Data presented here are for all 

workers covered by State and 

Federal unemployment insurance 

programs. For additional 

information, contact Richard 

Holden, Regional Commissioner, 

U.S. Bureau of Labor Statistics. 

E-mail: holden.richard@bls.gov.

Telephone: 415-625-2245. 

Co-authors of this report were 

Charles R. Real, Supervising 

Engineering Geologist, California 

Geological Survey, Seismic 

Hazards Assesment Program;

and Donna Bahls, Research 

Program Specialist (GIS), 

California Employment 

Development Department, Labor 

Market Information Division.

Information in this summary 

will be made available to sensoryimpaired individuals upon 

request. Voice phone: (202) 691-

5200. Federal Relay Service: 

1-800-877-8339. This summary 

report is in the public domain 

and may be reproduced without 

permission. 

...from inside

U.S. BUREAU OF LABOR STATISTICS

Postal Square Building, Rm. 2850

2 Massachusetts Ave., NE

Washington, DC 20212-0001

Official Business

Address Service Requested
magnitude 6.9 on the Hayward 

fault. As is apparent, the most 

intense (MMI VIII+) zone would 

be primarily within the borders of 

Alameda County.

Moreover, 

when we overlaid 

employers on 

shaking intensity 

zones, as shown 

in Chart 2, we 

found that a 

large number 

of employers 

are located in 

areas which 

are expected to 

experience the 

greatest intensity as measured 

by MMI. (The MMI it correlates 

closely with measured shaking 

levels, and is by definition a 

measure of projected damage.) 

Using the tabulating tools in 

geographical information systems 

(see table 1), we estimate that: 

 Total exposures in the counties 

in the San Francisco Bay Area in 

MMI-VII (very strong shaking) 

and MMI-VIII+ (severe shaking) 

zones, combined, could include 

87,000 employers, 1.5 million 

jobs, and quarterly wages 

approaching $25 billion. 

 In the wide area circumscribed 

by shake intensity zones MMI-VII 

or MMI-VIII+, the employment 

and earnings exposures would 

fall, in descending order, primarily 

upon the counties of Alameda, 

Santa Clara, San Francisco, and 

Contra Costa. 

 Approximately 84 to 89 percent 

all of the exposure in the shaking 

zone MMI-VIII+ would fall in 

Alameda County.

Focusing on Alameda County 

(see table 2), we estimate that:

 Approximately 90 percent 

of the businesses, employees, 

and payrolls are located in or 

attributed to the most intense 

shaking zones on the map(MMIVII and MMI-VIII and higher). 

 More than half of the 

businesses, employees, and 

payrolls are in the zones 

characterized as having severe 

shaking and moderate to heavy 

damage (MMI-VIII+).

 There are more than 600,000 

employees in the most intense 

shaking zones earning $8.2 billion 

in quarterly payrolls. 

 The interruption to business 

from a M6.9 Hayward earthquake 

could affect nearly all businesses 

and employees in Alameda County.

As shown in Chart 3, the 

exposures of various industries 

to damage ranges across the 

board, but affect particularly large 

numbers of jobs in health care and 

social assistance, manufacturing, 

and trade. The potential economic 

TABLE 2: Exposure from a Magitude 6.9

earthquake along the Hayward Fault

Alameda County, 2006	 Shaking Intensity Areas

County Totals	 MMI VIII+	 MMI VII	 Combined

Employers	 40,851	 25,753	 11,567	 37,320

Jobs	 681,821	 400,462	 210,870	 611,332

Quarterly Wages	 $9.3B	 $5.1B	 $3.1B	 $8.2B

CHART 2

Employers in Shaking Inten- sity Zones in a Potential San 

Francisco Bay Area Magni- tude 6.9 Earthquake on the 

Hayward Fault

...from cover

About the Modified

Mercalli Intensity Scale

Seismic intensity is a measure of the 

effects of an earthquake at different

sites. Intensity differs from magnitude in that the effects of any one 

earthquake vary greatly from place 

to place, so there may be many 

intensity values measured from one 

earthquake. Each earthquake, on 

the other hand, should have just 

one magnitude (often measured by 

the moment magnitude scale or by 

the Richter scale). The Modified 

Mercalli Intensity (MMI) scale is 

commonly used to gauge the severity 

of earthquake effects. Intensity ratings 

are expressed as Roman numerals 

between I at the least destructive and 

XII at the most destructive. At MMIVIII, while damage may be slight in 

specially designed structures, there 

is often considerable damage and 

partial collapse even in substantial 

ordinary buildings.

Modified Mercalli Intensity Scale

Zone Value

 VIII or greater: Severe shaking, moderate/

heavy damage

 VII: Very strong shaking, moderate damage

 VI: Strong shaking, light damage

 V: Moderate shaking, very light damage

 IV: Light shaking, No damage
magnitude 6.9 on the Hayward 

fault. As is apparent, the most 

intense (MMI VIII+) zone would 

be primarily within the borders of 

Alameda County.

