Shear Wave Velocity and Site Amplification Factors for 

25 Strong-Motion Instrument Stations Affected by the 

M5.8 Mineral, Virginia, Earthquake of August 23, 2011

By Robert E. Kayen, Brad A. Carkin, Skye C. Corbett, Aliza Zangwill, Ivan Estevez, and Lena Lai

Open-File Report 2015–1099

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia 2015

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment—visit

http://www.usgs.gov/ or call 1–888–ASK–USGS (1–888–275–8747).

For an overview of USGS information products, including maps, imagery, and publications,

visit http://www.usgs.gov/pubprod/.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply

endorsement by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also may

contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items

must be secured from the copyright owner.

Suggested citation:

Kayen, R.E, Carkin, B.A., Corbett, S.C., Zangwill, Aliza, Estevez, Ivan, and Lai, Lena, 2015, Shear wave 

velocity and site amplification factors for 25 strong-motion instrument stations affected by the M5.8 Mineral, 

Virginia, earthquake of August 23, 2011: U.S. Geological Survey Open-File Report 2015–1099, 66 p., 

http://dx.doi.org/10.3133/ofr20151099.

ISSN 2331-1258 (online)
iii

Contents

Abstract ...................................................................................................................................................................... 1

Introduction................................................................................................................................................................. 1

Rayleigh Wave Dispersion........................................................................................................................................ 12

Adjustments for Missing 1st Wrapped Phase......................................................................................................... 14

Inversion of the Vs Profile...................................................................................................................................... 15

Results...................................................................................................................................................................... 16

Site Data................................................................................................................................................................... 17

Resources ................................................................................................................................................................ 17

Acknowledgments..................................................................................................................................................... 17

References Cited...................................................................................................................................................... 18

Appendix 1. Site Summaries..................................................................................................................................... 19

Figures

1. Map showing spectral analysis of surface waves (SASW) test sites visited in Pennsylvania, West 

Virginia, and Virginia in 2012. ........................................................................................................................ 5

2. Map showing spectral analysis of surface waves (SASW) test sites visited in Virginia in 2011 and 

2012............................................................................................................................................................... 6

3. Map showing spectral analysis of surface waves (SASW) test sites visited in Washington, D.C., and 

vicinity in 2012. .............................................................................................................................................. 7

4. Map showing spectral analysis of surface waves test sites (SASW) visited in Virginia, North Carolina, 

and Tennessee in 2012. ................................................................................................................................ 8

5. The U.S. Geological Survey Velociraptor spectral analysis of surface waves (SASW) trailer ready for 

testing, positioned southeast of the Washington Monument in front of the Sylvan Theater stage, site 

955WM, on June 15, 2012............................................................................................................................. 9

6. The U.S. Geological Survey Velociraptor spectral analysis of surface waves (SASW) trailer positioned 

at the south transept of the Washington National Cathedral, site 943WNC, on April 28, 2012.................... 10

7. The USGS Velociraptor spectral analysis of surface waves (SASW) trailer set up for testing at site 

935RES on December 8, 2012.................................................................................................................... 11

8. Seismometer array set up adjacent to Caputo Hall, Millersville University, Millersville, Pennsylvania, 

site 940MVL, on April 25, 2012. The USGS Velociraptor spectral analysis of surface waves (SASW) 

trailer is at the far end of the array............................................................................................................... 12

Tables

1. Shear wave velocity testing sites in Mid-Atlantic states in 2011 and 2012, site data..................................... 2

2. Shear wave velocity testing sites in Mid-Atlantic states in 2011 and 2012, measured site parameters. ........ 3
Shear Wave Velocity and Site Amplification Factors for 25 

Strong-Motion Instrument Stations Affected by the M5.8 

Mineral, Virginia, Earthquake of August 23, 2011

By Robert E. Kayen, Brad A. Carkin, Skye C. Corbett, Aliza Zangwill, Ivan Estevez, and Lena Lai

Abstract

Vertical one-dimensional shear wave velocity (Vs) profiles are presented for 25 strong-motion 

instrument sites along the Mid-Atlantic eastern seaboard, Piedmont region, and Appalachian region, 

which surround the epicenter of the M5.8 Mineral, Virginia, Earthquake of August 23, 2011. Testing 

was performed at sites in Pennsylvania, Maryland, West Virginia, Virginia, the District of Columbia, 

North Carolina, and Tennessee. The purpose of the study is to determine the detailed site velocity 

profile, the average velocity in the upper 30 meters of the profile (VS,30), the average velocity for the 

entire profile (VS,Z), and the National Earthquake Hazards Reduction Program (NEHRP) site 

classification. The Vs profiles are estimated using a non-invasive continuous-sine-wave method for 

gathering the dispersion characteristics of surface waves. A large trailer-mounted active source was used 

to shake the ground during the testing and produce the surface waves. Shear wave velocity profiles were 

inverted from the averaged dispersion curves using three independent methods for comparison, and the 

root-mean square combined coefficient of variation (COV) of the dispersion and inversion calculations 

are estimated for each site.

Introduction

This project focuses on the measurement of the shear wave velocity (Vs) of near-surface 

materials at strong-motion recording stations in the Mid-Atlantic states at sites where instruments 

recorded motions from the M5.8 Mineral, Virginia, earthquake. During two seasons of testing in 2011 

and 2012, data were collected in Pennsylvania, Maryland, West Virginia, Virginia, the District of 

Columbia, North Carolina, and Tennessee. These states are regionally instrumented with permanent 

seismometer recording stations administered by a suite of entities: the U.S. Geological Survey (USGS)

National Strong-Motion Project (NSMP), the USGS Advanced National Seismic System (ANSS), the 

Geological Survey of Pennsylvania (GSPA), USGS-NetQuakes, Lamont-Doherty Geologic 

Observatory, Virginia Tech University, Washington Monument National Mall (NAMA) and White 

House Ellipse National Park Service NetQuakes affiliate, and the Mineral Virginia site response 

temporary deployment. 

