ALBERT

Description: Detailed documentations and assessments of the consequences of floods as well as flood risk analyses are essential for improvements of the flood risk management. However, flood documentation and flood damage collections are difficult and expensive, especially for frequent, small flood events. This results in a lack of data for flood management and research. Therefore, the Internet shall be used for the collection of flood loss information. To make use of the knowledge of the people affected by floods, a user-friendly interface is provided that allows them to communicate their estimation of flood event parameters like flood depth and flow velocity as well as flood damage. The data input is followed by an automatic quality control and analysis step with a direct feedback to the person providing the information. At the end of the process, general flood and flood mitigation information is given. On the one hand, these data collected via the web are stored in a flood damage data base, which supports damage assessments. On the other hand, the data is used to create community based flood maps for the improvement of risk awareness and communication. We aim to present our concept for a community-based data acquisition and map creation process in the context of flood damage estimation.

Description: Das sedimentäre Untere Perm (Rotliegend) ist ein bekannter Zielhorizont der Kohlen-Wasserstoff-Exploration im Norddeutschen Becken. Am Standort Groß Schönebeck wurde eine nicht-fündige Erdgasexplorationsbohrung im Jahr 2001 aufgewältigt und seither als in situ Geothermielabor genutzt. Im Jahr 2006 wurde eine zweite Bohrung abgeteuft, um eine geothermische Dublette, bestehend aus zwei etwa 4 300 m tiefen Bohrungen zu installieren. Damit soll die nachhaltige Nutzung tief liegender und Wasser führender Sedimente zur geothermischen Stromerzeugung gezeigt werden. Mit Hilfe dieser neuen Forschungsbohrung wurden speicherschonende Erschließungsverfahren unter Beachtung bohrtechnischer und sedimentologischer Rahmenbedingungen entwickelt und innovative Ansätze für eine potentielle Produktivitätserhöhung durch einen nichtvertikalen Aufschluss der Lagerstätte realisiert. Spezielle Stimulationsmaßnahmen in den aufgeschlossenen Zielhorizonten führten zur Steigerung der Produktivität. Ein abschließendes hydraulisches Kommunikationsexperiment zwischen beiden im Nutzhorizont ca. 475 m entfernten Bohrungen soll in einem weiteren Schritt die Nachhaltigkeit des Thermalwasserkreislaufes überprüfen. Anschließend ist geplant, ein geothermisches Kraftwerk am Standort Groß Schönebeck zu errichten.

Description: The sedimentary Lower Permian is a well known target for gas exploration in the North German Basin as part of the South Permian Basin System. At this site in Groß Schönebeck a non-productive gas exploration well was reopened in 2001 and is used since then as a geothermal in-situ laboratory. In 2006 a second well was drilled to complete a doublet with two wells of 4 300 m depth. The aim of this project is to show the sustainability of deep geothermal aquifers in sediments for geothermal power generation. In the focus of the drilling strategy was the mitigation of damages with respect to drilling technology and sedimentary constraints. Furthermore, innovative approaches were applied to enhance productivity with special stimulation treatments and by non vertical drilling to assess the reservoir rock. Finally, a hydraulic communication experiment between both wells (475 m distance in the reservoir) should prove the sustainability of the thermal life cycle and subsequently will lead to an installation of a power plant in Groß Schönebeck.

Description: Submarine landslides are one of the most dangerous tsunami sources. They can displace huge amounts of sediments from the continental slope into the deep ocean. Due to their long period signal, landslides can not be easily detected and recognized by common seismological methods. Here we present a method of detecting huge submarine landslides by means of tiltmeters, as a possible tool in future tsunami early warning systems. The dislocation of several hundred cube kilometers of sediment produces an elastic response of the earth. We analyze this response with a mathematical model and calculate the theoretical tilt signal. Further we describe an inversion routine providing the slide volume as well as the maximum slide velocity.

