Research project

Subduction zones produce large earthquakes which occur frequently along a certain section of the fault zone between the colliding plates, known as the seismogenic zone. The development of earthquakes is directly linked to changes of the incoming sediments. Change of aseismic to coseimic behaviour of the sediments proceeds in depths with a temperature range of 100-150°C. Several diagenetic and consolidation processes occur in this realm which can alter the mechanical properties of the initially weak sediments. However, the influences of possible physico-chemical processes on the mechanical properties of marine sediments are yet to be identified and researched. Possible processes could be the smectite-illite and opal-quartz conversion as well as carbonate, clay and zeolith cementation.

The main goal of this research area is to study the interaction between marine sediments and seawater under elevated PT conditions similar to the upper seismogenic zone and its influence on the mechanical properties. The following questions arise from the goal of this study:

- What is the influence of the mineralogical composition on deformation/consolidation processes?
- How do key parameters like porosity and hydraulic conductivity change with increasing stress and temperature?
- Which sediment-seawater-interactions occur in samples of different mineralogical compositions?
- Are there any significant mineral changes?
- What are the processes that influence the mechanical behavior of the sediments most?

To answer those questions via laboratory testing, a heated uniaxial deformation apparatus was built. Sedimentary samples can be loaded in this device up to effective stresses of 100MPa and 200°C. Through pore pressure and displacement measurements it is possible to determine the change of key properties such as permeability, void ratio and porosity. Different load cycles will be performed on artificial and natural sedimentary samples. The changes of the mechanical, mineralogical and geochemical properties will be studied by means of analyzing the differently deformed samples.