Moreover, 

when we overlaid 

employers on 

shaking intensity 

zones, as shown 

in Chart 2, we 

found that a 

large number 

of employers 

are located in 

areas which 

are expected to 

experience the 

greatest intensity as measured 

by MMI. (The MMI it correlates 

closely with measured shaking 

levels, and is by definition a 

measure of projected damage.) 

Using the tabulating tools in 

geographical information systems 

(see table 1), we estimate that: 

 Total exposures in the counties 

in the San Francisco Bay Area in 

MMI-VII (very strong shaking) 

and MMI-VIII+ (severe shaking) 

zones, combined, could include 

87,000 employers, 1.5 million 

jobs, and quarterly wages 

approaching $25 billion. 

 In the wide area circumscribed 

by shake intensity zones MMI-VII 

or MMI-VIII+, the employment 

and earnings exposures would 

fall, in descending order, primarily 

upon the counties of Alameda, 

Santa Clara, San Francisco, and 

Contra Costa. 

 Approximately 84 to 89 percent 

all of the exposure in the shaking 

zone MMI-VIII+ would fall in 

Alameda County.

Focusing on Alameda County 

(see table 2), we estimate that:

 Approximately 90 percent 

of the businesses, employees, 

and payrolls are located in or 

attributed to the most intense 

shaking zones on the map(MMIVII and MMI-VIII and higher). 

 More than half of the 

businesses, employees, and 

payrolls are in the zones 

characterized as having severe 

shaking and moderate to heavy 

damage (MMI-VIII+).

 There are more than 600,000 

employees in the most intense 

shaking zones earning $8.2 billion 

in quarterly payrolls. 

 The interruption to business 

from a M6.9 Hayward earthquake 

could affect nearly all businesses 

and employees in Alameda County.

As shown in Chart 3, the 

exposures of various industries 

to damage ranges across the 

board, but affect particularly large 

numbers of jobs in health care and 

social assistance, manufacturing, 

and trade. The potential economic 

TABLE 2: Exposure from a Magitude 6.9

earthquake along the Hayward Fault

Alameda County, 2006	 Shaking Intensity Areas

County Totals	 MMI VIII+	 MMI VII	 Combined

Employers	 40,851	 25,753	 11,567	 37,320

Jobs	 681,821	 400,462	 210,870	 611,332

Quarterly Wages	 $9.3B	 $5.1B	 $3.1B	 $8.2B

CHART 2

Employers in Shaking Inten- sity Zones in a Potential San 

Francisco Bay Area Magni- tude 6.9 Earthquake on the 

Hayward Fault

...from cover

About the Modified

Mercalli Intensity Scale

Seismic intensity is a measure of the 

effects of an earthquake at different

sites. Intensity differs from magnitude in that the effects of any one 

earthquake vary greatly from place 

to place, so there may be many 

intensity values measured from one 

earthquake. Each earthquake, on 

the other hand, should have just 

one magnitude (often measured by 

the moment magnitude scale or by 

the Richter scale). The Modified 

Mercalli Intensity (MMI) scale is 

commonly used to gauge the severity 

of earthquake effects. Intensity ratings 

are expressed as Roman numerals 

between I at the least destructive and 

XII at the most destructive. At MMIVIII, while damage may be slight in 

specially designed structures, there 

is often considerable damage and 

partial collapse even in substantial 

ordinary buildings.

Modified Mercalli Intensity Scale

Zone Value

 VIII or greater: Severe shaking, moderate/

heavy damage

 VII: Very strong shaking, moderate damage

 VI: Strong shaking, light damage

 V: Moderate shaking, very light damage

 IV: Light shaking, No damage
Data presented here are for all 

workers covered by State and 

Federal unemployment insurance 

programs. For additional 

information, contact Richard 

Holden, Regional Commissioner, 

U.S. Bureau of Labor Statistics. 

E-mail: holden.richard@bls.gov.

Telephone: 415-625-2245. 

Co-authors of this report were 

Charles R. Real, Supervising 

Engineering Geologist, California 

Geological Survey, Seismic 

Hazards Assesment Program;

and Donna Bahls, Research 

Program Specialist (GIS), 

California Employment 

Development Department, Labor 

Market Information Division.

Information in this summary 

will be made available to sensoryimpaired individuals upon 

request. Voice phone: (202) 691-

5200. Federal Relay Service: 

1-800-877-8339. This summary 

report is in the public domain 

and may be reproduced without 

permission. 

...from inside

U.S. BUREAU OF LABOR STATISTICS

Postal Square Building, Rm. 2850

2 Massachusetts Ave., NE

Washington, DC 20212-0001

Official Business

Address Service Requested