Section 4.2: Geomechanics and Rheology

We do research in geomechanics, rock physics and material sciences, using investigations of deformation and on transport phenomena in rocks of the Earth's crust. We perform rock experiments, for example on granite or porous rocks like sandstone. The laboratory tests are combined with field observations, for example in tectonically active areas of Turkey and in the deep mines of South Africa. There we focus on the analysis of processes that take place in the earthquake source. In experiments, in which we heat rocks and put them under high pressure, we investigate the metamorphic processes that take place deep in the Earth's crust. With our research we analyze the mechanical properties of rocks and provide the physical foundations needed for estimating geohazards and to understand the geomechanics of reservoirs and underground mines.

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 as an analogue to processes responsible for earthquakes in nature. We also analyze the rocks that come out of earthquake fault zones, such as in samples retrieved from a three kilometer deep borehole into the San Andreas Fault in California.

We combine these laboratory measurements with 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 very small 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 stress 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.

head of section

Profile photo of  Prof. Dr. Marco Bohnhoff

Prof. Dr. Marco Bohnhoff
Geomechanics and Rheology

Telegrafenberg
Building D, room 424
14473 Potsdam
tel. +49 331 288-1327

secretary

Profile photo of   Rita Hamlischer

Rita Hamlischer
Assistance of Geomechanics and Rheology

Telegrafenberg
Building D, room 426
14473 Potsdam
tel. +49 331 288-1321