pre-Grout ReMi, V30=673 ft/s -120 Post-Grout ReMi, V30=827

13 2003 Optim LLC Case Study: Loire Estuary, western France Purpose: Soil classification for harbor extension Rayleigh Wave Phase Velocity, m/s Data collected by SISMOCEAN SAS, France ( Modeled Dispersion Picked Dispersion Period, s , standard hydrophones, 5m spacing deployed along a linear array Source: 40 cu/in air gun. Hydrophone spread and air gun towed along seabed at 2 knots

sismocean.com) Modeled Dispersion Picked Dispersion Period, s 0 0.1 0.2 0.3 0.4 0.5 0.6 0.

14 2003 Optim LLC Case Study: Loire Estuary, western France Layer 1: Gravel with fine layer of mud Depth, m Layer 2: Fine sand and clay Layer 3: Fine sand and clay Layer boundaries from drill hole data V30 = 328 m/s (NEHRP D) Layer 4: Bedrock (Gneiss) Shear-Wave Velocity, m/s The resulting ReMi S-wave velocity profile revealed boundaries that correlated well with logged cores from drill holes, and also provided the same soil classification standard as the drill holes. Contact Jerome Adamy (jerome.adamy@sismocean.com) for data acquisition and project details

15 2003 Optim LLC SeisOpt ReMi Market Applicability ReMi V s profiles can be used for: Earthquake site response Liquefaction analysis Mapping the subsurface and estimating the strength of subsurface material Complementing seismic refraction analysis in areas characterized by near-surface velocity reversals Finding buried cultural features, such as dumps and fill material in submerged structures Determining soil classification for offshore projects

$seismic refraction analysis in areas characterized by near-surface velocity reversals Finding buried cultural$

16 2003 Optim LLC Conclusion: SeisOpt ReMi Compares well with previously used 1-D shear wave measurement techniques: Economic, accurate and reliable Correlates with SCPT measurements Detects velocity reversals Matches average velocities obtained using OYO logger Greater depth of investigation compared to borehole and surface methods Trends similar to velocity measurements from cross-hole Data acquisition and analysis takes about 3 to 4 hours Determine shear strength of subsurface material Concrete, water saturation material, buried fill material, etc. Save money in performing seismic site characterization studies Minimizes number of boreholes required No permitting required Can be carried out in urban settings Uses ambient noise as seismic energy source Uses standard seismic refraction recording equipment Offshore application Determine seismic soil classification standards for offshore projects

acquisition and analysis takes about 3 to 4 hours Determine shear strength of subsurface material Concrete, water saturation material, buried fill material, etc.

REFRACTION MICROTREMOR AND OPTIMIZATION METHODS AS ALTERNATIVES TO BOREHOLES FOR SITE STRENGTH AND EARTHQUAKE HAZARD ASSESSMENTS.

REFRACTION MICROTREMOR AND OPTIMIZATION METHODS AS ALTERNATIVES TO BOREHOLES FOR SITE STRENGTH AND EARTHQUAKE HAZARD ASSESSMENTS John N. Louie and Robert E. Abbott, University of Nevada, Reno, NV Satish