Seismology at light speed: how fibre-optic telecommunications cables deliver a close-up view of NZ's Alpine Fault

• Painstaking geological research has revealed it produces very large (magnitude 7-8) earthquakes about every 300 years – with the most recent one in 1717.
• Scientists estimate there’s a 75% chance of a large Alpine Fault earthquake in the next 50 years.
• Despite the unparalleled quality of the paleo-seismic record of past Alpine Fault earthquakes, the next big earthquake will come without warning.

The Haast DAS experiment

• A new experiment in Haast, a small, remote community near the coast in South Westland, is using technology called Distributed Acoustic Sensing (DAS).
• The Haast DAS experiment is a trans-Tasman collaboration between geophysicists from the Australian National University and Victoria University of Wellington Te Herenga Waka.

Fibre-optic seismology

• Vibrations of the fibre caused by passing seismic waves modulate this scattering and can be detected by recording the scattered light pulses.
• This produces a staggering volume of data: about 1Gb of new data every minute, or 1Tb of data every day.
• The density of DAS measurements across the Alpine Fault provides an entirely new way of studying the fault’s internal structure.

Big data provides detailed information

• High-performance computing and artificial intelligence techniques (AI) are being developed and adapted to these data to enable researchers to recognise and distinguish signals of different origins.
• Being able to separate out these two types of information is a task well suited to AI.
• In the future, it is likely AI will help tease apart DAS data to detect otherwise unrecognised signals produced by atmospheric and subterranean processes.