In the depths of a gold mine in South Africa, scientists are planning to drill deeper still in order to reach the fault line of an earthquake. It might sound like the start of a low-budget sci-fi horror film, but it could help us understand more about how energy is released when a rupture spreads.
Drilling into a fault line is typically an incredibly expensive venture, often costing tens of millions of dollars. In South Africa, however, fault lines rupture several times a year just tens of meters from active working mine shafts. This gives researchers an incredible opportunity to get close to these lines and study what is going on within them.
In 2014, one of these lines slipped right next to a gold mine 3 kilometers (1.8 miles) below the surface near the South African town of Orkney. It caused a M5.5 earthquake, the largest the nation has experienced in at least half a century, with aftershocks continuing to ripple from the fault line. As part of the ongoing Drilling into Seismogenic Zones project, the researchers want to enter the mine and drill down a further 750 meters (2,450 feet) to the fault.
The South African mine offers a rare chance to get a view of a fault line at relatively little cost. Not only that, it will also give the geologists a glimpse of what a new fault looks like. Most of the time, researchers only get access to fault lines – like the San Andreas fault – that have ruptured hundreds, perhaps thousands of times. These active faults fill with rock flour, or fine-powered rock, and muddy the waters.
But it's thought that the fault at the bottom of the mine has only ever ruptured once, or possibly a handful of times at most. This means that it is relatively free of the detritus and wear of more active faults. The researchers hope it can therefore provide insight into how the energy released from the rupture is dissipated into heat, strain, seismic waves, and the crushing of rock.
They also hope to answer some other questions from the bowels of the mine. Some of the researchers are keen to know whether or not the faults favor certain microbes. They will place equipment that is triggered by seismic activity into the fault in order to find out. The theory is that when the lines rupture, they release a pulse of hydrogen, which bacteria thrive on.
The work will also help the mine operators. In such a seismically active region, the companies are obviously concerned about triggering more quakes, which have previously caused fatalities. This research, therefore, may provide insight into how human activity can trigger earthquakes.
[H/T: Science Magazine]