Rhine Graben Research Articles

Life cycle assessment of Organic Rankine Cycles for geothermal power generation considering low-GWP working fluids

In this study, a life cycle assessment (LCA) for geothermal power generation by binary power plants is carried out. The selected case scenarios are based on representative geothermal conditions in Germany. For this purpose, subcritical one-stage and two-stage Organic Rankine Cycle (ORC) power systems as well as supercritical cycles are considered. The LCA evaluates potential power plant concepts under consideration of working fluid losses and the associated environmental impact. Due to the restrictive regulations by the European Union for the use of fluorinated refrigerants, a special focus is laid on the evaluation of so-called low-GWP working fluids in ORC systems. In particular, the substitution of R245fa and R134a by working fluids like R1233zd and R1234yf or natural hydrocarbons is examined by a second law analysis. In addition, the environmental impact of the considered power plant concepts is calculated. The results show that the investigated low-GWP fluids lead to equivalent second law efficiency and significant lower environmental impact in comparison to common fluorinated working fluids. In case of a low-temperature heat source, the second law efficiency decreases by 2% and the global warming impact of the ORC is reduced by 78% by using R1233zd as a working fluid instead of R245fa. For the supercritical cycle with R1234yf an efficiency increase of 37% and also a significant decrease of the CO2-equivalent is obtained. For geothermal conditions with higher temperatures of the geothermal fluid and a limitation of the reinjection temperature, like in the Upper Rhine Rift Valley, the considered optimization approaches lead to an efficiency increase of up to 7%. In this context, the concept of a two-stage ORC is favorable. Compared to a subcritical one-stage system with R245fa as a working fluid, the two-stage ORC with R1233zd leads to 2% higher exergetic efficiency and a reduction of the global warming impact from 78gCO2/kWhe to 13gCO2/kWhe.

Evidence for an independent third Usutu virus introduction into Germany

Usutu virus (USUV) is an arbovirus within the genus flavivirus, which was first introduced to Southern Europe approximately twenty years ago causing epizootics among wild and captive birds. In Germany USUV was initially discovered in wild birds, mainly Common blackbirds (Turdus merula), in the Upper Rhine valley in southwest of the country in 2011 and has not spread much northwards since. Phylogenetic analyses revealed that the still ongoing USUV epidemic is caused by two different USUV strains, USUV-Germany belonging to the USUV Europe 3 lineage and USUV-Bonn belonging to the USUV Africa 3 lineage. The two strains were introduced independently.In August 2015 a new USUV strain, named USUV-Berlin, was isolated in Vero cells from two carcasses of juvenile Great grey owls (Strix nebulosa) kept in the Zoological Garden Berlin, which had suffered from a hyperacute fatal systemic infection. Both owls carried high USUV genome loads. Full-length USUV genomes sequences were determined and phylogenetic analysis demonstrated a close relationship with a Spanish mosquito-derived sequence from 2006. Immunohistochemical antigen detection in organ samples of the owls showed the typical USUV infection patterns.According to the phylogenetic analysis, USUV-Berlin belongs to the Africa 2 lineage, and can thus be distinguished from the other strains circulating in Germany. Repeated findings of different USUV strains suggest more frequent introductions into Central Europe and a higher mobility of this virus than assumed to date.

An overview on source rocks and the petroleum system of the central Upper Rhine Graben

