U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2011–1203

Liquefaction Hazard for the Region of Evansville, Indiana

In collaboration with the Evansville Area Earthquake Hazards Mapping Project (EAEHMP)
Liquefaction Hazard for the Region of Evansville, Indiana

By Jennifer S. Haase, Yoon S. Choi, Robert L. Nowack, Chris H. Cramer, Oliver S. Boyd, and 

Robert A. Bauer

In collaboration with the Evansville Area Earthquake Hazards Mapping Project (EAEHMP)

Open-File Report 2011–1203

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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Suggested citation:

Haase, J.S., Choi, Y.S., Nowack, R.L., Cramer, C.H., Boyd, O.S., and Bauer, R.A., 2011, Liquefaction 

hazard for the region of Evansville, Indiana: U.S. Geological Survey Open-File Report 2011–1203, 37 p.

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endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

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

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

Choice of Scenario Earthquakes for Liquefaction Study ............................................................................................ 1

Approach to Liquefaction-Hazard Assessment .......................................................................................................... 3

Data............................................................................................................................................................................... 4

Surface Geology ........................................................................................................................................................ 4

CPT Data ................................................................................................................................................................... 6

Method of Calculation of Factor of Safety and Liquefaction Potential Index .................................................................. 7

Liquefaction Calculation for CPT Sites .........................................................................................................................11

Results for the River Alluvium Group ........................................................................................................................16

Results for the Outwash Terrace Group....................................................................................................................17

Results for the Lacustrine Terrace Group .................................................................................................................17

Evaluating Liquefaction Potential for Silty and Clayey Soil .......................................................................................17

Liquefaction Calculation for non-CPT Sites ..................................................................................................................19

Generalization of Soil Profile Type............................................................................................................................19

Determining Soil Thickness and Water Table ...........................................................................................................19

Mapping Liquefaction Potential using a Probability-Based Method...........................................................................21

Discussion ....................................................................................................................................................................26

Conclusions..................................................................................................................................................................28

Acknowledgments ........................................................................................................................................................29

Appendix 1....................................................................................................................................................................30

References ...................................................................................................................................................................35

Figures

Figure 1. Merged surficial geologic map from the 1:50,000- and 1:500,000-scale maps including 

cone-penetrometer test sites with shear wave measurements................................................................ 5

Figure 2. Example of the series of calculations for the factor of safety for profile VHC006, a typical 

profile located in unit Qall alluvium levee deposits................................................................................ 11

Figure 3. Peak ground acceleration in terms of the percent of the acceleration of gravity predicted 

for an M7.7 New Madrid earthquake and an M6.8 Wabash Valley earthquake..................................... 12

Figure 4. Liquefaction potential index calculated from the cone-penetrometer test profiles for an 

M7.7 New Madrid event and an M6.8 Wabash Valley event................................................................. 13

Figure 5. Soil-behavior-type index, Ic, and friction ratio in percent, F, plotted for all clay-rich soil 

elements in the cone-penetrometer test dataset. .................................................................................. 16

Figure 6. Test datasets of plasticity index, water content, and liquid limit from clay units near the 

cone-penetrometer test profiles within Lacustrine Terrace group that required further testing to 

determine liquefaction susceptibility...................................................................................................... 18

Figure 7. Contoured bedrock depth. The steep-sided ancient bedrock valley is evident beneath the 

flood plain of the present-day meandering Ohio River .......................................................................... 20

Figure 8. Examples of the variation of: A, the tip resistance, qc; and B, sleeve friction, fs, with depth 

for all profiles in River alluvium group. Examples of the variation of: C, tip resistance, qc; 

and D, sleeve friction, fs, with depth for all profiles in Outwash terrace group. Examples of 

the variation of: E, tip resistance, qc; and F, sleeve friction, fs, with depth for all profiles in 

Lacustrine terrace group ....................................................................................................................... 23
iv

Figure 9. Mean liquefaction potential index for: A, magnitude (M) 7.7 New Madrid scenario 

earthquake and B, M6.8 Wabash River valley scenario earthquake ..................................................... 24

Figure 10. Probability that the liquefaction potential index (LPI) is greater than 5 for: A, a magnitude (M) 

7.7 New Madrid scenario earthquake and B, an M6.8 Wabash River valley scenario 

earthquake. Probability that LPI is greater than 12 for: C, an M7.7 New Madrid scenario 

earthquake and D, an M6.8 Wabash River valley scenario earthquake................................................ 25

Figure 1-1. Group 1, River alluvium, profiles and calculated factor of safety, with soil units taken from 

Holzer (2003). Units with soil-behavior index less than 2.6 do not contribute to the liquefaction 

potential index and are indicated with the factor of safety in red........................................................... 31

Figure 1-2. Western profiles from group 2, Outwash terrace, and factor of safety with soil units taken from 

Holzer (2003). Units with soil-behavior index less than 2.6 do not contribute to the liquefaction 

potential index and are indicated with the factor of safety in red........................................................... 32

Figure 1-3. Eastern profiles from group 2, Outwash terrace, and calculated factor of safety with soil units 

taken from Holzer (2003). Units with soil-behavior index less than 2.6 do not contribute to the 

liquefaction potential index and are indicated with the factor of safety in red........................................ 33

Figure 1-4. Lacustrine terrace, profiles and calculated factor of safety with soil units taken from Holzer 

(2003). Units with soil-behavior index less than 2.6 do not contribute to the liquefaction 

potential index and are indicated with the factor of safety in red........................................................... 34

Tables

Table 1. Soil types associated with variable propensity for liquefaction as adapted from Robertson and 

Wride (1998) ...........................................................................................................................................6

Table 2. Liquefaction potential index for each cone-penetrometer test measurement listed by surficial 

geologic unit and grouped based on similarities in soil behavior type and similarities in the 

lithologic descriptions of the surficial geologic units ..............................................................................14

Table 3. Comparison of liquefaction potential index calculated using nearby standard-penetration test 

(SPT) and cone-penetrometer test (CPT) data for several sites within the Lacustrine terrace 

group. See Holzer (2003) for identification of individual CPT profile locations ......................................27

Table 4. Comparison of liquefaction potential index calculated using nearby standard-penetration test 

and cone-penetrometer test data for several sites within the River alluvium group...............................27
1

Liquefaction Hazard for the Region of Evansville, Indiana

By Jennifer S. Haase,1 Yoon Seok Choi,2 Robert L. Nowack,

1 Chris H. Cramer,3 Oliver S. Boyd,4 and 

Robert A. Bauer5

Abstract

We calculated liquefaction potential index for a grid of sites in the Evansville, Indiana

area for two scenario earthquakes—a magnitude 7.7 in the New Madrid seismic zone and a M6.8 

in the Wabash Valley seismic zone. For the latter event, peak ground accelerations range from 

0.13 gravity to 0.81 gravity, sufficiently high to be of concern for liquefaction.

Recently acquired cone-penetrometer test data at 58 sites were used to estimate the factor 

of safety against liquefaction and liquefaction potential index at each site. To extend the 

estimation of liquefaction hazard to a grid of sites in the area, the soil columns at these grid sites 

were divided into three categories, and for each category a sufficient number of conepenetrometer test sites were available to characterize statistically each group’s conepenetrometer test tip resistance and sleeve friction. At each grid site, Monte Carlo sampling was 

used to generate values for these two parameters at 2-meter intervals for depths down to 20 

meters or bedrock. The groundwater table at each grid site was likewise sampled from a mean 

value and group-dependent standard deviation. For each grid site, 25,000 realizations of the soil 

profile were generated and a probability distribution of liquefaction potential index values was

obtained.

Maps of liquefaction hazard for each scenario earthquake present (1) Mean liquefaction 

potential index at each site, and (2) Probabilities that liquefaction potential index values exceed 5 

(threshold for expression of surface liquefaction) and 12 (threshold for lateral spreading). Values 

for the liquefaction potential index are high in the River alluvium group, where the soil profiles 

are predominantly sand, while values in the Lacustrine terrace group are lower, owing to the 

predominance of clay. Liquefaction potential index values in the Outwash terrace group are less 

consistent because the soil profiles contain highly variable sequences of silty sand, clayey sand, 

and sandy clay, justifying the use of the Monte Carlo procedure to capture the consequences of 

this complexity.

Introduction

Choice of Scenario Earthquakes for Liquefaction Study

For the purpose of this and the related studies (Haase and others, 2011a and b), the 

Evansville Area Earthquake Hazards Mapping Project Technical Working group (a group 

composed of geoscientists and community professionals) was tasked with the goal of producing 

 1 Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47906.

2 School of Civil Engineering, Purdue University, West Lafayette, IN.

3 Center for Earthquake Research and Information, University of Memphis, Memphis, TN.

4 United States Geological Survey, Memphis, TN.

5 Illinois State Geological Survey, Champaign, IL.
2

relevant urban hazard mapping products for the Evansville urban area. The selection of scenario 

events for deterministic studies took into account the following information.

Evansville, Ind., is a current focus of urban seismic hazard mapping in the Central United 

States because of its proximity to the New Madrid seismic zone (NMSZ), where a sequence of 

three earthquakes with magnitude (M) greater than 7 occurred in 1811–1812 (Johnston, 1996; 

Hough and others, 2000; Bakun and Hopper, 2004). Both the NMSZ and the Wabash Valley 

seismic zone (WVSZ) are potential source areas for triggering liquefaction in and around 

Evansville, Ind., and Henderson, Ky., which lie on sequences of alluvial and lacustrine sediments 

adjacent to the Ohio River. Quarries and river banks in the nearby Wabash Valley show evidence 

of historic liquefaction, due to two events in the WVSZ at approximately 6,100 years before 

present (B.P.) and 12,000 B.P. (Munson and Munson, 1996). This study describes liquefactionhazard maps constructed for the Evansville area—these maps are intended as a complement to 

recent work on scenario earthquake ground motions (Haase and others, 2011b) and a 

probabilistic seismic hazard analysis (Haase and others, 2011a). 

The three large New Madrid earthquakes that occurred in 1811–1812 generated ground 

shaking throughout the central and eastern United States. Moment magnitudes ranging from 

magnitude (M) 7.4 to 8.1 have been assigned to the largest of the events based on

preinstrumental intensity reports (Johnston, 1996; Hough and others, 2000; Bakun and Hopper, 

2004). In southern Indiana, the reported intensities ranged from Modified Mercalli Intensity 

(MMI) VI to VII (Nuttli, 1973; Street, 1984). 

