The main topic of our research is the development of innovative seismic methods to image the subsurface. We use seismic methods to study geodynamic structures and processes. Seismic methods allow insight into deeper parts of the Earth which are not directly accessible. These methods use seismics waves from artificial sources or natural sources. The analysis yield images of the subsurface which allow inferences about the Earth's structures, material properties and processes. Moreover, also the sources itself can be studied with seismic observations (focal parameters, locations).In order to process our seismic measuring data we use the Landmark ProMAX/SeisSpace software as well as other self-developed program routines.
One focus of our research is the development of new seismic methods to image the subsurface including methods for integrated interpretation. Currently, we are working on the following topics (among others): Markov chain Monte Carlo inversion, Pn tomography and H/V analysis of submarine data.
Markov Chain Monte Carlo Tomography
We develop Markov chain Monte Carlo (McMC) methods for tomographic imaging and local earthquake localization. The main advantage of the methods is that they extensively sample the solution space and thus produce (velocity) models as well as estimates of the uncertainties. Compared to conventional methods, no initial models are necessary, data errors are automatically estimated, and the parametrization is automatically adjusted.
We developed a tomographic method to invert seismic Pn phases sampling Earth‘s uppermost mantle and applied the method to a controlled-source dataset from northern Namibia acquired within the DFG Priority Programme SPP SAMPLE. The analysis provide insight into the upper mantle of the landfall of the oceanic Walfish ridge, especially regarding the complex processes during continental break-up.
Projects: SPP SAMPLE
H/V analysis of submarine permafrost data
We showed that passive seismological measurements in the seafloor can be used to study the distribution and depth of the submarine permafrost layer. In particular, we use the H/V analysis of ambient seismic noise, which is well known from engineering seismology, in concert with specifically shallow water underwater seismic sensors.
Publications: Overduin et al., 2015
We use reflection and refractions seismic methods at different scales as well as earthquake observations and ambient noise to investigate geodynamic key processes. Particularly, we investigate processes at continental shear zones, active and passive continental margins and plumes. For this research we conduct large field experiments.
Convergent margins: Subduction zones and continental collision
At convergent margins two (or more) tectonic plates move against each other. At subduction zones, an oceanic plate thrusts underneath another oceanic or continental plate. The collision of continents often cause the formation of mountain chains and continental plateaus. In any case, the deformation processes active at convergent margins shape the Earth's surface and are also responsible for the most severe earthquakes.
Passive continental margins
A passive continental margin is the transition between oceanic and continental crust which has originally been formed after continental break-up and rifting. Studies at passive margins provide insight into the processes of continental break-up, the onset of the creation of the sea floor and eventually of the mechanisms behind the movement of lithospheric plates.
Continental shear zones accommodate the relative horizontal motions between continental plates. Prominent examples are the San Andreas fault and the Dead Sea Transform. Earthquakes related to these motions pose a significant threat to the population. Seismic methods provide insight into the deeper structure of the shear zones and their internal architecture.
The development of innovative measurement technology is an importanat aspect of experiemental research. The staff of the Geophysical Instrument Pool Potsdam (GIPP) works on developments of new data recorders and other instrument systems.
Seismic data recorder
The Cube data recorder had been specifically developed for seismic measurements. The strengths of this autonomous recorder are the high data quality, extremely low power consumption, robustness and small size/weight.