The petroleum system of the Upper Rhine Graben (URG) comprises multiple reservoir rocks and four major oil families, which are represented by four distinct source rock intervals. Based on geochemical analyses of new oil samples and as a review of chemical parameter of former oil fields, numerous new oil–source rock correlations were obtained. The asymmetric graben resulted in complex migration pathways with several mixed oils as well as migration from source rocks into significantly older stratigraphic units. Oldest oils originated from Liassic black shales with the Posidonia Shale as main source rock (oil family C). Bituminous shales of the Arietenkalk-Fm. (Lias α) show also significant source rock potential representing the second major source rock interval of the Liassic sequence. Within the Tertiary sequence several source rock intervals occur. Early Tertiary coaly shales generated high wax oils that accumulated in several Tertiary as well as Mesozoic reservoirs (oil family B). The Rupelian Fish Shale acted as important source rock, especially in the northern URG (oil family D). Furthermore, early mature oils from the evaporitic-salinar Corbicula- and Lower Hydrobienschichten occur especially in the area of the Heidelberg-Mannheim-Graben (oil family A). An overview on potential source rocks in the URG is presented including the first detailed geochemical source rock characterization of Middle Eocene sediments (equivalents to the Bouxwiller-Fm.). At the base of this formation a partly very prominent sapropelic coal layer or coaly shale occurs. TOC values of 20–32 % (cuttings) and Hydrogen Index (HI) values up to 640–760 mg HC/g TOC indicate an extraordinary high source rock potential, but a highly variable lateral distribution in terms of thickness and source rock facies is also supposed. First bulk kinetic data of the sapropelic Middle Eocene coal and a coaly layer of the ‘Lymnaenmergel’ are presented and indicate oil-prone organic matter characterized by low activation energies. These sediments are considered as most important source rocks of numerous high wax oils (oil family B) in addition to the coaly source rocks from the (Lower) Pechelbronn-Schichten (Late Eocene). Migration pathways are significantly influenced by the early graben evolution. A major erosion period occurred during the latest Cretaceous. The uplift center was located in the northern URG area, resulting in SSE dipping Mesozoic strata in the central URG. During Middle Eocene times a second uplift center in the Eifel area resulted in SW-NE-directed shore lines in the central URG and contemporaneous south-southeastern depocenters during marine transgression from the south. This structural setting resulted in a major NNW-NW-directed and topography-driven migration pattern for expelled Liassic oil in the fractured Mesozoic subcrop below sealing Dogger α clays and basal Tertiary marls.

The Late Variscan control on the location and asymmetry of the Upper Rhine Graben

The NNE-trending Upper Rhine Graben (URG) of the European Cenozoic Rift System developed from c. 47 Ma onwards in response to changing lithospheric stresses in the northwestern foreland of the Alps. The composite graben structure consists of three segments, each c. 100 km long and 30–40 km wide, but flares to c. 60 km near its southern and to c. 80 km near its northern termination. Normal faulting induced a total extension of 5–8 km of the 1–2 km thick Mesozoic sedimentary Franconian platform and underlying Variscan basement rocks. However, distribution of an up to 3.5 km thick sedimentary graben fill and cumulative displacements near Eastern and Western Main Border fault systems suggest that subsidence of the graben floor and shoulder uplift created strong cross-sectional asymmetries. Cumulative W-down displacements >3 km along strongly segmented transfer faults in the east contrast with E-down displacements 600 km long zone that delimits the trailing edge of a SW-moving lithospheric block. In the URG area, NE–SW-oriented seismic anisotropy at sublithospheric depths of c. 60–80 km suggest active mantle flow in this direction as a possible driving force for the reactivation of pre-graben lithospheric shear zones.

Étude archéométallurgique de parures hallstattiennes en alliage cuivreux du Rhin supérieur