The Vs profiles presented in this report are useful for calibration of site amplification models

based on direct measurement of velocity, topography, or surface geologic unit. Data presented here were 

gathered using the continuous sine wave source spectral analysis of surface waves (CSS-SASW) test 

presented by Kayen and others (2004), which uses a stepped-sine method similar to that of the 

University of Texas and a wave-notch-filtered technique of receiving signals that improves on the 

approach of Satoh and others (1991). The unique aspect of the USGS surface wave vibration system is a 

large parallel array of electromechanical shakers mounted to a trailer frame that is transported to each 
2

site. The trailer is called the Velociraptor. The CSS-SASW technique is an inexpensive and efficient 

means of non-invasively estimating the near-surface Vs of the ground. Though it is possible to measure 

Vs in cased boreholes or during penetration tests, these approaches tend to be not useful for evaluation of 

any of the strong-motion sites tested in this study as they cannot reach the meaningful depths required 

for seismic site response analysis without expensive drilling and casing. Because many of the sites are 

located in or near the Appalachian Mountains with thin soil cover over in-place weathered rock, 

penetration methods are not useful. 

The Vs profiles presented in this report—for local site conditions in six states and the District of 

Columbia, tested between December 8, 2011, and June 27, 2012—are reported in tables 1 and 2.

Table 1. Shear wave velocity testing sites in Mid-Atlantic states in 2011 and 2012, site data. [Columns (left to right) record (1) the U.S. Geological Survey (USGS) station name; (2) seismometer station location; (3) 

latitude (LAT); (4) longitude (LONG); (5) seismometer station owner/operator; (6) date of data collection]

USGS site Location LAT LONG Operator Date tested

935RES Reston Fire Station, Reston, Va. 38.9505 -77.33614 NSMP, 2555 December 8, 2011

936CBN USGS CORBIN Observatory, 

Fredericksburg, Va.

38.20361 -77.37281 ANSS Backbone, 

USCBN

December 8, 2011

938MAR Martinsburg VA Hospital, 

Martinsburg, W. Va.

39.41641 -77.90707 NSMP, 2511 April 24, 2012

939PAG Penn. Geological Survey, 

Harrisburg, Pa.

40.2271 -76.7232 GSPA.PAGS April 25, 2012

940MVL Millersville Univ., Millersville, 

Pa.

39.9992 -76.3506 Lamont-Doherty. 

MVL

April 25, 2012

941PSB Penn. State Univ., Brandywine, 

Pa.

39.92696 -75.4512 GSPA, PSUB April 26, 2012

942DXL Drexel University, Lancaster 

Ave, Philadelphia, Pa.

39.9571 -75.1896 NSMP, 2648 April 27, 2012

943WNC Washington National Cathedral, 

Washington, D.C.

38.9301 -77.0706 NetQuakes, WNC 

WNC—NQ—01

April 28, 2012

944MIN Mineral, Va. 38.02831 -77.84045 NSMP, 2560 April 28, 2012

945JSR J. Sargeant Reynolds C.C., 

Goochland, Va.

37.6952 -77.8798 Virginia Tech, 

JSRW

April 28, 2012

946CMB Cumberland Volunteer Fire 

Station, Cumberland, Va.

37.4881 -78.563 NSMP, 2558 April 29, 2012

947UVR University of Richmond, 

Richmond, Va.

37.5709 -77.534 Virginia Tech, 

URVA

April 29, 2012

948LWR Mineral area near Lake Anne, 

Va.

38.07712 -77.75008 NetQuakes, 

GS.LWRD

April 30, 2012

949NQ1 USGS National Headquarters, 

Reston, Va.

38.936 -77.332 NetQuakes, 

RestonUSGS 

NQ1

April 30, 2012
3

USGS site Location LAT LONG Operator Date tested

950PRB Giles County Courthouse, 

Pearlsburg, Va.

37.3275 -80.7345 NSMP, 2549 June 11, 2012

951ETU James H. Quillen College of 

Medicine & VA Medical 

Center, Eastern Tennessee 

State Univ., Johnson City, 

Tenn.

36.307 -82.37951 NSMP, 2405 June 13, 2012

952ASH Charles George VA Hospital, 

Asheville, N.C.

35.5912 -82.4844 NSMP. 2510 June 13, 2012

953TZN Tazewell, Tenn. 36.5433 -83.5504 USGS. USTZTN June 13, 2012

954SAL W. G. (Bill) Hefner VA Medical 

Center, Salisbury, N.C.

35.6851 -80.4888 NSMP, 2506 June 14, 2012

955WM Washington Monument, Sylvan 

Stage, East Ellipse, 

Washington, D.C.

38.6885 -77.0346 Washington 

Monument 

NAMAr

June 15, 2012

956PRZ White House, Presidents Park,

Ellipse, Washington, D.C.

38.8952 -77.0394 NetQuakes, CAPTL June 15, 2012

957SI Smithsonian Institution, 

Museum Support Facilities, 

Suitland, Md.

38.84198 -76.94073 Mineral, Virginia 

Site Response

June 26, 2012

958NNC Cliffs of the Neuse State Park, 

Seven Springs, N.C.

35.2398 -77.8906 ANSS Backbone, 

USCNNC

June 26, 2012

959MWV West Virginia Geological & 

Economic Survey, 

Morgantown, W. Va.

39.658 -79.846 ANSS Backbone, 

USMCWV

June 27, 2012

Table 2. Shear wave velocity testing sites in Mid-Atlantic states in 2011 and 2012, measured site parameters.

