ALBERT

Description: The GeoDataNode project, funded by the Federal Ministry for Research and Education (BMBF) conducted a survey of data management practices at GFZ. The aim was to assess the state of current practices and needs, and their alignment to institutional and national guidelines for data management. The target audience included scientific and technical employees at all levels. A response rate of 24% of the target demographic was achieved. The survey revealed a general need for improvement and structuring of research data handling. This includes provision of adequate storage space, back-up schedules, and the familiarization of young researchers with good scientific practice.

Description: We report on a study to explore the deep electrical conductivity structure of the Dead Sea Basin (DSB) using magnetotelluric (MT) data collected along a transect across the DSB where the left lateral strike-slip Dead Sea transform (DST) fault splits into two fault strands forming one of the largest pull-apart basins of the world. A very pronounced feature of our 2-D inversion model is a deep, subvertical conductive zone beneath the DSB. The conductor extends through the entire crust and is sandwiched between highly resistive structures associated with Precambrian rocks of the basin flanks. The high electrical conductivity could be attributed to fluids released by dehydration of the uppermost mantle beneath the DSB, possibly in combination with fluids released by mid- to low-grade metamorphism in the lower crust and generation of hydrous minerals in the middle crust through retrograde metamorphism. Similar high conductivity zones associated with fluids have been reported from other large fault systems. The presence of fluids and hydrous minerals in the middle and lower crust could explain the required low friction coefficient of the DST along the eastern boundary of the DSB and the high subsidence rate of basin sediments. 3-D inversion models confirm the existence of a subvertical high conductivity structure underneath the DSB but its expression is far less pronounced. Instead, the 3-D inversion model suggests a deepening of the conductive DSB sediments off-profile towards the south, reaching a maximum depth of approximately 12 km, which is consistent with other geophysical observations. At shallower levels, the 3-D inversion model reveals salt diapirism as an upwelling of highly resistive structures, localized underneath the Al-Lisan Peninsula. The 3-D model furthermore contains an E–W elongated conductive structure to the northeast of the DSB. More MT data with better spatial coverage are required, however, to fully constrain the robustness of the above-mentioned off-profile features.

Description: River flooding is among the most destructive of natural hazards globally, causing widespread loss of life, damage to infrastructure and economic deprivation. Societies are currently under increasing threat from such floods, predominantly from increasing exposure of people and assets in flood-prone areas, but also as a result of changes in flood magnitude, frequency, and timing. Accurate flood hazard and risk assessment are therefore crucial for the sustainable development of societies worldwide. With a paucity of hydrological measurements, evidence from the field offers the only insight into truly extreme events and their variability in space and time. Historical, botanical, and geological archives have increasingly been recognized as valuable sources of extreme flood event information. These different archives are here reviewed with a particular focus on the recording mechanisms of flood information, the historical development of the methodological approaches and the type of information that those archives can provide. These studies provide a wealthy dataset of hundreds of historical and palaeoflood series, whose analysis reveals a noticeable dominance of records in Europe. After describing the diversity of flood information provided by this dataset, we identify how these records have improved and could further improve flood hazard assessments and, thereby, flood management and mitigation plans.

Description: The paper presents a methodology for the multi-hazard fragility analysis of fluvial earthen dikes in earthquake- and flood-prone areas due to liquefaction. The methodology has been applied for the area along the Rhine River reach and adjacent floodplains between the gauges at Andernach and Düsseldorf. Along this domain, the urban areas are partly protected by dikes, which may be prone to failure during exceptional floods and/or earthquakes. The fragility of the earthen dikes is analysed in terms of liquefaction potential, characterized by the factor of safety estimated using the procedure of Seed and Idriss (1971). Uncertainties in the geometrical and geotechnical dike parameters are considered in a Monte Carlo simulation (MCS). Failure probability of the earthen structures is presented in the form of a fragility surface as a function of both seismic hazard and hydrologic/hydraulic load.

Description: The MT repository contains geophysical data sets collected in field experiments from all over the world. The acronym MT stands for magnetotelluric, a geophysical method used to probe the Earth's deep interior for its electrical conductivity distribution through electromagnetic (EM) induction. MT is based on EM fields generated by natural processes in the Earth's atmosphere and magnetosphere. But the repository also contains data from Controlled Source Electromagnetic (CSEM) projects, for which man-made EM sources are used. The principle form of data in the repository are time-series of EM field components acquired with heterogeneous sets of sensors, recording instruments, and sampling rates. It is the main purpose of this archive or repository to provide the links between the data and their physical meaning by means of metadata. To achieve this, the repository is organized as a combination of data files and associated meta-data in a well defined folder (directory) structure, with the data files being sorted into subfolders. Meta-data are provided as XML (Extensible Markup Language) formatted file.

Description: The sources for the magnetotelluric method are naturally occurring electromagnetic field variations. Electromagnetic currents are excited over a wide frequency range in the earth’s ionosphere by solar activity and global lighting discharges. While these source are available everywhere on earth and at all times, their signal strength varies considerably. The so-called remote-reference technique is an effective way to improve magnetotelluric data quality by referencing the electromagnetic fields recorded at a local site to simultaneously recorded, undisturbed fields at a remote site. The remote reference approach has become standard for magnetotelluric field work, particularly in areas with high levels of man-made electromagnetic noise; i.e. almost everywhere in central Europe. Identifying a suitable location for a clean remote site is difficult and time-consuming. Maintaining such a site in addition to normal field operations is expensive and logistically challenging. A permanently installed reference station simplifies MT measurements considerably. The radius for which source fields are coherent depends mostly on the frequency content of the signals and the latitude of observations. According to our own tests, signals are coherent at frequencies of up to 10 kHz over distances of 1000 km. After a reconnaissance operation during which several locations all over Germany were tested, we could eventually identify an urban forest near the town of Wittstock in northern Germany as a suitable location for a reference station. A preliminary installation of the reference station was accomplished by mid-2010. The permanent installation in a wooden hut and operating with a range of sensors and sampling rates is available since November 2010. Meanwhile the data of the Wittstock site have been used very successfully to re-process a number of magnetotelluric stations in Germany. This report describes the installation, the type of sensors and the recorded data sets, which are freely available on request. For updated material, please refer to our webpages (http://www.gfz-potsdam.de/en/section/geophysical-deep-sounding/servicesinfrastructure/geophysical-instrument-pool-potsdam-gipp/archive/mt-reference-site/)