La vallée du Rhin supérieur se distingue, au premier âge du Fer, par une production métallique caractéristique ; la présente étude a pour objectif d’en approfondir la définition, en complétant l’analyse des formes par celle des traditions métallurgiques. Elle vise également à combler un déficit de la recherche sur les alliages cuivreux, où l’âge du Fer est encore faiblement représenté. Un corpus de parures de types régionaux a été sélectionné (bracelets de type Bade-Alsace, parures annulaires massives de section circulaire, fermées et lisses), couvrant une large période allant du Ha C2 au Ha D3, soit du viie au milieu du ve siècle avant notre ère. Le protocole est basé sur l’étude macroscopique des parures et l’analyse de leur composition élémentaire, avec pour objectif d’établir différents types de composition chimique et d’en proposer une interprétation archéologique. Les analyses ont été réalisées au Centre de recherche et de restauration des musées de France (C2RMF) à l’aide de la méthode PIXE, principalement sur des prélèvements faits dans les parties saines des parures. Les résultats montrent de nettes différences de composition chimique selon la typologie ; les bracelets de type Bade-Alsace sont ainsi réalisés suivant la recette classique du bronze à l’étain et montrent une variation du spectre d’impuretés qui dépend principalement de la forme du bracelet (variantes A1, B1 et B2). À l’inverse, de nombreuses parures fermées lisses possèdent un taux élevé de plomb, allant jusqu’à 36 %. Ce phénomène pose la question des raisons qui motivent cette forte présence du plomb dans l’alliage ; un rôle plus économique que technique peut être invoqué, avec une volonté d’augmenter la masse globale de métal par l’adjonction de plomb au bronze recyclé. La pratique des bronzes au plomb trouverait ici pour explication l’appauvrissement des stocks de matière première, et traduirait ainsi des changements profonds dans les dynamiques économiques, touchant plus particulièrement aux ressources disponibles. L’analyse est complétée par la recherche des compositions jumelles, qui correspondent à des objets présentant une composition chimique identique. La mise en évidence de jumeaux de lingot et de creuset permet de proposer l’existence de liens d’ordre technologique entre certaines pièces, qui appartiennent parfois à des ensembles ou à des sites différents. Leur distribution dans l’ensemble du Rhin supérieur, autant sur ses deux rives que dans ses parties nord et sud, atteste l’existence d’un réseau de relations soutenues entre les artisans et la population. L’homogénéité des traditions métallurgiques va ainsi de pair avec celle de la typologie, ajoutant à la cohésion déjà forte de la culture matérielle du Rhin supérieur.

Upper Pleistocene blow flies (Diptera: Calliphoridae) trapped in fossilized crania of large mammals discovered from gravel pits in the Rhine rift valley from Hesse (Germany)

Upper Pleistocene blow flies (Diptera: Calliphoridae) trapped in fossilized crania of large mammals discovered from gravel pits in the Rhine rift valley from Hesse (Germany)

Provenance of Palaeo‐Rhine sediments from zircon thermochronology, geochemistry, U/Pb dating and heavy mineral assemblages

AbstractSediments deposited in the Late Cenozoic basins of the Central European Rift System, including the Upper Rhine Graben (URG) and the Lower Rhine Embayment (LRE), document the drastic extension of the Rhine's catchment towards the Central Alps in the Late Pliocene by distinct heavy mineral assemblages. This outstanding change in principal sediment sources should be accompanied by a change towards distinctly younger (i.e. Tertiary) detrital mineral cooling ages. Therefore, it provides a particularly well‐suited framework to explore the thermochronological provenance record in relation to heavy mineral assemblages. In this multi‐proxy approach we (i) exploit and elaborate detrital zircon (U–Th)/He thermochronology (ZHe) for sediment provenance surveys, (ii) document shortcomings if only a single geochronological method is employed, and (iii) obtain tighter constraints on the sources of Paleo‐Rhine sediments. Our results are based on Pliocene and Pleistocene sediment samples from the northern URG (drill core Ludwigshafen P36) and the LRE (lignite mine Hambach). In a Late Pliocene URG sample, Variscan and Permo‐Triassic cooling ages dominate the age spectra of the ZHe and Zircon fission track (ZFT) thermochronometers. The youngest ages are Late Cretaceous and these zircons show rare earth element signatures that suggest derivation from hydrothermally affected basement rocks of the URG margins. In contrast, a Lower Pleistocene URG sample contains significant Tertiary age components that unequivocally indicate Alpine sources. This cardinal difference coincides well with a significant change in the heavy mineral assemblage. The extension of the catchment of the Rhine towards the Central Alps is considered to occur no earlier than the latest Pliocene (i.e. after ~3.0 Ma). Despite strongly contrasting heavy mineral compositions, the Pliocene and Pleistocene samples from the LRE show largely similar ZHe and ZFT age distributions dominated by Permo‐Triassic and Variscan ages. Admixture of zircon‐dominated, but overall heavy mineral‐poor sediment derived from local drainages of the Rhenish Massif likely explains this apparent contradiction in sediment provenance proxies. Tertiary cooling ages occur in both Pliocene and Pleistocene LRE samples. Zircon Th/U ratios and U/Pb ages reveal that the young age component in Late Pliocene sediments from the LRE is not derived from the Alps but from Oligocene trachytic members of the Central European volcanic centres of the Vogelsberg, Westerwald, and/or Siebengebirge. The integration of ZHe and ZFT techniques with zircon geochemistry and U/Pb geochronology adds the respective advantages of each method and allows for a very detailed picture of detrital zircon provenance.

