Shattered earth

New Zealand’s most dangerous faultline—and one of the most dangerous ones in the world—is the Alpine Fault, which runs along the west of the South Island. It produces a M8 earthquake once every three centuries, more or less, and the last one was around 1717. So, scientists are going to drill into it.

It might seem like a risky idea, but it’s not particularly new. Scientists have drilled into faults before, usually after an earthquake. But with the Alpine Fault, they have a chance to look at a fault that hasn’t ruptured in nearly 300 years, but which has a high probability of producing a severe M8 earthquake sometime in the next 50 years. On average, the fault ruptures every 330 years, give or take 60 years.

So, scientist are drilling into it in a project called the Deep Fault Drilling Project (DFDP). They hope to better understand if better, and also maybe even find ways of providing advance warning.

A common question, included on GNS’ “DFDP-2 FAQs”, is: “Will drilling into the Alpine Fault cause a large earthquake?” We non-scientists naturally wonder about that. They answer:

No, for several reasons. The volume of rock affected by drilling is extremely small (with dimensions of the order of a few metres) compared to the scale of the Alpine Fault itself (with dimensions on the orders of tens to hundreds of kilometres), and the depth of penetration (1.3 km) is very shallow compared to the depths at which most earthquakes nucleate (several kilometres). Drilling operations will be conducted using techniques that minimize the degree of pressurization in the borehole and no large-volume fluid injection experiment will be undertaken. Finally, the low levels of earthquakes occurring naturally within several kilometres of the DFDP-2 drill-site, and their low magnitudes, indicate that the rock mass is generally not close to failing.

Nevertheless, local councils have emergency plans in place, just in case, but that’s something they’d have anyway—we still have no idea when the fault will rupture, and local councils have to be prepared all the time, just like local councils do in every other part of the country. In other words, the fact they’re drilling into the Alpine Fault doesn’t increase the need for emergency preparedness—it’s the same as it always was.

Hopefully, the DFDP will gain all the data they’re wishing for, yes, but also maybe it will help the development of early warning systems. Anything that does that is a good thing, and this project isn’t nearly as scary as it may sound.