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.