Monitoring of a geothermal reservoir by hybrid gravimetry; feasibility study applied to the Soultz-sous-Forêts and Rittershoffen sites in the Rhine graben

The study is devoted to the monitoring of a geothermal reservoir by hybrid gravimetry combining different types of instruments (permanent superconducting gravimeter, absolute ballistic gravimeter, and micro-gravimeters) and different techniques of measurements (both time-discrete and recording data collection). Using a micro-gravimetric repetition network around a reference station, which is regularly measured, leads to the knowledge of the time and space changes in surface gravity. Such changes can be linked to the natural or anthropic activities of the reservoir. A feasibility study using this methodology is applied to two geothermal sites in the Alsace region (France) of the Rhine graben. We show the results in terms of gravity double differences from weekly repetitions of a network of 11 stations around the geothermal reservoir of Soultz-sous-Forets, separated into 5 loops during July–August 2013 and 2014 as well as preliminary results from 2 stations near Rittershoffen (ECOGI). We point out the importance of a precise leveling of the gravity points for the control of the vertical deformation. A first modeling of surface gravity changes induced by realistic geothermal density perturbations (Newtonian attraction) is computed in the frame of the existing geological model and leads to gravity changes below the μGal level being hence undetectable. However, and for the same case, borehole gravity modeling showed a significant anomaly with depth that can be used as a complementary monitoring method. We show that in the limit of our uncertainties (SD ~ 5 μGal), we do not detect any significant gravity change on the geothermal site of Soultz in agreement with the fact that there was indeed no geothermal activity during our analysis period. On the contrary, the measurements near Rittershoffen show a signal above the noise level which correlates in time with a production test but cannot be explained in terms of Newtonian attraction effects according to our basic numerical simulation.

Estimation of small surface displacements in the Upper Rhine Graben area from a combined analysis of PS-InSAR, levelling and GNSS data

The intra-plate deformation of the Upper Rhine Graben (URG) located in Central Europe is investigated using geodetic measurement techniques. We present a new approach to calculate a combined velocity field from InSAR, levelling and GNSS measurements. As the expected tectonic movements in the URG area are small (less than 1mma−1), the best possible solutions for linear velocity rates from single-technique analyses are estimated in a first step. Second, we combine the velocity rates obtained from InSAR (line of sight velocity rates in ascending and descending image geometries), levelling (vertical velocity rates) and GNSS (horizontal velocity rates) using least-squares adjustment (LSA). Focusing on the Northern URG area, we analyse SAR data on four different image stacks (ERS ascending, ERS descending, Envisat ascending, Envisat descending) using the Persistent Scatterer (PS) approach. The linear velocity rates in ascending and descending image geometries, respectively, are estimated in an LSA from joint time-series analysis of ERS and Envisat data. Vertical velocity rates from levelling are obtained from a consistent adjustment of more than 40 000 measured height differences using a kinematic displacement model. Horizontal velocity rates in east and north direction are calculated from a time-series analysis of daily coordinate estimates at 76 permanently operating GNSS sites in the URG region. As the locations, at which the measurement data of PS-InSAR, levelling and GNSS reside, do not coincide, spatial interpolation is needed during several steps of the rigorous processing. We use Ordinary Kriging to interpolate from a given set of data points to the locations of interest with a special focus on the modeling and propagation of errors. The final 3-D velocity field is calculated at a 200 m grid, which carries values only close to the location of PS points, resulting in a mean horizontal and vertical precision of 0.30 and 0.13 mm a−1, respectively. The vertical component of the combined velocity field shows a significant subsidence of about 0.5 mm a−1 in the northern part of the graben coinciding with a well-known quaternary basin structure. Horizontal displacement rates of up to 0.8 mm a−1 in southeast direction are observed outside the graben, in reasonable alignment with the average direction of maximum horizontal stress. Within the graben, the velocity directions rotate toward east in the non-subsiding part, while an opposite trend is observed in the subsiding part of the graben. The complexities of the observed velocity field are compatible to the geomechanical situation in our investigation area which is characterized by a transition from a restraining to a releasing bend setting. Glacial isostatic adjustment is another potential source influencing the observed velocity field, as well as anthropogenic signals due to mining, oil exploration and groundwater usage that have been identified in some places.

