i traveled to haiti with my graduate student, melinda

• I traveled to Haiti with my graduate student, Melinda Jean-Louis (a Haitian native) and Haiti Engineering in July 2013 to perform surface wave testing and present our project to interested parties. We visited Haiti for 10 days and completed seismic testing at 8 sites in Haiti. We used seismic surface wave testing to derive shear wave velocity profiles performed seismic site response analyses with the derived profiles. We calculated design spectral acceleration values and presented them in a report to Haiti Engineering (attached). Haiti Engineering passed this information along to interested parties who will performing reconstruction, including the Catholic Church and the Samuel Dalembert Foundation.

• While in Haiti, I gave a presentation to the Papal Nuncio to Haiti along with other

representatives from the Catholic Church, local engineering firms, and Prof. Christian Rousseau from the University of Haiti on how our methods could be used to improve capabilities for seismic design in Haiti.

• We developed a user’s manual on how to use the field equipment to perform seismic

surface wave testing, analyze the data, and perform seismic site response analysis. We also provided information on how to use the shear wave velocity data derived from surface wave testing for various geotechnical design applications as a replacement to traditional soil borings. Since there are only a few drill rigs in the entire country, the local geoscientists are very interested in being able to use seismic surface wave testing as a replacement to soil borings.

• We sent the equipment to Haiti Engineering along with the User’s Manual (attached) so they can perform the testing themselves.

• The University of Kentucky online daily publication UK Now contained a feature story

on our efforts in Haiti.

• We appeared on the local NBC affiliate WLEX (Channel 18) as part of their “Making a Difference” spot on the 5:00 news. The story aired on November 20, 2013.

• As a result of the experience we acquired in Haiti, we are now in a position to solicit

funds for similar projects in other nations that may result in as much as $14 million in sponsored research. This would not have been possible without the GWB experience in Haiti, which demonstrates that the GWB project will most likely lead to humanitarian engineering efforts around the world.

• The University of Kentucky chapter of Engineers Without Borders is very interested in our work in Haiti and would like to participate in future projects, which is likely.

• Graduate student Melinda Jean-Louis will earn her Master’s degree in May 2014 based

on the work she did on this project.

• We will present the results of our study at the 2014 SEG Annual Meeting and submit them for publication in the SEG peer-reviewed journal Interpretation

September 18, 2013 Mr. Herby G. Lissade, P.E. Haiti Engineering, Inc. 9384 Boulder River Way Elk Grove, CA 95624 RE: Field Seismic Testing and Seismic Site Response Analyses at Selected Sites in Haiti Dear. Mr. Lissade, SUMMARY

Spectral-Analysis-of-Surface-Waves (SASW) testing was performed in July 2013 at selected sites in Haiti to measure the shear wave velocity (vs) profiles. The shear wave velocity information was used to perform seismic site response analyses in accordance with the 2012 International Building Code, which incorporates ASCE Standard 7-10 by reference. This information was used in the General Procedure (ASCE 7-10 Section 11.4) to calculate short-period and long-period design ground surface spectral acceleration values (SDS and SD1) for each site, which can be used to perform seismic design for buildings DERIVATION OF SHEAR WAVE VELOCITY PROFILES The SASW method involves the use of an impulsive seismic energy source and a pair of receivers spaced an equal distance apart in a straight line as shown in Fig. 1. When the ground is impacted, surface waves are generated. As they pass the two receivers, the energy recorded at each receiver is analyzed for spectral content. Differences in phase between the two receivers are calculated at each frequency, and this information is used to calculate variations in surface wave velocity with wavelength, or “dispersion.” Since shorter-wavelength velocities only depend on shallow material and longer-wavelength velocities depend upon deeper material, variations in velocity with wavelength are indicative of variations in shear wave velocity (vs) with depth. By inverting the data using numerical analysis, the vs profile (vs as a function of depth) is derived.

Testing was performed at several sites in Haiti in July 2013. Test locations are summarized in Table 1 and their locations are depicted in Fig. 2. Field data were recorded using a Data Physics Quattro dynamic signal analyzer with 4.5-Hz geophones as receivers. A sledge hammer was used as an impulsive energy source with receiver spacings of 10, 20, and 40 ft. By combining dispersion curves derived using a range of

Seismic Site Response Analysis at Selected Sites in Haiti

Page 1 of 22

receiver spacings, a “composite” dispersion curve is derived. The composite dispersion curve is defined over a broader bandwidth, which helps constrain the inversion process.

