ASSESSMENT OF LOSSES FOR SELECTED POTENTIAL CALIFORNIA EARTHQUAKES
A. INTRODUCTION
As part of a program that FEMA and its predecessor agencies have had
underway for a number of years, property loss and casualty estimates
were prepared in 1972 and 1973 for a number of potential maximum
credible earthquakes that could impact on the San Francisco and the
Los Angeles areas--North San Andreas (Richter magnitude 8.3), Hayward
(Richter magnitude 7.4), South San Andreas (Richter magnitude 8.3),
and Newport-Inglewood (Richter magnitude 7.5). These estimates have
now been updated as part of the current assessment.
Estimates of property loss and casualties are based on the expected
type and distribution of damage for each postulated earthquake as
determined by the size and location of the earthquake and the
distribution and character of the buildings and structures within the
affected area. Methodologies for estimates of this type are
approximate at best. Consequently, the figures shown below may vary
upward or downward by as much as a factor of two or three. This degree
of uncertainty does not affect the validity of the conclusions of this
report, however, since there are greater uncertainties in all other
aspects of emergency response planning.
B. PROPERTY LOSS ESTIMATES
The property loss estimates were obtained by first estimating the
total replacement dollar value of buildings and their contents,
multiplying them by percentage loss factors (inferred from the
anticipated strength of shaking in each county), and then summing to
obtain the aggregate loss. Included in the estimates are private as
well as Federal, State, and local government buildings, insured and
uninsured. Excluded from consideration is the replacement value of
transportation and communication facilities, dams, utility
installations, and special purpose structures (e.g., convention
centers and sports arenas). Also excluded is the potential damage
resulting from a major dam failure or the indirect dollar losses due
to such factors as higher unemployment, lower tax revenue, reduced
productivity, and stoppage of industrial production. Experience
indicates that indirect losses could be approximately equal to the
dollar amounts lost in buildings and their contents. The property loss
estimates for four postulated earthquakes on the faults listed below
are as follows.
TABLE 2
ESTIMATES OF PROPERTY LOSSES FOR REPRESENTATIVE EARTHQUAKES[1]
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Loss to Loss of
Building Contents Total Loss
Fault ($ in Billions) ($ in Billions) ($ in Billions)
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Northern San Andreas 25 13 38
Hayward 29 15 44
Newport-Inglewood 45 24 69
Southern San Andreas 11 6 17
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[1] Uncertain by a possible factor of two to three.
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C. CASUALTY ESTIMATES
Deaths and injuries in these earthquakes principally would occur from
failures of man-made structures, particularly older, multistory, and
unreinforced brick masonry buildings built before the institution of
earthquake-resistant building codes. Experience has shown that some
modern multistory buildings--constructed as recently as the late
1960's, but not adequately designed or constructed to meet the current
understanding of requirements for seismic resistance--are also subject
to failure. Consequently, the number of fatalities will be strongly
influenced by the number of persons within high-occupancy buildings,
capable of collapsing, or by failure of other critical facilities such
as dams. Additional imponderables are the degree of saturation of the
ground at the time of the event and the possibility of weather
conditions conducive to the spread of fire. A conflagration such as
occurred in the 1906 San Francisco earthquake, is not considered
likely to occur in any of the analyzed events, however, because of
improvements in fire resistance of construction and firefighting
techniques. Nonetheless, numerous smaller fires must be anticipated in
any of the analyzed events and a "Santa Ana type" wind could cause
serious problems.
An additional element of uncertainty in estimating casualties from
earthquake stems from not knowing where most of the population will be
at the time of the earthquake. In the early morning (i.e., 2:30 a.m.)
most people are at home, by far the safest environment during a
seismic emergency. At 2:00 in the afternoon, on the other hand, the
majority of people are at their places of employment and therefore
vulnerable to collapse of office buildings. Around 4:30 p.m. many more
people are in the streets and thus subject to injury due to falling
debris or failures of transportation systems. Consequently, depending
on the time of day, wide variations in the number of casualties can be
expected.
Following are estimates of dead and injured (requiring
hospitalization) for each of the four representative faults and for
the three time periods just discussed.
TABLE 3
ESTIMATES OF CASUALTIES[1]
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Fault Time Dead Hospitalized[2]
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Northern San Andreas 2:30 a.m. 3,000 12,000
2:00 p.m. 10,000 37,000
4:30 p.m. 11,000 44,000
Hayward 2:30 a.m. 3,000 13,000
2:00 p.m. 8,000 30,000
4:30 p.m. 7,000 27,000
Southern San Andreas 2:30 a.m. 3,000 12,000
2:00 p.m. 12,000 50,000
4:30 p.m. 14,000 55,000
Newport-Inglewood 2:30 a.m. 4,000 18,000
2:00 p.m. 21,000 83,000
4:30 p.m. 23,000 91,000
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[1] Uncertain by a possible factor of two to three.
[2] Injuries not requiring hospitalization are estimated to be
from 15 to 30 times the number of deaths.
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D. OVERVIEW OF OTHER TYPES OF DAMAGE
For this assessment, estimates of damage to substantial numbers of
different type facilities essential to the immediate response
capability were updated. Earthquakes associated with the same four
major fault systems identified earlier in this chapter were used as a
basis for these estimates. The types of facilities analyzed included
_hospitals_, _medical supply storages_, _blood banks_, and _custodial
care homes_, together with their essential services and personnel
resources. Although newer hospitals in California are being built
according to substantially improved seismic safety standards and
practices, older hospital facilities can be expected to be poorly
resistant to earthquakes.