[Columns (left to right) record (1) the U.S. Geological Survey (USGS) site name; (2–3) depth of investigation by forward 

and manual inversions, in meters (m); (4–5) maximum shear wave velocity of forward and manual inversion profiles, in 

meters per second (m/s); (6–7) site parameter VS30, defined as 30 meters divided by the shear wave travel time to 30 meters 

depth, for forward and manual inversions, in meters per second (m/s); (8–9) average shear wave velocity of entire profile, for 

forward and manual inversions, in meters per second (m/s); and (10) National Earthquake Hazards Reduction Program 

(NEHRP) site classifications]

USGS site Depth of 

investigation (m) Vs,max (m/s) Vs,30 (m/s) Average Vs for 

entire profile (m/s)

Site 

class 

(NEHRP)

Forward Manual Forward Manual Forward Manual Forward Manual

935RES 38 42 821 634 341 364 382 413 D

936CBN 64 65 364 389 269 280 312 320 D

938MAR 42 49 828 1,133 372 389 437 482 C

939PAG 36 43 325 242 431 525 353 362 C

940MVL 69 47 2,735 2,107 720 672 1,182 873 C
4

941PSB 46 50 1,336 1,243 353 391 452 515 C

942DXL 59 50 1,856 1,588 617 609 871 781 C

943WNC 44 50 690 664 353 357 403 426 C

944MIN 71 81 1,099 959 526 607 713 738 C

945JSR 34 35 786 916 481 477 502 515 C

946CMB 65 65 865 959 371 362 500 488 C

947UVR 50 50 749 758 351 359 429 450 D

948LWR 66 66 964 1,096 329 325 499 498 D

949NQ1 49 51 2,100 2,043 648 655 856 882 C

950PRB 30 30 883 824 523 498 523 498 C

951ETU 30 30 1,810 1,171 711 633 711 633 C

952ASH 42 49 721 788 359 358 418 444 D

953TZN 31 31 1,168 1,376 709 714 718 727 C

954SAL 30 31 1,492 1,340 396 431 396 437 C

955WM 64 70 1,011 1,095 346 342 484 502 D

956PRZ 64 69 1,021 1,052 342 334 480 487 D

957SI 80 82 609 628 275 272 393 397 D

958NNC 65 68 425 417 296 286 335 332 D

959MWV 38 40 2,992 2,379 1,465 1,483 1,632 1,645 B

The Mid-Atlantic sites tested in 2011 and 2012 are plotted on regional maps in figures 1 through 

4. The National Earthquake Hazards Reduction Program (NEHRP) A–E site classification is as follows: 

(1) blue square, A; (2) green circle, B; (3) yellow diamond, C; (4) red triangle, D; and (5) purple 

triangle, E. Figures 5 through 8 show the Velociraptor SASW trailer positioned at several sites during 

typical testing conditions.
5

Figure 1. Map showing spectral analysis of surface waves (SASW) test sites visited in Pennsylvania, West 

Virginia, and Virginia in 2012. Symbols indicate National Earthquake Hazards Reduction Program site 

classifications, where green circle is a B site, yellow diamonds are C sites, and red triangle is a D site.
6

Figure 2. Map showing spectral analysis of surface waves (SASW) test sites visited in Virginia in 2011 and 2012. 

Symbols indicate National Earthquake Hazards Reduction Program site classifications, where yellow diamonds are 

C sites and red triangles are D sites. The epicenter of the M5.8 Mineral, Virginia, earthquake of August 23, 2011, is 

shown by the yellow star.
7

Figure 3. Map showing spectral analysis of surface waves (SASW) test sites visited in Washington, D.C., and 

vicinity in 2012. Symbols indicate National Earthquake Hazards Reduction Program site classifications, where red 

triangles are D sites.
8

Figure 4. Map showing spectral analysis of surface waves test sites (SASW) visited in Virginia, North Carolina,

and Tennessee in 2012. Symbols indicate National Earthquake Hazards Reduction Program site classifications, 

where yellow diamonds are C sites and red triangle is a D site.
9

Figure 5. The U.S. Geological Survey Velociraptor spectral analysis of surface waves (SASW) trailer ready for 

testing, positioned southeast of the Washington Monument in front of the Sylvan Theater stage, site 955WM, on 

June 15, 2012.
10

Figure 6. The U.S. Geological Survey Velociraptor spectral analysis of surface waves (SASW) trailer positioned 

at the south transept of the Washington National Cathedral, site 943WNC, on April 28, 2012.
11

Figure 7. The USGS Velociraptor spectral analysis of surface waves (SASW) trailer set up for testing at site 

935RES on December 8, 2012. The red, 11-kilowatt generator at the back of the trailer powers all equipment during 

testing.
12

Figure 8. Seismometer array set up adjacent to Caputo Hall, Millersville University, Millersville, Pennsylvania,

site 940MVL, on April 25, 2012. The USGS Velociraptor spectral analysis of surface waves (SASW) trailer is at the 

far end of the array. 

Rayleigh Wave Dispersion 

Active-source surface wave analysis testing typically profiles the upper tens of meters of the 

ground using drop weights or harmonic sources. The upper 30 meters (m) are needed to compute the 

widely used site parameter VS,30, defined as 30 m divided by the shear wave travel time to a depth of 30 

m. The SASW method employed in this study by the USGS is a technique that uses a parallel array of 

mass shakers. This method allows for profiling to 100 m without the use of massive drop weights or 

heavy track-mounted machinery. For this method, we substitute an array of many low frequency (1–100 

hertz [Hz]) electromechanical shakers. Surface waves are generated with an array of between two and 

eight APS Dynamics Model 400 shakers and amplifier units, powered by a generator and controlled by 

a spectral analyzer.

The shakers have a long stroke capable of cycling to as low as 1 Hz. The output signal from the 

spectral analyzer is split into a parallel circuit and sent to the separate amplifiers. The amplifiers power 

the shakers to produce a continuously vibrating, coherent, in-phase harmonic wave that vertically loads 

the ground. Most of this energy produces Rayleigh retrograde elliptical surface waves that propagate 

away from the source in a vertical, cylindrical wavefront perpendicular to the ground surface. The 
13

amplitude of the surface waves decay exponentially with depth, such that the energy of the wavefront is

centered at a depth of approximately one-third to one-half the wavelength.

Frequency-domain analyses are made on two or more signals received by sensors placed in the 

field in the linear array some distance from the source. First, all channels of time-domain data are 

transformed into their equivalent linear spectrum in the frequency domain using a Fourier transform. 

