The Civil Defence Minister is staunch on the need for mobile emergency alerts. 

An alert sent at 6.30am warned people to stay away from water, beaches, harbours, marinas, and estuaries - with uncertain sea conditions triggered by yesterday's massive Russia quake. 

It applies until further notice. 

But many received multiple messages, and others got none. 

Mark Mitchell told Kerre Woodham they'll be looking into it, but early warning is important. 

He says in the past emergencies with fatalities, it's because of optimism bias, but New Zealand doesn't have that luxury anymore. 

LISTEN ABOVE 

See omnystudio.com/listener for privacy information.