Tsunami waves can travel vast distances

PANAJI: Though the higher than usual surge of sea level on Goa’s coast after Saturday’s tsunami near Indonesia is yet to be fully studied, this phenomenon triggered by underwater landslides or volcanic eruptions can affect the shoreline in Goa, say experts.
A study by Anthony Joseph, a (now retired) scientist of National Institute of Oceanography, Prakash Mehra and others, states the research of past episodes shows that powerful waves travelling from far off distances manifested as weak tsunami in Goa.
“But it showed well-defined tsunami characteristics,” the study states.
Goa experienced the weaker impact of a tsunami in 2004 and in 2007. In coastal areas, a few country craft and boats had experienced some damage due to the waves then.
The waves travelling from Indonesia were additionally amplified inside the Aguada bay of the Mandovi estuary due to harbour resonance, Joseph’s study states.
Any water body like estuary has its own resonance frequency, depending on its length, breadth and depth. “The waves caused by atmospheric disturbances like tsunami entering the harbour or the estuary may lead to amplified oscillations," a scientist explained.
The massive eruptions under sea at a depth of 4,000 to 5,000m generate waves with a speed of 400 to 500 km per hour.
“The fury of the waves may not manifest in mid-ocean but once they come toward the shore, they pile over the waves already moving ahead. The wave height increases due to the piling up effect, ” an expert said.