One of the sensor’s signals (typically the sensor closest to the source) is used for a reference input 

signal, and the other sensor signals are used to compute the linear spectra of the output. The separation 

distance from the reference seismometer to each output seismometer (ds – dref) is later used to compute 

the wave velocity. The cross power spectrum Gxy(ω) is determined by multiplying the complex 

conjugate of the linear spectrum of the input signal Sx

*

(ω) and the real portion of the linear spectrum of 

the output signal Sy(ω). The cross power spectrum is defined as

Gxy(ω) = Sx

*

(ω) × Sy(ω) (1)

The autopower spectrum, a measure of the energy at each frequency of the sweep, can be used to 

determine the strength of individual frequencies and is equal to the linear spectrum of a given sensor 

times its complex conjugate pair:

Gxx(ω) = Sx (ω) × Sx

*

(ω), and (2)

Gyy(ω) = Sy (ω) × Sy

*

(ω). (3)

A cross power spectrum can be represented by its real and imaginary components for its phase,

θ, and magnitude, m. The phase is the relative lag between the signals at each frequency, and the 

magnitude is a measure of the power between the two signals at each frequency. Because the phases are 

relative, they can be stacked to enhance signal-to-noise ratio of the phase lag at each frequency. 

The phase of the cross power spectrum is computed as the inverse tangent of the ratio of the 

imaginary and real portions of the cross power spectrum:

θxx(ω) = tan−1 II�Gxx(ω)�

RR�Gxx(ω)� (4)

The travel time t(ƒ) of one cycle of a wave of frequency (ƒ) is computed as

t(ƒ) = θ(ω)/ω (5)

and the wavelength, λ, at each frequency is

λ(θ) = (ds–dref)/ θ(ƒ) (6)

The Rayleigh wave velocity, Vr , is computed as

Vr(ƒ) = (ds – dref)/t(ƒ) (7)

 = ƒ(ds–dref) 360°/θ (degrees)

 = ƒ(ds–dref) 2π/θ(φ) (radians)

 = ƒλ (ƒ)

The SASW procedure maps the change in θ across the frequency spectrum and merges these 

phase lags with the sensor array geometry to measure velocity. Typically, with the shaker source, the 

discrete frequencies are cycled in a swept-sine (stepped) fashion across a range of low frequencies (1–

200 Hz). Rayleigh wave phase velocity is then mapped in frequency or wavelength space. This velocity 

map or profile is called a dispersion curve and characterizes changes in the frequency-dependent 
14

Rayleigh wave velocity. The evaluation of velocities is constrained to the wavelength zone where λ(ƒ)/3 

< (ds – dref) < 2λ(ƒ) for typical data and λ(ƒ)/3 < (ds – dref) < 3 λ(ƒ) for excellent data, corresponding to 

phase lags of 180°–1,080° (typical data) and 120°–1,080° (excellent data). At longer and shorter 

wavelengths, the data become unreliable for computing velocities.

Because the usable wavelengths are constrained by the seismometer separation, the array is 

expanded to capture Rayleigh wave dispersion representative of a specific range of wavelengths. The 

near surface is characterized by short wavelengths and high frequencies, whereas the deeper portion of 

the profile is characterized by long wavelengths and low frequencies. Each wavelength range requires a 

separate independent test that is merged together with other wavelength ranges to determine an average 

dispersion curve for the site. 

At the largest seismometer separations, the increasing area of the wavefront causes the wave 

amplitude to diminish, owing to geometric damping, and the overall quality of the data diminishes. Two 

measures of data quality are used to evaluate the field measurements in the frequency domain. 

Coherence, γ

2

(ω), is a normalized real function with values between 0 and 1, corresponding to the ratio 

of the power of the cross power spectrum, Gyx(ω) • Gyx*

(ω), to the autopower spectrum of the outboard 

seismometer, Gxx(ω) • Gyy(ω). Values close to 1 indicate high correlation between the reference and 

outboard seismometers across narrow frequency bands. This is a useful data quality parameter for 

hammer impact data.

γxx

2 (ω) = G (ω)•G ∗(ω)

Gxx(ω)•G (ω) (8)

For swept-sine data, where discrete frequencies are used to compute phase rather than narrow 

frequency bands, the frequency response function (FRF) is a complex measure of the data quality of the 

output (outboard) seismometer and is sometimes called the transfer function:

FRF(ω) = G (ω)

Gxx(ω) (9)

where x is the input (reference) signal and y is the response (output) signal.

The frequency response function is a two-sided complex parameter. To convert to the frequency 

response gain (magnitude) that is used to evaluate the amplitude of the output response to the input 

stimulus, a rectangular-to-polar coordinate conversion is used. 

Adjustments for Missing 1st Wrapped Phase

At some sensor separations, the field data have a poorly formed 1st phase such that the first clear 

wrapped-phase crossing occurs not at 180°, but at 540°. For these dispersion data files, a simple 

reprocessing was done to add one phase jump (360°, 2π) to the dispersion curves preceding the 540° 

jump to adjust the file to the correct wrapped-phase number. This adjustment corrects the wavelength 

calculation as follows:

λ(corrected)= 2πd/(θ+2π) (10)

With the wavelength adjusted, the velocity, Vr, decreases by

Vr = ƒ•2πd/(θ+2π) (11)

The effect of correcting the phase wrap and reducing the calculated wavelength is to reduce the 

depth of influence of the adjusted dispersion curve. 
15

Inversion of the Vs Profile

The relation between Rayleigh wave (VR), shear wave (VS) and compression wave (VP) velocities 

can be formulated through Navier's equations for dynamic equilibrium. On the surface of the ground, 

and in the case of plane strain, the following characteristic equation can be applied:

Vr

Vs

6

− 8 Vr

Vs

4

+ (24 − 16 � 1−2ν

2(1−ν)

�)

Vr

Vs

2

+ 16 �� 1−2ν

2(1−ν)

� − 1� = 0 (12)

where ν is the Poisson ratio and 

VS

VP

= γ = �� 1−2ν

2(1−ν)

� (13)

For reasonable values of Poisson ratio for earth materials, between 0.30 and 0.49, Viktorov 

(1967) shows that the shear wave velocity ranges between 105 and 115 percent of the measured 

Rayleigh wave velocity.

VR

VS

= K = 0.87+1.12ν

1+ν (14)

such that across the range 0.2 < ν < 0.49, the range of K is 0.87 < K < 0.96.

