Scientists intend to drill into the Alpine Fault on New Zealand's West Coast, one of the world's biggest fault lines.
The fault runs the length of the South Island.
GNS Science says it is entering its window of opportunity for a large rupture which could cause an earthquake about 10 times as powerful as the Canterbury 7.1-magnitude quake on 4 September last year.
Drilling will start on 24 January near Whataroa and will continue for the next 30 years.
Scientists from GNS Science, Otago and Victoria universities and from overseas will drill two holes 150 metres deep to start with and install instruments to measure shaking, temperature and pressure.
The Alpine Fault last ruptured 290 years ago and moved the ground 27 metres horizontally along 300km - about 10 times the movement which occurred in the Canterbury quake.
Professor Kevin Furlong, from Penn State University in the United States, says the best estimate is that such a rupture could occur again some time in the next 200 years.
Most of the damage would be on the West Coast.