The composite dispersion curves derived from field testing were analyzed using the WinSASW forward modeling software package developed at the University of Texas. Forward modeling is performed iteratively by assuming a model vs profile and deriving a theoretical dispersion curve. The model vs profile is refined until an acceptable match between the theoretical dispersion curve and the experimental dispersion curve is achieved. Experimental and theoretical surface wave dispersion curves are shown in Appendix A, and the resulting vs profiles are illustrated in Appendix B. Shear wave velocity profiles derived for each test are also given in Appendix C. APPLICATION OF ASCE 7-10 TO CALCULATE SEISMIC DESIGN PARAMETERS The vs data recorded during SASW testing were used to perform seismic site response analyses according to the General Procedure (ASCE 7-10 Section 11.4). To apply the General Procedure, the average shear wave velocity within the upper 100 ft (

sv ) was calculated using the following equation:

∑

∑=

=

=n

1i si

i

n

1ii

s

vd

dv , (ASCE 7-10 Eqn. 20.4-1)

where di and vsi are the thickness and shear wave velocity in the ith layer of a layered soil/rock profile, and the total thickness of the top n layers is 100 ft. Using the above equation, average shear wave velocities were calculated, and the sites were classified. Seismic site classifications are included in Table 1 for each test point. Application of the General Procedure starts with estimating the Maximum Considered Earthquake (MCE). The MCE has associated peak and spectral acceleration values which have a 2% probability of being exceeded during a 50-year exposure period. Information regarding MCE bedrock shaking for Haiti was published by Frankel et al1. For the sites in Haiti, the short-period (0.2 s) and long-period (1.0 s) spectral acceleration associated with the MCE, SS and S1, are included in Table 1. The MCE parameters SS and S1 represent bedrock spectral acceleration, but they must be corrected to account for the effect of the soil column, which tends to amplify strong ground motion. To make this correction, the site coefficients Fa and Fv are derived based on site class and bedrock spectral acceleration. Short-period and long-period surface spectral acceleration, SMS and SM1, are expressed as:

1Frankel, A., Harmsen, S., Mueller, C., Calais, E., and Haase, J., 2011, “Seismic Hazard Maps for Haiti,” Earthquake Spectra, Vol. 27, No. S1, pp. S23-S41.


Page 2 of 22

SMS = FaSS (ASCE 7-10 Eqn. 11.4-1) and SM1 = FvS1. (ASCE 7-10 Eqn. 11.4-2) The coefficient Fa is selected using ASCE 7-10 Table 11.4-1, and the coefficient Fv is selected using ASCE 7-10 Table 11.4-2. The spectral acceleration values SMS and SM1 represent spectral acceleration levels at the ground surface corresponding to the MCE. For design purposes, these values are multiplied by 0.667 to derive design ground surface spectral acceleration values SDS and SD1. Values of SDS and SD1 for each location are included in Table 1. Given SDS and SD1, the design response spectrum is calculated according to ASCE 7-05 Section 11.4.5. For periods less than T0=0.2SD1/SDS, spectral acceleration (Sa) is expressed as:

DS0

DSa ST

TS

S 0.40.6 += (ASCE 7-10 Eqn. 11.4-5)

For periods between T0 and TS=SD1/SDS, Sa is equal to SDS. For periods greater than TS, Sa is expressed as: Sa = SD1/T. (ASCE 7-10 Eqn. 11.4-6) The ground surface design response spectra calculated for each site class are depicted in Fig. 3. Regards, Michael E. Kalinski Michael E. Kalinski, Ph.D. Associate Professor Attachments: Tables and Figures

Appendices


Page 3 of 22

Table 1. Description of Test Sites in Haiti

Site Date Tested

Profile No.

Latitude (deg. N)

Longitude (deg. W)

SS (g)

S1 (g)

sv (ft/s)

Site Class

SDS (g)

SD1 (g)

Samuel Dalembert Community Center

July 22, 2013

1 19.0619 -71.9844

1.10 0.38

1,890

C 0.73 0.36 2 19.0620 -71.9848 1,877 3 19.0622 -71.9849 1,944 4 19.0623 -71.9842 2,419 5 19.0626 -71.9843 1,753

St. Famine Church July 20, 2013

1 18.4761 -72.6535 1.61 0.75 821 D 1.07 0.75 2 18.4761 -72.6533 885

St. Gerard Church July 20, 2013

1 18.5305 -72.6227 1.30 0.45

2,103 C 0.87 0.40 2 18.5308 -72.6224 2,104 3 18.5308 -72.6226 2,527 B 0.87 0.30

St. Immaculate Church

July 20, 2013 1 18.5485 -72.5761 1.22 0.42 1,159 D 0.82 0.44

St. Michel Church July 18, 2013

1 18.5406 -72.5874 1.26 0.44

1,803 C 0.84 0.40 2 18.5408 -72.5868 1,502

3 18.5410 -72.5873 1,717

Petit Goave School July 23, 2013

1 18.4191 -72.8532 1.61 0.60 2,181 C 1.07 0.52 2 18.4192 -72.8532 2,421 St. Rose de Lima

Church July 16,

2013 2 18.5106 -72.6328 1.43 0.49 937 D 0.95 0.49


Page 4 of 22

Figure 1. Experimental configuration for SASW testing.


Page 5 of 22

Figure 2. Map of Test Locations in Haiti.

19.2

19.0

18.8

18.6

18.4

18.2

Latit

ude

(Deg

rees

Nor

th)

-73.0 -72.8 -72.6 -72.4 -72.2 -72.0 -71.8Longitude (Degrees West)

Petit Goave

St. MichelSt. GerardSt. Rose

St. Famine

Dalembert

St. Immaculate


Page 6 of 22

Figure 3. Ground Surface Design Response Spectra for Each Site.