The inversion method seeks to infer an acceptable best-fit model of seismic shear wave velocity, 

VS, of the ground given the measured dispersive characteristics of Rayleigh waves observed in the 

frequency domain and the estimated profile of Poisson ratio and material density. The inversion 

attempts to build a model from observations, as opposed to the normal prediction of behavior based

upon a model. If the inversion model is simple and linear, it will result in a unique and stable solution. 

The French mathematician Hadamard defined mathematical problems that have solutions that exist, are 

unique, and are stable as “well-posed” (Zhdanov, 2002). On the other hand, surface wave inversion is an 

“ill-posed” inverse problem, as solutions are not unique, the solutions may become unstable, and 

multiple shear wave velocity profiles can result in approximately the same dispersion curve (Hisada, 

1994; Zhdanov, 2002).

The dispersive characteristic of Rayleigh wave propagation allows us to infer the VS at depth 

based on measurements at the free surface. The inversion problem computes the Rayleigh wave phase 

velocity (VR) from laterally constant layers of an infinite half space. For each of these layers, the shear 

modulus, Poisson ratio, density, and thickness are unknown. Displacements for a vertically acting 

harmonic point load can be computed as follows in the far field if we neglect body wave components:

uβ(r, z, ω) = Fz ∙ Gβ ∙ (r, z, ω) ∙ ei[ωω−ψβ(r,z,ω)] (15)

where β stands for the generic component either vertical or radial, Gβ (r,z,ω) is the Rayleigh geometrical 

spreading function, and Ψβ (r,z,ω) is the composite phase function (Lai and Rix, 1998).

Regularization methods have been developed for solving the ill-posed inversion problem: for 

example, the velocity profiles computed here. The Levenberg-Marquardt method, also called damped 

least squares, is one example of a regularization method. These and other techniques, such as artificial 

neural networks and genetic algorithms, are discussed by Santamarina and Fratta (1998). One cost of 

these stochastic methods is that they often require many more iterations, and so they are much more 

computationally intensive.
16

The parameters of the inversion problem can be chosen such that the difference between the 

observational dispersion data and the output of the inversion problem are minimized. Such a constraint 

is insufficient for ill-posed problems because many solutions can fit the data equally well and some of 

these solutions will be physically unrealistic. The most common approach is to constrain the inversion 

solution space by selecting the smoothest solution from a suite of solutions that all exhibit a sufficient 

goodness-of-fit to the observed data, as indicated by a root-mean-square (RMS) error minimum

(Constable and others, 1987).

An empirical approach serves as a counterpoint to the inversion methods used in this report. 

Pelekis and Athanasopoulos (2011) advanced the work of Satoh and others (1991) in a technique termed 

the SIM (simplified inversion method) that computes the shear wave velocity profile as a function of the 

incremental slope of the Rayleigh wave dispersion curve, where Dn is the depth at layer n:

VSS, n nn d dd d = 1.1 ∙

V�RRD −V�RR−1D −1

D −D −1

(16)

VSS,i i d dd d = 1.1 ∙ D −D −1

D V�⁄ RR− D −1 V�⁄ RR−1

(17)

The dispersion curve, VR, plotted against λR is converted into an apparent velocity (V�R) and 

depth (z) by converting λR to an estimated depth of z e = aR ∙ λR ≈ 0.635λR. The parameter aR is a 

penetration depth coefficient optimized to achieve a minimum weighted average difference between the 

simplified velocity profile and that computed through the more advanced inversion of Pelekis and 

Athanasopoulos (2011). The apparent phase velocity, VR���, is approximated as the velocity at each 

segment node (layer interface) of a multilinear curve fit to the dispersion curve. A positive slope of a 

segment indicates normal dispersion; a negative slope indicates inverted dispersion. The value of Vs for 

each individual layer is calculated using the equations above for the cases of normal dispersion or 

inverted dispersion, respectively. The approach of Pelekis and Athanasopoulos (2011) improves on the 

Satoh and others (1991) method notably by optimizing the penetration depth coefficient aR.

Results

We provide two profile solutions at each site (inversion and SIM). We varied the assumptions 

about the layer thicknesses and the threshold RMS error that determines if the inversion has converged 

to best characterize the site. The decision as to whether or not the more complex model is warranted by 

the fit of the theoretical dispersion curve (TDC) to the empirical dispersion curve (EDC) is subjective. 

Table 1 summarizes results and provides the SASW site ID, the site description, the date of data 

collection, the latitude and longitude of the SASW test site, and the VS30.

Appendix A includes plots of the model profiles and the EDC and TDCs for each site. Appendix 

A also includes the site photos and a vicinity map for each site. Where possible, we have indicated the 

location of the strong-motion station in the site photographs and vicinity maps to assess the distance 

between the SASW survey and the strong-motion station. NEHRP classification is used to average the 

site conditions in the upper 30 m of ground (Vs,30 from the IBC, 2002). Equation 18 is used to compute 

this average velocity based on the unit layer thickness (di) and the corresponding interval-velocity (VSi).

VS −d d h− a = ∑ di i=1

∑ di

VS i=1

(18)

These site categories are used to assign design spectra in the evaluation of performance for new 

and built structures.
17

A statistical analysis of the shear wave velocity of the upper 30 m was computed by determining 

the average coefficient of variation (COVDIS) of the dispersion curve from the group phase velocity and 

the average coefficient of variation (COVINV) of shear wave velocity profiles computed in the inversions 

that satisfied the minimum acceptable inversion model variance.

The mean values of the group dispersion curves where calculated by binning the dispersion 

curve values in terms of wavelength (for example, in 1-m bins) or frequency (for example, 1-Hz bins), 

and then averaging the values within each bin. The coefficient of variation was calculated by dividing 

the binned standard deviation of the velocity values by the binned mean values. The mean and standard 

deviation of the shear wave velocity layers of the inversion were calculated by averaging the layer 

values for the suite of profiles that satisfy the lowest possible root-mean-square error, separating the 

theoretical inversion-based and empirical field-dispersion curves.