A recurrence of a New Madrid type event is of concern in urban areas such as Evansville,

Ind., where some earthquake damage could occur. There is evidence from ancient sand blows 

that one large earthquake occurred about A.D. 300 and three additional sequences of large 

earthquakes occurred about A.D. 900, A.D. 1450 and 2350 B.C. in the NMSZ (Tuttle and others, 

2002; Tuttle and others, 2005). The sequence in A.D. 1450 may not have ruptured the 

northernmost arm of the New Madrid fault, and the record might not be complete between 2350 

BC and 1450 AD. Based on these data, the recurrence interval for a New Madrid type event has 

been estimated to be 500 to 1,000 years (yr). However, Calais and Stein (2009) claim that low 

rates of deformation observed by GPS in the midcontinent indicate that present-day recurrence 

intervals for a New Madrid type event might be longer than 1,000 yr or that the deformation is 

not steady in time. Currently a recurrence interval of 500 to 1,000 years has been retained for the 

calculation of the 2008 United States Geological Survey (USGS) National Seismic Hazard Maps 

(Petersen and others, 2008). 

These recent national maps were de-aggregated (Harmsen and others, 1999) to 

investigate what earthquake magnitude and location contributes the most to the probabilistic 

seismic hazard for the Evansville region. We found that a M7.7 earthquake at a distance of 180 

km (that is, a New Madrid type event) makes the greatest contribution to the seismic hazard at all 

periods for 2-percent probability of exceedance in 50 years (or 1 chance in ~2,500 in any year).

Therefore, this type of event was selected for simulation deterministically as a scenario 

earthquake (Haase and Nowack, 2009) and is used here as one of the scenarios for evaluating 

liquefaction hazard. 

Previous work in the Wabash Valley has revealed paleoliquefaction evidence of four past 

earthquakes of magnitude greater than 6 in the last 12,000 yr (Munson and others, 1995; Munson 

and Munson, 1996; Pond, 1996; McNulty and Obermeier, 1999; Green and others, 2005; Olson 

and others, 2005). The closest of those to Evansville was the Skelton-Mt.Carmel earthquake that 

occurred approximately 12,000 ± 1,000 yr B.P. and had an estimated magnitude of 6.7–6.8. 

Although evidence of liquefaction from this pre-historic earthquake is not exposed in Evansville, 

liquefaction has been observed at greater distances, so this type of Wabash Valley event is of 

concern (Munson and Munson, 1996). 
3

The repeat time of earthquakes having M greater than 6 in all of southern Indiana and 

Illinois is about 1,500 yr; however, it is much lower for any one individual fault. Much of the 

hazard of the WVSZ in the 2008 USGS National Seismic Hazard Maps is based on seismicity 

rates derived from catalogs of earthquakes with magnitude 3.0 or greater from 1700 through 

2006 (assuming a maximum magnitude of M7.5). The support for a high maximum magnitude in 

the Wabash Valley relative to the rest of the central United States is based on the 

paleoliquefaction evidence cited above and worldwide studies of maximum observed earthquake 

magnitudes in stable continental regions (Johnston, 1994). 

The deaggregation of the probabilistic seismic-hazard maps shows that a Wabash-Valley 

type of event does not make a large contribution to the hazard at a 2-percent probability of 

exceedance in 50 years, compared to that of the NMSZ. However, because of the proximity of 

the potential seismic source area to Evansville, and the extensive observations in other locations 

of historic liquefaction from a Wabash Valley source, a Wabash-Valley type of event was also 

judged worthy of investigation. 

In accord with the above consideration, the Working Group selected two scenario events 

for detailed investigation: a M7.7 earthquake on the New Madrid fault at an average distance of 

180 km southwest of the center of the study region, and an M6.8 earthquake approximately 40 

km northwest of the center of the study region. 

Approach to Liquefaction-Hazard Assessment

Peak ground acceleration is an essential element in the determination of likelihood of 

liquefaction for a given soil column. The seismic-hazard assessment of ground motions from 

these two scenario earthquakes (Haase and others, 2011b) and the probabilistic seismic hazard 

analysis for the region (Haase and others, 2011a) were carried out using subsurface information 

on shear-wave velocity, soil type, and soil thickness, in order to incorporate the near-surface 

amplification or de-amplification due to local site effects into the hazard assessments. These 

studies revealed that the soils present in the river alluvium in the low-lying regions and in the 

loess-covered uplands have significantly different properties that affect the spatial distribution of 

amplification and thus the expected acceleration levels. Within the thickest sediments of the 

Ohio River Valley, distinct resonant periods between 0.6 to 0.8 seconds (s) create high 

amplification at 1-s period. There is also some amplification at higher frequencies outside the 

river valley. The peak ground acceleration (PGA) having a 2-percent probability of being 

exceeded in 50 years is 0.3–0.5 gravity (g) for much of the study region, with values locally as 

high as 0.66 g. The accelerations resulting from the scenario ground motion analyses, when 

taking into account the soil response, showed lateral variations similar to the probabilistic 

analysis for acceleration levels that are important to consider in a study of liquefaction. 

Previous studies have investigated the soil conditions present along the Wabash and Ohio 

Rivers and evaluated the hazard from liquefaction. A study of the glacial outwash deposits at the 

boundary of the river alluvium in Evansville was carried out using a combination of data from 

the standard penetration test (SPT) and the cone penetrometer test (CPT). The study showed that 

the liquefaction hazard had a large range in these deposits (Kayabali, 1993; Kayabali and West, 

1994).

Bobet and others (2001) evaluated ground accelerations and liquefaction potential for 

nine sites in southwestern Indiana to estimate the damage potential to pile foundations at bridge 

sites. They found soil liquefaction and lateral spreading to be likely at some sites in the thick

alluvial deposits of both the Ohio and Wabash River Valleys. While their study investigated 

individual sites, it did not provide an estimate of liquefaction hazard over the entire Evansville 

region.
4

Recently, more extensive sets of CPT data have been collected to allow better 

characterization of the soils on a regional scale (Holzer, 2003), detailed surficial mapping has 

been completed (Moore and others, 2009), and a 3D model of soil depth and properties has been

created (Haase and others, 2011a).

Several approaches have been developed to provide an integrated map view of 

liquefaction hazard, which otherwise depends on depth-dependent soil characteristics. Holzer 

and others (2006) used liquefaction potential curves (cumulative frequency distributions of the 

liquefaction potential index—LPI) for soil profiles in different surficial geologic materials to 

evaluate the liquefaction potential in the greater Oakland, Calif., area. They calculated LPI

values for each CPT sounding based on M6.6 and 7.1 scenario earthquakes and determined the 

percentage of the area predicted to liquefy for each earthquake. Lenz and Baise (2007) evaluated 

the spatial variability of LPI in the same area using CPT and SPT data assuming (1) the peak 

ground accelerations from the 10-percent chance in 50 years (2002 USGS National Seismic 

Hazard Map) and (2) an M6.8 earthquake on the San Andreas Fault. Lenz and Baise suggested

that a geo-statistical method for the interpolation of LPI is appropriate to construct a detailed 

liquefaction map. Rix and Romero-Hudock (2003) produced a liquefaction hazard map for 

Shelby County (Memphis), Tenn., based on the method of Holzer and others (2009) for a New 

Madrid scenario earthquake. Cramer and others (2008) used the liquefaction potential curves for 

Memphis (Rix and Romero-Hudock, 2003) to generate probabilistic liquefaction-hazard maps 

that provide the probability that liquefaction will occur, given all possible ground motions from 

all known sources.

The approach in the present study is to use the CPT data of Holzer (2003) that sample the 

principal surficial geologic units in the Evansville area and to calculate the factor of safety and 

LPI given the mean peak ground accelerations obtained in our scenario study (Haase and others, 

2011b). In successive sections, we 

• describe the surface geology and CPT data of the Evansville area,

• review the calculation of the factor of safety and LPI using the method of Robertson and 

Wride (1998), which is based on the cyclic resistance ratio and cyclic stress ratio and the 

properties of the soil column,

• present the results for the CPT sites,

• present the statistics of gridded site soil properties and development of the distribution of 

LPI at each site, and mapping of the results,

• discuss a comparison of results with previous work and assessment of uncertainty, and

• summarize the conclusions. 

Data

Surface Geology

As a precursor to the study of the probabilistic hazard of ground shaking in the Evansville 

region (Haase and others, 2011a), surficial geologic mapping was carried out at 1:50,000 scale 

for seven of the nine USGS map quadrangles surrounding the cities of Evansville and Henderson 

in the southwestern part of Indiana and Kentucky (Moore and others, 2009). The region was 

mapped using 23 units with descriptions based on lithology and depositional environment. For 

the Daylight and Kasson quads (northwestern and northeastern quads), the previously available 

surficial geologic maps at 1:500,000 scale (Gray, 1989) were used, with revisions to the 

nomenclature for the units to be consistent with the recent mapping.
5

The surficial geology along the Ohio River Valley near Evansville consists of a variety of 

glacial and interglacial lithologic sequences characterized by a series of fluvial and lake 

depositional events and also by later deposition of relatively thick Ohio River fluvial deposits

(Eggert and others, 1996, 1997a, b) (fig. 1).

