An Assessment of the Consequences and Preparations for a Catastrophic California Earthquake: Findin | Page 9

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]
-------------------------------------------------------------------------- Loss to Loss of Building Contents Total Loss Fault ($ in Billions) ($ in Billions) ($ in Billions) -------------------------------------------------------------------------- Northern San Andreas 25 13 38 Hayward 29 15 44 Newport-Inglewood 45 24 69 Southern San Andreas 11 6 17 ---------- [1] Uncertain by a possible factor of two to three. --------------------------------------------------------------------------
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]
------------------------------------------------------------------- Fault Time Dead Hospitalized[2] ------------------------------------------------------------------- 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 ---------- [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. -------------------------------------------------------------------
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