Assuming a catastrophic earthquake, a variety of secondary problems could also be expected. Search and rescue operations--requiring heavy equipment to move debris--would be needed to free people trapped in collapsed buildings. It is likely that injuries, particularly those immediately after the event, could overwhelm medical capabilities, necessitating a system of allocating medical resources to those who could be helped the most. Numerous local fires must be expected; nevertheless, a conflagration such as that which followed the Tokyo earthquake of 1923, or the San Francisco earthquake of 1906, is improbable, unless a "Santa Ana type" wind pattern is in effect. Since the near failure of a dam in the San Fernando, California, earthquake of 1971 (which was a moderate event), substantial progress has been made in California to reduce the hazard from dams, in some cases through reconstruction. For planning purposes, however, experts believe that the failure of at least one dam should be anticipated during a catastrophic earthquake in either the Los Angeles or San Francisco regions. Experience in past earthquakes, particularly the 1971 San Fernando earthquake, has demonstrated the potential vulnerability of commercial telephone service to earthquakes, including the possibility of damage to switching facilities from ground shaking and rupture of underground cables that cross faults. This is especially serious because immediately following earthquakes, public demand for telephone services increases drastically. This increased demand overloads the capability of the system, even if it had not been damaged, and therefore management action to reduce the availability of service to non-priority users and to accommodate emergency calls is mandatory. Radio-based communication systems, particularly those not requiring commercial power, are relatively safe from damage, although some must be anticipated. The redundancy of existing communication systems, including those designed for emergency use, means that some capability for communicating with the affected region from the outside would almost surely exist. Restoration of service by the commercial carriers should begin within 24 to 72 hours as a result of maintenance and management actions; however, total restoration of service would take significantly longer. While numerous agencies have the capability for emergency communication within themselves, non-telephonic communication among entities and agencies in the affected area is minimal. This is true for Federal, State, and local agencies. This weakness has been pointed out repeatedly by earthquake response exercises, and the problem is raised by almost every emergency preparedness official at every level of government. Consequently, a major problem for resolution is the operational integration of communications systems and networks among the relevant Federal, State, and local agencies.