ALBERT

Description: The International Geomagnetic Reference Field (IGRF) is a very frequently used model of the Earth’s main magnetic field by both the science community and the industry. This model is updated every five years. We present here the second generation of the GRIMM magnetic field model that was derived to contribute to the IGRF-11. The model has been developed from a newly, reprocessed CHAMP satellite data set covering nearly 10 years. It has a temporal and spatial resolution significantly improved compared to previous models.

Description: This paper presents the application of two different active contour models for the segmentation of high-resolution TerraSAR-X data. Both methods facilitate the detection of land-water-boundaries in semi-automated procedures and can be used to delineate flood extent and to map open water surfaces in general. For the extraction of smooth water bodies amplitude thresholding approaches are quite common and often applied. For rough water bodies however the application of amplitude thresholding methods is not successful. This paper demonstrates the poten-tials and limitations of active contour models for mapping both smooth and rough water bodies in high-resolution SAR data. Examples of both different segmentation methods are presented.

Description: The addition of clay to growing media aims at constant supply of potassium, phosphorus and micro nutrients, pH-buffering, improvement of rewettability, and cohesion of growing media. The identification of suitable clays and their classification is a prerequisite for product and cultivation safety. A range of different clays highly variable in their mineral parameters were selected for experiments on nutrient buffering (P) and Mn toxicity, their ability to improve the rewettability and binding capacity of growing media. From batch experiments and growth trials it was derived that a threshold value for the sum of exchangeable and easy reducible Mn in clays for growing media is not justified, as even very high Mn contents in clay were not phytotoxic. The P binding capacity of clays was strongly correlated with the oxalate extractable Fe and Al content. A newly developed capillary rise method (WOK) was used to characterize the rewettability of growing media. The speed of rewetting mainly depends on the fineness of the amended clay. Surface free energy (SFE) data of the growing media indicate that those with a good rewettability show also high values for SFE. Compared to the kaolinitic and illitic clay amendments, bentonites show no significant increase in the SFE. Surfaces of clay minerals exhibiting originally polar and hydrophilic surfaces, can render hydrophobic when coated with weakly or non-polar organic matter moieties. Dissolved organic carbon (DOC) sorption was found to be positively correlated with the specific surface area (SSA), cation exchange capacity (CEC) and amount of dithionite extractable Al and Fe. Clays containing expandable clay minerals with high CEC and SSA (e.g. smectites) and those rich in Al- and Fe-oxides seem to be less effective for improving rewettability, whereas an addition of non-expandable clays with lower SSA, CEC (e. g. kaolinitic and illitic clays) and amorphous oxide content appears more promising. New insights on the adsorption of DOM on clay mineral`s surfaces will be obtained in the third year by chemical analysis of the surface with X- ray photoelectron spectroscopy (XPS), surface topography analysis and contact angle measurements. A new method for the determination of the binding capacity of clays in blocking media is currently being tested and will be studied together with determinations on K-dynamics.

Description: The Sumatra-Andaman earthquake with a magnitude of 9.3, and the subsequent destructive tsunami which caused more than 225 000 fatalities in the region of the Indian Ocean, happened on 26 December 2004. Less than one month later, the United Nations (UN) World Conference on Disaster Reduction took place in Kobe, Japan to commemorate the 1995 Kobe earthquake. The importance of preparedness and awareness on regional, national and community levels with respect to natural disasters was discussed during this meeting, and resulted in the approval of the Hyogo Declaration on Disaster Reduction. Based on this declaration the UN mandated the Intergovernmental Oceanographic Commission (IOC) of UNESCO (United Nations Education, Science and Cultural Organization), taking note of its over 40 years of successful coordination of the Pacific Tsunami Warning System (PTWC), to take on the international coordination of national early-warning efforts for the Indian Ocean and to guide the process of setting up a Regional Tsunami Early Warning System for the Indian Ocean.

Description: We present an attenuation model for midperiod Rayleigh waves in Central Asia and surrounding regions. This model is defined by maps of attenuation coefficient across the region of study in the period band 14–24 s. The model is constructed to characterize the regional variations in attenuation of seismic waves in the crust, which are related to the tectonic history of the studied territory, to calibrate the regional surface-wave magnitude scale, and to extend the teleseismic 'surface-wave magnitude – body wave magnitude' (Ms-mb) discriminant to regional distances. The construction of the model proceeds in three stages. The first stage in model construction is the measurement of Rayleigh wave spectral amplitudes. We collected and processed waveform data for 200 earthquakes occurring from 2003 to 2006 inside and around Eurasia, and used records of about 135 broadband permanent and temporary stations. This data set provided a sufficient number of spectral amplitude measurements between 14 and 24 s periods for the construction of two–dimensional tomographic maps of attenuation coefficients. At the second stage of the work, the integral of attenuation coefficients along given paths is estimated using both inter-station measurements and single-station measurements corrected for source and receiver terms. The third stage includes the refining of source parameters, recalculation of attenuation coefficient integrals after this refinement, grooming of resulting coefficients, and multistage tomographic inversion of the data. Tomographic maps for the set of periods from 14 to 24 s, which exhibit clear correlation with geology and tectonics of the territory under study, were obtained. Validation of these maps using the inter-station measurements confirms their accuracy in predicting the observations.

Description: An ascorbic acid extraction at pH 7.5 has been examined to assess the influence of reaction conditions (pH, ascorbic acid concentration) on the dissolution of Fe from synthetic 2-line ferrihydrite and from other Fe-bearing minerals. The method was highly selective for Fe in ferrihydrite with only small amounts of Fe extracted from other (oxyhydr)oxides or clays. The labile Fe extracted from the synthetic 2-line ferrihydrite stored as a slurry decreased with time, and high resolution microscopy showed that the older materials formed networked aggregates that slow down the dissolution. The apparent rate constant for the dissolution of fresh 2-line ferrihydrite (similar to 10(-3) s(-1)) was an order of magnitude larger than that for aged suspensions (similar to 10(-4) s(-1)). Fresh 2-line ferrihydrite that was filtered, freeze-dried, frozen and freeze-dried, and stored in the dry was even less readily dissolved (apparent rate constants similar to 10(-6) s(-1)). These ferrihydrites also contained networked aggregates and, additionally, appear to occur as granular aggregates (visible to the naked eye) during the early stages of dissolution. Storage of filtered, freeze-dried, and frozen and freeze-dried ferrihydrites, whether in water or air, produced similar dissolution behaviour because aggregation caused by de-watering decreases the labile Fe content and is not reversed by re-hydration. The determination of labile Fe in ferrihydrite requires that natural samples should be collected, stored and extracted wet. The most aged samples dissolved by parabolic dissolution kinetics indicate that the rates of dissolution were controlled by the diffusion of reactant into the internal porosity of aggregates. (C) 2010 Elsevier B.V. All rights reserved.

Description: The seismicity data file used for this study is represented by the earthquake catalogue CENEC for Europe north of 44°N (Grünthal et al. 2009a). This paper describes in detail how this homogeneous data file in terms of moment magnitudes Mw (with Mw greater than 3.5) has been derived. The degree of harmonization achieved in CENEC is quantitatively analysed in Grünthal et al. (2009b).