For both the dispersion curve and the inversion-based coefficients of variation, the average 

coefficient of variation was determined for the profiles. The overall model coefficient of variation was 

computed as the root-mean-square of the dispersion COV and the inversion COV (equation 19).

CC MM MM = �CCVD

2 + CC II2 (19)

For the deep, stiff soil sites, the combined dispersion and inversion COV was typically less than 

0.07, reflecting the remarkably good dispersion data sets and the gentle monotonic increasing nature of 

the velocity profiles. For sites situated on rock, the combined COV ranges from 0.12 to 0.23, reflecting 

greater variance in the field-dispersion data and the inverted profiles.

Site Data

The following pages present the individual site location photographs, location map, field and 

computed velocity data, dispersion curves, and inversion profiles. Vs values for 30 meters and the 

maximum profile depth are presented for the three inversion methods as well as the coefficient of 

variation of these parameters.

Resources

We have used the SWAMI Fortran routines that are freely available at 

http://geosystems.ce.gatech.edu/soil_dynamics/research/surfacewavesanalysis/ (distributed under the 

terms of the GNU General Public License). 

Acknowledgments

This work is supported through the USGS Earthquake Science Center and the USGS Pacific 

Science Center.
18

References Cited

Constable, S.C., Parker, R.L., and Constable, G.G., 1987, Occam's inversion—A practical algorithm for 

generating smooth models from electromagnetic sounding data: Geophysics, v. 52, no. 3, p. 289–300.

Hisada, Y., 1994, An efficient method for computing Green’s functions for a layered half-space with 

sources and receivers at close depths: Bulletin of the Seismological Society of America, v. 84, no. 5, 

p. 1456–1472.

Kayen, R., Seed, R.B., Moss, R.E. Cetin, O., Tanaka, Y., and Tokimatsu, K., 2004, Global shear wave 

velocity database for probabilistic assessment of the initiation of seismic-soil liquefaction: 

Proceedings of the 11th International Conference on Soil Dynamics and Earthquake Engineering,

Berkeley, Calif., 2004, v. 2, p. 506–512. 

Lai, C.G., and Rix, G.J., 1998, Simultaneous inversion of Rayleigh phase velocity and attenuation for 

near-surface site characterization: Georgia Institute of Technology, School of Civil and 

Environmental Engineering, Report No. GIT-CEE/GEO-98-2, 258 p.

Pelekis, P.C., and Athanasopoulos, G.A., 2011, An overview of surface wave methods and a reliability

study of a simplified inversion technique. Soil Dynamics and Earthquake Engineering, v. 32, no. 12, 

p. 1654–1668, doi:10.1016/j.soildyn.2011.06.012.

Santamarina, J.C., and Fratta, D., 1998, Introduction to discrete signals and inverse problems in civil 

engineering: Reston, Va., American Society of Civil Engineers Press, 327 p.

Satoh, T., Poran, C.I., Yamagata, K., and Rondriquez, J.A., 1991, Soil profiling by spectral analysis of

surface waves, in Proceedings of the Second International Conference On Recent Advances in

Geotechnical Earthquake Engineering and Soil Dynamics, Vol. II, St. Louis, Mo., March 11–15, 

1991: University of Missouri-Rolla, Paper No. 10.23, p.1429–1434.

Zhdanov, M.S., 2002, Geophysical inverse theory and regularization problems; Methods in 

Geochemistry and Geophysics, 36: Amsterdam, Elsevier, 628 p.
19

Appendix 1. Site Summaries

Figure 1–1. Site ID, location, and average shear wave velocity (left) for surface wave test site 935RES; 

average dispersion curve in black and individual empirical dispersion curves in gray (center plot); shear wave 

velocity profile computed by two inversion methods (right plot).
20

Figure 1–2. Surface wave test site 935RES located on the Washington and Old Dominion Trail (W&OD) at 

the intersection of Wiehle Avenue and Sunset Hills Road, Reston, Virginia (lat 38.9505, long −77.3361). A,

View looking west down the seismometer array on the W&OD. B, Closer view of the shaker trailer. C, View 

looking east. D, USGS seismometer located in the fire station on Wiehle Avenue adjacent to the test site. E,

Satellite view of the local site, yellow bar is seismometer array. F, Site location in Virginia near Washington, 

D.C.
21

Figure 1–3. Site ID, location, and average shear wave velocity (left) for surface wave test site 936CBN; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
22

Figure 1–4. Surface wave test site 936CRB located at the Fredericksburg Geomagnetic Center, Corbin, 

Virginia (lat 38.2037, long −77.3728). A, View northward towards the seismometer array. B, Another view 

northward from the shaker trailer. C, View northwest at the shaker trailer. D, Sign at the entrance to the 

observatory. E, Satellite view of the local site, yellow bar is seismometer array. F, Site location in Virginia, 82 

kilometers south-southwest of Washington, D.C.
23

Figure 1–5. Site ID, location, and average shear wave velocity (left) for surface wave test site 938MAR; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
24

Figure 1–6. Surface wave test site 938MAR located at the Martinsburg VA Medical Center, Martinsburg, 

West Virginia (lat 39.4161, long −77.9068). A, View looking north along the seismometer array. B, View 

southward to the shaker trailer. C, View to the west from the shaker trailer. D, Another view to the west from 

the shaker trailer. E, Satellite view of the local site, yellow bar is seismometer array. F, Site location in 

Martinsburg, W. Va.
25

Figure 1–7. Site ID, location, and average shear wave velocity (left) for surface wave test site 939PAG; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
26

Figure 1–8. Surface wave test site 939PAG located at the Pennsylvania Geological Survey, Middletown, 

Pennsylvania (lat 40.2271, long −76.7232). A, View looking southwest in the direction of the seismometer 

array. B, View northwest to the shaker trailer. C, View northeast from the shaker trailer. D, Another view to the 

northeast at the shaker trailer location. E, Satellite view of the local site, yellow bar is seismometer array. F, 

Site location in Middletown, Pa.
27

Figure 1–9. Site ID, location, and average shear wave velocity (left) for surface wave test site 940MVL; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
28

Figure 1–10. Surface wave test site 940MVL located adjacent to Caputo Hall, Millersville University, 

Millersville, Pennsylvania (lat 39.9992, long −76.3490). A, View looking westward along the seismometer 

array on an extension of E. Frederick Street. B, View eastward to the shaker trailer. C, Another view eastward 

to the shaker trailer. D, View eastward from near the end of the seismometer array. E, Satellite view of the 

local site, yellow bar is seismometer array. F, Site location in Millersville, Pa.
29

Figure 1–11. Site ID, location, and average shear wave velocity (left) for surface wave test site 941PSB; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
30

Figure 1–12. Surface wave test site 941PSB located at the maintenance building on the Pennsylvania 

State University Brandywine campus in Media, Pennsylvania (lat 39.9270, long −75.4512). A, View looking 

southeast towards the shaker trailer. B, View southwest along the seismometer array from the shaker trailer. 

