Possibility of under-sea Christchurch quake to be studied

File Photo / Jim Eagles

The possibility of future under-sea earthquakes in the Christchurch region is to be studied in an extensive marine survey beginning tomorrow.

A National Institute of Water and Atmospheric Research (Niwa) vessel is on its way to Lyttelton, the epicentre of last month's devastating earthquake, and will use seismic survey gear to study the area.

Scientists will be checking whether there are any fault lines in the coastal marine area that could lead to undersea quakes off the Canterbury coast. The area has never been comprehensively surveyed and there is very little marine geological information. Scientists were trying to identify any faults in the area and the likelihood of a rupture off the Banks Peninsula coast, Niwa voyage leader Philip Barnes said.

Six scientists will survey out to 40km off the New Brighton coast and 30km north of the Lyttelton Heads in the seven-day expedition.

Seismic acoustic systems will project sound waves down and look at how they are reflected. A mix of multi-channel and seismic boomer equipment means scientists can look as deep as 1.5km, at faults that have not been activated or reactivated, for some time.

"We don't know what we will find. There is no evidence for a fault zone off-shore based on existing information. If the fault has not ruptured in the past tens of thousands of years, we won't see anything," Dr Barnes said.

The faults that had been ruptured in the recent Christchurch earthquakes were very old faults that had been reactivated.

Scientists also hope to learn how different faults relate to each other, in an effort to model earthquake risk.

- NZPA