Description: A mobile volcano fast response system (VFRS) that can be used for volcano monitoring in case of volcanic unrest anywhere in the world is currently under development in Germany. The main goal of the project called Exupéry is to provide the communication technology for stations in the field and an expert system that collects all data from various sources, assembles them in a database, and allows users to assess the data through one common web GIS interface. The system also includes an integrated automatic alert level including the alert level estimation in order to characterize the activity state of the volcano. The web GIS interface serves as a decision support system to assist scientists and local authorities in deciding how to react in the case of volcanic unrest.

Description: Fifteen earthquakes (Mw 4.1–6.4) occurring at ten major segments of the Sumatran Fault Zone (SFZ) were analyzed to identify their respective fault planes. The events were relocated in order to assess hypocenter uncertainty. Earthquake source parameters were determined from three-component local waveforms recorded by IRIS-DMC and GEOFON broadband lA networks. Epicentral distances of all stations were less than 10°. Moment tensor solutions of the events were calculated, along with simultaneous determination of centroid position. Joint analysis of hypocenter position, centroid position, and nodal planes produced clear outlines of the Sumatran fault planes. The preferable seismotectonic interpretation is that the events activated the SFZ at a depth of approximately 14–210 km, corresponding to the interplate Sumatran fault boundary. The identification of this seismic fault zone is significant to the investigation of seismic hazards in the region.

Description: This study attempts to constrain the lithospheric strength in Central Tibet by studying the rebound of the lithosphere and uppermost mantle subjected to loading or unloading due to lake Siling Co water level fluctuations.This lake is a large endhoreic lake at 4500~m elevation located North of the strike-slip right lateral Gyaring Co fault, and South of the Bangong Nujiang suture zone, on which numerous left-lateral strike slip faults are branching. The Siling Co lake water level has strongly changed in the past, as testified by numerous traces of palaeo-shorelines, clearly marked until 60 m above present-day level. Altimetric measures show that during the period 2003-2008 the Siling Co water level increased by about 0.7~m/yr, a remarkably fast rate given the large lake surface (1600~km2). To extent the lake level observation duration, we extract the lake contour from all cloud-free LANDSAT images available on the USGS GLOVIS server. The lake surface, used as a proxy for lake elevation, shows that the water level in the Siling Co lake in Tibet was more or less stagnant from 1973 to 1999 and increased between 2000 and 2010 at an average rate of 0.8 m/yr. A clear seasonal signal is superimposed on the interannual trend. The ground motion associated to the water level increase is studied by InSAR using all ERS and Envisat data on tracks 491 and 219 in the period 1992-2010, obtained through the Dragon ESA-MOST cooperation program. A redundant network of small baseline interferograms is computed with perpendicular baseline smaller than 500~m. The coherence is quickly lost with time (over one year), particularly to the North of the lake because of freeze-thaw cycles. The interferograms covering the period 1992-1999 show no detectable deformation, whereas the ones covering the period 2000-2010 present bowl shape pattern centered on the lake that extend from the shore to about ~100 km from the lake center. The amplitude is about 5 mm/yr close to the lake shores. The interferograms are also affected by decorrelation noise, residual orbital ramp and atmospheric delays. To increase the signal to noise ratio, they are first analysed in time assuming a constant deformation shape. We then obtain the temporal evolution of the deformation amplitude : the amplitude remains constant for the period 1992-1999, and increased from 2000 until 2010. This curve follows closely the lake level temporal evolution. An average velocity map for the period 2000-2010 is also produced to better assess the shape of the ground displacement. Both the amplitude temporal evolution and the average velocity map are used to explore possible rheological models : the elastic model could explain the amplitude evolution if static moduli are set about twice lower than the dynamic moduli derived from the lithosphere seismic velocity profiles. A visco-elastic model with a low viscosity lower crust can also adjust the data. We will discuss to what extent the models can be constrained considering the available data and its noise.

Description: In order to increase our knowledge on the lithosphere rheological structure under the Tibetan plateau, we study the loading response due to lake Siling Co water level changes. The challenge here is to measure the deformation with an accuracy good enough to obtain a correct sensivity to model parameters. InSAR method in theory allow to observe the spatio-temporal pattern of deformation, however its exploitation is limited by unwrapping difficulties linked with temporal decorrelation and DEM errors in sloppy and partially incoherent areas. This lake is a large endhoreic lake at 4500~m elevation located North of the strike-slip right lateral Gyaring Co fault, and just to the south of the Bangong Nujiang suture zone, on which numerous left-lateral strike slip are branching. The Siling Co lake water level has strongly changed in the past, as testified by numerous traces of palaeo-shorelines, clearly marked until 60 m above present-day level. In the last years, the water level in this lake increased by about 1~m/yr, a remarkably fast rate given the large lake surface (1600~km2). The present-day ground subsidence associated to the water level increase is studied by InSAR using all ERS and Envisat archived data on track 219, obtained through the Dragon cooperation program. We chose to compute 750~km long differential interferograms centered on the lake to provide a good constraint on the reference. A redundant network of small baseline interferograms is computed with perpendicular baseline smaller than 500~m. The coherence is quickly lost with time (over one year), particularly to the North of the lake because of freeze-thaw cycles. Unwrapping thus becomes hazardous in this configuration, and fails on phase jumps created by DEM contrasts. The first work is to improve the simulated elevation field in radar geometry from the Digital Elevation Model (here SRTM) in order to exploit the interferometric phase in layover areas. Then, to estimate DEM error, we mix the Permanent Scattered and Small Baseline methods. The aim is to improve spatial and temporal coherence. We use as a reference strong and stable amplitude points or spatially coherent areas, scattered within the SAR scene. We calculate the relative elevation error of every point in the neighbourhood of reference points. A global inversion allows to perform spatial integration of local errors at the radar image scale. Finally, we evaluate how the DEM correct ion of wrapped interferograms improves the unwrapping step. Furthermore, to help unwrapping we also compute and then remove from the wrapped interferograms the residual orbital trend and the phase-elevation relationship due variations in atmospheric stratification. Stack of unwrapped small baseline interferograms show clearly the average subsidence rate around the lake of about 4 mm/yr associated to the present-day water level increase. To compare the observed deformation to the water level elevation changes, we extract from satellite images in the period 1972 to 2009 the water level changes. The deformation signal is discussed in terms of end-members visco-elastic models of the lithosphere and uppermost mantle.