Figure 1. Merged surficial geologic map from the 1:50,000- (Moore and others, 2009) and 1:500,000-

(Gray, 1989) scale maps including cone-penetrometer test sites with shear wave measurements (red 

symbols). Mapped units are Quaternary: Qc, colluvium; Qal, alluvium; Qall, levee deposit alluvium; 

Qas, alluvium in modern flood plain sloughs; Qaf, alluvium in alluvial fans; Qafp, river flood plain 

alluvium; Qat, low terrace alluvium; Qa, creek and sheetwash alluvium; Qes, dune sand; Qel, loess; 

Qot1o, reworked Ohio River terrace outwash alluvium; Qot1g, reworked Green River terrace alluvium; 

Qltm, upland marginal lacustrine deposits; Qlt, lacustrine terrace slackwater deposits; Qot1, low terrace 

outwash alluvium; Qlot, lacustrine and outwash terrace deposits; Qotp, paleolevee deposits on 

outwash terrace; Qot2, high terrace outwash alluvium; QTg, Quaternary and Tertiary upland gravel; Pz, 

Paleozoic bedrock; af1, af2, af3, modern artificial fill. Red symbols indicate cone-penetrometer test 

sites with shear-wave measurements; they are grouped by soil characteristics explained in table 2. Red 

triangles are in group 1 (River alluvium group—includes recent and old Ohio River sediments mapped 

as surficial map units Qaf, Qafp, Qal, Qall, Qas, Qat, Qot1, Qot1g, Qot1o), red circles are in group 2 

(Outwash terrace group—includes Qlot, Qot2, Qotp), and red squares are in group 3 (Lacustrine 

terrace group—includes Qlt, Qa, Qlt, Qltm).
6

The fluvial deposits include primarily alluvium and outwash (Qal) and are composed of 

chiefly fine- to medium-grained lithic quartz sand interbedded with lenses of clay, clayey silt, 

silt, coarse sand, granules, and gravel (Moore and others, 2009). The typical depositional

sequence consists of gravelly sand to sandy gravel at greater depth, predominantly sand at 

intermediate depths, and silt and clay near the top. A series of terrace deposits bordering the 

Ohio River Valley are composed primarily of lacustrine and outwash deposits (Qlot). The main 

urban area of Evansville is constructed on these terrace deposits. Ancient Ohio River tributary 

valleys are filled with silty and clayey lacustrine terrace deposits (Qlt). The surficial geology in 

the northern portions of the Evansville region includes loess (Qel) covering the bedrock and 

lacustrine units.

CPT Data

Cone-penetrometer tests were carried out at 58 sites (Holzer, 2003) measuring tip 

resistance, sleeve friction, and shear-wave travel time. The soil type of the layers (table 1) was 

categorized indirectly by behavior of the tip resistance and sleeve resistance using the method of 

Roberson and Wride (1998). Based on similarities of the soil types present in the sampled 

profiles and similarities in the lithologic descriptions of the surficial geologic units, the data from 

the nine-quadrangle map area (fig. 1) were divided into three groups for analysis as follows: 

group 1, the River alluvium group, includes recent and old Ohio River sediments mapped as 

surficial map units Qaf, Qafp, Qal, Qall, Qas, Qat, Qot1, Qot1g, Qot1o; group 2, the Outwash 

terrace group, includes Qlot, Qot2, Qotp; and group 3, the Lacustrine terrace group, includes Qlt, 

Qa, Qltm. Among these, 11 CPT measurements were carried out in surficial geologic units 

included in the River alluvium group, 20 CPT measurements in units included in the Lacustrine 

terrace group, 24 CPT measurements in units included in the Outwash terrace group (fig. 1), and 

3 measurements were taken in other units. An example of the CPT data from one site in the 

River alluvium group is shown in figure 2. Several profiles constituting cross-sections through 

the different depositional environments are provided in Appendix 1.

Table 1. Soil types associated with variable propensity for liquefaction as adapted from Robertson and 

Wride (1998).

Soil type Description

1 sensitive, fine grained

2 peats

3 silty clay to clay

4 clayey silt to silty clay

5 silty sand to sandy silt

6 clean sand to silty sand

7 gravelly sand to dense sand

8 very stiff sand to clayey sand (heavily overconsolidated or cemented)

9 very stiff, fine grained (heavily overconsolidated or cemented)
7

Method of Calculation of Factor of Safety and Liquefaction Potential Index

The method of Youd and others (2001) was used to evaluate the liquefaction potential for 

the Evansville area. Two values are required to calculate the factor of safety for liquefaction: the

seismic demand on a soil layer and the soil’s capacity to resist liquefaction. The seismic demand 

is based on the surface peak ground acceleration and the depth to the soil layer through a cyclic 

stress ratio (CSR). The capacity of the soil to resist is based on the CPT data through a cycle 

resistance ratio. The factor of safety (FS) is calculated as a function of the cyclic resistance ratio 

(CRR) for an M7.5 earthquake (CRR7.5), the cyclic stress ratio, and a magnitude scaling factor 

(MSF), to adjust for other magnitudes, and is determined by equation 1.

(1)

A recommended MSF is defined for moment magnitude (M) by the following equation (Youd 

and others, 2001).

(2)

The simplified equation for CSR quantifies the stresses produced in the soil by an 

earthquake and is given by equation 3.

(3)

where:

amax is the peak ground surface acceleration,

g is the acceleration of gravity, 

σv0 is the total vertical stress,

rd is the stress-reduction factor at the depth of interest, and

σ'v0 is the average effective vertical stress (a function of depth below the water table). 

The stress-reduction factor as a function of depth, z, is approximated by the following 

equation (Youd and others, 2001).

(4)

The liquefaction resistance of the soil is quantified with the cyclic resistance ratio (CRR)

obtained from field cone-penetrometer-test data (CPT) or standard-penetration tests (SPT). For 

CPT data, the CRR is related to the normalized cone-penetration tip resistance corrected to a 

clean sand, , and normalized to 100 kilopascals (kPa), and is given by equation 5 

(Robertson and Wride, 1998).

(5)

FS = CRR7.5

CSR

 

   

  × MSF

MSF = 102.24

M2.56

max 0

0

0.65 '

   =      

v

d

v

a CSR r

g

σ

σ

rd = 1.000 − 0.4113 × z

0.5 + 0.04052 × z + 0.001753 × z

1.5

1.000 − 0.4177 × z

0.5 + 0.05729 × z − 0.006205 × z

1.5 + 0.001210 × z

2

q( c1N )

cs

CRR7.5

=

0.833

q( c1N )

cs

1000

















+ 0.05 if q( c1N )

cs < 50

93

q( c1N )

cs

1000

















3

+ 0.08 if 50 ≤ q( c1N )

cs < 160


















8

The normalized cone-tip resistance is corrected for overburden stress in the following 

manner.

 with (6)

where:

Pa is the atmospheric pressure equal to 100 kPa, 

CQ is the normalizing factor for cone-penetration resistance, 

n is an exponent that varies with soil type, and

qc is the cone tip resistance measured in the field. 

A correction factor, Kc, which is a function of soil-behavior-type index, Ic, is applied to 

correct for the apparent fines content in the soil as shown below.

(7)

where:

(8)

The soil-behavior-type index, Ic, is a function of the cone tip resistance qc and the 

measured sleeve resistance, fs, and is given by equation 9.

(9)

where:

(10)

and

(11)

Here, n is 0 or 1 depending on the type of soil. 

Figure 2 shows the entire calculation for LPI for a typical profile located in the river 

alluvium. The CPT measurements of tip resistance and sleeve friction are shown in figures 2A

and B. Soil behavior type classification is shown in figure 2C. The series of calculations for the 

factor of safety is shown in figures 2D through J. Figure 2D shows the normalized CPT 

penetration resistance. Figures 2F and G show soil-behavior-type index (Ic) and correction factor 

(Kc), necessary to correct soils with fines content to a reference clean sand. Figure 2I shows 

corrected tip resistance. Figure 2H shows normalized CPT resistance corrected for overburden 

stress. The other figures are understandable as labeled.

This soil-column example, VHC006, (fig. 2C) shows three typical soil-behavior types 

that are found in many of the profiles. It has a sequence of 6 meters (m) of predominantly silty 

clay to clay layers (soil behavior type 3), overlying a 5-m sequence of predominantly sandy silt 

to clayey silt (soil behavior type 6), overlying a 9-m sequence of old Ohio River sands and 

gravelly sand (soil behavior type 8 and 9). The near surface (top 2 m) in the clay sequence has a 

1

  =    

c

c N Q

a

q q C

P 0 '

  =    

n

a

Q

v

P C

σ

q( c1N )

cs = Kc

qc1N

Kc = 1.0 for Ic ≤ 1.64

−0.403Ic

4 + 5.581Ic3 − 21.63Ic2 + 33.75Ic − 17.88 for Ic > 1.64









Ic = (3.47 − logQ)

2

+ (1.22 + log F)

2 

 

0.5

Q = qc − σ ( v0 )

Pa

















Pa

σ '

v0





 





n

F = fs

(qc −σv0 )

 

 

  

 

 

  ×100%
9

relatively high corrected tip resistance, (qc1N)cs, leading to a sufficiently high factor of safety to 

inhibit liquefaction. Ic and Kc are high in the top sequence, which is identified as clay. The 

intermediate-depth sequence also indicates significant fines content leading to a moderate 

correction factor Kc. The intermediate depth silty sand sequence has a slow increase in CSR due 

to the increase in effective vertical stress below the water table at 0.8 m (fig. 2J). 

In addition, this sequence has a relatively low corrected-tip resistance and a low sleeve 

friction. This leads to a low factor of safety. Figures 2K and L show that many points in the clay 

sequence that have a low factor of safety are excluded from the calculation of liquefaction 

potential index because they have been identified as soils with Ic greater than or equal to 2.6; that 

is, they are not susceptible to liquefaction because of their very high clay content. Overall, the 

liquefaction potential index is high for this site because of the low factor of safety in this 

intermediate-depth silty sand sequence (fig. 2K).

The factor of safety is calculated for each soil measurement within the profile at 5-cm 

depth intervals. The LPI integrates this information over the entire profile and gives a single 

number that is representative of the probability that any of the susceptible soils will liquefy. The 

LPI is defined by Iwasaki and others (1982) as

(12)

where:

for FS ≤ 1

for FS > 1 or Ic > 2.6

and z is the depth below the ground surface in meters, The integral in equation 12 is calculated 

for the first 20 m below the surface. The weights, w(z), in the integrand tend to reduce the overall 

influence of the contributions from deep soil layers. The LPI can be considered primarily as a 

function of the thickness of the liquefiable layer, the proximity of the liquefiable layer to the 

surface, and the value of the layer’s FS when the FS is less than 1. Note that most clay and silty 

clay layers at shallow and intermediate depths in this profile are excluded from the calculation 

when their soil behavior index Ic is less than 2.6. This will be discussed in more detail in a later 

section. 

The liquefaction potential was originally classified by Iwasaki and others (1982) to relate 

the LPI to whether severe liquefaction was likely, based on standard penetration test data. Toprak 

and Holzer (2003) found that during the Loma Prieta earthquake in 1989, the median value of 

LPI for soundings where sand boils occurred was 5, and 25 percent of soundings that showed 

sand boils had LPI greater than 10. The median value of LPI for soundings where lateral 

spreading occurred was 12, with 25 percent of soundings that showed lateral spreading having 

LPI greater than 17. Based on these calibrated values, it was proposed that the LPI greater than 5 

criteria be used to predict the probability of surface manifestations of liquefaction, and the LPI

greater than 12 criteria be used to predict the probability of lateral spreading (Holzer, 2008). We 

have adopted these criteria for the Evansville liquefaction hazard maps.