C, View northeast toward the shaker trailer. D, Looking north to the shaker trailer with the maintenance 

building in the background. E, Satellite view of the local site, yellow bar is seismometer array. F, Site location 

in Media, Pa.
31

Figure 1–13. Site ID, location, and average shear wave velocity (left) for surface wave test site 942DXL; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
32

Figure 1–14. Surface wave test site 942DXL located on Cuthbert Street on the Drexel University campus, 

Philadelphia, Pennsylvania (lat 39.9571, long −75.1896). A, View looking southeast towards the shaker trailer. 

B, View northwest to the shaker trailer, Rush Building on the left. C, View westward down the seismometer 

array. D, View eastward along the seismometer array. E, Satellite view of the local site, yellow bar is 

seismometer array. F, Site location in Philadelphia, Pa.
33

Figure 1–15. Site ID, location, and average shear wave velocity (left) for surface wave test site 943WNC; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
34

Figure 1–16. Surface wave test site 943WNC located at the Washington National Cathedral, Washington, 

D.C. (lat 38.9301, long −77.0706). A, View looking northwest towards the shaker trailer at the south transept 

of the cathedral. B, View westward to the seismometer array. C, View east along the seismometer array 

toward the shaker trailer. D, View to the northeast toward the shaker trailer. E, Satellite view of the local site, 

yellow bar is seismometer array. F, Site location in Washington, D.C.
35

Figure 1–17. Site ID, location, and average shear wave velocity (left) for surface wave test site 944MIN; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
36

Figure 1–18. Surface wave test site 944MIN located 6.5 km NE of Mineral, Virginia (lat 38.0289, long 

−77.8421). Testing took place on a dirt road between State Route 700 and railroad tracks. A, Photo looking 

northeast from the shaker trailer down the seismometer array, railroad tracks on the left. B, View looking 

southwest toward the shaker trailer. C, Another view southwest to the shaker trailer. D, The shaker trailer 

parked at the Mineral fire station. E, Satellite view of the local site, yellow bar is seismometer array. F, Site 

location near Mineral, Va.
37

Figure 1–19. Site ID, location, and average shear wave velocity (left) for surface wave test site 945JSR; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
38

Figure 1–20. Surface wave test site 945JSR located at J. Sargeant Reynolds Community College, 

Goochland, Virginia (lat 37.6952, long −77.8798). A, Photo looking northwest towards the shaker trailer 

parked beneath the covering. B, View southward toward the shaker trailer. C, View southeast to the shaker 

trailer. D, View to the northwest along the seismometer array. E, Satellite view of the local site, yellow bar is 

seismometer array. F, Site location near Goochland, Va.
39

Figure 1–21. Site ID, location, and average shear wave velocity (left) for surface wave test site 946CMB; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
40

Figure 1–22. Surface wave test site 946CMB located at the volunteer rescue squad fire station, 

Cumberland, Virginia (lat 37.4881, long −78.2563). A, View looking southeast towards the shaker trailer and

trend of the seismometer array. B, View northwest to the shaker trailer. C, View from the shaker trailer 

southwest to the fire station. D, Another view to the southeast along the direction of the seismometer array. E,

Satellite view of the local site, yellow bar is seismometer array. F, Site location in Cumberland, Va.
41

Figure 1–23. Site ID, location, and average shear wave velocity (left) for surface wave test site 947UVR; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
42

Figure 1–24. Surface wave test site 947UVR located at the east margin of the intramural fields, University 

of Richmond, Richmond, Virginia (lat 37.5709, long −77.5374). A, View to the north to the shaker trailer. B, 

Another view northward to the shaker trailer. C, View west to the shaker trailer. D, View to the south along the 

seismometer array toward the shaker trailer. E, satellite view of the local site, yellow bar is seismometer array. 

F, Site location in Richmond, Va.
43

Figure 1–25. Site ID, location, and average shear wave velocity (left) for surface wave test site 948LWR; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
44

Figure 1–26. Surface wave test site 948LWR located on Gentry Lane about 16 kilometers northeast of 

Mineral, Virginia, and 66 kilometers northwest of Richmond, Virginia (lat 38.0796, long −77.7515). A, View 

looking northwest to the shaker trailer on Gentry Lane. B, View north-northeast from the shaker trailer to the 

seismometer array. C, Another view to the north-northeast to the shaker trailer. D, View to the southsouthwest along seismometer array to the shaker trailer. E, Satellite view of the local site, yellow bar is 

seismometer array. F, Site location northwest of Richmond, Va.
45

Figure 1–27. Site ID, location, and average shear wave velocity (left) for surface wave test site 949NQ1; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
46

Figure 1–28. Surface wave test site 949NQ1 located at the U.S. Geological Survey National Center in

Reston, Virginia (lat 38.9477, long −77.3673). A, View looking southeast from the shaker trailer to the 

seismometer array. B, View northwest to the shaker trailer. C, View to the north to the shaker trailer and nearend of the seismometer array. D, Closer view of the shaker trailer looking north. E, Satellite view of the local 

site, yellow bar is seismometer array. F, Site location in Reston, Va.
47

Figure 1–29. Site ID, location, and average shear wave velocity (left) for surface wave test site 950PRB; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
48

Figure 1–30. Surface wave test site 950PRB located next to city/county buildings in Pearisburg, Virginia

