As television channels broadcast news on Wednesday of how a tsunami, possibly the eighth worst in the last ten years, might hit the coast in the evening, residents waited in anxiety, fearing the worst. People rushed out of their homes and offices as soon as the first tremors were felt at around 2.15 p.m. The adventurous, however, went to catch a glimpse of the sea, thinking it would soon turn wild.

Officials at the highest level in government offices though, stayed back in their offices, making calls and trying to initiate disaster-management mechanisms. The response started with Chief Secretary Debendranath Sarangi and Commissioner of Revenue Administration (CRA), Disaster Management and Mitigation, K. Gnanadesikan, also State Disaster Commissioner, alerting District Collectors, the police department, hospitals, ambulances and the Fisheries Department.

Outgoing Corporation Commissioner P.W.C. Davidar ordered staff to hop into autorickshaws to sound a tsunami alert in sea-touching zones such as Tiruvottiyur, Tondiarpet, Royapuram, Teynampet, Adyar, Perungudi and Sholinganallur. Officials were instructed over the wireless to keep schools and community centres open for residents in coastal areas — should the tsunami hit.

Health workers and engineering staff were also kept on high alert at all the 200 divisions of the city to cope with the disaster. A control room – to receive information from CRA and the public through toll free helpline 1913 – was readied at the Ripon Buildings. Areas with a past history of the tsunami such as Nochikuppam, Santhome, Foreshore Estate, Besant Nagar and Kasimedu were other focus areas.

Through text messages and phone calls, the fisheries department told its officers and coastal district collectors to ask fishermen not to venture out into the sea. Those out in shallow waters were asked to return. Mobile phones came in handy even on the seas, and hundreds of fishermen returned to the shore. The department also kept in touch with the Navy in Andhra Pradesh and Tamil Nadu and with the Coast Guard.

State authorities alerted the city police who in turn mobilised more than 500 personnel to coastal areas including Marina and Elliot's beach. The Marina was cordoned off and Kamarajar Salai choked with vehicles as offices closed by 4.30 p.m. Senior police officers including commissioner J.K. Tripathy visited the beach to check on security measures.

By evening however, the untoward was averted. But one thought lingered with everyone: What if the tsunami had struck?

Chennai, formerly in the relatively safe Zone II of seismic activity, was shifted to Zone III in 2001 — which means it is as prone to earthquakes as are Mumbai and Kolkata.

“The problem is, the city has many buildings built before 2001 that do not follow the recommended design standards for zone III,” said S. Rajarathnam, director, Centre for Disaster Management and Mitigation, Anna University.

Most multi-storeyed buildings have car parking areas that do not follow recommended designs. “They are open from all areas and the base pillars do not have the adequate girth, which makes them more vulnerable to vibrations. This is applicable to most buildings and malls,” Prof. Rajarathnam said.

With regard to the tsunami, if the coastal topographic elevation is gentle, the tsunami waters will enter more land area. This is what happened in 2004, said Professor Rajarathnam.

“What is needed now is continuous monitoring of the behaviour, especially at the Andaman's Island because it will take just about two hours for the effect to reach the city from there,” said R. R. Krishnamoorthy, Associate Professor, Applied Geology, Madras University. “A tsunami was being predicted mainly because the magnitude of the earthquake was on the higher side. But what also triggers a tsunami is the depth of occurrence and the movement of the ocean floor. There was no upward ocean floor movement this time, and the depth was 33 km so there is no need to panic.”