ALBERT

Beschreibung: Due to the recent eruptive and highly disruptive volcanic events in 2010 in Iceland, scientific and societal interest is overwhelming in gaining as much information as possible about the volcanic structures and processes to enhance the understanding of the partially glacier‐covered Eyjafjallajökull and Katla volcanic systems. Numerous petrological, geochemical and geophysical investigations of these systems have already been published. However, to date no electrical or electromagnetic data have been acquired on these two volcanoes to attempt to image the resistivity structure beneath and around them, although electromagnetic methods are far more sensitive to fluid distribution (in this case partial melt) than any other geophysical method. In July 2011, a pilot study took place to collect broadband magnetotelluric (MT) data around the Eyjafjallajökull. The MT data are supplemented with transient electromagnetic (TEM) measurements. This data set is the first one collected at these volcanic systems and will complement the existing geophysical data. Very fresh data and preliminary results from the experiment will be shown.

Beschreibung: Drei Minuten. Nicht mehr. Kein PowerPoint. Nur das, was man am Körper tragen kann. Und damit das eigene Forschungsgebiet kurz, knapp, verständlich und mitreißend vorstellen. "FameLab" ist der Name dieses Wissenschaftlerwettbewerbs , der dieses Jahr seine Deutschlandpremiere feiert. Der regionale Vorentscheid für Brandenburg und Berlin wurde am 18. Februar bei uns auf dem Telegrafenberg ausgetragen. Wissenschaftskommunikation in Höchstform, Spaß inklusive.

Beschreibung: Throughout the Phanerozoic, the primary inorganic marine calcium carbonate mineralogy oscillated between calcite and aragonite, reflecting changes in seawater chemistry. These variations in seawater composition also appear to have influenced the evolution of calcifying organisms. However, the processes controlling these mineralogical and biological changes are poorly constrained. Previous work has focused mainly on the Mg/Ca ratio in seawater as the primary driver. Here, we examine the role of dissolved SO4 in these processes by performing controlled laboratory precipitation experiments and geochemical modeling of evaporite formation. We show that an increase in dissolved SO4 decreases the Mg/Ca ratio at which calcite is destabilized and aragonite becomes the dominant CaCO3 polymorph. Our data suggest that the Mg/Ca and SO4 thresholds for formation of calcite seas are significantly lower than previous estimates and are mutually dependent. This shows that our understanding of Phanerozoic changes in seawater chemistry and the models relating this to primary CaCO3 mineralogy need reevaluation.

Beschreibung: Results obtained from S and P receiver functions produced a clear image of the top and bottom of the subducting Nazca lithosphere beneath northern Chile. Using data from the teleseismic events recorded at 15 permanent Integrated Plate Boundary Observatory Chile (IPOC) stations, we obtained new constraints on the geometry and thickness of the descending Nazca lithosphere. We observed the subducted crust of the Nazca plate at depths ranging from 50 km beneath the Coastal Cordillera down to 110 km beneath the Western Cordillera. We found significant along‐strike variations in the geometry of the Nazca plate beneath northern Chile. On closer inspection, it appears that the oceanic Nazca plate is divided into two distinct segments as it descends beneath the continental South American plate. The transition from the relatively steeper (∼23°) and deeper slab to the north of 21°S to the flatter southern segment (∼19°) is shown reasonably clearly by our data. This feature could well be associated with variations in the curvature of the plate margin and the geometry of the Chile trench, which is mainly curved to the north of 21°S. We have also mapped the continental Moho of the South American plate at depths ranging between 60 and 70 km to the east of the Longitudinal Valley. Beneath the Coastal Cordillera, this boundary becomes invisible, probably due to the serpentinization of the forearc mantle wedge that reduces the velocity in the uppermost mantle. The base of the subducted Nazca plate was clearly identified as a sharp boundary in the results obtained from the P and S receiver functions. The thickness of the subducted oceanic Nazca plate, which has an age of ∼50 My, is estimated to be ∼50 km. Although this thickness is consistent with that predicted by thermal gradients, the explanation of the sharpness of the lithosphere‐asthenosphere boundary may require another mechanism such as hydration or melting.

Beschreibung: An early detection of the presence of rupture directivity plays a major role in the correct estimation of ground motions and risks associated to the earthquake occurrence. We present here a simple method for a fast detection of rupture directivity, which may be additionally used to discriminate fault and auxiliary planes and have first estimations of important kinematic source parameters, such as rupture length and rupture time. Our method is based on the inversion of amplitude spectra from P-wave seismograms to derive the apparent duration at each station and on the successive modelling of its azimuthal behaviour. Synthetic waveforms are built assuming a spatial point source approximation, and the finite apparent duration of the spatial point source is interpreted in terms of rupture directivity. Since synthetic seismograms for a point source are calculated very quickly, the presence of directivity may be detected within few seconds, once a focal mechanism has been derived. The method is here first tested using synthetic datasets, both for linear and planar sources, and then successfully applied to recent Mw 6.2–6.8 shallow earthquakes in Peloponnese, Greece. The method is suitable for automated application and may be used to improve kinematic waveform modelling approaches.

