Geomechanics and Rheology

Each earthquake and every rock fall demonstrate that "solid rock" is not as solid and permanent as we always think. When the mechanical forces on it are large enough, rock can burst, break or slowly deform plastically. We investigate the details of how such ruptures happen and under which physical condition rock can begin to flow, that is how it deforms.

For these purposes, we have a laboratory equipped with many tools for rock physics experiments. For example, we can put rock samples under pressure using various hydraulically or gas-driven presses. With other tools, we investigate the pore space that is the empty space between the particles making up a rock. We also induce brittle fracture in rock samples. That is the same process that is responsible for earthquakes in nature. We also analyze the rocks that come out of earthquake fault zones, such as serpentinite that was retrieved from a three kilometer deep borehole into the San Andreas Fault in California.

We extend these laboratory measurements with comparative field investigations. These are mainly concentrated on the North Anatolian Fault in western Turkey, one of the most dangerous earthquake zones in the world. For this purpose, we have installed a network of seismometers on two of the small islands in the Marmara Sea off the coast of Istanbul. With it, we can record even the smallest earthquakes that occur in the region. Corresponding instruments installed on the seafloor complete the system. In the same region, we also investigate why some segments of faults slowly creep, while in others, so much tension can build up that they rupture in an earthquake.

In one of the deepest mines in the world, the gold mine Mponeng in South Africa, we have also installed our instruments. There we record the occurrence of extremely tiny fractures in the rock generated by the ore extraction process.