Small tsunamis several metres high hit Hawaii about six hours after the earthquake struck. People were warned to stay out of the water but a swimmer suffered cuts after being sucked through an opening in a seawall as the water receded just before the swells arrived.
Coastal Philippine towns received their initial tsunami warnings via text messages which prompted many to flee to the hills nearby until the alert was revised hours later.
Renato U Solidum Jr, director of the Philippine Institute of Volcanology and Seismology, told Al Jazeera that immediate warnings must be issued for big earthquakes and national agencies had to make their own evaluations based on the information received.
For areas close to the earthquake epicentre, the standard operating procedure is to issue tsunami alerts.
“It is based on calculations and modelling, on the depth and magnitude of a quake as well as the shoreline geometry but the protocol is to use the conservative estimate at all times”
Renato U Solidum Jr, director of Philippine Institute of Volcanology and Seismology
He said whether or not a tsunami forecast – the height and arrival time of a tsunami – actually materialises depends on several factors.
“It is based on calculations and modelling, on the depth and magnitude of a quake as well as the shoreline geometry but the protocol is to use the conservative estimate at all times.
“The critical factor, however, is how the message is conveyed to the ground.”
The Japanese operate their own tsunami warning centre but the Pacific Tsunami Warning Centre in Hawaii issues a general forecast to national agencies for immediate action.
Plans to install the region’s first Indian ocean tsunami warning system are under way in Thailand almost two years after the devastating tsunami on December 26 which claimed over 200,000 lives around the region.