Finding out about faults

There are some rumours floating around about what I do. Am I a secret agent geologist working for the NZ government on earthquake risk? No. Am I a famous fault mechanics researcher? No. I have a scholarship from the University of Canterbury to study rocks formed when earthquakes happen about 1-4 km under the Earth's surface. My main field area is the Alpine Fault, located on the West Coast of the South Island. Right now, I collect rocks at two places: Hare Mare (pronounced Hairy Mary) Creek and Gaunt Creek.



Question: Do Alpine Fault rocks flow like Gaunt Creek, or do they jam during earthquakes?

I use these rocks to understand where the minerals in them formed, the chemistry of the fluids moving through the fault zone, and their frictional strength. Friction? What? It basically means, how will the rocks behave when there's an earthquake? Is there so much friction that the rupture stops (like spikes on cleats keep you from slipping on wet grass)? Or are they weak, allowing the two plates on each side of the fault to slide past each other? To answer these questions, I use a lot of tools.

The most exciting tools are the friction testing devices. I have a fellowship to visit Penn State University next May to use their slow rock deformation devices. I am building a fast rock deformation device here at the University of Canterbury. It shears rocks at speeds approaching 1 meter per second. I have done some experiments so far and have some cool results... like I've made smoke and strange noises, cracked steel, and almost seized 9 kW motor. Here's a picture of my machine (called a rheometer, from the Greek "rheos" meaning "stream" and "metron" meaning "measure"). I've also shown that Alpine Fault rocks are not very strong, and that might explain why we have a record of 7000 years of surface rupture earthquakes with an average magnitude of M8. Alpine Fault earthquakes occur about every 250 years, and the last event was 1710 AD.