LPI = F × w(z)dz

0m

20m

∫

F = 1− FS

0

   

w(z) =10 − 0.5z
10

A B C

D E F

G H I
11

J K L

Figure 2. Example of the series of calculations for the factor of safety for profile VHC006, a typical profile 

located in unit Qall alluvium levee deposits. A, qc: tip resistance; B, fs: sleeve friction; C, soil behavior 

type (Robertson, 1990); D, Q: normalized penetration resistance; E, F: normalized sleeve friction; F, Ic: 

Soil behavior type index; G, Kc: correction factor; H, qc1N: tip resistance normalized for overburden 

stress; I, (qc1N)cs,: tip resistance corrected to a clean sand; J, CSR and CRR; K, factor of safety with 

dotted line indicating FS=1, above which there is no contribution to the LPI; and L, weighted 

liquefaction potential integrand . (MN, megaNewtons; kN, kiloNewton; m, meter).

Liquefaction Calculation for CPT Sites

For each site, including CPT sites, peak ground accelerations were calculated for the two 

scenario events described above: an M7.7 earthquake on the New Madrid fault at an average 

distance of 180 km southwest of the center of the study region, and an M6.8 earthquake 

approximately 40 km northwest of the center of the study region. The calculation uses a suite of 

alternative seismic-attenuation relations and corresponding weights consistent with the 

attenuation relations and weights used in the 2008 USGS national seismic hazard maps. The 

calculation incorporates subsurface geological information to take into account site effects, 

including amplitude-dependent amplifications (Haase and others, 2011b). The predicted peak 

ground accelerations (amax) for these two events are shown in figure 3 and range from 0.13–0.81

g for the M6.8 event and 0.09–0.24 g for the M7.7 event (Haase and others, 2011b).

FL × w(z)
12

Figure 3. Peak ground acceleration in terms of the percent of the acceleration of gravity (g) predicted for 

(left) an M7.7 New Madrid earthquake and (right) an M6.8 Wabash Valley earthquake. (PGA, peak 

ground acceleration)

The LPI is calculated using the procedure described in the previous section at each CPT 

site for the two scenario earthquakes (fig. 4). Two sites in the River Alluvium group have LPI 

greater than 5 for the New Madrid event and four sites greater than 5 for the Wabash Valley 

event, indicating a high probability for liquefaction. The Outwash Terrace group has six sites 

with LPI greater than 5 for the New Madrid event and seven sites for the Wabash Valley event. 

Four of these sites have LPI greater than 12 for both scenario events, indicating a high 

probability of lateral spreading due to liquefaction. The Lacustrine Terrace group has no sites 

with LPI greater than 5, hence no sites with a high probability of liquefaction. The LPI is very 

low or exactly zero for many sites in this group, because many soil layers had Ic greater than or 

equal to 2.6, indicating clay content high enough that the layers did not contribute to the LPI. 

Within the Outwash Terrace sites, the sites that are located farther to the west in unit Qlot 

lacustrine and outwash terrace deposits have higher LPI than those sites to the east for both 

scenario events. This is because of amplified PGA values to the west within this unit due to site 

conditions in the unconsolidated soils (figure 3).
13

Figure 4. Liquefaction potential index (LPI) calculated from the cone-penetrometer test (CPT) profiles for 

(left) an M7.7 New Madrid event and (right) an M6.8 Wabash Valley event.

The LPI results are listed in table 2 for each of the CPT profiles from the three groups to 

illustrate how the surficial geology correlates with the results of the liquefaction calculation. 

Several examples of typical CPT profiles from each group, and their corresponding factor of 

safety (calculated assuming a value of amax of 0.37 g), are shown in Appendix 1. The cumulative 

frequency distributions of LPI are calculated for each group for the larger amax event, the M6.8 

Wabash Valley event. For group 1, River Alluvium, 25 percent of the LPI values exceed 5 (high 

probability for liquefaction). For group 2, Outwash Terrace, 33 percent of the LPI values exceed 

5. For group 3, Lacustrine Terrace, 8 percent of the LPI values exceeds 5.
14

Table 2. Liquefaction potential index (LPI) for each cone-penetrometer test measurement listed by surficial 

geologic unit and grouped based on similarities in soil behavior type and similarities in the lithologic 

descriptions of the surficial geologic units. 

Sounding Latitude

(N)

Longitude

(W)

LPI 

(M=7.7)

LPI 

(M=6.8)

Label Geological Description Group

VHC005 37.9411 -87.5680 3.40 5.62 Qafp Alluvium, river flood plains (Holocene) 1

VHC009 37.9155 -87.5278 1.96 2.35 Qafp Alluvium, river flood plains (Holocene) 1

VHC010 37.9229 -87.5453 3.29 3.80 Qafp Alluvium, river flood plains (Holocene) 1

HNC005 37.8721 -87.7019 9.84 13.73 Qafp Alluvium, river flood plains (Holocene) 1

VHC001 37.9278 -87.4928 0.21 0.21 Qall Alluvium, natural levee deposits (Holocene) 1

VHC002 37.9329 -87.4714 0.10 0.08 Qall Alluvium, natural levee deposits (Holocene) 1

VHC006 37.9318 -87.5595 7.62 9.00 Qall Alluvium, natural levee deposits (Holocene) 1

VHC007 37.9294 -87.5023 0.59 0.66 Qall Alluvium, natural levee deposits (Holocene) 1

VHC008 37.9072 -87.5120 1.82 2.59 Qall Alluvium, natural levee deposits (Holocene) 1

VHC003 37.9463 -87.4712 4.73 5.01 Qot1

Alluvium, outwash, low terrace (upper 

Pleistocene) 1

HNC004 37.8552 -87.6978 2.04 2.83 Qot1

Alluvium, outwash, low terrace (upper 

Pleistocene) 1

VHC013 37.9894 -87.4738 0.07 0.19 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC015 37.9840 -87.4774 0.14 0.18 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC016 37.9775 -87.4880 8.73 10.02 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC018 37.9828 -87.5016 0.71 0.87 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC019 37.9880 -87.5017 1.18 1.70 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC020 37.9732 -87.4519 0.57 0.94 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC021 37.9920 -87.5474 23.80 30.59 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC023 37.9892 -87.5277 0.34 0.70 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC026 37.9873 -87.5623 0.78 1.74 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC027 37.9856 -87.5779 0.74 3.50 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC028 37.9824 -87.5855 0.00 0.05 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC032 37.9797 -87.5937 0.88 1.81 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC033 37.9840 -87.5816 8.04 9.16 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC034 37.9890 -87.5521 12.52 17.09 Qlot

Lacustrine and outwash terrace deposits 

(upper Pleistocene) 2

VHC025 37.9810 -87.5528 2.35 5.44 Qot2

Alluvium, outwash, high terrace 

(upper Pleistocene) 2

VHC035 37.9742 -87.5659 12.19 17.47 Qot2

Alluvium, outwash, high terrace (upper 

Pleistocene) 2

HNC003 37.8382 -87.6908 12.29 15.58 Qot2

Alluvium, outwash, high terrace (upper 

Pleistocene) 2

VHC017 37.9763 -87.5019 3.51 4.44 Qotp

Paleolevee deposits on outwash terrace 

(upper Pleistocene) 2

VHC024 37.9843 -87.5190 0.80 1.16 Qotp

Paleolevee deposits on outwash terrace 

(upper Pleistocene) 2

HNC006 37.8204 -87.7073 3.10 4.44 Qotp Paleolevee deposits on outwash terrace 2
15

(upper Pleistocene)

VHC036 37.9796-87.6256 0.64 1.34 Qa

Creek alluvium and sheetwash alluvium 

(Holocene)3

VHC037 37.9602-87.6341 0.31 1.26 Qa

Creek alluvium and sheetwash alluvium 

(Holocene)3

VHC011 37.9913-87.4582 0.06 0.09 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC014 38.0275-87.4714 0.20 0.59 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC022 38.0080-87.5264 0.00 0.11 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC030 38.0495-87.4738 0.08 0.11 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC031 38.0349-87.4919 0.00 0.00 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC038 38.0250-87.5949 0.56 1.34 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC039 38.0135-87.5978 0.19 0.45 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC040 38.0532-87.5050 0.24 1.21 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

WKC001 37.9911-87.4456 0.35 0.64 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

WKC002 38.0058-87.4454 2.84 3.25 Qlt

Lacustrine terrace deposit 

(upper Pleistocene)3

WKC003 38.0067-87.4365 0.24 0.69 Qlt

Lacustrine terrace deposit 

(upper Pleistocene)3

WKC004 38.0201-87.4365 0.16 0.35 Qlt

Lacustrine terrace deposit 

(upper Pleistocene)3

WKC005 38.0274-87.4274 0.12 0.20 Qlt

Lacustrine terrace deposit 

(upper Pleistocene)3

WKC006 38.0885-87.4658 4.69 6.11 Qlt

Lacustrine terrace deposit 

(upper Pleistocene)3

WKC008 37.9802-87.4503 0.40 0.83 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

WKC009 38.0781-87.4658 4.50 6.29 Qlt

Lacustrine terrace deposit 

(upper Pleistocene)3

WKC010 38.0677-87.4659 0.00 0.00 Qlt

Lacustrine terrace deposit 

(upper Pleistocene)3

HNC001 37.8153-87.5922 3.18 3.19 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

HNC002 37.8043-87.6669 2.67 3.30 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

PSY001 37.9806-87.7167 0.56 3.38 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC029 38.0381-87.4728 0.02 0.09 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

WKC007 38.0583-87.4729 0.00 0.02 Qlt

Slackwater deposits, lacustrine terrace (upper 

Pleistocene)3

VHC004 37.9510-87.5722 1.64 2.78 af1 Artificial fill, engineered (modern)4

VHC012 37.9765-87.4735 8.52 9.90 af1 Artificial fill, engineered (modern)4

VHC041 38.0281-87.5405 0.00 0.00 af1 Artificial fill, engineered (modern)4
16

Results for the River Alluvium Group

Cone penetrometer test profiles in the River Alluvium group, which are found primarily 

within the Ohio River flood plain, (see fig. 1-11) typically have extensive sand and gravelly sand 

units below about 10 m, and finer silt and clay layers above that. Overall, calculated LPI is high 

for the River alluvium group. The factor of safety for liquefaction for group 1 profiles is 

calculated using the method described above. The factor of safety in the deeper, older Ohio River 

sand and gravel deposits is highly variable below 10 m in most profiles, primarily because the tip 

resistance is quite variable (figure 2A) and sometimes sufficiently high to give the CRR high 

enough values to resist liquefaction. Those layers that do not have a sufficiently high CRR to 

resist liquefaction make a large contribution to the LPI. Surprisingly, some profiles with sand 

units near the surface, such as VHC007, do not have a large LPI, because of very high tip 

resistances in these units. The intermediate-depth silty sand layers do make a significant 

contribution to the LPI. The unit in the top 2 m was identified in many of the CPT profiles in this 

region as having high clay and clayey silt content. When the soil-behavior-type index of these 

layers was evaluated, they typically have Ic greater than or equal to 2.6 indicating that they are 

clay layers that are not susceptible to liquefaction (see discussion below). 

