Another tsunami can flood up to 2km into Chennai

If a tsunami strikes again, seawater may enter nearly half a kilometre into the land on East Coast Road and a 30km stretch from Nemili to Kadalur Periyakuppam including Mamallapuram and Kalpakkam may go under 3m to 4m water.
Royapuram, Beach Railway Station, Triplicane, Lighthouse and Santhome may go under 3m deep water, while areas around Napier’s Bridge (over Cooum) and Elphinstone Bridge (over Adyar) may get inundated up to 2m.
These are findings from a simulated study by Chennai-based National Centre for Coastal Research (NCCR) and Hyderabad-based Indian National Centre for Ocean Information Services (INCOIS), taking the 2004 tsunami, triggered by a 9. 3 magnitude earthquake off north Sumatra coast, as the worst-case scenario.

The two labs have developed tsunami hazard maps for the 7,500km Indian coast based on various earthquake scenarios for issuing tsunami early warnings.
“In 2004, districts like Cuddalore and Nagapattinam were inundated up to 3km inland. In Chennai, it was around 1km into the land while at Visakhapatnam, water entered only 500m. It depends on the topography.
If the terrain is flat, water travels more into land than compared to an incline off the shore,” said INCOIS scientist Ajay Kumar B.
According to the study, northern suburbs like Pazhaverkadu, which has Pulicat lake, may see inundation of up to 1m beyond 1km into the land and 1m to 3m water level near the coast.
Similarly, up to 200m of land from Besant Nagar up to Panaiyur along East Coast Road may go under 2-3m water. From Uthandi to Muttukadu water may go up to 3m up to 500m into land.
Some places in and around Mamallapuram and Salavankuppam may go under 2m water depth up to 1km into the land. Beyond that, much of East Coast Road is likely to face inundation of 2m to 3m along the coast.
NCCR director M V Ramana Murthy said they run a numerical model with probable earthquake scenarios to compute the wave height at the source (epicentre) and calculate its impact as it reaches the coast, for which data on the topography, physical features of the coast and sea bathymetry are taken into account.
“In the delta regions of the state, wave height might be amplified and cause more inundation as the seabed bathymetry in these areas have a mild slope,” he said.
So, will the 2004-tsunami happen again on the east coast? INCOIS scientists say there are chances of an earthquake of nearly 8m in Andaman and Nicobar as quakes of 8m have a return period of 100 years +20 years. The last quake of 7. 9m in Andaman and Nicobar was in 1881 that triggered a tsunami.