Description: The mechanism of green rust sulfate (GR-SO(4)) formation was determined using a novel in situ approach combining time-resolved synchrotron-based wide-angle X-ray scattering (WAXS) with highly controlled chemical synthesis and electrochemical (i.e., Eh and pH) monitoring of the reaction. Using this approach,GR-SO(4) was synthesized under strictly anaerobic conditions by coprecipitation from solutions with known Fe(II)/Fe(III) ratios (i.e., 1.28 and 2) via the controlled increase or pH. The reaction in both systems proceeded via a three-stage precipitation and transformation reaction. During the first stage,schwertmannite (Fe(8)O(5)(OH)(4.5)(SO(4))(1.75)) precipitated directly from solution at pH 2.8-4.5. With increasing pH ( 〉5), Fe(2+) ions adsorb to the surface of schwertmannite and catalyze its transformation to goethite (alpha-FeOOH) during the second stage of the reaction. In the third stage, the hydrolysis of the adsorbed Fe(2+) ions on goethite initiates its transformation to GR-SO(4) at pH 〉7, The GR-SO(4) then continues to crystallize up to pH similar to 8.5. These results suggest that with an Fe(II)/Fe(III) ratio of 〈= 2 in the initial solution the structural Fe(II)/Fe(III) of the GR-SO(4) will be close to that of the starting composition.

Description: The German geoscience satellite CHAMP (CHAllenging Minisatellite Payload) has collected the currently longest available time series of GPS radio occultation (RO) data comprising nearly eight years. Around 570,000 occultation measurements were performed between Feb. 2001 and Oct. 2008. This time series is continued by the U.S./German GRACE (Gravity Recovery And Climate Experiment) mission. To generate a homogeneous and high quality long-term set of GPS-RO data for climatological applications and trend analyses, a consistent reprocessing is needed. Major objectives of the GEOTECHNOLOGIEN research project ATMO-CHAMP/GRACE therefore are: a) improve ment of the scientific GPS RO processing software, b) consistent reprocessing of the CHAMP/GRACE GPS-RO long-term data set applying this improved software and c) the demonstration of climatological applications for the long-term data set. In this paper the status of the CHAMP/GRACE processing is overviewed and climatological applications regarding global temperature and tropopause trends and irregularities of the ionospheric E-region are demonstrated.

Description: The Open Geospatial Consortium (OGC) addresses the requirement of integrating sensor information into spatial information infrastructures by developing service interfaces, protocols and data types in the Sensor Web Enablement (SWE) specification series. Using web-based services as tools for interdisciplinary data exchange, as well as for the extensive usage of heterogeneous data resources is an important step towards addressing today’s larger scale environmental problems (Bacharach, 2008). By making measurements and results discoverable and accessible over the internet, data producers can reduce data redundancy and existing data sets can be used to their full capacity. Even though SWE services are designed to be a foundation for »plug&play« access to sensors and sensor networks, questions about how to apply standards for information providers still have to be answered. Compared to the »state of the art« of specialised mass-market ready sensor and communication technology, SWE standards appear bloated, impractical and hard to implement. The project SLEWS (Sensor-based Landslide Early Warning System) uses existing commercial sensor products, implementing SWE technologies on top as a middleware layer to provide the data in an open and interoperable manner as a proof-of-concept. Results of the project’s work outline approaches to improve the process of providing sensor data in a SWE-enabled format using today’s commonly used internet technologies. The components considered are based on the Open Source Spatial Data Infrastructure framework deegree. It is outlined which components comprise the system, how spatial information can be accessed by users and which technologies are relevant. Based on the concept of grid-computing, a proposal for ensuring fail-safe operation is laid out.

Description: Rapid improvements in telemetry technology and the general decrease in communication costs have raised a growing interest in low-cost wireless sensing units. This is especially the case for structural monitoring purposes, where they are becoming a more valuable alternative to conventional wired monitoring system. The main advantages associated with the use of wireless sensing unit include a considerable decrease in installation costs, decentralization of data analysis, and the possibility of broadening the functional capabilities by exploiting the use, at the same time and place, of different sensors. In this work, the design of a low-cost wireless sensing unit able both to collect, analyze, store, and communicate data and estimated parameters is presented. The suitability of a network of these low-cost wireless instruments for monitoring the vibration characteristics and dynamic properties of strategic civil infrastructures is validated during a ambient vibration recording field test on the Fatih Sultan Mehmet Bridge in Istanbul, Turkey.

Description: We determined a high-resolution 3-D S-wave velocity model for a 26 km × 12 km area in the northern part of the basin of Santiago de Chile. To reach this goal, we used microtremor recordings at 125 sites for deriving the horizontal-to-vertical (H/V) spectral ratios that we inverted to retrieve local S-wave velocity profiles. In the inversion procedure, we used additional geological and geophysical constraints and values of the thickness of the sedimentary cover already determined by gravimetric measurements, which were found to vary substantially over short distances in the investigated area. The resulting model was derived by interpolation with a kriging technique between the single S-wave velocity profiles and shows locally good agreement with the few existing velocity profile data, but allows the entire area, as well as deeper parts of the basin, to be represented in greater detail. The wealth of available data allowed us to check if any correlation between the S-wave velocity in the uppermost 30 m (v30S) and the slope of topography, a new technique recently proposed by Wald and Allen, exists on a local scale. We observed that while one lithology might provide a greater scatter in the velocity values for the investigated area, almost no correlation between topographic gradient and calculated v30S exists, whereas a better link is found between v30S and the local geology. Finally, we compared the v30S distribution with the MSK intensities for the 1985 Valparaiso event, pointing out that high intensities are found where the expected v30S values are low and over a thick sedimentary cover. Although this evidence cannot be generalized for all possible earthquakes, it indicates the influence of site effects modifying the ground motion when earthquakes occur well outside of the Santiago basin.

Description: In the frame of the R&D-programme GEOTECHNOLOGIEN thirteen joint interdisciplinary projects have been launched in April 2008. The object of research is the better understanding of the multiple physical and chemical reactions at mineral surfaces. The abstract volume summarizes the scientific results presented during the status seminar at the Johannes Gutenberg University in Mainz, Germany in October 2010.

Description: The lithosphere–asthenosphere boundary (LAB) remains a controversial subject in Earth sciences, and beneath cratonic regions appears to be a particularly difficult boundary to consistently image. Seismic methods give different indicators on the velocity structure of the upper mantle: tomographic models provide estimates of the velocity variations at a variety of lateral scales, but have limited vertical resolution; receiver function techniques provide good indication of the depth to seismic discontinuities, but less information on the absolute velocities. This study assesses whether the different methods give consistent estimates for the depth of the LAB in southern Africa. Using a surface wave dataset with nearly 12,000 paths in the African region, new tomographic models of central and southern Africa are calculated. To show the non-unique nature of tomography, results are presented for two different parameterisations. The models indicate varying velocity structure beneath the cratonic regions of central and southern Africa, which yield estimates of the LAB depth from around 150 km depth in Tanzania, to approximately 200 km depth beneath the Kalahari Craton, down to depths of 225–250 km beneath parts of the Congo. At a broad-scale these depth estimates are compatible with geothermometry from kimberlite xenoliths. In regions such as Tanzania, the kimberlite magmatism is observed to occur along strong horizontal gradients in upper mantle seismic velocity structure — potentially edge features in lithospheric structure. In contrast, a detailed comparison beneath the Kalahari Craton indicates that in this region, and given the present resolution of the tomography, there is no clear link between the kimberlites and velocity gradients. However, in general the kimberlites do not sample the regions of fastest seismic velocities. The relationship between LAB depth estimates from the tomographic modelling and those estimates from receiver functions is not clear. Results from receiver function techniques beneath southern Africa tend to place discontinuities at either shallower (100–150 km), or deeper (300–350 km), depths than the thermally defined LAB estimates. As such, particular care should be taken in automatically associating a discontinuity from fast to slow seismic velocities as the same location as a thermally defined lithosphere–asthenosphere boundary.

