The massive earthquake near Indonesia on Wednesday failed to trigger a tsunami strong enough to flood the city's coastal areas. But the news elicited an unusual flooding of traffic in mobile networks as over 75 lakh anxious mobile subscribers in the city attempted to enquire about the safety of family and friends.

Lakhs of subscribers such who continued to work at their office, were unable to tell their family members that they were safe. “A mobile phone call made by my family members got disconnected. I tried to call them on my mobile but was unable to as the network was busy,” said R. Muralidharan, SBI AGM.

This sudden traffic surge on mobile networks, set off by anxious callers, choked GSM networks across operators. During the hour-long communication impasse, many mobile users complained that neither mobile-to-mobile or mobile-to-fixed line calls were going through.

According to technical personnel who maintain mobile networks, repeated attempts by desperate callers in such times of perceived threats only compounds the network congestion, and in a worst case scenario, could even trigger a network collapse.

While private operators refused to share details on network loads, a BSNL Chennai Telephones spokesperson said, though virtually all of its mobile switching nodes were facing an overload, the CellOne GSM network had held up rather well.

Call traffic roughly jumped by between two to three times in the 2 p.m-4 p.m. range, he said.

BSNL Chennai Telephones Chief General Manager A. Subramanian said most modern GSM network systems have in-built safeguards to terminate calls as a temporary measure to prevent a network crash.