As in Los Angeles, Japanese companies set up free voice mailboxes where callers to parties in a damaged building would reach and leave recordings. Networks are not crippled by shock but by congestion. Because everyone was trying to call at the same time, nobody got through. Networks are designed to handle about ten percent of its subscribers at the same time. This is not a short term problem for disaster areas.
Experience shows that the volume of calls stays much heavier than before for a long time.
In most economic activities, increase in the demand while reducing supply in a scarce resource would lead to a higher price. But in a public emergency this would not be acceptable. In fact, phone companies tend to drop charges for many calls as part of their contribution to disaster relief. In the California emergencies incoming long-distance calls were blocked in favor of outgoing calls. Congestion quickly emerged when too many people called from payphones.