Beschreibung: Soil moisture is a key state variable that controls runoff formation, infiltration and partitioning of radiation into latent and sensible heat. However, the experimental characterisation of near surface soil moisture patterns and their controls on runoff formation remains a challenge. This subject was one aspect of the BMBF-funded OPAQUE project (operational discharge and flooding predictions in head catchments). As part of that project the focus of this dissertation is on: (1) testing the methodology and feasibility of the Spatial TDR technology in producing soil moisture profiles along TDR probes, including an inversion technique of the recorded signal in heterogeneous field soils, (2) the analysis of spatial variability and temporal dynamics of soil moisture at the field scale including field experiments and hydrological modelling, (3) the application of models of different complexity for understanding soil moisture dynamics and its importance for runoff generation as well as for improving the prediction of runoff volumes. To fulfil objective 1, several laboratory experiments were conducted to understand the influence of probe rod geometry and heterogeneities in the sampling volume under different wetness conditions. This includes a detailed analysis on how these error sources affect retrieval of soil moisture profiles in soils. Concerning objective 2 a sampling strategy of two TDR clusters installed in the head water of the Wilde Weißeritz catchment (Eastern Ore Mountains, Germany) was used to investigate how well “the catchment state” can be characterised by means of distributed soil moisture data observed at the field scale. A grassland site and a forested site both located on gentle slopes were instrumented with two Spatial TDR clusters that consist of up to 39 TDR probes. Process understanding was gained by modelling the interaction of evapotranspiration and soil moisture with the hydrological process model CATFLOW. A field scale irrigation experiment was carried out to investigate near subsurface processes at the hillslope scale. The interactions of soil moisture and runoff formation were analysed using discharge data from three nested catchments: the Becherbach with a size of 2 km², the Rehefeld catchment (17 km²) and the superordinate Ammelsdorf catchment (49 km²). Statistical analyses including observations of pre-event runoff, soil moisture and different rainfall characteristics were employed to predict stream flow volume. On the different scales a strong correlation between the average soil moisture and the runoff coefficients of rainfall-runoff events could be found, which almost explains equivalent variability as the pre-event runoff. Furthermore, there was a strong correlation between surface soil moisture and subsurface wetness with a hysteretic behaviour between runoff soil moisture. To fulfil objective 3 these findings were used in a generalised linear model (GLM) analysis which combines state variables describing the catchments antecedent wetness and variables describing the meteorological forcing in order to predict event runoff coefficients. GLM results were compared to simulations with the catchment model WaSiM ETH. Hereby were the model results of the GLMs always better than the simulations with WaSiM ETH. The GLM analysis indicated that the proposed sampling strategy of clustering TDR probes in typical functional units is a promising technique to explore soil moisture controls on runoff generation and can be an important link between the scales. Long term monitoring of such sites could yield valuable information for flood warning and forecasting by identifying critical soil moisture conditions for the former and providing a better representation of the initial moisture conditions for the latter.zeige weniger

Beschreibung: Abflussentwicklung, Infiltration und die Umverteilung von Strahlung in latenten und sensiblen Wärmestrom werden maßgeblich durch die Bodenfeuchte der vadosen Zone gesteuert. Trotz allem, gibt s wenig Arbeiten die sich mit der experimentellen Charakterisierung der Bodenfeuchteverteilung und ihre Auswirkung auf die Abflussbildung beschäftigen. Der Fokus dieser Dissertation wurde darauf ausgerichtet: (1) die Methode des Spatial TDR und deren Anwendbarkeit einschließlich der Inversion des TDR Signals in heterogenen Böden zu prüfen, (2) die Analyse der räumlichen und zeitlichen Dynamik der Bodenfeuchte auf der Feldskala einschließlich Feldexperimenten und hydrologischer Modellierung, (3) der Aufbau verschiedener Modellanwendungen unterschiedlicher Komplexität um die Bodenfeuchtedynamiken und die Abflussentwicklung zu verstehen und die Vorhersage des Abflussvolumens zu verbessern. Um die Zielsetzung 1 zu erreichen, wurden verschiedene Laborversuche durchgeführt. Hierbei wurde der Einfluss der Sondenstabgeometrie und verschiedener Heterogenitäten im Messvolumen bei verschiedenen Feuchtegehalten untersucht. Dies beinhaltete eine detaillierte Analyse wie diese Fehlerquellen die Inversion des Bodenfeuchteprofils beeinflussen. Betreffend der Zielsetzung 2, wurden 2 TDR-Cluster in den Quellgebieten der Wilden Weißeritz installiert (Osterzgebirge) und untersucht, wie gut der Gebietszustand mit räumlich hochaufgelösten Bodenfeuchtedaten der Feldskala charakterisiert werden kann. Um die Interaktion zwischen Evapotranspiration und Bodenfeuchte zu untersuchen wurde das hydrologische Prozessmodell CATFLOW angewendet. Ein Beregnungsversuch wurde durchgeführt um die Zwischenabflussprozesse auf der Hangskala zu verstehen. Die Interaktion zwischen Bodenfeuchte und Abflussentwicklung wurde anhand von drei einander zugeordneten Einzugsgebieten analysiert. Statistische Analysen unter Berücksichtigung von Basisabfluss, Bodenvorfeuchte und verschiedenen Niederschlagscharakteristika wurden verwendet, um auf das Abflussvolumen zu schließen. Auf den verschiedenen Skalen konnte eine hohe Korrelation zwischen der mittleren Bodenfeuchte und dem Abflussbeiwert der Einzelereignisse festgestellt werden. Hierbei konnte die Bodenfeuchte genauso viel Variabilität erklären wie der Basisabfluss. Im Hinblick auf Zielsetzung 3 wurden “Generalised liner models” (GLM) genutzt. Dabei wurden Prädiktorvariablen die den Gebietszustand beschreiben und solche die die Meteorologische Randbedingungen beschreiben genutzt um den Abflussbeiwert zu schätzen. Die Ergebnisse der GLMs wurden mit Simulationsergebnissen des hydrologischen Gebietsmodells WaSiM ETH verglichen. Hierbei haben die GLMs eindeutig bessere Ergebnisse geliefert gegenüber den WaSiM Simulationen. Die GLM Analysen haben aufgezeigt, dass die verwendete Messstrategie mehrerer TDR-Cluster in typischen funktionalen Einheiten eine viel versprechende Methode ist, um den Einfluss der Bodenfeuchte auf die Abflussentwicklung zu verstehen und ein Bindeglied zwischen den Skalen darstellen zu können. Langzeitbeobachtungen solcher Standorte sind in der Lage wichtige Zusatzinformationen bei der Hochwasserwarnung und -vorhersage zu liefern durch die Identifizierung kritischer Gebietszustände für erstere und eine bessere Repräsentation der Vorfeuchte für letztere.zeige weniger