Figure 5 shows the soil-behavior-type index Ic computed for all clay-rich soils in the CPT 

datasets as a function of normalized friction ratio F. Superimposed on this is the domain of 

susceptible liquefaction from Robertson and Wride (1998) and Youd and others (2001). These 

layers, indicated with a red ‘x’ for the factor of safety in figure 1-11, do not contribute to the LPI. 

Figure 5. Soil-behavior-type index, Ic, and friction ratio in percent, F, plotted for all clay-rich soil elements 

in the cone-penetrometer test (CPT) dataset.
17

Results for the Outwash Terrace Group

The soil profiles within the deposits of the Outwash Terrace group are more complex 

than those in the River Alluvium group, as they contain highly variable sequences of silty sand, 

clayey sand, and sandy clay from overlapping transitional depositional environments (see figs.

1-12 and 1-13). There is little horizontal continuity of the soils present in these profiles in the 

terraces north of the current Ohio River flood plain. On the west side of the sampled terrace 

region, sandy silt and silty sand that may correspond to river overbank deposits appear midway 

through the profiles. The depths of these deposits vary with distance from the current Ohio 

River, and extensive layers of clay could be present in locations where the soil profile might be 

filling in older stream valleys that accumulated clay soils in the lacustrine high-stands (for 

example, Pigeon Creek). 

The farthest west profiles of the sampled terrace region typically have high tip resistance 

and a resulting high factor of safety for the intermediate-depth sandy silt units in the 3 to 11 m 

depth range (see fig. 1-12). Clay units below this depth are predominantly excluded from the LPI

calculation, once again because of the Ic greater than or equal to 2.6 criterion. Silty sand units 

below this intermediate depth make a large contribution to the LPI. Toward the center of the 

sampled terrace region, there are more extensive sandy silt and silty sand units that do not have 

high tip resistance. These have a much lower factor of safety and contribute greatly to the LPI. 

The profiles farthest east within the terrace region have most values of Ic greater than or 

equal to 2.6 and therefore have low LPI values. Due to the high variation of the soil properties 

and the resulting liquefaction potential, it is very difficult to extrapolate the soil-profile 

properties to nearby sites. In order to construct a liquefaction hazard map for this transition

region of terraces between the flood plain and the uplands, a probabilistic method is appropriate. 

Results for the Lacustrine Terrace Group

Profiles in the Lacustrine Terrace group (see fig. 1-14) typically have extensive clay and 

silt layers in the upper 20 m. The method that is used to calculate liquefaction potential was

originally developed for sandy soil, so there is a criterion that the soil-behavior index Ic should 

be less than 2.4 for the method to be used. Soils with behavior index greater than or equal to 2.6 

are clay soils that are not susceptible to liquefaction (Robertson and Wride, 1998). This is the 

case for most of the profiles in the Lacustrine Terrace group. The relatively homogeneous clay 

layers exhibit different properties in approximately the upper 7 m where tip resistances are much 

greater. This results in greater factors of safety. The factor of safety for profiles within the 

lacustrine region is also shown in Appendix 1. Those data with Ic greater than or equal to 2.6 are 

indicated with a red ‘x’ in the factor of safety profiles. Data with Ic between 2.4 and 2.6, which 

require additional testing to determine their liquefaction susceptibility, are examined in more 

detail in the next section. Silt and silty clay that have a soil-behavior-type index between 2.4 and 

2.6 critically affect the values of LPI. 

Evaluating Liquefaction Potential for Silty and Clayey Soil

Generally, two criteria based on soil properties are used to evaluate liquefaction hazard in 

silty and clayey soils. The first method is based on soil-behavior index (Ic) and the normalized

friction ratio (F) from CPT data (Robertson and Wride, 1998). According to the first method, 

soils are not susceptible to liquefaction if Ic greater than 2.6 and F greater than 1.0 percent. Soils 

with Ic between 2.4 and 2.6 or with Ic greater than 2.6 and F less than or equal to 1 percent

require further laboratory testing before their susceptibility to liquefaction can be determined.

Another such testing method was developed by Bray and Sancio (2006) for the evaluation of 
18

liquefaction susceptibility, which uses the plasticity index and the ratio of water content to the 

liquid limit to evaluate clayey soils for liquefaction susceptibility. 

To examine the extent of this problem in our dataset, soils containing clay-rich layers in 

the CPT data are plotted on an Ic-based criteria chart (fig. 5). We presume that soils with Ic less 

than 2.4 will be vulnerable to liquefaction, so the factor of safety is computed and used for the 

LPI. For soils with Ic greater than 2.6 and normalized friction ratio F greater than 1.0 percent, we 

presume that they are not susceptible to liquefaction, so the contribution to LPI is set to zero at 

that particular depth point even though the factor of safety is less than 1. If the soils lie in the

“test required” zone, then the assessment of liquefaction susceptibility requires more 

investigation. The profiles containing soil layers that fell into this category were confined mostly 

to a relatively localized region near profiles WKC006 and WKC009 in the northern part of unit

Qlt—Lacustrine terrace slackwater deposits (fig. 1).

Because data on the Atterberg limits, a measure of under what water content a soil’s 

mechanical behavior transitions from solid to plastic to liquid, were not collected with this CPT

dataset, we used the properties of similar soils from other geotechnical studies in the same 

localized region (M. Wigger, written comm.), which did include Atterberg limits and the derived 

plasticity index. These were compiled and plotted on a plasticity index-based criteria chart (fig.

6). From these tests, we see that 80 percent of the soil samples in this region belong to the zone 

of “not susceptible” to liquefaction. Therefore, we assume that for this case, clay-rich soils that 

fall into the “test required” region have low probability of being susceptible to liquefaction and 

make no contribution to the calculation of the LPI. This assumption was retained in the final 

liquefaction maps.

Figure 6. Test datasets of plasticity index, water content, and liquid limit from clay units near the conepenetrometer test profiles within Lacustrine Terrace group that required further testing to determine 

liquefaction susceptibility.
19

Liquefaction Calculation for non-CPT Sites

Generalization of Soil Profile Type

There are sufficient CPT data in the three groups defined in table 2 to characterize their 

properties statistically, even though these data are not uniformly distributed. Loess makes up the 

majority of the remainder of the surface area. With only two CPT profiles in units containing 

loess, there were not sufficient data to characterize this statistically; however, these areas 

typically have a thin layer of silt deposits over bedrock and are not expected to liquefy. Other 

minor units include artificial fill that we cannot characterize based on their geologic 

environment. Characterization of these units will require engineering data on their in-situ 

condition, which is beyond the scope of this study.

To perform the liquefaction-hazard calculation, the CPT properties of tip resistance and 

sleeve resistance are necessary information. These will be characterized probabilistically for each 

group. Other required, location-dependent information for calculating the factor of safety and 

LPI are the total thickness of the soil above bedrock and the depth of the groundwater table. 

These are obtained separately from the group characteristics.

Determining Soil Thickness and Water Table 

The bedrock depth below the surface was determined from logs and refraction profiles in 

a previous study, as it was also required for the site amplification calculation for the probabilistic 

and deterministic hazard analyses (Haase and others, 2011a; Haase and others, 2011b). In brief, 

the bedrock depth (fig. 7) is based on a compilation of 900 Indiana Geological Survey water well 

logs from the iLITH database (Bleuer, 2000), 230 bedrock depth measurements interpreted from 

P-wave refraction profiles (Rudman and others, 1973; Whaley and others, 2002), and bedrock 

elevation points from the Kentucky Geological Survey oil, gas, and water well logs. Bedrock 

depth is interpolated using kriging in the uplands regions. Bedrock elevation is interpolated for

the lowlands using the bedrock-elevation data. These two sets of contours were merged and 

refined by hand to replicate the steep-sided bedrock valley walls, then converted to a 50-m raster 

that optimizes the hydrological continuity on the bedrock surface. The uncertainty in the bedrock 

depth is plus or minus 3 m. For more details see Haase and others (2011a).
20

Figure 7. Contoured bedrock depth. The steep-sided ancient bedrock valley is evident beneath the flood 

plain of the present-day meandering Ohio River. (m, meters).

The depth to the groundwater table affects the calculation of LPI, because liquefaction 

requires saturated soil, and the effective stresses of the soil that determine the resistance to

liquefaction depend on the depth below the water table. The groundwater table is quite shallow 

in this region, and it fluctuates seasonally. The water-well databases available for the region were 

not useful for determining the groundwater table because they did not contain information 

verifying whether or not the level provided is the first piezometric surface encountered. Most 

indicated the piezometric surface of a confined aquifer, as defined by a sealed screen section at 

depth. 

Lacking this information, we constructed water-table depths using an alternative method. 

Information from the United States Department of Agriculture soil surveys for nearby counties 

indicates a range of water-table depths from 0 to 2 m in typical soils. A groundwater surface was 
21

constructed that followed 2 m below the surface topography except where bedrock was 

shallower than 2 m. In that case the groundwater table was set to just above bedrock. The 

groundwater surface was required to rise linearly from 2 m to 0 m at the elevation of the Ohio 

River. At the locations of the CPT profiles where the groundwater table was measured, there is 

acceptable agreement with these groundwater-surface values. Based on the statistics of this 

agreement for each group, an uncertainty of 0.6 m is assigned to the depth of the water table for 

profiles within group 1, an uncertainty of 0.2 m is assigned for group 2, and an uncertainty of 0.8 

m is assigned for group 3. 