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Spe

ctra

l Acc

eler

atio

n (g

)

0.012 3 4 5 6 7 8 9

0.12 3 4 5 6 7 8 9

12 3 4 5 6 7 8 9

10

Period (seconds)

D

D

D D D D D D D DD

D

D

D

DD

D

DD

DD D

DD D D D D D D D

F

F

F

F F F F F F F F F F

F

F

F

F

F

F

F

FF

FF

FF F F

F F F

GB

GB

GB GB GB GBGBGB

GB

GB

GB

GB

GB

GB

GBGB

GB

GBGB

GBGBGB

GBGBGBGBGBGBGBGB GB

GC

GC

GC GC GC GCGCGCGCGC

GC

GC

GC

GC

GC

GC

GC

GC

GCGC

GCGC

GCGCGCGCGCGCGCGC GC

I

I

I I I I I I I I II

I

I

I

I

I

I

II

II

II I I I I I I I

M

M

M M M M M M M M

M

M

M

M

M

M

M

MM

MM

MM

M M M M M M M M

P

P

P P P P P P P P

P

P

P

P

P

P

P

P

PP

PP

PP

P P P P P P P

R

R

R R R R R R R R R

R

R

R

R

R

R

R

RR

RR

RR

R R R R R R R

D DalembertF St. Famine

GB St. Gerard Site Class BGC St. Gerard Site Class C

I St. ImmaculateM St. MichelP Petit GoaveR St. Rose de Lima


Page 7 of 22

Appendix A

Experimental and Model Dispersion Curves

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

Dalembert Profile 1

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

Dalembert Profile 2


Page 8 of 22

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

Dalembert Profile 3

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

Dalembert Profile 4

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

Dalembert Profile 5


Page 9 of 22

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

St. Famine Profile 1

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model


2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

St. Gerard Profile 1


Page 10 of 22

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model


2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model


2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

St. Immaculate Profile 1


Page 11 of 22

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

St. Michel Profile 1

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

1002

Wavelength (ft)

Experimental Model


2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

1002

Wavelength (ft)

Experimental Model



Page 12 of 22

2500

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

1002

Wavelength (ft)

Experimental Model

Petit Goave Profile 1

2500

2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

1002

Wavelength (ft)

Experimental Model


2000

1500

1000

500

0

Surfa

ce W

ave

Velo

city

(ft/s

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

Wavelength (ft)

Experimental Model

St. Rose de Lima Profile 2


Page 13 of 22

Appendix B Shear Wave Velocity Profile Graphs

100

80

60

40

20

0

Dep

th (f

t)

40003000200010000Shear Wave Velocity (ft/s)

Dalembert Profile 1100

80

60

40

20

0

Dep

th (f

t)


Dalembert Profile 2

100

80

60

40

20

0

Dep

th (f

t)



80

60

40

20

0

Dep

th (f

t)


Dalembert Profile 4


Page 14 of 22

100

80

60

40

20

0D

epth

(ft)



80

60

40

20

0

Dep

th (f

t)40003000200010000

Shear Wave Velocity (ft/s)


100

80

60

40

20

0

Dep

th (f

t)



100

80

60

40

20

0

Dep

th (f

t)




Page 15 of 22

100

80

60

40

20

0D

epth

(ft)



100

80

60

40

20

0

Dep

th (f

t)40003000200010000



100

80

60

40

20

0

Dep

th (f

t)



100

80

60

40

20

0

Dep

th (f

t)




Page 16 of 22

100

80

60

40

20

0D

epth

(ft)



100

80

60

40

20

0

Dep

th (f

t)40003000200010000



100

80

60

40

20

0

Dep

th (f

t)



80

60

40

20

0

Dep

th (f

t)




Page 17 of 22

100

80

60

40

20

0D

epth

(ft)




Page 18 of 22

Appendix C Shear Wave Velocity Profile Data

Dalembert Profile 1

Depth Interval (ft)


0.0-2.5 350 2.5-7.5 1500

7.5-42.5 1800 42.5-100.0 2500

Dalembert Profile 2

Depth Interval (ft)


0.0-5.0 500 5.0-25.0 1300

25.0-65.0 2600 65.0-100.0 2800

Dalembert Profile 3

Depth Interval (ft)


0.0-5.0 580 5.0-15.0 1300

15.0-95.0 2400 95.0-100.0 2800

Dalembert Profile 4

Depth Interval (ft)


0.0-7.0 500 7.0-27.0 2900

27.0-67.0 3400 67.0-100.0 3800


Page 19 of 22

Dalembert Profile 5 Depth Interval

(ft) Shear Wave Velocity

(ft/s) 0.0-5.0 500

5.0-25.0 1000 25.0-65.0 2600 65.0-100.0 3000


Depth Interval (ft)


0.0-15.0 420 15.0-35.0 800 35.0-75.0 900 75.0-100.0 1500


Depth Interval (ft)


0.0-4.0 320 4.0-12.0 500

12.0-20.0 600 20.0-60.0 900 60.0-100.0 1500


Depth Interval (ft)


