Quake study probes deep sea trench

A deep marine trough off the New Zealand coast will help international scientists understand more about the world's largest earthquakes.

The Hikurangi Trench, or subduction zone, lies less than 100 kilometres off the east coast of the North Island and runs south to the waters off Kaikoura.

It marks the boundary between two crustal plates and the margin where the Pacific Plate, to the east, is being dragged underneath the Australian Plate.

Visiting United States seismologist Kevin Furlong said the trough, and two similar trenches off the coast of North America and Alaska, would form the focus of a major global study of megathrust earthquakes, which could often be of magnitude 9.0 or higher and could cause large tsunami.

The Pennsylvania State University professor was at Canterbury University on Thursday outlining new research on subduction zone quakes.

Recent megathrust earthquakes include: Japan, March 2011, magnitude 9.0; Sumatra, Boxing Day 2004, magnitude 9.1; Alaska, Good Friday 1964, magnitude 9.2; and Chile, 1960, magnitude 9.5 (the largest quake known).

Mr Furlong said detailed scientific understanding of subduction quakes was still in its infancy.

Plate tectonics had developed only since the mid-1960s as a theory to explain processes and events such as quakes and vulcanism.

"Before plate tectonics really got developed, the last big [megathrust] one was the 1964 Alaskan quake," he said.

"But then there was a 40-year window between then and the Boxing Day 2004 Sumatran quake."

The Hikurangi Trench was one of the world's big seismic unknowns, he said.

"It could be as hazardous to New Zealand, especially the eastern North Island, as a similar zone that caused Japan's devastating magnitude-9.0 quake and tsunami in March 2011."

Researchers plan to drill into the subduction zone.

Fairfax NZ

Kaikoura Star