Description: Overall goal of this GEOTECHNOLOGIEN project called »The impact of mineral and rock surface topography on colloid retention« is a systematic approach to determine, characterize, and quantify the interaction between rough mineral surfaces and colloidal particles. A previous systematic study using pitted calcite single crystal surfaces yielded results about the general correlation between surface roughness parameters and the efficiency of colloidal retention under electrostically unfavorable conditions (Darbha et al. 2010). Here we present results about (i) the controlled variation of colloidal retention at well-defined, artificial surface structures, (ii) the characterization and quantification of sources and sinks of natural particles in a quasi-closed system that is used as a test site for field experiments, and (iii) the quantitative experimental results about the retention of particles on natural rock surfaces that allows for a predictive approach to natural systems. In detail, the following results are discussed in this report: (i) As an analog to rough mineral surfaces with halfpores in the submicron size, the deposition behavior of latex colloids was studied on a regular pit pattern (pit diameter = 400 nm, pit spacing = 400 nm, pit depth = 100 nm). Effects of hydrodynamics and colloidal interactions in transport and deposition dynamics of a colloidal suspension were investigated in a parallel plate flow chamber. The experiments were conducted at pH ~6.6 under both favorable and unfavorable conditions (in terms of electrostatic forces) using carboxylate functionalized colloids to study the impact of surface topography on particle retention. The influence of particle diameter variation (0.3-2 μm) on retention of monodisperse as well as polydisperse suspensions as a function of flow velocity over a wide range was studied. The impact of surface topography deviations was found to be more significant for smaller colloids (0.3 and 0.43 μm). Larger colloids (1 and 2 μm) beyond a critical velocity of 7 x 10-5 and 3 x 10-6 m/s tend to detach from the surface irrespective of the impact of roughness since drag forces exceed adhesion forces. For polydisperse suspensions, an increase in both polydi- spersity and fluid flow velocity resulted in the decrease of colloid deposition efficiency due to enhanced double layer repulsions. Hematite colloids of quasi-spherical shape with diameters of about 950 nm showed a higher deposition flux compared to spherical latex colloids of equivalent size. These experimental results provide quantitative constraints for the prediction of particle retention as a function of fluid-flow velocity, polydispersity, and particle shape and size. (ii) The investigation of the source (iron sulfidebearing rocks), the processes of particle generation (oxidative weathering, acidic mine water conditions, mine water mixing), the particle transport, and the deposition of particles at water-rock interfaces within the well-defined system of an abandoned alum slate mine enables a first-order approach for balancing of particle retention at rough surfaces in nature. The quantification of particle concentration in the mine outflow as well as the quantification of the deposited material enables an estimation of the kinetics of particles retention within such a system. For comparison, experiments were conducted to get laboratory results about the kinetics of particle retention using substrates with similar ranges of topography variations. (iii) Colloid adsorption experiments at natural rock samples were performed using black slate and micrite limestone as substrates. Micrite samples were etched to obtain variances in surface roughness and topography. Generally, surface steps at grain boundaries are the major cause for the overall roughness variations. A positive correlation between surface roughness of micrite surfaces and the surface-normalized density of adsorbed particles was found. For surface sections 〈 20 μm, a remarkable dispersion of the surface-normalized particle density was found. We conclude that the variance in surface reactivity responsible for the recognized variance in particle deposition is caused by the density of grain boundaries of the rock material. An analog experiment using a grid pattern with varying grid line density confirmed this conclusion: A strong correlation between line density and adsorbed particle density was found. The results presented here show the quantitative impact of surface topography variations on colloid retention under electrostically unfavorable conditions. An important application of these results is their utilization as an input parameter for predictive approaches to the fate of colloids in the environment.

Description: An array of broadband seismometers transecting the Talamanca Range in southern Costa Rica was operated from 2005 until 2007. In combination with data from a short-period network near Quepos in central Costa Rica, this data is analyzed by the receiver function method to image the crustal structure in south-central Costa Rica. Two strong positive signals are seen in the migrated images, interpreted as the Moho (at around 35 km depth) and an intra-crustal discontinuity (15 km depth). A relatively flat crustal and Moho interface underneath the north-east flank of the Talamanca Range can be followed for a lateral distance of about 50 km parallel to the trench, with only slight changes in the overall geometry. Closer to the coast, the topography of the discontinuities shows several features, most notably a deeper Moho underneath the Talamanca Mountain Range and volcanic arc. Under the highest part of the mountain ranges, the Moho reaches a depth of about 50 km, which indicates that the mountain ranges are approximately isostatically compensated. Local deviations from the crustal thickness expected for isostatic equilibrium occur under the active volcanic arc and in south Costa Rica. In the transition region between the active volcanic arc and the Talamanca Range, both the Moho and intracrustal discontinuity appear distorted, possibly related to the southern edge of the active volcanic zone and deformation within the southern part of the Central Costa Rica Deformed Belt. Near the volcanoes Irazu and Turrialba, a shallow converter occurs, correlating with a low-velocity, low-density body seen in tomography and gravimetry. Applying a grid search for the crustal interface depth and vp/vs ratio cannot constrain vp/vs values well, but points to generally low values (〈1.7) in the upper crust. This is consistent with quartz-rich rocks forming the mountain range.

Description: Powdered calcium carbonates from natural sources are being widely used as fillers in adhesive systems to improve processing and in service performance characteristics. The converting of limestone and marble to adhesive filler materials typically includes grinding and in some cases precipitation and coating to adjust particle size, processability and chemical reaction with the adhesive. It has been frequently observed that calcium carbonate powder batches with apparently similar particle-specific characteristics (e. g. density, chemical composition and particle size distribution) may exhibit significantly varying processing properties in terms of their effect on rheology, curing and adhesive performance of the adhesives formulation. This indicates that different calcium carbonates as raw materials for fillers obviously feature intrinsic characteristics which have not yet been identified and examined sufficiently and whose effect on the processing and product characteristics of highly filled reactive adhesive systems is essential to achieve a sufficient level of process stability, batch-to-batch reproducibility and last not least uniform product quality. The aim of this research project therefore is to reveal the structure-property- relationship between the manifold calcium carbonate particle characteristics on one hand and the physicochemical and technical properties of the resulting adhesives formulation on the other hand.

