Earthquake disrupts East Coast cell phone service - Aug. 23, 2011

NEW YORK (CNNMoney) -- Cell service along the East Coast was spotty for about a half hour following a Virginia-based earthquake that was felt as far away as New England.

There were no reports of downed cell towers or wires, but mobile providers said the fact that millions of people tried to make cell phone calls at the same time overwhelmed cellular relay stations.

Verizon Wireless reported network congestion for some customers in the Eastern U.S. for about 20 minutes following the earthquake, which hit just before 2 p.m. ET. The quake measured at 5.9 on the Richter scale.

"We are seeing no reports of damage to our wireless network," said Verizon (VZ, Fortune 500) spokesman Jeff Nelson. "Everything returned to normal quickly once the tremors ended. We'll continue to monitor the network."

Nelson said the mobile company's infrastructure was built to withstand earthquakes of such a magnitude. Verizon's super switching centers in Florida, for instance, are designed to withstand a Category 5 hurricane.

AT&T (T, Fortune 500) spokesman Mark Siegel also said that there was no infrastructure damage, but the network continues to see "heavy call volumes." He said customers that could not connect might try to communicate by text message, which requires far less bandwidth than phone calls.

Sprint (S, Fortune 500) told customers via Twitter that the provider is experiencing intermittent delays connecting phone calls following the earth quake, citing a "temporary mass calling event."

A T-Mobile spokesman also confirmed that the network was experiencing higher call volumes in all earthquake-affected areas. The company is advising customers that cannot place calls to communicate by e-mail or text messages until call volumes return to normal.

Cell service disruptions occur during periods of heavy call volumes, because of a bottle-necking factor: Like a highway that gets congested during rush hour, cellular infrastructure is not designed to handle the amount of calling traffic that occurs during emergency situations.

"We don't engineer pipes to handle every call at the same time," said Akshay Sharma, wireless infrastructure consultant at Gartner. "Even though we have redundancy built in, guess what, most of that feeds into same pipes."

Calls are typically routed from relay station to relay station in the shortest distance between the two points of a call. But if one switching station gets overwhelmed, calls then need to be relayed around that station, and delays occur.

Sometimes, congested infrastructure simply results in calls that cannot go through.  

First Published: August 23, 2011: 3:08 PM ET

via money.cnn.com