0.0-3.5 420 3.5-13.5 1200

13.5-100.0 2800

St. Gerard Profile 2 Depth Interval


(ft/s) 0.0-4.2 480

4.2-29.2 1200 29.2-100.0 4000


Page 20 of 22

St. Gerard Profile 3 Depth Interval


(ft/s) 0.0-6.2 570

6.2-18.2 1500 18.2-100.0 4000


Depth Interval (ft)


0.0-25.0 460 25.0-45.0 2100 45.0-85.0 2400 85.0-100.0 2600


Depth Interval (ft)


0.0-5.0 520 5.0-25.0 1200

25.0-65.0 2400 65.0-100.0 2800


Depth Interval (ft)


0.0-6.6 500 6.6-48.6 1200

48.6-100.0 2800

St. Michel Profile 3 Depth Interval


(ft/s) 0.0-8.0 700

8.0-15.0 1150 15.0-45.0 1200 45.0-100.0 3500


Page 21 of 22

Petit Goave Profile 1 Depth Interval


(ft/s) 0.0-5.0 750

5.0-10.0 1100 10.0-20.0 2000 20.0-100.0 2700


Depth Interval (ft)


0.0-4.5 800 4.5-10.5 1100

10.5-22.5 2000 22.5-100.0 3200


Depth Interval (ft)


0.0-3.5 450 3.5-13.5 800

13.5-100.0 1000


Page 22 of 22

TUTORIAL FOR PERFORMING FIELD SASW SEISMIC TESTING TO OBTAIN SHEAR WAVE VELOCITY DATA

Prepared by:

Prof. Michael E. Kalinski, Ph.D., P.E. Melinda Jean-Louis

University of Kentucky Department of Civil Engineering

161 Raymond Bldg. Lexington, KY 40506-0281 Tel: (001) 859-257-6117

Email: [email protected]

October 30, 2013

Table of Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Acquiring Field SASW Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 Deriving the Shear Wave Velocity Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4 Deriving the Design Response Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5 Correlating Shear Wave Velocity to Other Geotechnical Parameters . . . . . . . 26 6 Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

1. Introduction

Seismic surface wave testing is a nondestructive geophysical method where

surface waves are generated and measured at the ground surface. There are several

methods used in practice today, but the oldest and simplest method is the Spectral-

Analysis-of-Surface-Waves (SASW) method. The SASW method involves the use of an

impulsive seismic energy source and a pair of receivers (geophones) spaced an equal

distance apart in a straight line as shown in Fig. 1. When the ground is impacted,

surface waves are generated. As they pass the two receivers, the energy recorded at

each receiver is analyzed for spectral content. Differences in phase between the two

receivers are calculated at each frequency, and this information is used to calculate

variations in surface wave velocity with wavelength, or “dispersion.” Since shorter-

wavelength velocities only depend on shallow material and longer-wavelength velocities

depend upon deeper material, variations in velocity with wavelength are indicative of

variations in shear wave velocity (vs) with depth. By modeling the data using numerical

analysis, the vs profile (vs as a function of depth) is derived. Modeling is performed

using the WinSASW software, which is described in detail later in this tutorial.

To perform the field test, a dynamic signal analyzer is used. A dynamic signal

analyzer is similar to an oscilloscope with the added feature of real-time spectral

analysis. The system provided to Haiti Engineering includes a Data Physics Quattro

analyzer as depicted in Fig. 2. The Quattro is accompanied by a PC that operates

using the Windows XP platform. The user is encouraged to read the accompanying

Quattro User’s Manual that was provided by Data Physics. Herein, a detailed step-by-

1

step tutorial is provided to allow the field technician to successfully use the Quattro to

acquire SASW data.

Figure 1. Experimental configuration for SASW testing

Figure 2. The Data Physics Quattro Dynamic Signal Analyzer.

2

2. Acquiring Field SASW Data

Step 1: Identify a location to perform field SASW testing. A flat or gently sloping

stretch of land is recommended with at least 120 ft of unobstructed alignment to

accommodate the entire length of the SASW array. Use a GPS to acquire latitude and

longitude data, which will be used later to perform the seismic site response analysis.

Step 2: Power up the PC. Power up the PC that is provided as part of the system. A

450-watt power inverter is also provided. Use the inverter during testing to prevent

power loss during the test.

Step 3: Connect the Quattro to the PC. Use the cable that is included with the

Quattro to connect the Quattro to a USB port on the PC.

Step 4: Launch the Driver Software. Click on the “Start” menu in the bottom left

corner of the PC screen and launch the “Signal Calc 240 Dynamic Signal Analyzer”

software.

Step 5: Select the Appropriate Data Acquisition Configuration for SASW Testing.

Draw down the “Test” menu in the software (Fig. 3). Select “Open” and then select

“newtest.trf” (Fig. 4). This will select the appropriate parameters and display windows

for SASW testing. Once “newtest.trf” is selected, a screen with four windows will

appear (Fig. 5). The four windows, from upper left going clockwise, are:

Window 1: Wrapped phase difference (H1,2). This is the frequency-domain difference in phase between the two receivers in the array in degrees, with one cycle corresponding to 360 degrees. It is also referred to as a transfer function. Window 2: Time-domain record from near receiver (X1). This is voltage plotted as a function of time for the geophone that is located nearest the source location corresponding to Channel 1 on the dynamic signal analyzer.