Description: A series of linked marine and land studies have recently targeted the Sumatra subduction zone, focusing on the 2004 and 2005 plate boundary earthquake ruptures in Indonesia. A collaborative research effort by scientists from the United Kingdom (UK Sumatra Consortium), Indonesia, United States, France, and Germany is focusing on imaging the crustal structure of the margin to examine controls on along-strike and updip earthquake rupture propagation. The fundamental science objective is to examine how margin architecture and properties control earthquake rupture location and propagation.

Description: In the past two decades, the behavior of lithium (Li) isotopes has been studied in various marine systems, including mid-ocean ridge and sediment-hosted hydrothermal systems, subduction zone settings and normal coastal and deep-sea sediments recovered by the Ocean Drilling Program (ODP). Major processes identified to cause deviations from the seawater isotopic composition are adsorption/desorption reactions, formation and transformation of silicate minerals, and leaching of Li from sediments or underlying crust at high temperature. As a result of the accomplished work, Li isotopes are considered a promising tracer for the diagenetic evolution and provenance of pore fluids in overpressured sedimentary environments. Here, we present Li concentration and isotope data of 18 cold seep locations and reference fluids from shallow marine sediments, a sediment-hosted hydrothermal system and two Mediterranean brine basins. The new reference data and literature data of hydrothermal fluids and pore fluids from the ODP follow an empirical relationship reflecting increasing Li release and decreasing isotope fractionation during clay mineral authigenesis with increasing temperature. Lithium concentration and isotope data of cold seep fluids are mostly in agreement with this empirical relationship. Ubiquitous diagenetic signals of clay dehydration in all cold seep fluids indicate that authigenic smectite-illite is an important sink for light pore water Li in deeply buried continental margin sediments. Deviations from the general relationship are attributed to the varying proportion of weatherable (e.g. volcanogenic) components and to transport-related fractionation trends. A simple transport-reaction model was applied to simulate Li isotope fractionation during upwelling of pore fluids to the seafloor. It is demonstrated that slow pore water advection (order of mm a-1) suffices to convey much of the deep-seated diagenetic Li signal into shallow sediments. If carefully applied, Li isotope systematics may, thus, provide a valuable record of fluid/mineral interaction that has been inherited several hundreds or thousands of meters below the seafloor.

Description: Microbial biofilms are an extremely successful way of life. Bacteria and fungi benefit in this symbiotic life form of metabolic exchange, protection and genetic flexibility. They produce a matrix of organic molecules in which they are embedded and which offers new habitats to other organisms, such as other bacteria or fungi. Biofilms cannot be avoided to colonize surfaces in unsterile habitats. So, they can be found everywhere in nature and in technical systems, but they play an ambivalent role. On the one hand biofilms are essential to degrade and transform water contaminations, but on the other hand they can diminish product qualities and damage capital equipment. Biofilms can cover medical equipment such as catheters and pathogenic bacteria, which may be living in the biofilms, are a continuous source of infection of the patients. In addition, the metabolism of the biofilm microorganisms may change the composition of the fluids or contaminate them with their products. As biofilms are all-round, the understanding of the biofilm formation and its manipulation are of prime importance in microbiology and material sciences. The choice of a material and the corresponding surface properties like mechanical properties, structure, polarity, and chemistry influence the binding of various molecules and cells. The surface properties affect the biocompatibility of a material and consequently also bacterial adhesion, and biofilm growth. In this project hydrophobins are used as a novel modification of surfaces to change surface properties like hydrophobicity and thus might have an effect on biofilm formation. Hydrophobins are fungal proteins, which selfassemble on hydrophobic as well as hydrophilic surfaces into extremely stable monolayers. Recombinant hydrophobins provide the opportunity to use these highly surface-active proteins for large-scale surface coatings. Hydrophobins are non-toxic and can be used for surface modification and functionalization (with e.g. enzymes) of industrial relevant materials like steel, plastics, and ceramics. In this project hydrophobin coated surfaces and their properties are studied with respect to bacterial cell adhesion, cell differentiation, and cellular growth with the aim to influence biofilm formation. In the first part of the project recombinant hydrophobins were produced and purified. Different surfaces were coated with hydrophobins and characterized, since the coating efficiency is the basis for subsequent biofilm formation studies. Biofilms were grown on natural as well as hydrophobin coated surfaces and different methods were established to analyse biofilm formation. Since the hydrophobin coated surfaces did not reduce microbial growth, we designed modified fusion hydrophobins and attached cationic antimicrobial peptides (AMPs) to the hydrophobins.

Description: We present and discuss a set of 77 moment tensor solutions for earthquakes in the Iberia–Maghreb region from mid 2005 to the end of 2008, with moment magnitudes ranging from 3.2 to 6.0. Inversion is based upon full, three-component, intermediate period waveforms recorded at regional seismic broadband stations. Following the recent densification of permanent broadband networks and large scale temporary deployments, at present more than 150 stations are recording in Spain, Portugal and Morocco. This unprecedented station density allows analysis of small events from available short-distance recordings, and in general leads to more reliable source estimates due to data redundancies that permit elimination of waveforms affected by noise or complicated propagation effects. The solutions for 2005–2008 constitute an important upgrade of the Iberia–Maghreb moment tensor inventory to 225 solutions to date, enhancing the image of seismotectonics at the compressive N-Algerian margin, in the Betic–Alboran shear zone and at the transpressive SW-Iberian margin, as well as providing valuable constraints on seismic deformation in the western Betics and the Iberian foreland where little information has been previously available. New solutions for the foreland and three recent seismic series in the western Betics show strike-slip and reverse faulting style, contrasting with the dominance of normal faulting in the adjacent areas towards east. In these areas, as well as at the SW-Iberian margin, faulting orientations are heterogeneous, including solutions with opposite kinematics. This indicates control by local stress conditions, and points to fault interaction. Along the N-Algerian margin, a counterclockwise rotation of slip vectors of thrust events from east to west becomes apparent. Several solutions for the area offshore Cape St. Vincent are located at sub-Moho depths between 40 and 60 km, supporting a large brittle layer thickness in the oceanic lithosphere.

Description: The transformation of ferrihydrite (5Fe(2)O(3)center dot 9H(2)O) to hematite (alpha-Fe2O3) under alkaline condition in the presence and absence of lead was for the first time investigated using in situ, time-resolved synchrotron-based energy dispersive X-ray diffraction combined with off-line chemical characterization and imaging. The results showed that the crystallization of hematite occurred via a two-stage process with goethite (alpha-FeOOH) as an intermediate phase. The presence of lead enhanced the formation of hematite and reduced the induction times (similar to 20-30%) but had little effect on the mechanism of the transformation reactions. The reaction rates for the two systems (with and without lead) ranged from 12 to 259 x 10(-4) s(-1) and 19 to 461 x 10(-5) s(-1) for the first and second stage, respectively. The activation energies of nucleation of the two systems were 16(+/- 3) and 9(+/- 2) kJ/mol, while the activation energies for crystallization ranged from 41(+/- 7) to 77(+/- 14) kJ/mol. During the hematite crystallization, the majority of the lead in the system was rapidly and irreversibly incorporated into the final hematite, while only minor amounts of lead were released back into solution.