Beschreibung: Über den Aufbau des CAWa-Messnetzes in Zentralasien wird es eine TV-Doku geben, die Anfang des kommenden Jahres gesendet werden soll. Dass auch für TV-Teams die Arbeit im Gelände nicht immer einfach ist, erläutert uns der Kameramann und Co-Autor Armin Fausten (Kick-Film,Berlin), der zusammen mit dem TV-Regisseur Arno Trümper die GFZ-Aktivitäten auf den Gletschern Kirgisistans filmte.

Beschreibung: Hazard and risk assessments for river reaches protected by dikes have not adequately considered the inundation processes up to now. Particularly, the processes of dike failures and their influence on the hinterland inundation and flood wave propagation lack comprehensive consideration. This study focuses on the development and application of a new modelling system which allows a comprehensive flood hazard assessment along diked river reaches considering dike failures. The Inundation Hazard Assessment Model (IHAM) developed at the GFZ German Research Centre for Geosciences comprises three models interactively coupled at runtime. These are: (1) 1D unsteady hydrodynamic model for river channel and floodplain between dikes, (2) probabilistic dike breach model, which assesses dike breach probabilities, breach widths and flow rates through the breach, and (3) 2D raster-based diffusion wave storage cell model of the hinterland areas behind the dikes. IHAM generates probabilistic flood hazard maps that show spatial characteristics of inundation depths, flow velocities and other flood intensity indicators. These maps explicitly indicate uncertainties of these characteristics. Furthermore, IHAM enables the identification of endangered dike sections and computation of their failure probabilities. The knowledge gained with IHAM can significantly contribute to the planning of flood protection measures and risk analyses.

Beschreibung: The deep structure of the Upper Rhine Graben (URG), a continental rift in SW Germany and E France, is still poorly known. This deficit impedes a full understanding of the geodynamic evolution of this prominent rift. We study the lithosphere–asthenosphere structure using teleseismic waveforms obtained from the passive broad-band TIMO project across the central URG. The recovered, crust-corrected traveltime residuals relative to the iasp91 earth model are tiny (mostly less than 0.2–0.3 s). The average measured slowness (〈1 s deg−1) and backazimuth (〈5°) deviations are also very small and do not show any systematic wave front anomalies. These observed perturbation values are smaller than expected ones from synthetic 3-D ray tracing modelling with anomalies exceeding 2–3 per cent seismic velocity in the mantle. Thus there is no significant hint for any deep-seated anomaly such as a mantle cushion, etc. This result means that the rifting process did not leave behind a lower lithospheric signature, which could be clearly verified with high-resolution teleseismic experiments. The only significant traveltime perturbation at the central URG is located at its western side in the upper crust around a known geothermal anomaly. The upper crustal seismic anomaly with traveltime delays of 0.2–0.3 s cannot be explained with increased temperature alone. It is possibly related to a zone of highly altered granite. In the west of our network a traveltime anomaly (0.6–0.7 s delay) related with the Eifel plume is confirmed by the TIMO data set.

