How fluid viscosity affects earthquake intensity

The study formed part of wider research into geothermal energy projects which, like other underground activities, can trigger earthquakes -- a process known as induced seismicity, as opposed to natural seismicity, where earthquakes occur without human intervention.

"Subsurface exploration projects such as geothermal power, injection wells and mining all involve injecting pressurized fluids into fractures in the rock," explains Cornelio. "Studies like this show how a better understanding of the properties and effects of fluids is vital to preventing or attenuating induced earthquakes. Companies should factor these properties into their thinking, rather than focusing solely on volume and pressure considerations."

Like soap

Cornelio ran 36 experiments, simulating earthquakes of varying intensity, and propagating at different speeds, in granite or marble, with fluids of four different viscosities. Her findings demonstrated a clear correlation between fluid viscosity and earthquake intensity.

"Imagine these fluids working like soap, reducing the friction between your hands when you wash them, or like the oil you spray on mechanical parts to get them moving again," explains Marie Violay, an assistant professor and the head of the LEMR. "Moreover, naturally occurring earthquakes produce heat when the two plates rub together. That heat melts the rock, creating a lubricating film that causes the fault to slip even further. Our study also gives us a clearer picture of how that natural process works."