Description: Ambient noise tomography is applied to the significant data resources now available across Tibet and surrounding regions to produce Rayleigh wave phase speed maps at periods between 6 and 50 s. Data resources include the permanent Federation of Digital Seismographic Networks, five temporary U.S. Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL) experiments in and around Tibet, and Chinese provincial networks surrounding Tibet from 2003 to 2009, totaling ∼600 stations and ∼150,000 interstation paths. With such a heterogeneous data set, data quality control is of utmost importance. We apply conservative data quality control criteria to accept between ∼5000 and ∼45,000 measurements as a function of period, which produce a lateral resolution between 100 and 200 km across most of the Tibetan Plateau and adjacent regions to the east. Misfits to the accepted measurements among PASSCAL stations and among Chinese stations are similar, with a standard deviation of ∼1.7 s, which indicates that the final dispersion measurements from Chinese and PASSCAL stations are of similar quality. Phase velocities across the Tibetan Plateau are lower, on average, than those in the surrounding nonbasin regions. Phase velocities in northern Tibet are lower than those in southern Tibet, perhaps implying different spatial and temporal variations in the way the high elevations of the plateau are created and maintained. At short periods (〈20 s), very low phase velocities are imaged in the major basins, including the Tarim, Qaidam, Junggar, and Sichuan basins, and in the Ordos Block. At intermediate and long periods (〉20 s), very high velocities are imaged in the Tarim Basin, the Ordos Block, and the Sichuan Basin. These phase velocity dispersion maps provide information needed to construct a 3-D shear velocity model of the crust across the Tibetan Plateau and surrounding regions.

Description: This volume contains 23 short papers which summarise the main subjects of talks and posters presented at the eighth TRACE (Tree Rings in Archaeology, Climatology and Ecology) conference organized by Jožica Gričar, Tom Levanič, Špela Jagodic, Robert Krajnc and Polona Hafner and held in Otočec, Slovenia on April 16th - 19th, 2009.

Description: The tectonic context of south-east Asia is dominated by subduction. One such major convergent boundary is the Java-Sunda trench, where the Australian–Indian plates are being subducted beneath the Eurasian plate. We measure shear-wave splitting in local and teleseismic data from 12 broadband stations across Sumatra and Java to study the anisotropic characteristics of this subduction system, which can provide important constraints on dynamical processes involved. Splitting in -waves from local earthquakes between 75 and 300 km deep show roughly trench parallel fast directions, and with time-lags 0.1–1.3 s (92% 0.6 s). Splitting from deeper local events and SKS, however, shows larger time-lags (0.8–2.0 s) and significant variation in fast direction. In order to infer patterns of deformation in the slab we apply a hybrid modelling scheme. We raytrace through an isotropic subduction zone velocity model, obtaining event to station raypaths in the upper mantle. We then apply appropriately rotated olivine elastic constants to various parts of the subduction zone, and predict the shear-wave splitting accrued along the raypath. Finally, we perform grid searches for orientation of deformation, and attempt to minimise the misfit between predicted and observed shear-wave splitting. Splitting from the shallow local events is best explained by anisotropy confined to a 40 km over-riding plate with horizontal, trench parallel deformation. However, in order to explain the larger lag times from SKS and deeper events, we must consider an additional region of seismic anisotropy in or around the slab. The slab geometry in the model is constrained by seismicity and regional tomography models, and many SKS raypaths travel large distances within the slab. Models placing anisotropy in the slab produce smaller misfits than those with anisotropy outside for most stations. There is a strong indication that inferred flow directions are different for sub-Sumatran stations than for sub-Javanese, with 〉60 change over 375 km. The former appear aligned with the subduction plate motion, whereas the latter are closer to perpendicular, parallel to the trench direction. There are significant differences between the slab being subducted beneath Sumatra, and that beneath Java: age of seafloor, maximum depth of seismicity, relative strength of the bulk sound and shear-wave velocity anomaly and location of volcanic front all vary along the trench. We speculate, therefore, that the anisotropy may be a fossilised signature rather than due to contemporary dynamics.

Description: RECAWA intends to develop a fundamental understanding of the reactivity and dynamics of calcite surfaces during crystal growth in aquatic systems. Therefore, the calcite-water surface has been characterised at different hydrochemical conditions and surface diffraction measurements have been applied to probe if changes in zeta potential are accompanied by changes in the calcite-water interface structure. The interaction of calcite with Selenium is investigated in a mixed flow reactor (MFR) study which is accompanied by GI- EXAFS analyses to characterize the Se adsorption species. The interaction of calcite surfaces with phosphate and phosphonates is the focus of two subprojects. The sorption/precipitation mechanisms of PO43- and HPO32+, respectively, on different calcite powders (precipitated calcium carbonates and limestone powders) are investigated to determine sorption isotherms and phase transformations on the applied surfaces which is of great interest with regard to phosphate recycling and/or water treatment. Analytical work includes SEM, XRD and XAFS spectroscopy for a detailed characterisation of the calcite powders in different sections of the isotherms. Experimental investigations on the interaction of limestone powder and two superplasticizers have been conducted with regard to concreting. These experiments were done at alkaline conditions and lead to massive reactions and changes in the zeta potential of the solutions and limestone powder when superplasticizers added. Additional results of quantum-mechanical calculations and force-field modelling demonstrated that the Double Defect Method is able to quantitatively predict mixing properties of various isostructural binary and ternary carbonate solid solutions. In particular, low equilibrium retention levels of SO42- and SeO42- in carbonates imply that the reasonably large concentrations SO42- and SeO42- in carbonates reported in previous studies should be attributed to non-equilibrium entrapment effects. Data obtained from atomistic modelling complement our data determined using lab methods. Further experimental and analytical, work including in-situ AFM studies using Iceland spar single crystals, is in progress and will help to interconnect the present results of the sub-projects.

Description: Various concepts for future satellite-gravimetric missions are investigated within the German joint research project »Concepts for future gravity field satellite missions«, funded by the German Geotechnologies program »Observation of the Earth system from space« of the German Federal Ministry of Education and Research (BMBF). One of the project goals is to define and assess different scenarios of satellite formation flight (SFF) configurations by implementing full-scale simulations. To this end, we create simulated measurements for these satellite configurations, compute and assess closed-loop results and finally optimize the mean and time-varying gravity field determination in terms of spatio-temporal resolution and error isotropy. Our full-scale simulations are performed using the software system GROOPS (Gravity field Recovery Object-Oriented Programming System) developed in the Group of Astronomical, Physical and Mathematical Geodesy at the Institute of Geodesy and Geoinformation (APMG-IGG) at Bonn University. Our results are used in the joint project for developing concepts and designs required for the next generation (i.e. after CHAMP, GRA CE and GOCE) of future satellite gravity missions.