Beschreibung: The kinetics and mechanisms of nanoparticulate amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite, were studied at a range of environmentally relevant temperatures (7.5-25 degrees C) using synchrotron-based in situ time-resolved Energy Dispersive X-ray Diffraction (ED-XRD) in conjunction with high-resolution electron microscopy, ex situ X-ray diffraction and infrared spectroscopy. The crystallization process occurs in two stages; firstly, the particles of ACC rapidly dehydrate and crystallize to form individual particles of vaterite; secondly, the vaterite transforms to calcite via a dissolution and reprecipitation mechanism with the reaction rate controlled by the surface area of calcite. The second stage of the reaction is approximately 10 times slower than the first. Activation energies of calcite nucleation and crystallization are 73 +/- 10 and 66 +/- 2 kJ mol(-1), respectively. A model to calculate the degree of calcite crystallization from ACC at environmentally relevant temperatures (7.5-40 degrees C) is also presented.

Beschreibung: On 2001 May 7, following unintentional water injection, a moderate size induced earthquake struck the Ekofisk oil field, North Sea. Despite of its relatively moderate magnitude, clear low-frequency waveforms could be recorded up to more than 2000 km epicentral distance, suggesting a slow rupture at very shallow depth and wave propagation through low-velocity shallow structures. The event poses a rare opportunity to constrain rupture velocity, duration and rise time of a superficial M 〉 4 event occurring on a horizontal plane in soft, water-saturated sediments. Two previous studies discussed the earthquake point source finding vertical dip-slip focal mechanisms with opposite senses of P and T axes. A further investigation was thus required to provide a basis for a deeper discussion of the failure dynamics. We significantly improve the used data set, test different earth models and derive a point source as well as a kinematic rupture model. We carefully discuss parameter uncertainties and effects related to shallow sources and wave propagation through different crustal structures to resolve the previous controversy. We additionally provide a kinematic rupture model, based on apparent source times derived from Rayleigh and Love waves. The waveforms resolve a predominant unilateral rupture along a horizontal plane at about 2 km depth. We derive an unusually slow rupture, consequence of a slow rupture velocity of about 500 m s –1 and a long rise time of about 7 s. An independent modelling of GPS- based static displacements allows to confirm the focal mechanism polarity and to locate the centroid at the eastern side of the field, resulting in a much larger seismic moment in comparison with dynamic seismic moment. The rupture directivity is confirmed by the relative location of the centroid with respect to the epicentre, which is set at the site of water injection.

Beschreibung: The Dead Sea Transform (DST) is a major left-lateral strike-slip fault that accommodates the relative motion between the African and Arabian plates, connecting a region of extension in the Red Sea to the Taurus collision zone in Turkey over a length of about 1100 km. The Dead Sea Basin (DSB) is one of the largest basins along the DST. The DSB is a morphotectonic depression along the DST, divided into a northern and a southern sub-basin, separated by the Lisan salt diapir. We report on a receiver function study of the crust within the multidisciplinary geophysical project, DEad Sea Integrated REsearch (DESIRE), to study the crustal structure of the DSB. A temporary seismic network was operated on both sides of the DSB between 2006 October and 2008 April. The aperture of the network is approximately 60 km in the E—W direction crossing the DSB on the Lisan peninsula and about 100 km in the N—S direction. Analysis of receiver functions from the DESIRE temporary network indicates that Moho depths vary between 30 and 38 km beneath the area. These Moho depth estimates are consistent with results of near-vertical incidence and wide-angle controlled-source techniques. Receiver functions reveal an additional discontinuity in the lower crust, but only in the DSB and west of it. This leads to the conclusion that the internal crustal structure east and west of the DSB is different at the present-day. However, if the 107 km left-lateral movement along the DST is taken into account, then the region beneath the DESIRE array where no lower crustal discontinuity is observed would have lain about 18 Ma ago immediately adjacent to the region under the previous DESERT array west of the DST where no lower crustal discontinuity is recognized.

Beschreibung: Subducted slab roll-back, lithospheric instability and asthenospheric extrusion have all been proposed as mechanisms that explain the evolution of the extensional Pannonian Basin, within the convergent arc of the Alpine–Carpathian mountain system in central Europe. We determine the P- and S-wave velocity structure of the mantle to depths of 850 km beneath this region using tomographic inversion of relative arrival-time residuals from 225 (P waves) and 124 (S waves) teleseismic earthquakes recorded by 56 stations of the Carpathian Basins Project (CBP) temporary seismic network (16-month duration) and 44 permanent seismic stations. The observed median P-wave relative arrival-time residuals vary between −1.13 s (early) in the Alps and 1.12 s (late) at the western end of the Carpathians; S-wave relative arrival-time residuals are about twice as large (−2.13 s and 3.39 s). We tested the effect of deterministic corrections on our relative arrival-time residuals using crustal velocity models from controlled source experiments, but show that the use of station terms in the inversion provides a robust method of correcting for near-surface crustal variation. Our tomographic models reduce the P-wave rms residual by 71 per cent to 0.130 s and our S-wave rms residual by 59 per cent to 0.624 s. At shallow sublithospheric depths we image several localized lower velocity regions, correlated with higher heat flow and interpreted as upwelling asthenosphere. We image a high velocity structure down to depths of about 350 km beneath the Eastern Alps. Further east, beneath the Pannonian Basin, a deeper continuation of the Eastern Alps fast anomaly is imaged trending E–W from ∼300 km depth and extending into the mantle transition zone (MTZ). In the MTZ we image a fast anomaly extending outwards as far as the Carpathians, the Dinarides and the Eastern Alps. This higher velocity mantle material is interpreted as being produced by a mantle downwelling, whose detachment from the lithosphere above may have triggered the extension of the Pannonian Basin.

