CRC 526 | Projectarea C

Projectarea C: Mechanical coupling and localised deformation between the tectonic plates in subduction zones

C4 Seismicity of the Hellenic Subductions zone - microseismicity and large earthquakes

Bohnhoff, Meier, Friederich

Summary
The current state of seismically active faults and of volcanically active regions may be investigated using microseismicity. The main question that will be addressed is the relation between microseismicity and large earthquakes. Do large earthquakes occur in regions with high microseismic activity or does low microseismicity indicate a locked state of a fault and the preparation of another large earthquake?

The first target of the project section is the study of microseismicity. Clustering of microseismic activity in the Cyclades has been detected in the previous project using CYCNET - its spatio-temporal variability will be investigated by the proposed project. Together with project section C6 a temporary broad-band onshore-offshore network in the southern Aegean region is proposed into which CYCNET will be integrated. This network will allow us to study shallow microseismicity in the forearc and microseismicity in the Benioff zone beneath the Cretan Sea - where a subduction channel is expected - with unprecedented accuracy. The second target is the study of large earthquakes and the determination of source parameters by waveform modelling. The series of large events in the Cyclades with magnitudes up to 7 that occurred in 1956 will be analysed and compared to the observed microseismicity. Furthermore, the proposed network would provide a unique opportunity to study source mechanisms of seismic events in the forearc with magnitudes larger than about 4 using data of stations in the source region itself.

C6 Elastic and anelastic properties of the Hellenic Subduction zone - plate contact and mantle wedge

Friederich, Meier

Summary
Seismic waves can provide a snapshot of the in-situ elastic and anelastic properties of the Earth’s interior. Using a dense network of broad-band ocean-bottom and land seismographs, we perform a tomographic investigation into the elastic and anelastic properties of the Hellenic subduction
zone with the following main targets:

  1. the contact zone between the subducted African lithosphere and the overlying Aegean mantle, including Aegean crust and uppermost lithosphere beneath the forearc,
  2. the mantle wedge above the slab and
  3. lateral variations in properties ofthe slab itself.

The following key questions will be adressed: Does a low-viscosity subduction channel exist in the plate contact zone? Was or is subducted material pushed upwards in this channel and accumulated beneath the forearc? Are there plumes rising from the subducted slab carrying fluids and melt that create the volcanic centers in the Cyclades? Do lateral variations of slab properties affect slab geometry?

C7 Numerical modelling of dynamic processes in the Hellenic Subduction zone

Fischer, Casten

Summary
Rheological parameters like viscosity and plasticity influence the deformation, stress state, and the mechanical interaction between the subducting and overriding plates in a subduction zone. Numerical modelling will be performed to identify relevant dynamic processes and to quantify the relation between rheological parameters and observables like seismicity, gravity, topography, or deformation. Particular targets will be

  1. interplate coupling and the generation of large inter-plate earthquakes,
  2. the role of density heterogeneities and topography in the deformation process, and
  3. stress transfer along and between faults and earthquake triggering.


C9 Subduction channels - structure, mechanisms, scales from the geological record

Stöckhert, Trepmann

Summary
The overall goal is to use the geological record (the only approach with the required resolution, though subject to the inherent limitations of a fossil system) to get insight into the structures, length scales, materials, deformation processes, stress history and transport properties in subduction channels, and to derive a generic model of a subduction channel to be used for the interpretation of seismological information from active subduction zones. Emphasis is on transient processes and properties, which can be correlated with present day seismological and geodetic observations, as silent earthquakes, non-volcanic tremor, and surface deformation.


nach oben

C1 (1999/2-2008/1)

Dr. F. Rummel, Prof. B. Stöckhert, Prof. J. Renner


C2 (1999/2-2005/1)

Prof. U. Casten, Prof. L. Dresen


C3 (1999/2-2002/1)

Dr. H.-P. Harjes, Dr. M. Jost


C5 (2002/2-2005/1)

Prof. F. Roth