Description: The main goal of the REAL-GOCE WP320 is the computation of a high-resolution gravity field model up to degree and order 720 or higher in terms of spherical harmonics with a global coverage and an outstanding quality. Compared to the recently available combined gravity field models like EIGEN-5C (Förste et al. 2008), EIGEN-51C (Bruisma et al 2010), EGM 2008 (Pavlis et al. 2008) or GGM03C (Tapley et al. 2007), such a combined model including GOCE data should benefit from the accuracy of the new GOCE satellite gradiometry data in the medium wavelength components (i.e. spatial resolution between about 70 and 100 km) of the Earth’s gravity field. Since July 2010 a first cycle (i.e. about two months) of GOCE gradiometry data is available. Additionally, the first GOCE-only global gravity field models were published by ESA. One of these first GOCE-only models has been computed by GFZ Potsdam and GRGS Toulouse within ESA’s GOCE High Level Processing Facility (GOCE-HPF) by using the so-called direct approach. This model is called GO_CONS_GCF_2_DIR (Bruinsma et al. 2010; Pail et al. 2010) and its data has been used by GFZ within the REAL-GOCE WP320 to compute a preliminary GRACE/GOCE combined satellite-only model. This is an important milestone for the further computation of a combined model including terrestrial data.

Description: The ionosphere is a part of the upper atmosphere stretching from a height of about 60 km to more than 1 000 km. A certain fraction of the gas particles in that region is ionised by solar extreme ultra violet radiation. Since electromagnetic waves are influenced and significantly modified by ionospheric free charge carriers, the altitude range is of great scientific interest. GPS satellites emit electromagnetic waves on L – band frequencies travelling through the ionosphere and lower neutral atmosphere. Subsequently, they are received by low–Earth orbiting satellites. Consequently, the signals are affected by strong electron density gradients at altitudes above approximately 80km and by atmospheric density, pressure and water vapour content in the troposphere and stratosphere. This measurement method is termed radio occultation technique and it allows to receive a global picture of ionospheric and lower neutral atmospheric conditions. This study focusses on the detection and analysis of sporadic E layers from GPS radio occultation measurements on a global scale. Sporadic E layers are localised patches of relatively high electron density appearing in the E region of the ionosphere. They are represented in GPS signals as intense fluctuations. This work reveals that global sporadic E occurrence rates underlie variations on different time scales. It is demonstrated that the sporadic E occurrence depends on several geophysical parameters and it is subject to coupling processes between the neutral atmosphere and ionosphere. For example, the global sporadic E occurrence is oriented along Earth’s magnetic field. It is shown additionally that sporadic E altitudes are subject to tidal winds and that its annual cycle varies with meteor influx.

Description: The combined project »Early Warning System Transport«, funded by Bundesministerium für Bildung und Forschung (BMBF) and Deutsche Forschungsgemeinschaft (DFG), is looking for realizing the architecture of a warning system for earthquakes using different functional blocks. In one block sensors and their connection to the transport infrastructure play a major role which is described in this contribution. The following section 1.2 gives an overview about the amplitude of sensor signals which may be excited through earthquakes and which will be contrasted in section 1.3 to the comparatively high magnitude of such signals which are to be expected adjacent to the track during train operations and due to temperature.

Description: The magnitude-8.8 Maule (Chile) earthquake of 27 February 2010 ruptured a segment of the Andean subduction zone megathrust that has been suspected to be of high seismic potential1,2,3,4,5,6. It is the largest earthquake to rupture a mature seismic gap in a subduction zone that has been monitored with a dense space-geodetic network before the event. This provides an image of the pre-seismically locked state of the plate interface of unprecedentedly high resolution, allowing for an assessment of the spatial correlation of interseismic locking with coseismic slip. Pre-seismic locking might be used to anticipate future ruptures in many seismic gaps6,7,8,9,10,11,12, given the fundamental assumption that locking and slip are similar. This hypothesis, however, could not be tested without the occurrence of the first gap-filling earthquake. Here we show evidence that the 2010 Maule earthquake slip distribution correlates closely with the patchwork of interseismic locking distribution as derived by inversion of global positioning system (GPS) observations during the previous decade. The earthquake nucleated in a region of high locking gradient and released most of the stresses accumulated in the area since the last major event in 1835. Two regions of high seismic slip (asperities) appeared to be nearly fully locked before the earthquake. Between these asperities, the rupture bridged a zone that was creeping interseismically with consistently low coseismic slip. The rupture stopped in areas that were highly locked before the earthquake but where pre-stress had been significantly reduced by overlapping twentieth-century earthquakes. Our work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future great earthquakes, which thus might be anticipated by geodetic observations.

Description: We present new shear-wave splitting measurements performed at 16 stations on the East European Craton, and discuss their implications in terms of upper-mantle anisotropy for this geophysically poorly-known region. Previous investigations of mantle anisotropy in Central Europe have shown fast directions aligning smoothly with the craton's margin and various suggestions have been proposed to explain their origin such as asthenospheric flow or lithospheric frozen-in deformation. Here, we aim at investigating the continuation of this shear-wave splitting pattern further to the East, into the East European Craton. For the craton, the interpretation appears to be less ambiguous than for central Europe since several arguments support lithospheric anisotropy in this region: 1) The large-scale coherence within either of the four constituting blocks and the significant variations between the blocks on a small-scale, 2) the weak correlation with absolute plate motion vectors, and 3) the good correlation between anisotropy and crustal features, for which we use magnetic field alignments as a proxy. Rather good correlation of these magnetic features with seismic fast orientations strongly supports the idea of vertically coherent deformation throughout upper mantle and crust. The observed splitting orientations thus reflect the last tectonic events of each block, frozen-in into the lithosphere for hundreds of millions of years.

Description: The adhesive properties of smectites are widely used in many industrial applications. These pro- perties are mainly due to the reversible expansion and contraction of their interlayer spaces as a function of water activity. Being part of moulding sands, smectites are responsible for the required mechanical strength of moulds. Due to the need of industry for castings of increasing complexity but decreasing weight, it becomes essential to tailor moulding-sand mixtures beyond their current abilities. So far, however, it has not been discovered in detail why changes occurring during the casting process are partially reversible in the laboratory, but not in the circuit of the moulding sands. In general at temperatures below 300 °C and in the laboratory, de- and rehydration are reversible processes. It is therefore important to understand the complex kinetics of de- and rehydration of smectites and their influence on the mechanical behaviour of the moulding sands, before improvements can be achieved. Smectites are also widely used as adsorbents, e.g., for water. Lower water adsorption capacities and reduced adsorption rates of industrially-dried bentonites compared with bentonites dried to the same water content in the laboratory show that the kinetics of drying apparently influences interface processes. Smectites exposed to hot water vapour do not fully rehydrate in contrast to dry-heated smectites, which is another important aspect. Due to contact angle measurements, increasing hydrophobicity could be observed after vapour treatment, which, however, might depend on physical changes of aggregation (pore volume). Nevertheless, other parameters such as CEC or X-ray diffraction patterns of the 00l- reflexes did not show any conspicuous changes. Initial investigations led to the assumption that coordination of Al3+-Ions can be made responsible for these processes. However this has to be confirmed. Not only the hydration energy of the cations, but also size and charge as well as the water to smectite ratio, achievement/attainment of dispersion, speed of drying and further variables have an influence on the dynamics of dehydration (and possibly rehydration). The objective of the current project is the detailed examination of the aforementioned basic mechanisms from atomic to industrial scale in order to understand them as well as to optimize the casting processes. The following is a summary of the experiments and first interpretations of the results carried out by the project partners.