Beschreibung: The 9th TRACE conference (Tree Rings in Archaeology, Climatology and Ecology) was organized by the Institute for Forest Growth, University of Freiburg, on April 22nd – 25th 2010 in Freiburg, Germany. [...] This volume of TRACE Proceedings contains 26 short papers and gives an overview of the wide spectrum of fields in tree-ring research.

Beschreibung: Im Rahmen dieses BMBF-geförderten Projektes 1 kommt die Long-Offset Transient Elektromagnetik (LOTEM) Methode in mariner Umgebung zum Einsatz. Ziel ist die Kartierung eines relativ schlechtleitenden Aquifers unter den gutleitenden Meeressedimenten. In diesem Beitrag werden 1D Ergebnisse der Messungen aus den Jahren 2009 und 2011 vorgestellt.

Beschreibung: Central Asia was identified as one of the regions of the world with the highest seismic hazard and risk. However, the actual lack and heterogeneity of available seismological and vulnerability data make any possible seismic risk scenario highly uncertain. In order to improve seismic risk assessment in Central Asia efforts must be carried out to both increase the seismological knowledge in the area and to update and harmonise the existing vulnerability data set in the different countries. To this regard, within the Central Asia Cross-Border Natural Disaster Prevention (CASCADE) project, financed by the German Federal Foreign Office, a cross-border seismological and strong motion network in Central Asia (CAREMON) was installed. Microzonation studies in the capitals of Kyrgyzstan and Uzbekistan were started, and those for Kazakhstan, Tajikistan and Turkmenistan were triggered. The collection of a harmonised (in terms of the European Macroseismic Scale EMS) building vulnerability data base was also achieved, and a capacity building and training program accompanied all the different tasks of the project. All these activities were carried out within the framework of, and supported by, the Global Change Observatory Central Asia (GCO-CA). The digital data collected by the CAREMON network will allow to improve localisation of the seismicity in the area and to improve completeness of earthquake catalogues necessary for sounded seismic hazard assessment at regional scale. The results of the microzonation will be exploited for improving the seismic hazard and risk assessment in the capitals. Attempts were already carried out for Bishkek. Follow-up activities, including the establishment of a vertical array of accelerometer in Bishkek, are foreseen for further improving seismic hazard and risk analysis in Central Asia.

Beschreibung: Krylov subspace methods are well-known as iterative solvers for linear systems of equations. Using the same basic projection methodology these can also be used to approximate the solution of least squares problems, while avoiding the explicit construction of the sensitivity matrix. We point out how Krylov subspace methods such as CGNR – as well as its more robust variant LSQR – take into account the least squares origin of the normal equations, thereby ameliorating the ill-conditioning inherent in the inverse problem. These observations are illustrated with examples from the inversion of 3-D helicopter electromagnetic data. The research is carried out in an interdisciplinary project called ‘AIDA – From Airborne Data Inversion to In-Depth Analysis’.

Beschreibung: Observations show that the fractional solubility of Fe (FS-Fe, percentage of dissolved to total Fe) in dust aerosol increases considerably from 0.1% in regions of high dust mass concentration to 80% in remote regions where concentrations are low. Here, we combined laboratory geochemical measurements with global aerosol model simulations to test the hypothesis that the increase in FS-Fe is due to physical size sorting during transport. We determined the FS-Fe and fractional solubility of Al (FS-Al) in size-fractionated dust generated from two representative soil samples collected from known Saharan dust source regions using a customized dust re-suspension and collection system. The results show that the FS-Fe is size-dependent and ranges from 0.1-0.3% in the coarse size fractions (〉 1 mu m) to similar to 0.2-0.8% in the fine size fractions (〈 1 mu m). The FS-Al shows a similar size distribution to that of the FS-Fe. The size-resolved FS-Fe data were then combined with simulated dust mass concentration and size distribution data from a global aerosol model, GLOMAP, to calculate the FS-Fe of dust aerosol over the tropical and subtropical North Atlantic Ocean. We find that the calculated FS-Fe in the dust aerosol increases systematically from similar to 0.1% at high dust mass concentrations (e. g., 〉 100 mu gm(-3)) to similar to 0.2% at low concentrations (〈 100 mu gm(-3)) due to physical size sorting (i.e., particle gravitational settling). These values are one to two orders of magnitude smaller than those observed on cruises across the tropical and sub-tropical North Atlantic Ocean under an important pathway of Saharan dust plumes for similar dust mass concentrations. Even when the FS-Fe of sub-micrometer size fractions (0.18-0.32 mu m, 0.32-0.56 mu m, and 0.56-1.0 mu m) in the model is increased by a factor of 10 over the measured values, the calculated FS-Fe of the dust is still more than an order of magnitude lower than that measured in the field. Therefore, the physical sorting of dust particles alone is unlikely to be an important factor in the observed inverse relationship between the FS-Fe and FS-Al and the atmospheric mineral dust mass concentrations. The results suggest that processes such as chemical reactions and/or mixing with combustion particles are the main mechanisms to cause the increased FS-Fe in long-range transported dust aerosols.