Among residential buildings, single family homes are expected to
suffer structural damage and loss of contents. Damage to multifamily
dwellings--particularly older buildings--would, in all likelihood, be
more extensive. Analysis of expected damage indicates that temporary
housing for as many as 200,000 families might be needed--a requirement
calling for careful planning and exceptional management skills.
Schools are judged to be among the safest facilities exposed to the
earthquakes. Since passage of the Field Act in 1933, after the Long
Beach earthquake, school buildings in California have been
continuously improved to withstand seismic hazards.
As a result of continuing and substantial upgrading of design and
construction practices in the past 10 years, dams and reservoirs can
be expected to show an improved performance in an earthquake.
Nonetheless, on a contingency basis, one dam failure might be assumed
for each planning effort.
Realizing the fact that 84 key communications facilities, earth
stations, Department of Defense voice and data switches, commercial
transoceanic cable heads, Federal Telecommunications System switches,
and major direct distance dial switches are located within 55 miles of
either Los Angeles or San Francisco, damage must be expected to occur.
With this realization, priorities have been assigned to all critical
circuits transiting the key facilities, based on established criteria
of criticality of service continuity. _National warning systems
circuitry, command and control circuits, and circuits supporting
diplomatic negotiations_ (of which a high concentration exists in
California) are examples of those circuits carrying high-restoration
priority.
In the civil sector there would be 24 to 72 hours of minimal
communications, with a possible blackout of telephonic communications
in the area immediately following an earthquake. The commercial
carriers would institute network control procedures to regain control
of the situation as fast as possible.
The impact on transportation facilities in any of the four
hypothesized earthquakes could be massive. Since the magnitude and
severity is unprecedented in recent years, conclusions regarding
losses must be accepted as tentative. As in the case of hospitals,
however, the lessons learned in earthquakes during the past 10 years
are being incorporated in the design and construction of new
facilities.
In general, all major transportation modes would be
affected--_highways_, _streets_, _overpasses and bridges_, _mass
transit systems_, _railroads_, _airports_, _pipelines_, and _ocean
terminals_, although major variances in losses are expected among the
modes. From a purely structural standpoint, the more rigid or elevated
systems (such as railroads and pipelines) which cross major faults on
an east-west axis would incur the heaviest damage, with initial losses
approaching 100 percent. Other major systems (such as highways,
airports, and pile-supported piers at water terminals) have better
survivability characteristics and therefore would fare much better,
with damage generally in the moderate range of 15 to 30 percent. These
transportation facility loss estimates are stated in terms of
immediate post-quake effects. They do not reflect the impact of
priority emergency recovery efforts and expedient alternatives that
are available, some within hours, to aid in restoration of
transportation capacity. In addition, transportation systems generally
have an inherently significant degree of redundancy and flexibility.
Consequently, an unquantified but significant movement capability in
all transport modes is expected to survive. Finally, these loss
estimates do not take into account the question of availability of
essential supporting resources, particularly petroleum fuels,
electricity, and communications. In the initial response phase, these
could prove to be the most limiting factors in the capability of the
transportation system.
Business and industry would be affected by damage to office buildings,
plants, and other support facilities. Although the 1971 San Fernando
earthquake occurred on the margin of a largely suburban area,
industrial facilities incurred significant damage. For example,
several buildings of the kind commonly used for light industry or
warehouses suffered from collapsed roofs or walls. Generally, building
codes do not apply to special industrial facilities, and the ability
of these structures to resist earthquake shaking will depend largely
on the foresight of the design engineer. For example, a major
electrical power switching yard and a water filtration plant were
seriously damaged in the 1971 San Fernando earthquake.
About 10 percent of the population and industrial resources of the
Nation are located in California. Over 85 percent of these resources
(or about 8.5 percent of the Nation's total) are located in the 21
California counties that are subject to the possibility of damage from
a major earthquake. Much of the aerospace and electronics industry is
centered in California. For example, about 56 percent of the guided
missiles and space vehicles, 40 percent of the semiconductors, 25
percent of the electronic computer equipment, and approximately 21
percent of the optical instruments and lenses manufactured in the
Nation are manufactured in these 21 counties. The probability that all
these counties would be affected by one earthquake is extremely
remote; yet the significant concentration of key industries remains a
concern. For example, about 25 percent of the Nation's semiconductors
are manufactured in Santa Clara County, an area along the Northern San
Andres fault that suffered very heavy damage in the 1906 San Francisco
earthquake. Estimates of damage to these industrial facilities and the
resulting loss of production have not been made. Similarly, the
resulting impact of possible damage to national production has not
been adequately analyzed.
Federally regulated financial institutions were generically analyzed
to determine their ability to continue to promote essential services
in the event of a major earthquake like those that have been
postulated for this assessment. The conclusion reached thus far is
that large-magnitude earthquakes pose no significant or unanticipated
problems of solvency and liquidity for such institutions. The Federal
Reserve System and other regulatory entities have procedures in place
that are designed--and have been tested--specifically to provide for
the continued operation of financial institutions immediately
following an earthquake or other emergency.