Description: For the first time, ambient noise tomography is used to clearly image the magma chamber beneath Lake Toba caldera, one of the largest Quaternary calderas on Earth. Using data from 40 seismic stations deployed between May and October 2008 around Lake Toba, empirical Green's functions are extracted from long term cross-correlations of continuous records. These functions are dominated by Rayleigh waves, whose group velocities can be measured in the period range from 2.5 to 12 seconds. Arrival times of these waves are picked for a given period and inverted using 2-D tomography to calculate lateral variations in velocity for the given period. This was done for six different periods, which all correspond to different sampling depths. Thus the six 2-D models presented together provide information on velocity variations with depth. The results show a low-velocity body coincident with the Lake Toba caldera, representing the magma chamber under the volcano. The chamber is observed to have a complex 3-D geometry, with at least two separate sub-chambers underlying the caldera. Other results include a deep low velocity body, possibly another magma chamber, south west of the lake with an upper limit of ∼7 km depth. The maximum depth to which this body reaches could not be resolved. The Sumatra Fault marks a velocity contrast, but only down to depths not greater than 5 km. The reliability of the results was further confirmed by checkerboard recovery tests.

Description: The Hawaiian Islands are the canonical example of an age-progressive island chain, formed by volcanism long thought to be fed from a hotspot source that is more or less fixed in the mantle. Geophysical data, however, have so far yielded contradictory evidence on subsurface structure. The substantial bathymetric swell is supportive of an anomalously hot upper mantle, yet seafloor heat flow in the region does not appear to be enhanced. The accumulation of magma beneath pre-existing crust (magmatic underplating) has been suggested to add chemical buoyancy to the swell, but to date the presence of underplating has been constrained only by local active-source experiments. In this study, teleseismic receiver functions derived from seismic events recorded during the PLUME project were analysed to obtain a regional map of crustal structure for the Hawaiian Swell. This method yields results that compare favourably with those from previous studies, but permits a much broader view than possible with active-source seismic experiments. Our results indicate that the crustal structure of the Hawaiian Islands is quite complicated and does not conform to the standard model of sills fed from a central source. We find that a shallow P-to-s conversion, previously hypothesized to result from the volcano-sediment interface, corresponds more closely to the boundary between subaerial and subaqueous extrusive material. Correlation between uplifted bathymetry at ocean-bottom-seismometer locations and presence of underplating suggests that much of the Hawaiian Swell is underplated, whereas a lack of underplating beneath the moat surrounding the island of Hawaii suggests that underplated crust outward of the moat has been fed from below by dykes through the lithosphere rather than by sills spreading from the island centre. Local differences in underplating may reflect focusing of magma-filled dykes in response to stress from volcanic loading. Finally, widespread underplating adds chemical buoyancy to the swell, reducing the amplitude of a mantle thermal anomaly needed to match bathymetry and supporting observations of normal heat flow.

Description: Western Anatolian lithosphere comprises several sutures and major continental fragments with Laurasian and Gondwanan affinities, assembled prior the Oligocene. One of the major tectonic features shaping its structure is the Menderes metamorphic massif, which consists of several assembled and imbricated terrains exhumed by the Late Miocene during the extension that affected the entire Aegean province. A predominant opinion is that the Menderes is a core complex delineated by low-angle detachment faults. An alternative explanation associates it with shallow subduction of Neotethyan oceanic lithosphere that was later delaminated. To distinguish between these possibilities, direct evidence from the Western Anatolian mantle lithosphere would be ideal, because of the compositional differences of the continental and oceanic mantle lithosphere. In the absence of mantle xenoliths, mantle-derived volcanics and their macrocrystal populations, offer the only information about the composition of the mantle-lithosphere under the Menderes.

Description: The actively spreading Chile Ridge has been subducting beneath Patagonian Chile since the Middle Miocene. After subduction, continued separation of the faster Nazca plate from the slow Antarctic plate has opened up a gap—a slab window—between the subducted oceanic lithospheres beneath South America. We examined the form of the asthenospheric mantle flow in the vicinity of this slab window using S waves from six isolated, unusual 2007 earthquakes that occurred in the generally low-seismicity region just north of the ridge subduction region. The S waves from these earthquakes were recorded at distant seismic stations, but were split into fast and slow orthogonally polarized waves at upper mantle depths during their passage through the slab window and environs. We isolated the directions of fast split shear waves near the slab window by correcting for upper mantle seismic anisotropy at the distant stations. The results show that the generally trench-parallel upper mantle flow beneath the Nazca plate rotates to an ENE trend in the neighborhood of the slab gap, consistent with upper mantle flow from west to east through the slab window.

Description: We investigate microseismic activity at the convergent plate boundary of the Hellenic subduction zone on- and offshore south-eastern Crete with unprecedented precision using recordings from an amphibian seismic network. The network configuration consisted of up to eight ocean bottom seismometers as well as five temporary short-period and six permanent broadband stations on Crete and surrounding islands. More than 2,500 local and regional events with magnitudes up to M L = 4.5 were recorded during the time period July 2003–June 2004. The magnitude of completeness varies between 1.5 on Crete and adjacent areas and increases to 2.5 in the vicinity of the Strabo trench 100 km south of Crete. Tests with different localization schemes and velocity models showed that the best results were obtained from a probabilistic earthquake localization using a 1-D velocity model and corresponding station corrections obtained by simultaneous inversion. Most of the seismic activity is located offshore of central and eastern Crete and interpreted to be associated with the intracrustal graben system (Ptolemy and Pliny trenches). Furthermore, a significant portion of events represents interplate seismicity along the NNE-ward dipping plate interface. The concentration of seismicity along the Ptolemy and Pliny trenches extends from shallow depths down to the plate interface and indicates active movement. We propose that both trenches form transtensional structures within the Aegean plate. The Aegean continental crust between these two trenches is interpreted as a forearc sliver as it exhibits only low microseismic activity during the observation period and little or no internal deformation. Interplate seismicity between the Aegean and African plates forms a 100-km wide zone along dip from the Strabo trench in the south to the southern shore-line of Crete in the north. The seismicity at the plate contact is randomly distributed and no indications for locked zones were observed. The plate contact below and north of Crete shows no microseismic activity and seems to be decoupled. The crustal seismicity of the Aegean plate in this area is generally confined to the upper 20 km in agreement with the idea of a ductile deformation of the lower crust caused by a rapid return flow of metamorphic rocks that spread out below the forearc. In the region of the Messara half-graben at the south coast of central Crete, a southward dipping seismogenic structure is found that coalesces with the seismicity of the Ptolemy trench at a depth of about 20 km. The accretionary prism south of Crete indicated by the Mediterranean Ridge showed no seismic activity during the observation period and seems to be deforming aseismically.