(lat 37.3275, long −80.7345). A, View looking southwest to the shaker trailer, Giles County courthouse in the 

background. B, View west-southwest down the seismometer array from the shaker trailer. C, View eastnortheast to the shaker trailer from near the far end of the array. D, Closer view of the shaker trailer looking 

east-northeast. E, Satellite view of the local site, yellow bar is seismometer array. F, Site location in 

Pearisburg, Va.
49

Figure 1–31. Site ID, location, and average shear wave velocity (left) for surface wave test site 951ETU; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
50

Figure 1–32. Surface wave test site 951ETU located adjacent to Building 52, James H. Quillen College of 

Medicine, East Tennessee State University, Johnson City, Tennessee (lat 36.307, long −82.3795). A, View

eastward to the shaker trailer. B, View westward to the seismometer array. C, Another view eastward to the 

shaker trailer. D, Limestone bedrock outcrop about 500 meters east-northeast of the shaker trailer location. E,

Satellite view of the local site, yellow bar is seismometer array. F, Site location in Johnson City, Tenn.
51

Figure 1–33. Site ID, location, and average shear wave velocity (left) for surface wave test site 952ASH; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
52

Figure 1–34. Surface wave test site 952ASH located at the Charles George VA Medical Center, Asheville, 

North Carolina (lat 35.5912, long −82.4844). A, View looking northwest toward the shaker trailer. B, View east 

to the seismometer array. C, View west to the shaker trailer from the seismometer array. D, View to the 

southeast of the shaker trailer. E, Satellite view of the local site, yellow bar is seismometer array. F, Site 

location in Asheville, N.C.
53

Figure 1–35. Site ID, location, and average shear wave velocity (left) for surface wave test site 953TZN; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
54

Figure 1–36. Surface wave test site 953TZN located on Parks Lane about 10 kilometers north-northeast of 

Tazewell, Tennessee (lat 36.5433, long −83.5504). A, View looking northeast towards the shaker trailer. B, 

View looking south from the shaker trailer. C, View southwest from shaker trailer to the seismometer array. D,

View eastward to the shaker trailer. E, Satellite view of the local site, yellow bar is seismometer array. F, Site 

location near Tazewell, Tenn.
55

Figure 1–37. Site ID, location, and average shear wave velocity (left) for surface wave test site 954SAL; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
56

Figure 1–38. Surface wave test site 954SAL located at the Hefner VA Medical Center, Salisbury, North 

Carolina (lat 35.6851, long −80.4888). A, View westward to the shaker trailer. B, View to the north along the 

seismometer array. C, View to the southeast across the seismometer array, shaker trailer on the right. D, View 

to the northwest from the shaker trailer. E, Satellite view of the local site, yellow bar is seismometer array. F,

Site location in Salisbury, N.C.
57

Figure 1–39. Site ID, location, and average shear wave velocity (left) for surface wave test site 955WM; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
58

Figure 1–40. Surface wave test site 955WM located at the Washington Monument, Washington, D.C. (lat 

38.8885, long −77.0346). A, View looking northwest from the Sylvan Theater stage towards the Washington 

Monument and shaker trailer. B, View southwest to the shaker trailer. C, View southward to the shaker trailer, 

Sylvan Theater in the background. D, View looking northwest to the Monument and the seismometer array 

crossing the path. E, Satellite view of the local site, yellow bar is seismometer array. F, Site location in 

Washington, D.C.
59

Figure 1–41. Site ID, location, and average shear wave velocity (left) for surface wave test site 956PRZ; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
60

Figure 1–42. Surface wave test site 956PRZ located at President’s Park at the intersection of 17th Street

NW and E Street NW near the northwest margin of The Ellipse (lat 38.8952, long −77.0394). A, View north 

towards to the shaker trailer on 17th Street. B, View south to the shaker trailer on 17th Street. C, View of the 

shaker trailer looking west. D, View northwest to the shaker trailer. E, Satellite view of the local site, yellow bar 

is seismometer array. F, Site location in Washington, D.C.
61

Figure 1–43. Site ID, location, and average shear wave velocity (left) for surface wave test site 957SI; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
62

Figure 1–44. Surface wave test site 957SI located at the Smithsonian Archive Warehouse, Suitland, 

Maryland (lat 38.84195, long −76.9408). A, View looking east-southeast along the seismometer array towards 

the shaker trailer. B, View northwest from the shaker trailer toward the seismometer array. C, View to the 

southeast of the shaker trailer. D, Students and researchers from Lehigh University, Virginia Tech, and the 

U.S. Geological Survey gathered at the test site. E, Satellite view of the local site, yellow bar is seismometer 

array. F, Site location in Suitland, Md.
63

Figure 1–45. Site ID, location, and average shear wave velocity (left) for surface wave test site 958NNC; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
64

Figure 1–46. Surface wave test site 958NNC located at the Cliffs of the Neuse State Park, Seven Springs, 

North Carolina, about 18 kilometers southeast of Goldsboro (lat 35.2398, long −77.8906). A, View looking 

northeast from the shaker trailer along the seismometer array. B, View looking southwest toward the shaker 

trailer. C, View southward to the shaker trailer and tow vehicle. D, Another view southward to the shaker 

trailer. E, Satellite view of the local site, yellow bar is seismometer array. F, Site location near Seven Springs, 

N.C.
65

Figure 1–47. Site ID, location, and average shear wave velocity (left) for surface wave test site 959MWV; 

average dispersion curve in dark gray and individual empirical dispersion curves in lighter gray (center plot); 

shear wave velocity profiles computed by two inversion methods (right plot).
66

Figure 1–48. Surface wave test site 959MWV located at the West Virginia Geological & Economic Survey, 

Morgantown, West Virginia (lat 39.6594, long −79.8499). A, View looking southeast towards the seismometer 

array in the upper parking lot. B, Another view southeast toward the shaker trailer. C, View southeast toward 

the shaker trailer at the entrance gate. D, View to the northwest of the shaker trailer. E, Satellite view of the 

local site, yellow bar is seismometer array. F, Site location near Morgantown, W. Va.