3

Window 3: Time-domain record from the far receiver (X2). This is voltage plotted as a function of time for the geophone that is located farthest from the source location corresponding to Channel 2 on the dynamic signal analyzer. Window 4: Coherence (C1,2). This is a frequency-domain cross-correlation between the two signals observed at the near and far receiver. A coherence value near 1.0 indicates a strong signal.

Figure 3. Opening a Data Acquisition Configuration File.

Figure 4. Selecting “newtest.trf” to perform SASW testing.

4

Figure 5. Configuration of Windows for SASW Testing using the Quattro.

Step 6: Deploy the Geophones. Place the geophones on the ground at a distance of

10 ft apart. If the ground is soil, use the spikes. If the ground is hard or paved, replace

the spikes with the heavy brass disks and place them on the ground. In either case, the

geophones should be vertically oriented to optimize data quality. Once the geophones

are deployed, place the rubber pad at a distance from one of the geophones that is

equal to the spacing between the geophones. For the 10-ft geophone spacing, the mat

should be placed 10 ft from the nearest geophone.

Step 7: Connect the Geophones to the Quattro. Connect the geophone nearest the

rubber pad to the “IN 1” BNC connector on the Quattro and connect the other geophone

to the “IN 2” BNC connector.

5

Step 8: Select an Appropriate Bandwidth for Acquisition. Data acquisition will be

performed using receiver spacings of 10 ft, 20 ft, and 40 ft. As the receiver spacing

increases, the acquisition bandwidth decreases. For these three spacings, change the

“FSpan” parameter in the upper left corner of the window to 400 Hz, 200 Hz, or 100 Hz,

respectively.

Step 9: Acquire SASW Data in the Forward Direction at a Receiver Spacing of 10

ft. Once you have placed the receivers 10 ft apart and placed the rubber pad 10 ft from

the near receiver, you can begin the test. Click the green “Start” button in the upper left

corner of the screen and have a worker begin repeatedly striking the rubber pad with a

sledge hammer. As the worker does this, you will observe hammer blows in Windows 2

and 3. In Window 1, you will observe the sawtooth pattern of the phase spectra

develop. As the worker continues to strike the pad, the signal adds up while the noise

cancels out, so the phase spectrum gets better and better. Data acquisition is complete

when the Number of Frames in the upper left corner of the screen reaches10 (“Frames:

10), which should take around 18 seconds for a 400-Hz bandwidth (NOTE: it will take

more time when acquiring at shorter bandwidths). Once the acquisition is complete,

click on the red box labeled “End” that appears in the upper left corner of the screen to

save the data.

The saved data will be located in the C:\SignalCalc\240\newtest.trf\ASCII00xxx

folder, where “xxx” is a counter that increases incrementally with every measurement

that you save. In this folder, you will find four files:

1. C1,2sv00000.txt – coherence function; 2. H1,2sv00000.txt – transfer function (phase spectrum); 3. X1sv00000.txt – time record for near receiver; and 4. X2sv00000.txt – time record for far receiver.

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You will use the first two files to derive the experimental dispersion curve in WinSASW.

When completed, the data should resemble the example shown in Fig. 6.

When acquiring data, the maximum time-domain amplitude can be read off of the

y-axis on Window 2 on the right side of the screen. To optimize the quality of the

spectra, the range of the instrument “Range (EU)” should not be more than an order of

magnitude larger than the observed values. For example, in Fig. 6, the maximum

amplitude on Window 2 is around 150 mV. As seen at the bottom of the screen, the

“Range (EU)” is set to 1.000 V for both channels, so it is set appropriately. If the

maximum amplitude in Window 2 is less than 100 mV, then the range should be

reduced to 100 mV.

Figure 6. Typical Data Acquired from SASW Testing in the Forward Direction

Using the Quattro with a 10-ft receiver spacing.

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Step 10: Acquire SASW Data in the Reverse Direction at a Geophone Spacing of

10 ft. Reverse the BNC connectors on the Quattro and move the pad to the other side

of the array so it is 10 ft from the other receiver. Repeat the measurement as described

in Step 9. You will combine this data with data acquired in the forward direction in

WinSASW. The data acquired in the reverse direction will be somewhat similar to the

data acquired in the forward direction (compare Figs. 6 and 7), but will be different due

to noise and slight differences in the response characteristics of the two geophones.

Figure 7. Typical Data Acquired from SASW Testing in the Reverse Direction

Using the Quattro with a 10-ft receiver spacing.

Step 11: Acquire SASW Data in the Forward and Reverse Directions for Receiver

Spacings of 20 ft and 40 ft. Repeat Steps 9 and 10 using receiver spacings of 20 ft

and 40 ft. For each of the three different receiver spacings, make sure that the center of

the array stays at one point as shown in Fig. 8. The data will appear similar to the data

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acquired a the 10-ft receiver spacing, but the bandwidth will be less and the length of

the time records will be longer as shown in Figs. 9 and 10.