Beschreibung: Since 1997 we maintain and systematically update the European–Mediterranean Regional Centroid Moment Tensor (RCMT) catalog, which contains seismic-moment tensors for earthquakes with moderate magnitude (4.5 〈 M 〈 5.5) in the Mediterranean and European regions. We present 354 new solutions for the period 2005–2008. The Catalog now spans 12 years and contains more than 1000 definitive RCMT solutions. In addition to definitive solutions, we maintain and update a dataset of recent ‘quick’ solutions that are computed soon after an earthquake occurs using the more limited set of data available in quasi-real time. We investigate the reliability of the moment tensor results in the RCMT catalog. Comparison with Global CMT results, which is possible for the larger events (M 〈 5.0) in the RCMT catalog, shows that for 75% of the events, the Kagan angle measure of the similarity of two moment tensors is smaller than 20°, reflecting good agreement of the results. We describe improvements and enhancements in the dissemination of the RCMT results through our web site.

Beschreibung: We analyse data from seismic stations surrounding the Alboran Sea between Spain and North Africa to constrain variations of the lithosphere–asthenosphere boundary (LAB) in the region. The technique used is the receiver function technique, which uses S-to-P converted teleseismic waves at the LAB below the seismic stations. We confirm previous data suggesting a shallow (60–90 km) LAB beneath the Iberian Peninsula and we observe a similarly shallow LAB beneath the Alboran Sea where the lithosphere becomes progressively thinner towards the east. A deeper LAB (90–100 km) is observed beneath the Betics, the south of Portugal and Morocco. The structure of the LAB in the entire region does not seem to show any indication of subduction related features. We also observe good P receiver function signals from the seismic discontinuities at 410 and 660 km depth which do not indicate any upper-mantle anomaly beneath the entire region. This is in agreement with the sparse seismic activity in the mantle transition zone suggesting the presence of only weak and regionally confined anomalies.

Beschreibung: The associated Legendre functions were historically calculated as closed power series. With the growing need for higher degrees and associated orders recursive algorithms have been developed, highly efficient for numerical processing. As ground–based gravity measurements are available that can be combined with existing and upcoming datasets of satellite systems ultrahigh degree spherical harmonic representation and transformation of the fields becomes a necessity. Moreover, for applications in spectral domain it is in general desirable to process the associated Legendre function directly, without a recursive antecessor that predefines the order of the sequence. The closed power series mentioned can not serve beyond certain degrees due to alternating signs with extraordinarily large rational numbers, leading to a considerable loss in numerical precision. The Fourier transform and recursive relations between the Fourier coefficients themselves instead turn out to be stable and widely useful.

Beschreibung: This thesis summarizes the results of the WSM project’s second phase (1996‐2008). In particular it presents the major achievements that have been accomplished with the WSM 2008 database release that has been compiled under the guidance of the author. Furthermore, the thesis briefly presents three of the author’s numerical models that aim at quantification the temporal changes of the crustal stress field.

Beschreibung: A Magnetotelluric (MT) field campaign was carried out in the SE Lower Saxony Basin, Germany, with the main goal of testing this method on imaging the regional Posidonia black shale sediments. Eightythree MT stations were deployed along a sixty-three kilometer long profile. Data was acquired successfully and we show examples of apparent resistivity and phase curves before and after remote reference processing. Also, in an attempt to correlate microscale with regional, macrosale electrical resistivity models, electrical resistivity measurements were made on a series of black shale samples from boreholes to study how electrical resistivity varies with different thermal maturity levels, organic carbon and mineral content, measurement orientation and water content. Results show that black shale conduct electrical currents highly anisotropic and that water content is a main controlling factor. So far, we cannot establish a simple correlation between electrical conductivity and intrinsic properties of black shale, like organic carbon, mineral composition, and thermal maturity.

Beschreibung: [...] In context of this work, a new damage mechanism is proposed: the mechanically induced fracture face skin. This new mechanism results from mechanical interactions between the proppants and the reservoir rock, due to the increasing stress on the rock-proppant system during production. Proppant embedment into the fracture face and proppant crushing leads to fines production and can impair the fracture performance. In order to achieve sustainable, longterm productivity from a reservoir, it is indispensable to understand the hydraulic and mechanical interactions in the rock-proppant system. In order to analyse the hydraulic and mechanical interactions, laboratory experiments using three different flow cells were conducted. These flow cells were used to localise and quantify the mechanical damage at the fracture face, as well as to investigate the long-term stability of a rock-proppant system under in-situ reservoir conditions. [...]