Description: We examine the micro-earthquake seismicity recorded by two temporary arrays of ocean bottom seismometers on the outer rise offshore southern Chile on young oceanic plate of ages 14 Ma and 6 Ma, respectively. The arrays were in operation from December 2004 January 2005 and consisted of 17 instruments and 12 instruments, respectively. Approximately 10 locatable events per day were recorded by each of the arrays. The catalogue, which is complete for magnitudes above 1.2 1.5, is characterized by a high b value, i.e., a high ratio of small to large events, and the data set is remarkable in that a large proportion of the events form clusters whose members show a high degree of waveform similarity. The largest cluster thus identified consisted of 27 similar events (average inter-event correlation coefficient 〉 0.8 for a 9.5 s window), and waveform similarity persists far into the coda. Inter-event spacing is irregular, but very short waiting times of a few minutes are far more common than expected from a Poisson distribution. Seismicity with these features (high b value, large number of similar events with short waiting times) is typical of swarm activity, which, based on empirical evidence and theoretical considerations, is generally thought to be driven by fluid pressure variations. Because no pronounced outer rise bulge exists on the very young plate in the study region, it is unlikely that melt is accessible from decompression melting or opening of cracks. A fluid source related to processes at the nearby ridge is conceivable for the younger segment but less likely for the older one. We infer that the fluid source could be seawater, which enters through fractures in the crust. Most of the similar-earthquake clusters are within the crust, but some of them locate significantly below the Moho. If our interpretation is correct, this implies that water is present within the mantle. Hydration of the mantle is also indicated by a decrease of Pn velocities below the outer rise seen on a refraction profile through one of the arrays [Contreras-Reyes, E., Grevemeyer, I., Flueh, E.R., Scherwath, M., Heesemann, M., 2007. Alteration of the subducting oceanic lithosphere at the southern central Chile trench-outer rise. Geochem., Geophys. Geosyst. 8, Q07003.]. The deepest events within the array on the 6 Ma old plate occur where the temperature reaches 500 600 °C, consistent with the value observed for large intraplate earthquakes within the mantle (650 °C), suggesting that the maximum temperature at which these fluid-mediated micro-earthquakes can occur is similar or identical to that of large earthquakes.

Description: A new method is presented for the separation of cells from a marine sediment matrix. Different methods and reagents were tested for detaching microbial cells from sediment particles; the highest yields were achieved in a solution of EDTA, Tween 80, sodium‐pyrophosphate, and methanol plus gentle ultrasonic treatment, followed by density centrifugation through a cushion of Nycodenz. If present, carbonates were dissolved before extraction. Comparison with untreated sediments and pure cultures verified that this technique minimizes cell lysis. The new procedure was tested on seafloor sediment from several locations and water depths (〈1 to 〉4000 m) and subseafloor sediment from the Arctic Ocean (IODP Expedition 302). Cell extraction efficiency was relatively high (65% to 100%) and consistent for each sediment type, with significantly (P 〈 0.01) lower variability of counts of separated cells compared with conventional counts on slurried sediments. Concentrating cells before enumeration allows for a much lower minimum detection limit and lower uncertainty than the conventional approach of simply slurrying sediment. Resolving relatively small differences in the distribution of microorganisms will allow for comparisons to other parameters (porewater chemistry, lithology, etc). Additionally, this method has potential for the use of molecular techniques that were previously difficult owing to coelution of interfering compounds from the sediment matrix.

Description: Fluid dynamical simulations were carried out in order to investigate the effect of the large-scale mantle flow field and the depth of the plume source on the structure of the Iceland plume through time. The time-dependent location and shape of the plume in the Earth's mantle was calculated in a global model and it was refined in the upper mantle using a 3D Cartesian model box. Global flow was computed based on density heterogeneities derived from seismic tomography. Plate motion history served as a velocity boundary condition in both models. Hotspot tracks of the plume conduits and the plume head were calculated and compared to actual bathymetry of the North Atlantic. If a plume source in the lowermost mantle is assumed, the calculated surface position of the plume conduit has a southward component of motion due to southward flow in the lower mantle. Depending on tomography model, assumed plume age and buoyancy the southward component is more or less dominating. Plume models having a source at the 660 km discontinuity are only influenced by flow in the upper mantle and transition zone and hence rather yield westward hotspot motion. Many whole-mantle plume models result in a V-shaped track, which does not match the straight Greenland–Iceland–Faroe ridge. Models without strong southward motion, such as for a plume source at 660 km depth, match actual bathymetry better. Plume tracks were calculated from both plume conduits and plume heads. A plume head of 120 K anomalous temperature gives the best match between plume head track and bathymetry.