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.