Alpine Fault - Major Ruptures

Major Ruptures

Over the last thousand years, there have been four major ruptures along the Alpine Fault causing earthquakes of about magnitude 8. These occurred in approximately 1100, 1450, 1620 and 1717 AD, at intervals between 100 and 350 years. The 1717 quake appears to have involved a rupture along nearly 400 km of the southern two thirds of the fault. Scientists say that a similar earthquake could happen at any time as the interval since 1717 is longer than between the earlier events.

GNS Science researchers have compiled an 8000-year timeline of 24 major quakes on the (southern end of the) fault from sediments at Hokuri Creek, near Lake McKerrow in north Fiordland. In earthquake terms, the 850km-long fault is remarkably consistent, rupturing on average each 330 years, at intervals ranging from 140 years to 510 years.

Large ruptures can also trigger earthquakes on the faults continuing north from the Alpine Fault. There is paleotsunami evidence of near-simultaneous ruptures of the Alpine fault and Wellington (and/or other major) faults to the North having occurred at least twice in the past 1,000 years.