10 ft

20 ft

40 ft

Figure 8. Position of receivers (triangles) for the 10-ft, 20-ft, and 40-ft spacings.

Figure 9. Typical Data Acquired from SASW Testing in the Forward Direction Using the Quattro with a 20-ft receiver spacing.

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Figure 10. Typical Data Acquired from SASW Testing in the Forward Direction Using the Quattro with a 20-ft receiver spacing.

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3. Deriving the Shear Wave Velocity Profile

Step 12: Prepare the ASCII files for input into WinSASW. Locate the six folders in

C:\SignalCalc\240\newtest.trf that contain the ASCII data acquired during the SASW

tests for your location. Each folder contains one coherence file “C1,2sv00000.txt” and

one transfer function file “H1,2sv00000.txt”. Delete the first nine lines of each file.

When saving the files, use the following naming convention:

“(C or T)(spg)(F or R).txt”,

where:

C = coherence function; T = transfer function; spg = receiver spacing: F = forward acquisition; and R = reverse acquisition. For example, a file named “C20R.txt” would be a coherence function recorded in the

reverse direction with a receiver spacing of 20 ft. Place all 12 files (3 receiver spacings

x 2 directions x (coherence function + transfer function)) in the same directory along

with a copy of the application “WSASW123.exe,” which can be found on the desktop of

the PC. This application can be copied as many times as necessary (Fig. 11).

Step 13: Read the Field Data into WinSASW. Click on the “WSASW123” icon in the

folder to launch the program. Begin by loading the forward and reverse spectra

corresponding to the 10-ft receiver spacing. Under “File” in the main menu, select

“Open ASCII Files”, which gives the screen shown in Fig. 12. Under “Test Profile(s)”,

select “Forward and Reverse Profiles” to use the data acquired in both directions. Once

all of the files are entered in the appropriate entry, click on “Read Files” to read the data.

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Step 14: Select an Appropriate Receiver Spacing. Select the “Data” option in the

main menu of WinSASW and enter the appropriate receiver spacing (Fig. 13).

Figure 11. Folder Containing Data from a SASW Test along with the WinSASW

Application.

Figure 12. Reading the SASW Data from the 10-ft Receiver Spacing into

WinSASW.

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Figure 13. Selecting the Correct Receiver Spacing in WinSASW.

Step 15: Mask the Phase Spectrum. Select “Procedure” in the main WinSASW menu

and then select “Masking” to generate a window showing the two pairs of overlapping

spectra (Fig. 14). The forward and reverse spectra are shown in blue and pink and the

average spectrum is shown in brown. The average spectrum is used to cancel out

variations in the response between the two geophones. Masking allows the user to edit

and remove noisy portions of the spectrum, which generally occur at the beginning and

end of the spectrum. Ideally, the spectrum should exhibit a sawtooth pattern.

To mask an interval of the spectrum, the low end and high end of the masked

interval must be defined. The low end is defined by clicking the “First” button and

clicking on the phase spectrum at the desired location. The high end is defined by

clicking on the “Second” button and then clicking on the spectrum at the desired

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location. Once the two boundaries are defined, the number of jumps is input. This

represents the estimated number of times the spectrum has jumped from -180 degrees

to 180 degrees by the end of the masked interval. For masked intervals at the low end

of the spectrum (Fig. 15), this number is typically zero. Once the low end, high end, and

number of jumps are input, the mask is saved by clicking on the “New” button.

Figure 14. Unmasked Spectra to be Edited in WinSASW

A second masking interval can be added to remove noisy high-frequency data.

The same approach is used to define this masked interval. Once the masking is

complete, only the unmasked data of high quality (shown in white in Fig. 16) is used to

derive the dispersion curve. To calculate the dispersion curve, click on “Dispersion” in

the Masking window and then click on “Calculate”.

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Step 16: Build the Composite Dispersion Curve. The dispersion curve calculated

using the field data acquired with a10-ft spacing can be viewed by going to the main

WinSASW window, clicking on “Procedure” and then clicking on “Dispersion Curves”.

When you do this, the experimental dispersion curve derived in the previous step will

appear (Fig. 17). The velocity axis should be rescaled to 0-2000 ft/s and the

wavelength axis should be scaled to 1-300 ft. Scaling the axes is achieved by clicking

on “View” and then “Set Attributes” in the Dispersion Curves window.

Figure 15. Spectra with One Masked Interval.

A “composite” dispersion curve consists of data from several different receiver

spacings. Composite dispersion curves are defined over a broader bandwidth, which

helps to constrain the modeling process. To develop a composite dispersion curve, the

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procedure described in Step 15 is repeated using the data from the 20- and 40-ft

receivers spacings. When the dispersion data are calculated, they are automatically

added to the original dispersion curve derived using the data from the 10-ft spacing (Fig.

18). The resulting composite dispersion curve should exhibit a general trend. If some

of the data do not follow the general trend, the number of jumps in the masking may be

adjusted in an interpretive manner until the data from the three different receiver

spacings coincide. Once the composite dispersion curve is complete, it should be

saved in the Dispersion Curves window by selecting “File” then “Save” then

“Experimental”. The experimental dispersion curve file has a .exd extension but can be

opened and viewed in Word or Notepad as an ASCII file.