To assess the sensitivity of the liquefaction hazard to the level of the water table, two sets 

of calculations were run: one with a high (2 m) and one with a low (5 m) groundwater table for 

the data at the CPT locations. Values of LPI were consistently about 40 percent lower for the 

lower groundwater table. The more conservative high groundwater table is used in the 

liquefaction calculations presented here. Future research efforts should collect more data for 

establishing better constraints on water-table depth, including seasonal variations.

Mapping Liquefaction Potential using a Probability-Based Method

The approach we applied was to determine at each 0.01 degree grid point in the study 

region, the distribution of the LPI based on Monte Carlo sampling of the distributions of the 

sleeve friction and tip resistance. The groundwater-table depth at each point was randomly 

selected from a distribution with mean given by the depth at the corresponding grid point, with a 

standard deviation of 0.6, 0.2, or 0.8 m depth for group 1, group 2, and group 3, respectively. 

The PGA value was a single value for the appropriate location from the map in figure 3 and was 

not varied in the Monte Carlo simulations. The bedrock depth below the surface was selected 

from the map in figure 7, so that the generic group soil profile was truncated at the bedrock depth 

if it was less than 20 m deep.

The CPT data were split into the three groups (table 2). The distributions of tip resistance 

and sleeve friction in the CPT profiles were evaluated for each group. The lognormal mean and 

standard deviation of tip resistance and sleeve friction were calculated at every 2-m depth 

interval. Examples are shown in figure 8 of the variation of properties with depth. Based on these

statistics, 25,000 random values of tip resistance and sleeve friction at each 2-m depth interval 

were generated for each grid point, selecting from the distribution for the appropriate group. We 

assume no correlation between tip resistance and sleeve friction or between neighboring depth 

intervals. This fact may reduce the width of the resulting probability density function of LPI

(David Perkins, written communication, February, 2011). At each grid point, 25,000 values of 

LPI were calculated from these profiles. The mean of the LPI values at each grid point was 

calculated. The spatial distribution of the mean LPI is shown in figure 9. The calculation was 

performed individually for each of the two scenario earthquakes of M6.8 and M7.7.
22

A B

C D
23

E F

Figure 8. Examples of the variation of: A, the tip resistance, qc; and B, sleeve friction, fs, with depth for all 

profiles in River alluvium group. Examples of the variation of: C, tip resistance, qc; and D, sleeve 

friction, fs, with depth for all profiles in Outwash terrace group. Examples of the variation of: E, tip 

resistance, qc; and F, sleeve friction, fs, with depth for all profiles in Lacustrine terrace group. (MN, 

megaNewtons; kN, kiloNewton; m, meter)
24

Figure 9. Mean liquefaction potential index (LPI) for: A, magnitude (M) 7.7 New Madrid scenario 

earthquake and B, M6.8 Wabash River valley scenario earthquake. (PGA, peak ground acceleration; g, 

acceleration of gravity).

From the cumulative frequency distribution of LPI at each grid point, the probability of 

exceeding LPI of a specific value (5 or 12) for each earthquake was then calculated. These 

results are shown in figures 10 and 11.
25

Figure 10. Probability that the liquefaction potential index (LPI) is greater than 5 for: A, a magnitude (M) 

7.7 New Madrid scenario earthquake and B, an M6.8 Wabash River valley scenario earthquake. 

Probability that LPI is greater than 12 for: C, an M7.7 New Madrid scenario earthquake and D, an M6.8 

Wabash River valley scenario earthquake. (g, acceleration of gravity).
26

For an M6.8 Wabash River valley event, the probability that LPI is greater than 5 (high 

probability for surface evidence of liquefaction) is about 60–80 percent for the River Alluvium 

group west of Evansville. For Outwash Terrace group type soils on which most of Evansville is 

built, the probability that LPI is greater than 5 is about 70–80 percent. Here the soil sequences 

are highly variable, so the probability that LPI is greater than 5 can vary greatly. Within the 

Lacustrine Terrace group, the probability that LPI is greater than 5 is less than 60 percent in most 

of the area, except in localized areas where PGAs are amplified. For an M6.8 Wabash River 

valley event, the probability that LPI is greater than 12 (high probability for lateral spreading) is 

less than 20 percent in almost the entire area for all groups. The exceptions are in the western 

part of the Outwash terrace where it can reach 60–80 percent and the northern edge of the 

ancient bedrock valley where ground motions are amplified, leading to 20–40 percent

probability. 

For an M7.7 New Madrid earthquake, the probability that LPI is greater than 5 is 40–60

percent for most of the area designated as River Alluvium group west of -87.5o longitude, and 

20–40 percent east of there. Within the Lacustrine Terrace group, the probability that LPI is 

greater than 5 is predominantly less than 20 percent north of the Ohio River and 40–60 percent

south of the Ohio River. Within the Outwash Terrace group, the probability that LPI is greater 

than 5 is 60–80 percent. The probability that LPI is greater than 12 is less than 20 percent almost 

everywhere for all groups.

Discussion

By carrying out a scenario calculation, we are implicitly not considering uncertainty in 

the ground accelerations due to the location or size of the source. Simulations of variations 

among reasonable assumptions for New Madrid source parameters, however, can lead to a mean 

shift in PGA. 

An M7.7 earthquake was chosen for the scenario because when the hazard is 

deaggregated, it contributes more than 14 percent of the hazard, whereas an M8.0 contributes 

only 9 percent and an M7.4 contributes less than 8 percent. An M8.0 scenario earthquake would 

produce ground motions that are 25 percent higher, on average, than an M7.7 earthquake, and an

M7.4 scenario earthquake would produce ground motions that are 20 percent lower, so it is 

necessary to keep in mind that the liquefaction hazard depends on the assumptions that are made 

for the source. We estimate that the calculated factors of safety would decrease almost 30 percent 

for an M8.0 event and increase almost 40 percent for an M7.4 event.

The literature contains many examples of the difficulty of reconciling values and 

interpretations of LPI calculated using SPT compared to those calculated using CPT (see Holzer, 

2008 and references therein). Keeping in mind these limitations, we calculated LPI using both 

SPT and CPT for a subset of sites where both types of data were available, in order to provide a 

basis for a qualitative discussion of our results relative to previous results. For the SPT data, we 

used the method of Youd and others (2001) to estimate liquefaction potential index for an M7.7 

event using an amax value of 0.37 g. There were four sites with several SPT logs available. 
27

Table 3. Comparison of liquefaction potential index (LPI) calculated using nearby standard-penetration test 

(SPT) and cone-penetrometer test (CPT) data for several sites within the Lacustrine terrace group. See 

Holzer (2003) for identification of individual CPT profile locations.

SPT Site LPI CPT Site LPI

I-164 site 1 0.0

 0.0

 0.0

 0.0

 0.0

 0.0

VHC030 0.06

I-164 site 2 0.0

 0.12

 0.0

 0.0

 0.0

VHC029 0.19

I-164 site 3 0.0

 0.0

 0.0

VHC014 0.85

Table 4. Comparison of liquefaction potential index (LPI) calculated using nearby standard-penetration test 

(SPT) and cone-penetrometer test (CPT) data for several sites within the River alluvium group.

SPT Site LPI CPT Site LPI

I-164 site 4 34.46

 31.12

 27.79

 29.89

 21.03

 32.53

VHC003 37.06

In this comparison, there was originally a large difference between the LPI calculated 

based on CPT and SPT data. We found that the high values for LPI from the SPT calculation 

were due to layers with soil behavior types 1–6 (Robertson, 1990)—in other words, fine-grained 

clay to silt. Because SPT data can give unreliable and inconsistent results in clays, the 

discrepancy is not unexpected. Given that these layers would likely be too clay- or silt-rich to 

liquefy (a similar philosophy as applying a criterion on Ic), we excluded these values from the 

calculation. After that adjustment, the LPI’s calculated from the SPT agreed acceptably with 

those from CPT data (tables 3 and 4). Having shown that the CPT and SPT data are comparable, 

we discuss our results in the context of previous studies.

Bobet and others (2001) performed a soil-response analysis at several SPT and borehole 

shear-wave-velocity measurement locations within the Wabash River valley in southwestern 

Indiana using the equivalent linear one-dimensional wave propagation analysis method (SHAKE 

program; Idriss and Sun, 1992). Using the profile of peak acceleration with depth obtained from 

the soil-response analysis, we compared the actual cyclic stress ratio and the critical cyclic stress 

ratio required to initiate liquefaction for sites near those in the Bobet and others (2001) study. 

One site from that study was near site VHC039 within the lacustrine terrace slackwater deposits 
28

(Qlt) north of the sharp river bend. This site showed no liquefaction potential in their analysis 

and had respective LPIs of 0.45 and 0.19 for our analysis for the WVSZ and NMSZ scenarios,

thus demonstrating agreement. Their second site was near site VHC035 within the high terrace 

outwash alluvium (Qot2), just to the east of the sharp river bend. This site showed the CSR 

exceeding the critical value within the top 8 m of the profile, for their WVSZ scenario, which 

agrees with the value of 17.5 (high probability for lateral spreading) calculated for LPI in this 

study. For the NMSZ scenario, their study showed the CSR just barely reaching the critical 

value, which agrees with the value of 12.2 (high probability for lateral spreading) calculated for 

LPI in this study.

Although the Bobet and others (2001) paper discusses only two sites in the two primary 

types of soils within Evansville, it nevertheless suggests a significant difference in liquefaction 

potential for these two types of soils. With the high-resolution mapping data, we were able to 

map out this contrast in properties more clearly, reinforcing our expectation of significantly 

higher LPI in the River Alluvium group. With a larger dataset our results give a good 

representation of the variability within each group as well.

Kayabali (1993) produced a map showing the vulnerability of Evansville soils to 

liquefaction using SPT and the stress-reduction factor determined from CPT data. He used 

sampled data primarily from within what we called the Outwash Terrace group. The work only 

evaluated the contribution to LPI from a single layer, which underestimates the liquefaction 

hazard from the full soil column; however, the general trend of the highest liquefaction potential 

very close to the Ohio River is consistent with our results. He also found very high variation of 

liquefaction potential within his smaller map region, which is consistent with our results with 

large variation of LPI within the Qlot lacustrine and outwash terrace deposit. 

