11.9

12.1

5.5

20.5

31.3

77.9

10.3

4.8

3.4

3.6

3.8

3.9

1.8

2.9

3.0

2.9

3.3

7.4

18.7

42.9

1.9

1.1

2.2

4.2

2.5

2.2

1.3

2.2

6.6

7.6

7.8

8.5

5.5

5.4

4.7

2.6

4.7

4.4

5.8

5.2

23.1

5.9 13.4

14.0

10.913.9

17.8

15.3

19.8

17.5

4.8

3.6

4.2

3.0

2.1

1.1

3.5

6.9

6.5

32.1

8.6

28.8

32.2

11.6

10.4

30.2

9.8

7.8

9.5

29.9

9.5

21.8

9.9

19.1

24.3

4.7

11.1

9.3 18.2

13.2 28.1

14.6 22.1

20.2

20.4

34.6

27.8

10.3

39.9

36.2

45.7

3.5

4.4

2.8

2.1

2.4

2.4

2.9

5.1 4.8

2.0

1.7

1.7

4.6

4.5

4.2

4.1

4.6

5.4

5.8

4.5

4.5

1.4

4.9

4.9

4.9 18.6

15.8

6.5

7.9

6.2

5.5

10.2

14.2

11.4

12.0

11.3

5.1

4.0

25

15

10

9

8

6

5

4

4

3

3

20

10

6

6

5

9

5

7

5

4

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5

4

7

6

5

4

3

2

8

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20

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7

2

6

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3

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1

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6 80

40

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20

25

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6

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2

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3

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60

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7

7

10

1

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30

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6

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3

2

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3

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60 30

 125° 120° 115° 110° 105° 100° 95° 90° 85° 80° 75° 70°

 50°

 65°

 115° 110° 105° 100° 95° 90° 85° 80° 75°

 25°

 30°

 35°

 40°

 45° 45°

 40°

 35°

 30°

 25°

50°

Digital data prepared with ArcGIS 9.3 running under

100 0 100 200 300 400 500 600 700 800 900 1000 MILES Windows XP

100 0 100 200 300 400 500 600 700 800 900 1000 KILOMETERS

SCALE 1:7 000 000

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3195

Sheet 1 of 6

Seismic-Hazard Maps for the Conterminous United States, 2008

Peak Horizontal Acceleration with 10 Percent Probability of Exceedance in 50 Years

By

Mark D. Petersen,1 Arthur D. Frankel,1 Stephen C. Harmsen,1 Charles S. Mueller,1 Kathleen M. Haller,1 Russel L. Wheeler,1 Robert L. Wesson,1

Yuehua Zeng,1 Oliver S. Boyd,1 David M. Perkins,1 Nicolas Luco,1 Edward H. Field,1 Christopher J. Wills,2 and Kenneth S. Rukstales1

2011 1U.S. Geological Survey

2California Geological Survey, Sacramento, Calif.

Shaded relief base from ESRI, Inc., 2008, Data and maps

All other base map data from ESRI, Inc., 1993, Digital Chart of the World

United States County base map from the U.S. Geological Survey National Atlas, available at http://nationalatlas.gov

Projection: Albers equal-area conic

Standard Parallels 29.5°N and 45.5°N

Central meridian 95°W

Any use of trade, product or firm 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 contains copyrighted materials as noted in the text. Permission to 

reproduce copyrighted items for other than personal use must be secured 

from the copyright owner.

Although these data have been processed successfully on a computer system 

at the U.S. Geological Survey, no warranty expressed or implied is made 

regarding the display or utility of the data on any other system, or for general 

or scientific purposes, nor shall the act of distribution constitute any such 

warranty. The U.S. Geological Survey shall not be held liable for improper or 

incorrect use of the data described and/or contained herein.

Publishing support provided by: 

Denver Publishing Service Center

Manuscript approved for publication on Nov. 29, 2011

This and other USGS information products are available at

http://store.usgs.gov/. 

U.S. Geological Survey

Box 25286, Denver Federal Center

Denver, CO 80225

To learn about the USGS and its information products visit

http://www.usgs.gov/. 

1-888-ASK-USGS

This report is available at:

http://pubs.usgs.gov/sim/3195/

For more information concerning this publication, contact:

Center Director, USGS Geologic Hazards Science Center 

Box 25046, Mail Stop 966

Denver, CO 80225

(303) 273-8579

Or visit the Geologic Hazards Science Center Web site at:

http://geohazards.usgs.gov/. 

Suggested citation:

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

Zeng, Yuehua, Boyd, O.S., Perkins, D.M., Luco, Nicolas, Field, E.H., Wills, C.J., and Rukstales, K.S., 

2011, Seismic-hazard maps for the conterminous United States, 2008: U.S. Geological Survey 

Scientific Investigations Map 3195, 6 sheets, scale 1: 7,000,000. 

CANAD A

MEXIC O

Prepared in cooperation with the

California Geological Survey

EXPLANATION

Peak acceleration expressed as a percent

of gravity (%g)

%g

> 100

80–100

60–80

40–60

30–40

25–30

20–25

15–20

10–15

9–10

8–9

7–8

6–7

5–6

4–5

3–4

2–3

1–2

0–1

Contours of peak acceleration expressed

as a percent of gravity (%g)

10 Onshore

10 Offshore

Point values of peak acceleration

expressed as a percent of gravity (%g)

6.6

Local maximum

2.6

Local minimum

4.9 Saddle point

DISCUSSION

The acceleration values contoured are the random horizontal component. 

Reference site condition is firm rock, defined as having an average shear-wave velocity 

of 760 m/s in the top 30 meters, corresponding to the boundary between NEHRP 

(National Earthquake Hazards Reduction Program) site classes B and C. Documentation, 

gridded values, interactive maps, and GIS data used to make the map are available 

online at http://earthquake.usgs.gov/hazmaps or http://pubs.usgs.gov/sim/3195. 

ACKNOWLEDGMENTS

We would like the thank the hundreds of workshop participants (see 

http://earthquake.usgs.gov/hazards/about/workshops) who made valuable suggestions 

that significantly improved the quality of the maps. The California part of the maps was 

produced jointly with the California Geological Survey.

REFERENCES

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

Wesson, R.L., Zeng, Yuehua, 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 

United States national seismic hazard maps: U.S. Geological Survey Open-File 

Report 2008–1128, 61 p.