Figure 16. Spectra with Two Masked Intervals

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Figure 17. Dispersion Curve Derived using One Receiver Spacing.

Figure 18. Composite Dispersion Curve Derived by Combing Dispersion Curves

from Several Different Receiver Spacings.

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Step 17: Forward Modeling of the Experimental Dispersion Curve. Forward

modeling is performed to derive a shear wave velocity profile for the site. To perform

forward modeling, go back to the main WinSASW window and click on “Procedure” and

then “Theoretical Curves” (NOTE: do not close the Dispersion Curves window while

modeling). This opens a window where you can input an initial estimate for the shear

wave velocity profile. The main parameters that you will vary are S-wave velocity and

layer thickness. For the initial estimate, a three-layer profile is used as shown in Fig.

19. Here, a soil site consisting of 35 ft of soil and weathered rock over intact rock is

estimated. Poisson’s ratio of 0.2 is estimated along with unit weights ranging from 120

pcf to 150 pcf. Initial P-wave velocity is calculated by clicking on the “Update” button as

shown in Fig. 20.

Figure 19. Initial Estimate for Shear Wave Velocity Profile Prior to Calculating P-wave

Velocities.

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Figure 20. Initial Estimate for Shear Wave Velocity Profile after Calculating P-wave

Velocities.

After calculating P-wave velocities, click on “SASWFI” to perform the modeling.

Set the parameters as shown in Fig. 21, and click “Run”. After clicking “Run”, the

theoretical dispersion curve appears in the Dispersion Curves window along with the

experimental dispersion curve. If the initial model is correct, then the theoretical and

experimental dispersion curves will match. However, it is more likely that there will be

differences between the two curves (Fig. 22). In this case, return to the Theoretical

Curves window, adjust your model (Fig. 23) and recalculate the theoretical dispersion

curve. Repeat this process iteratively until the theoretical and experimental dispersion

curves match (Fig. 24).

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Figure 21. Parameters for Calculating Model Surface Wave Dispersion Curve.

Figure 22. Theoretical Dispersion Curve (blue circles) Derived using the Initial

Model Estimate (Fig. 20) Along with Experimental Dispersion Curve (black dots).

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Figure 23. Revised Theoretical Model

Figure 24. Original and Revised Theoretical Dispersion Curves Derived from Original and Revised Models (Figs. 20 and 23) along with Experimental Dispersion Curve.

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Once you have identified a theoretical shear wave velocity profile that provides

an acceptable match to the experimental data, save the theoretical profile in the

“Theoretical” window by clicking on “File” and then “Save”. The profile will have a .prf

extension but is an ASCII file that can be viewed in Word or Notepad. The Dispersion

Curves window (Fig. 23) will show the current and previous theoretical dispersion

curves. Save the theoretical dispersion curve by clicking “File” then “Save” then

“Theoretical” in the Dispersion Curves window. The resulting file will have a .thd

extension but will be an ASCII file. All files generated during WinSASW analysis will be

saved in the same directory where the experimental surface wave data reside (Fig. 25).

Figure 25. File Directory Showing additional Files Generated by WinSASW.

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4. Deriving the Design Response Spectrum

The shear wave velocity data derived from SASW testing are used to perform

seismic site response analyses for seismic design according to the General Procedure

(ASCE 7-10 Section 11.4), which is used in the International Building Code. To apply

the General Procedure, the average shear wave velocity within the upper 100 ft ( sv ) is

calculated using the following equation:

∑

∑=

=

=n

1i si

i

n

1ii

s

vd

dv , (ASCE 7-10 Eqn. 20.4-1)

where di and vsi are the thickness and shear wave velocity in the ith layer of a layered

soil/rock profile, and the total thickness of the top n layers is 100 ft. Using the above

equation, average shear wave velocity is calculated and the site is classified according

to Table 1.

Table 1. Definition of Seismic Site Class based on Shear Wave Velocity. Seismic Site Class Site Description sv (ft/s)

A Hard Rock > 5,000 B Rock 2,500 – 5,000 C Very Dense Soil/Soft Rock 1,200 – 2,500 D Stiff Soil 600 – 1,200 E Soft Clay Soil < 600

F Liquefiable Soil/Very High Plasticity

Soil/Organic Soil/ Very Thick Soft Clay

Not applicable; site-specific site response analysis

required

Application of the General Procedure starts with estimating the Maximum

Considered Earthquake (MCE). The MCE has associated peak and spectral

acceleration values which have a 2% probability of being exceeded during a 50-year

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exposure period. Information regarding MCE bedrock shaking for Haiti was published

by Frankel et al1 based on the latitude and longitude. The short-period (0.2 s) and long-

period (1.0 s) spectral acceleration associated with the MCE, SS and S1, can be

obtained by visiting:

https://geohazards.usgs.gov/secure/designmaps/ww/application.php.