Eggert and others (1994) suggested that a more comprehensive evaluation of the 

liquefaction hazard in the Evansville area should be carried out. Our study complements this 

earlier study by extending it to a larger study area on both sides of the Ohio River.

The high values of LPI calculated at many sites in this study lead to the question of 

whether liquefaction has been observed in the geologic record. The known paleoliquefaction 

feature closest to Evansville is associated with the 12,000 before present (B.P.) event and is 

located N-NE of Evansville along the Wabash River. At this location, Holocene point-bar or late 

Wisconsinan braid-bar sands and gravels are overlain by a cap of silty clays (Obermeier, 1998). 

The next closest features are associated with the 6,100 B.P. event, also along the Wabash River 

(Green and others, 2005). No evidence of liquefaction was found in a large nearby excavation 

containing liquefiable sands of younger age beneath a lower terrace near Evansville or in the 

exposed banks of the Ohio River along the Indiana-Kentucky border (Munson and others, 1997). 

The authors of that work suggest that the lack of observations indicates that it is likely that the 

area has not experienced very strong shaking since the 6,100 B.P. event. On the other hand, the 

authors acknowledge that current river levels might be hiding any liquefaction features that could 

have developed below the depth of the cap of fine-grained soils in that area, as dams have raised 

water levels to ensure year round navigation. 

Conclusions

The objective of this study was to provide a detailed map for liquefaction hazard in and 

around Evansville, Ind. for two scenario earthquakes: an M6.8 Wabash River valley event 

approximately 40 km northwest of Evansville and an M7.7 New Madrid event approximately 

180 km southwest of Evansville. These choices are supported by historical liquefaction data in 

the Wabash River valley and the deaggregation of the probabilistic 2008 USGS National Seismic 

Hazard Maps. We used cone-penetrometer-test (CPT) data collected by Holzer (2003) that 
29

sampled the principal surficial geologic map units mapped by Moore and others (2009) as part of 

the Evansville project. The factor of safety against liquefaction for each CPT location was 

calculated using a standard method (Robertson and Wride, 1998) based on the cyclic resistance 

ratio, cyclic stress ratio, and the properties of the soil column. 

The calculations show high variability of liquefaction potential index (LPI) for samples in 

the Outwash Terrace group with higher values in the west, consistent with higher peak ground 

acceleration (PGA) values found in the site-dependent scenario ground-motion study (Haase and 

others, 2011b). Higher LPI values are found in the River Alluvium group and low LPI are found 

in the Lacustrine Terrace group. We established the probability distributions for liquefaction 

potential for each group using Monte Carlo sampling of the distributions of the properties of 

individual soil measurements of tip resistance and sleeve friction to determine the probability of 

exceeding LPI thresholds for surface expression (LPI greater than 5) and lateral spreading (LPI

greater than 12). We created maps of both the mean LPI and the probability of exceeding a given 

LPI. The resulting maps quantify the distribution of high liquefaction potential sites in the River 

Alluvium group where the soil profiles contain more sand; the maps also describe the contrasting 

Lacustrine Terrace group deposits that predominantly include clayey soil with lower liquefaction 

hazard.

Local variations of LPI are greatly dependent on local amplification due to site effects. 

For an M7.7 New Madrid earthquake, the probability that LPI is greater than 5 is 20–60 percent

for most of the group 1 units and 20–80 percent for most of the group 2 units. Within the 

Lacustrine Terrace group, the probability that LPI is greater than 5 is almost everywhere less 

than 40 percent. The probability that LPI is greater than 12 is less than 20 percent almost 

everywhere.

The lower probability of LPI being greater than 5 for a New Madrid earthquake is 

consistent with the fact that liquefaction features have not been found in the Ohio River valley 

that match documented New Madrid events, although features could have been eroded away 

(Obermeier, 1998). Also, evidence of liquefaction features from the New Madrid earthquakes 

appears to be limited to areas south of Saline Creek in southern Illinois (Obermeier, 1996).

For an M6.8 Wabash River valley event, the probability that LPI is greater than 5 (high 

probability of surface evidence of liquefaction) is about 60–80 percent for most of the River 

Alluvium group west of Evansville. For Outwash Terrace group type soils on which most of 

Evansville is built, the probability that LPI is greater than 5 is about 60–100 percent. Here the 

soil sequences are highly variable, so the probability that LPI is greater than 5 can vary greatly

by location. Within the Lacustrine Terrace group, the probability that LPI is greater than 5 is 0–

60 percent. For an M6.8 Wabash River valley event, the probability that LPI is greater than 12 

(high probability of lateral spreading due to liquefaction) is less than 20 percent for all groups 

except at the northern edge of the buried ancient bedrock valleys where ground motions are 

preferentially amplified. It is therefore possible that since evidence for liquefaction has not yet 

been found to have occurred in the Evansville area since 12,000 B.P. (Munson and others, 1997), 

ground shaking levels as have been estimated for a M6.8 Wabash River valley scenario event 

have not occurred in Evansville since that time.

Acknowledgments

This work was supported by USGS National Earthquake Hazards Reduction Program 

grant (07HQGR0058). We thank Tom Holzer and the liquefaction hazard group at the USGS for 

making the CPT data available. We thank Ron Counts at the Kentucky Geological Survey for

providing water well and borehole data. We thank Michael Wigger, from Earth Exploration, Inc., 

of Indianapolis, Ind. for the supplemental geotechnical data on Atterberg limits in Posey and 
30

Vanderbergh Counties, Ind. We thank Antonio Bobet for assistance with the liquefaction 

analysis method. We thank Tim Bowling for his help with GIS calculations. We thank Tom 

Holzer, Randy Jibson, and David Perkins for thorough reviews that helped improve the clarity 

and content of this manuscript.

Appendix 1

This appendix shows the soil behavior type and factor of safety for each soil layer for 

typical profiles from each of the three groups. Figure 1-1 shows profiles for group 1, River 

Alluvium, figure 12 shows the western profiles from group 2, Outwash Terrace, figure 13 shows 

the eastern profiles from group 2, Outwash Terrace, and figure 14 shows profiles from group 3,

Lacustrine Terrace.
31

Figure 1-1. Group 1, River alluvium, profiles and calculated factor of safety (FS), with soil units taken from Holzer (2003). Units with soil-behavior 

index (Ic) less than 2.6 do not contribute to the liquefaction potential index and are indicated with the factor of safety in red.
32

Figure 1-2. Western profiles from group 2, Outwash terrace, and factor of safety (FS) with soil units taken from Holzer (2003). Units with soilbehavior index (Ic) less than 2.6 do not contribute to the liquefaction potential index and are indicated with the factor of safety in red.
33

Figure 1-3. Eastern profiles from group 2, Outwash terrace, and calculated factor of safety (FS) with soil units taken from Holzer (2003). Units with 

soil-behavior index (Ic) less than 2.6 do not contribute to the liquefaction potential index and are indicated with the factor of safety in red.
34

Figure 1-4. Group 3, Lacustrine terrace, profiles and calculated factor of safety (FS) with soil units taken from Holzer (2003). Units with soilbehavior index (Ic) less than 2.6 do not contribute to the liquefaction potential index and are indicated with the factor of safety in red.
35

References

Bakun, W.H., and Hopper, M.G., 2004, Magnitudes and locations of the 1811-1212 New Madrid, 

Missouri, and the 1886 Charleston, South Carolina, earthquakes: Bulletin of the Seismological 

Society of America, v. 94, no. 1, p. 64–75.

Bleuer, N.K., 2000, iLITH database of the Indiana Geological Survey: Indiana Geological Survey Open 

File Study 00-8, CD-ROM.

Bobet, Antonio, Salgado, Rodrigo, and Loukidis, Dimitrios, 2001, Seismic design of deep foundations: 

Purdue University Joint Transportation Research Program Final Report FHWA/IN/JTRP-2000/22, 

Project No. C-36-36GG, File No. 6-14-33, 93 p.

Bray, J.D., and Sancio, R.B., 2006, Assessment of the liquefaction susceptibility of fine-grained soils: 

Journal of Geotechnical and Geoenvironmental Engineering, v. 1332, no. 9, p. 1165–1177.

Calais, Eric, and Stein, Seth, 2009, Time-variable deformation in the New Madrid Seismic Zone: 

Science, v. 323, no. 5920, p. 1442–1442.

Cramer, C.H., 2003, Site-specific seismic-hazard analysis that is completely probabilistic: Bulletin of 

the Seismological Society of America, v. 93, no. 4, p. 1841–1846.

Cramer, C.H., Rix, G.J., and Tucker, Kathy, 2008, Probabilistic liquefaction hazard maps for Memphis, 

Tennessee: Seismological Research Letters, v. 79, no. 3, p. 416–423.

Eggert, D.L., Samuelson, A.C., Bray, J.D., Chang, C.W., Eckhoff, W.R., Kayabali, Kamil, McClees, 

E.J., West, T.R., Woodfield, M.C., and Zheng, B., 1994, Final report to the city of Evansville—Shearwave and earthquake hazard mapping of Evansville, Indiana: Indiana Geological Survey Open-File 

Study, OFS94-19, 17 p.

Eggert, D.L., Woodfield, M.C., Bleuer, N.K., and Hartke, E.J., 1996, Geologic terrain map of the 

Indiana portion of the Newburgh quadrangle, Indiana-Kentucky: Indiana Geological Survey OpenFile Study, OFS96-09, scale 1:24,000.

Eggert, D.L., Woodfield, M.C., Bleuer, N.K., and Hartke, E.J., 1997a, Geologic terrain map of the 

Daylight quadrangle: Indiana Geological Survey Open-File Study, OFS97-17, 2 pls, scale 1:24,000.

Eggert, D.L., Woodfield, M.C., Bleuer, N.K., and Hartke, E.J., 1997b, Geologic terrain map of the 

Evansville region, Indiana: Indiana Geological Survey Open-File Study, OFS97-16, scale 1:24,000.

Gray, H.H., 1989, Quaternary geologic map of Indiana: Indiana Geological Survey Miscellaneous Map 

49, scale 1:500,000.

Green, R.A., Obermeier, S.F., and Olson, S.M., 2005, Engineering geologic and geotechnical analysis 

of paleoseismic shaking using liquefaction effects—Field examples: Engineering Geology, v. 76, 

p. 263–293.

