New Zealand's latest big earthquake has raised the prospect of a "worst case scenario" and a far more powerful shake.
The 7.5-magnitude tremor struck just after midnight on Monday near Hanmer and led to two deaths and widespread damage in the upper South Island.
Kevin McCue, an adjuct professor at Central Queensland University, says it was another major New Zealand earthquake not on the Alpine Fault system or any known major mapped faults in the region marking the Pacific and Australian Plate margin.
A landslide triggered by Monday's 7.5 magnitude quake covers State Highway 1 near Kaikoura. Photo: Supplied
"The consequent stress loading on the Alpine fault may be bringing it closer to failure and a magnitude 8 earthquake on the Wellington Fault must be in the minds of NZ emergency management, the worst case scenario," he said.
Professor McCue, who is Australian Earthquake Engineering Society president and Australian Seismological Centre director, said positives were that there weren't many casualties and seemingly only one building collapse.
He said landsliding on to the coastal railway and highway was to be expected given the terrain.
"The seismicity of NZ is going through an active phase, and in Australia too where there have been three times the expected number of magnitude 5-plus earthquakes in the last 2 years," he said.
That included one of 6.2 along the Northern Territory-South Australian border, " almost a one in 10-year earthquake".