The MCE parameters SS and S1 represent bedrock spectral acceleration, but

they must be corrected to account for the effect of the soil column, which tends to

amplify strong ground motion. To make this correction, the site coefficients Fa and Fv

are derived based on site class and bedrock spectral acceleration. Short-period and

long-period surface spectral acceleration, SMS and SM1, are expressed as:

SMS = FaSS (ASCE 7-10 Eqn. 11.4-1)

and

SM1 = FvS1. (ASCE 7-10 Eqn. 11.4-2)

The coefficients Fa and Fv are defined in ASCE 7-10 as described in Tables 2 and 3.

Table 2. Derivation of Fa. Site Class Ss < 0.25 g Ss = 0.5 g Ss = 0.75 g Ss = 1.0 g Ss > 1.25 g

A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 D 1.6 1.4 1.2 1.1 1.0 E 2.5 1.7 1.2 0.9 0.9 F Not applicable; site-specific site response analysis required

The spectral acceleration values SMS and SM1 represent spectral acceleration

levels at the ground surface corresponding to the MCE. For design purposes, these

1Frankel, A., Harmsen, S., Mueller, C., Calais, E., and Haase, J., 2011, “Seismic Hazard Maps for Haiti,” Earthquake Spectra, Vol. 27, No. S1, pp. S23-S41.

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https://geohazards.usgs.gov/secure/designmaps/ww/application.php

values are multiplied by 0.667 to derive design ground surface spectral acceleration

values SDS and SD1.

Table 3. Derivation of Fv. Site Class S1 < 0.1 g S1 = 0.2 g S1 = 0.3 g S1 = 0.4 g S1 > 0.5 g

A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.7 1.6 1.5 1.4 1.3 D 2.4 2.0 1.8 1.6 1.5 E 3.5 3.2 2.8 2.4 2.4 F Not applicable; site-specific site response analysis required

Given SDS and SD1, the design response spectrum is calculated according to

ASCE 7-10 Section 11.4.5. For periods less than T0=0.2SD1/SDS, spectral acceleration

(Sa) is expressed as:

DS0

DSa ST

TS

S 0.40.6 += (ASCE 7-10 Eqn. 11.4-5)

For periods between T0 and TS=SD1/SDS, Sa is equal to SDS. For periods greater than

TS, Sa is expressed as:

Sa = SD1/T. (ASCE 7-10 Eqn. 11.4-6)

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5. Correlating Shear Wave Velocity to Other Geotechnical Parameters

The International Building Code contains a simple correlation between shear

wave velocity (which can be obtained from SASW testing) and uncorrected SPT blow

count (which must be obtained from drilling) in its seismic site classification (Table 4).

Correlations using SPT blow count have been developed to estimate many important

geotechnical parameters including:

• undrained shear strength in clays (Table 5); • friction angle and relative density in sands (Table 6); • cyclic resistance in sands due to earthquake loading (Fig. 26) and • settlement potential of footings in sand (Fig. 27); and

Seismic SASW testing can be used to derive shear wave velocity information, which

can be used to estimate SPT blow count. The resulting SPT blow count can be used to

estimate the various geotechnical design parameters described above. Therefore,

SASW testing can be used as an alternative to traditional soil borings to greatly reduce

or eliminate the need for drilling while obtaining reliable estimates of the geotechnical

properties at a site.

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Table 4. Correlation between shear wave velocity and uncorrected SPT blow count with respect to seismic site classification.

Seismic Site Class


Uncorrected SPT Blow Count (blows/ft)

A > 5,000 n/a B 2,500 – 5,000 n/a C 1,200 – 2,500 > 50 D 600 – 1,200 15 – 50 E < 600 < 15

Table 5. Correlation between SPT Blow Count and Undrained Shear Strength in Clays.

Soil Consistency Uncorrected SPT Blow Count (blows/ft)

Undrained Shear Strength (psf)

Very Soft < 4 < 250 Soft 2 - 4 250-500

Medium 4 - 8 500-1,000 Stiff 8 - 15 1,000-2000

Very Stiff 15 - 30 2,000-4,000 Hard > 30 > 4,000

Table 6. Correlation between SPT Blow Count, Friction Angle, and Relative Density in Sands.

State of Packing

Uncorrected SPT Blow Count (blows/ft)

Relative Density (Percent)

Friction Angle (degrees)

Very Loose < 4 < 20 < 30 Loose 4 – 10 20 – 40 30 – 35

Compact 10 – 30 40 – 60 35 – 40 Dense 30 – 50 60 – 80 40 – 45

Very Dense > 50 > 80 > 45

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Figure 26. Relationship between Cyclic Resistance Ratio and Overburden-

Corrected SPT Blow Count in Sands.

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Figure 27. Procedure for Estimating Settlement in Sands Based on SPT Blow Count.

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6. Support

Support to assist the user in operating this system and performing the analyses

described herein will be provided free of charge at any time by contacting:

Prof. Michael E. Kalinski, Ph.D., P.E. University of Kentucky Department of Civil Engineering 161 Raymond Bldg. Lexington, KY 40506-0281 USA tel: (001) 859-257-6117 mobile: (001) 859-321-3057 email: [email protected]

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mailto:[email protected]

i traveled to haiti with my graduate student, melinda

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