Haase, J.S., and Nowack, R.L., 2009, Earthquake scenario ground motions for the urban area of 

Evansville, Indiana: U.S. Geological Survey Final Technical Report #G09AP00057, 16 p.

Haase, J.S., Nowack, R.L., Choi, Y.S., Bowling, T., Cramer, C.H., Boyd, O.S., and Bauer, R.A., 2011a, 

Probabilistic seismic hazard assessment including site effects for Evansville, Indiana, and the 

surrounding region: U.S. Geological Survey Open-File Report 2011–1231, 29 p.

Haase, J.S., Nowack, R.L., Cramer, C.H., Boyd, O.S., and Bauer, R.A., 2011b, Earthquake scenarios for 

the Evansville, Indiana, region: U.S. Geological Survey Open-File Report 2011–1260, 17 p.

Harmsen, S.C., Perkins, D.M., and Frankel, A.D., 1999, Deaggregation of probabilistic ground motions 

in the central and eastern United States: Bulletin of the Seismological Society of America, v. 89, no. 

1, p. 1–13.
36

Holzer, T.L., 2003, Earthquake Hazards: USGS CPT Data—Evansville Indiana area: United States 

Geological Survey Earthquake Hazards Program, accessed January 14th, 2004, at 

http://earthquake.usgs.gov/regional/nca/cpt/data.

Holzer, T.L., ed., 2008, Probabilistic liquefaction hazard mapping: Sacramento, Calif., American 

Society of Civil Engineers, v. Geotechnical Special Publication No. 181, p. 1–32.

Holzer, T.L., Bennett, M.J., Noce, T.E., Padovani, A.C., and Tinsley, J.C.I., 2006, Liquefaction hazard 

mapping with LPI in the greater Oakland, California, area: Earthquake Spectra, v. 22, no. 3, p. 693–708.

Holzer, T.L., Noce, T.E., and Bennet, M.J., 2009, Scenario liquefaction maps of Santa Clara Valley, 

Northern California: Bulletin of the Seismological Society of America, v. 99, no. 1, p. 367–381.

Hough, S.E., Armbruster, J.G., Seeber, L., and Hough, J.F., 2000, On the Modified Mercalli Intensities 

and magnitudes of the 1811–1812 New Madrid earthquakes: Journal of Geophysical Research—Solid 

Earth, v. 105, no. B10, p. 23839–23864.

Idriss, I.M., and Sun, J.I., 1992, User's manual for SHAKE91: Davis, Calif., Unievrsity of California, 

Deptartment of Civil and Environmental Engineering, Center for Geotechnical Modeling, 47 p.

Iwasaki, Toshio, Tokida, Ken-Ichi, Tatsuoka, Fumio, Watanabe, S., Yasuda, Susumu, and Sato, Hiroshi, 

1982, Microzonation for soil liquefaction potential using simplified methods, in International 

Conference on Microzonation, 3rd, Seattle, Wash., June 28–July 1, 1982, Proceedings: Washington, 

D.C., National Science Foundation, p. 1319–1330.

Johnston, A.C., 1994, Seismotectonic interpretations and conclusions from the stable continental region 

seismicity database, in Schneider, J.F., ed., The earthquakes of stable continental regions—Volume 1,

Assessment of large earthquake potential: Palo Alto, Calif., Electric Power Research Institute,

p. 4-1–4-103.

Johnston, A.C., 1996, Seismic moment assessment of earthquakes in stable continental regions—III. 

New Madrid 1811-1812, Charleston 1886 and Lisbon 1755: Geophysical Journal International, v. 

126, no. 2, p. 314–344.

Kayabali, Kamil, 1993, Earthquake hazard analysis for the city of Evansville, Ind.: West Lafayette, Ind., 

Purdue University, Ph.D. dissertation, 382 p.

Kayabali, Kamil, and West, T.R., 1994, Liquefaction susceptibility evaluation for the City of 

Evansville, Indiana: Bulletin of the Association of Engineering Geologists, v. 31, no. 2, p. 231–253.

Lenz, J.A., and Baise, L.G., 2007, Spatial variability of liquefaction potential in regional mapping using 

CPT and SPT data: Soil Dynamics and Earthquake Engineering, v. 27, no. 7, p. 690–702.

McNulty, W.E., and Obermeier, S.F., 1999, Liquefaction evidence for at least two strong Holocene 

paleo-earthquakes in central and southwestern Illinois, USA: Environmental and Engineering 

Geoscience, v. 5, no. 2, p. 133–146.

Moore, D.W., Lundstrom, S.C., Counts, R.C., Martin, S.L., Andrews, W.M., Jr., Newell, W.L., Murphy, 

M.L., Thompson, M.F., Taylor, E.M., Kvale, E.P., and Brandt, T.R., 2009, Surficial geologic map of 

the Evansville, Indiana and Henderson, Kentucky area: U.S. Geological Survey Scientific 

Investigations Map SIM-3069, 1:50,000 scale.

Munson, P.J., and Munson, C.A., 1996, Paleoliquefaction evidence for recurrent strong earthquakes 

since 20 000 yr BP in the Wabash Valley area of Indiana: Indiana University Final Technical Report 

for U.S. Geological Survey Grant #14-08-0001-G2117, 137 p.

Munson, P.J., Munson, C.A., and Pond, E.C., 1995, Paleoliquefaction evidence for a strong Holocene 

earthquake in south-central Indiana: Geology, v. 23, no. 4, p. 325–328.

Munson, P.J., Obermeier, S.F., Munson, C.A., and Hajic, E.R., 1997, Liquefaction evidence for 

Holocene and latest Pleistocene seismicity in the southern halves of Indiana and Illinois—A 

preliminary overview: Seismological Research Letters, v. 68, no. 4, p. 521–536.
37

Nuttli, O.W., 1973, The Mississippi Valley earthquakes of 1811 and 1812—Intensities, ground motion 

and magnitudes: Bulletin of the Seismological Society of America, v. 63, no. 1, p. 227–248.

Obermeier, S.F., 1996, Use of liquefaction-induced features for paleoseismic analysis—An overview of 

how seismic liquefaction features can be distinguished from other features and how their regional 

distribution and properties of source sediment can be used to infer the location and strength of 

Holocene paleo-earthquakes: Engineering Geology, v. 44, no. 1-4, p. 1–76.

Obermeier, S.F., 1998, Liquefaction evidence for strong earthquakes of Holocene and latest Pleistocene 

ages in the states of Indiana and Illinois, USA: Engineering Geology, v. 50, p. 227–254.

Olson, S.M., Green, R.A., and Obermeier, S.F., 2005, Revised magnitude-bound relation for the 

Wabash Valley seismic zone of the central United States: Seismological Research Letters, v. 76, 

no. 6, p. 756–771.

Petersen, M.D., Frankel, A.D., Harmsen, S.C., Mueller, C.S., Haller, K.M., Wheeler, R.L., Wesson, 

R.L., Zeng, Y.H., Boyd, O.S., Perkins, D.M., Luco, Nicolas, Field, E.H., Wills, C.J., and Rukstales, 

K.S., 2008, Documentation for the 2008 update of the national seismic hazard maps: U.S. Geological 

Survey Open-File Report 2008-1128, 60 p.

Pond, E.C., 1996, Seismic parameters for the central United States based on paleoliquefaction evidence 

in the Wabash Valley: Blacksburg, VA, Virginia Polytechnic Institute, Ph.D. dissertation, 583 p.

Rix, G.J., and Romero-Hudock, S., 2003, Liquefaction susceptibility mapping in Memphis/Shelby 

County, TN: Georgia Institute of Technology Final Technical Report for U.S. Geological Survey 

Grant #01HQAG0019, 27 p.

Robertson, P.K., 1990, Soil classification using the cone penetration test: Canadian Geotechnical 

Journal, v. 27, no. 1, p. 151–158.

Robertson, P.K., and Wride, C.E., 1998, Evaluating cyclic liquefaction potential using the cone 

penetration test: Canadian Geotechnical Journal, v. 35, no. 3, p. 442–459.

Rudman, A.J., Biggs, M.E., Blakely, R.F., and Whaley, J.F., 1973, Statistical studies of Indiana bedrock 

velocities—Mapping applications: Indiana Academy of Science, v. 83, no. 1973, p. 284–290.

Street, R.L., 1984, The historical seismicity of the central United States—1811–1928: U.S. Geological 

Survey Final Report for Contract 14-08-0001-21251, 557 p.

Toprak, Selcuk, and Holzer, T.L., 2003, Liquefaction potential index—Field assessment: Journal of 

Geotechnical and Geoenvironmental Engineering, v. 129, no. 4, p. 315–322.

Tuttle, M.P., Schweig, E.S., Cambell, Janice, Thomas, P.J., Sims, J.D., and Lafferty, R.H., 2005, 

Evidence for New Madrid earthquakes in A.D. 300 and 2350 B.C.: Seismological Research Letters,

v. 76, no. 4, p. 489–501.

Tuttle, M.P., Schweig, E.S., Sims, J.D., Lafferty, R.H., Wolf, L.W., and Haynes, M.L., 2002, The 

earthquake potential of the New Madrid seismic zone: Bulletin of the Seismological Society of 

America, v. 92, no. 6, p. 2080–2089.

Whaley, J.F., Blakely, R.F., Like, K.K., and James, C.L., 2002, Seismic refraction data for Indiana 

(Point Shapefile): Bloomington, Ind., Indiana Geological Survey, accessed Oct. 7, 2002, at 

http://inmap.indiana.edu/dload_page/geology.html.

Youd, T.L., Idriss, I.M., Andrus, R.D., Arango, Ignacio, Gastro, Gonzalo, Christian, J.T., Dobry, 

Richardo, Finn, W.D.L., Harder, L.F.J., Hynes, M.E., Ishihara, Kenji, Koester, J.P., Liao, S.S.C., 

Marcuson, W.F.I., Martin, G.R., Mitchell, J.K., Moriwaki, Yoshiharu, Power, M.S., Robertson, P.K., 

Seed, R.B., and Stokoe, K.H., 2001, Liquefaction resistance of soils—Summary report from the 1996 

NCEER and 1998 NCEER/NSF workshops on evaluation of liquefaction resistance of soils: Journal 

of Geotechnical and Geoenvironmental Engineering, v. 127, no. 10, p. 817–833.