Beschreibung: We implement the effects of gravitational self-attraction and loading (SAL) into a global baroclinic ocean circulation model and investigate effects on sea level patterns, ocean circulation, and density distributions. We compute SAL modifications as an additional force on the water masses at every time step by decomposing the field of ocean bottom pressure anomalies into spherical harmonic functions and then applying Love numbers to account for the elastic properties of the solid Earth. Considering SAL in the postprocessing turns out to be insufficient, especially in coastal waters and on subweekly time scales, where SAL modifies local sea level by around 0.6–0.8 cm on average; in the open ocean, changes mostly remain around 0.3 cm. Modifications of water velocities as well as of heat and salt distributions are modeled, yet they are small. Simple parameterizations of SAL effects currently used in a number of ocean circulation models suffer from the process's inhomogeneity in space and time. These parameterizations improve the modeled sea level patterns but fail to reproduce SAL impacts on circulation and density distributions. We therefore suggest to explicitly consider the full SAL effect in ocean circulation models, especially when investigating sea level variations faster than around 4 days.

Beschreibung: The use of ground-based electromagnetic methods (Transient Electromagnetics (TEM) and Radiomagnetotellurics (RMT)) is increased in last decades for hydrogeological purposes. However, airborne electromagnetic methods were also proposed as a possible tool for near surface investigations due to the capability to cover large areas in short time. By jointly inverting different kinds of geophysical measurements at a site, the ambiguity inherent in different geophysical methods can be avoided. In order to couple spatial data from frequency-domain helicopter-borne electromagnetics (HEM) with electromagnetic measurements from ground geophysics, a common 1D joint inversion algorithm for HEM, TEM and RMT data is developed. The depth of investigation of HEM data is rather limited compared to time-domain EM sounding methods on the ground. In order to improve the accuracy of model parameters of shallow depth as well as of the deeper crust, the HEM, TEM, and RMT measurements are combined using numerical joint inversion methodology. The 1D joint inversion algorithm is verified for the synthetic data of HEM, TEM and RMT. The proposed concept of the joint inversion takes advantage of each single method, which provides the capability to resolve near surface (RMT) and deeper electrical conductivity structures (TEM). Furthermore, the joint inversion is realized for the field data (HEM and TEM) measured in the Cuxhaven area, Germany.

Beschreibung: The Izmit earthquake of August 1999 with a magnitude 7.4 is the latest of an earthquake sequence that started in 1939 in Eastern Turkey. This sequence brought the plate boundary between the Anatolian plate and the Eurasian plate successively from East to West to fail. Thus, the next event in this series is expected to take place West of Izmit, i.e. South of Istanbul under the Marmara Sea. This segment is a so-called seismic gap – the stresses resulting from the plate motion have not been released since the last major earthquake in 1766. One important parameter for earthquake hazard assessment is the slip rate along plate boundaries. However, the precise estimation of these fault slip rates is difficult to determine in this area for two reasons. The plate boundary under the Marmara Sea is split into several splays with complex geometries. Furthermore, the main part of this fault system is below the Marmara Sea and classical observation methods cannot be applied. In order to estimate the fault slip rates a computer simulation is necessary. The simulation results show that the slip rate along the main fault is 10 to 45 % smaller than previously assumed and that it varies along the main fault by 40 %. The latter indicates that the accumulated stresses at this fault will potentially not be released with one strong earthquake, but in several events with smaller magnitude. However, it is important to emphasise that Istanbul, situated at a short distance to the main fault (15 km), still faces a very high seismic hazard.

Beschreibung: We present models of the 3-D shear velocity structure of the lithosphere and asthenosphere beneath the Hawaiian hotspot and surrounding region. The models are derived from long-period Rayleigh-wave phase velocities that were obtained from the analysis of seismic recordings collected during two year-long deployments for the Hawaiian Plume-Lithosphere Undersea Mantle Experiment. For this experiment, broad-band seismic sensors were deployed at nearly 70 seafloor sites as well as 10 sites on the Hawaiian Islands. Our seismic images result from a two-step inversion of path-averaged dispersion curves using the two-station method. The images reveal an asymmetry in shear velocity structure with respect to the island chain, most notably in the lower lithosphere at depths of 60 km and greater, and in the asthenosphere. An elongated, 100-km-wide and 300-km-long low-velocity anomaly reaches to depths of at least 140 km. At depths of 60 km and shallower, the lowest velocities are found near the northern end of the island of Hawaii. No major velocity anomalies are found to the south or southeast of Hawaii, at any depth. The low-velocity anomaly in the asthenosphere is consistent with an excess temperature of 200-250 °C and partial melt at the level of a few percent by volume, if we assume that compositional variations as a result of melt extraction play a minor role. We also image small-scale low-velocity anomalies within the lithosphere that may be associated with the volcanic fields surrounding the Hawaiian Islands.

Beschreibung: Frequent landsliding is one of the greatest natural hazards facing the inhabitants of Central Asia's Fergana Basin and the surrounding mountain ranges. Active tectonics in the region is rapidly building the Tien Shan, one of the highest mountain ranges on Earth, and the extreme topographic relief promotes frequent landslide activity, which causes major losses of life and property. In southwestern Kyrgyzstan alone, on average 10 people die and seven houses are destroyed each year in these sudden and rapidly moving landslides.

Beschreibung: The flux of bioavailable Fe from mineral dust to the surface ocean is controlled not only by the processes in the atmosphere but also by the nature and source of the dust. In this study, we investigated how the nature of Fe minerals in the dust affects its potential Fe solubility (Fe-psol) employing traditional and modern geochemical, mineralogical, and microscopic techniques. The chemical and mineralogical compositions, particularly Fe mineralogy, in soil samples as dust precursors collected from North African dust source regions were determined. The Fe-psol was measured after 3 days of contact with sulfuric acid at pH 2 to simulate acid processes in the atmosphere. Fe-psol of the soil dust samples were compared with calculated predictions of Fe-psol based on the amount of individual Fe-bearing minerals present in the samples and Fe solubilities of corresponding standard minerals. The calculated Fe-psol deviated significantly from the measured Fe-psol of the soil dust samples. We attributed this to the variability in properties of Fe minerals (e. g., size of Fe oxides and heterogeneity of chemical compositions of clay minerals) in soil dusts in comparison to the standard minerals. There were, however, clear relationships between the degree of chemical weathering of North African soils and Fe-psol. The Parker index and ratio of ascorbate plus dithionite Fe to total Fe ((FeA+FeD)/FeT) are positively and negatively correlated with Fe-psol, respectively. In addition, the ratio of FeA/(FeA+FeD), which decreases with aging of the Fe oxides, was found to be positively correlated with Fe-psol in the soil dusts. Overall, our results indicate that there is a significant regional variability in the chemical and Fe mineralogical compositions of dusts across North African sources, as a result of the differences in chemical weathering and aging of Fe oxides. Furthermore, the indices for these weathering processes can provide an estimate of the fraction of Fe which can be solubilized if acid processed in the atmosphere.

Beschreibung: We present current research associated with a common project of the TU Bergakademie Freiberg and the Deutsches Geoforschungszentrum Potsdam (GFZ). The aim of this project is to exploit the distinct sensitivity patterns of different EM methods to enhance the resolution. Here, we focus on combining the direct current and the transient electromagnetic method. Further methods to be integrated are magnetotellurics and controlled-source EM. For this purpose, we have properly reimplemented our finite element secondary field DC forward modelling approach on unstructured grids and proved its theoretical convergence rate of O(h2). We derive expressions for the Jacobian with respect to their efficient calculation in an inversion process and examine the spatial sensitivity pattern in order to design a coherent DC/TEM set-up.

Beschreibung: Am GFZ wurde in diesem Jahr ein neues UV-Femtosekunden Laser-Ablationssystem entwickelt. Dieses System ermöglicht es, Element und Isotopenanalysen im Mikrometerbereich durchzuführen.

Beschreibung: This short report describes the first attempt at obtaining a preliminary cross-border risk model for Central Asia starting from datasets that were already available at the beginning of the EMCA Project.

Beschreibung: Structural features of volcanic and hydrothermal systems can be used to infer the location of magma chambers or productive geothermal areas. The Hengill volcanic triple-junction complex has a well-developed geothermal system, which is being exploited to extract hot fluids that are used for electrical power and heat production. In the framework of the I-GET project, a 4-month temporary seismological network including seven high-dynamic broadband instruments was deployed and 1D transient electromagnetic soundings (TEM) and 3D magnetotelluric (MT) surveys were performed to improve the understanding of the relationships between structural features, seismic activity and fluid production at the Hengill geothermal system. The MT and TEM data set are analysed elsewhere. The analysis of the seismological data set allowed the detection and classification of more than 600 earthquakes, among which long-period (LP) earthquakes were observed for the first time in this area. This work focuses first on a joint inversion for the 3D velocity structure and determination of the locations of the hypocentres from about 250 local volcano-tectonic earthquakes with clear P- and S-wave arrival times. The results confirm those from earlier tomography studies in this area. Integrating the seismic velocity and resistivity models in a semi-quantitative approach by cross-plotting the resistivity model with the velocity ratio VP/VS delineates a structural body with a high seismic velocity ratio and low resistivity that is interpreted as the main heat source of the geothermal system.

Beschreibung: „Rot is‘ Backbord un‘ Steuerbord is‘ grün“? Nein, rot ist Förderbohrung und blau ist Injektionsbohrung, wenigstens im Naturschutzgebiet Schorfheide, am Geothermie-Forschungsstandort Groß Schönebeck des GFZ. Keine flatternden Fahnen, aber Zelte mit Biertischgarnituren, einem Rednerpult, dazu erklärende Poster in der Halle: hier wird offenbar was gefeiert, nämlich die Übergabe des Pokals „365 Orte der Ideen“.

Beschreibung: Der Vortrag wurde in der Session “Impacts of Earthquakes and Tsunamis on Urban Systems” gehalten.

Beschreibung: This study demonstrates that only a combination of a chromous chloride reduction with dual sequential extraction schemes can clearly separate the proportions of Se present in the sulphide versus the organic pools in shales. The data reveals that even small amounts of pyrite outcompete the organic matter for the available Se and pyrite oxidation will control the release of selenium during shale weathering. (C) 2011 Elsevier Ltd. All rights reserved.