Thermal maturity and petroleum kitchen areas of Liassic Black Shales (Lower Jurassic) in the central Upper Rhine Graben, Germany

In the central Upper Rhine Graben (URG), several major oil fields have been sourced by Liassic Black Shales. In particular, the Posidonia Shale (Lias e, Lower Toarcian) acts as excellent and most prominent source rock in the central URG. This study is the first comprehensive synthesis of Liassic maturity data in the URG area and SW Germany. The thermal maturity of the Liassic Black Shales has been analysed by vitrinite reflectance (VRr) measurements, which have been verified with T max and spore coloration index (SCI) data. In outcrops and shallow wells (<600 m), the Liassic Black Shales reached maturities equivalent to the very early or early oil window (ca. 0.50–0.60 % VRr). This maturity is found in Liassic outcrops and shallow wells in the entire URG area and surrounding Swabian Jura Mountains. Maximum temperatures of the Posidonia Shale before graben formation are in the order of 80–90 °C. These values were likely reached during Late Cretaceous times due to significant Upper Jurassic and minor Cretaceous deposition and influenced by higher heat flows of the beginning rift event at about 70 Ma. In this regard, the consistent regional maturity data (VRr, T max, SCI) of 0.5−0.6 % VRr for the Posidonia Shale close to surface suggest a major burial-controlled maturation before graben formation. These consistent maturity data for Liassic outcrops and shallow wells imply no significant oil generation and expulsion from the Posidonia Shale before formation of the URG. A detailed VRr map has been created using VRr values of 31 wells and outcrops with a structure map of the Posidonia Shale as reference map for a depth-dependent gridding operation. Highest maturity levels occur in the area of the Rastatt Trough (ca. 1.5 % VRr) and along the graben axis with partly very high VRr gradients (e.g. well Scheibenhardt 2). In these deep graben areas, the maximum temperatures which were reached during upper Oligocene to Miocene times greatly exceed those during the Cretaceous.

How do permeable fractures in the Triassic sediments of Northern Alsace characterize the top of hydrothermal convective cells? Evidence from Soultz geothermal boreholes (France)

The thermal regime of the Upper Rhine Graben (URG) is characterized by a series of anomalies near Soultz-sous-Forêts (France), Rittershoffen (France), and Landau (Germany). These temperature anomalies are associated with groundwater circulation in fractures and faults distributed in the Cenozoic and Mesozoic sedimentary cover associated with and connected to fractures originating deep within the Paleozoic basement. The present study helps to understand the convective cell structure in order to optimize geothermal borehole trajectories. The work concentrated on a detailed interpretation of the geophysical and geological logs from Soultz geothermal wells mainly from the topographic surface to the Triassic formations, at between 800- and 1,400-m depth above the deep granitic basement. The analysis of drilling mud logging data and geophysical well logging data from the deep Soultz geothermal wells (GPK-2, GPK-3, GPK-4) reveals the occurrence of nine fracture zones situated at depths greater than 900 m in the limestones of the Muschelkalk (Middle Trias) and the sandstones of the Buntsandstein (Lower Trias). Based on indications of total or partial mud losses, these fracture zones have been classified as permeable or impermeable. Permeable fractures between circa 900-m depth and 1,400-m depth are connected to a large-scale fault and control the top of the convective cells. There is no indication of permeability in the formations above the Keuper layer, and the uppermost part of the sedimentary cover acts as a cap rock, insulating the convective regime in the Triassic sediments and the granitic basement.

Spatial variations of earthquake occurrence and coseismic deformation in the Upper Rhine Graben, Central Europe

Seismic activity in the densely populated Upper Rhine Graben (URG) is an aspect in the public, political, and industrial decision making process. The spatial analysis of magnitude–frequency distributions provides valuable information about local seismicity patterns and regional seismic hazard assessment and can be used also as a proxy for coseismic deformation to explore the seismo-tectonic setting of the URG.We combine five instrumental and one historic earthquake bulletins to obtain for the first time a consistent database for events with local magnitudes ML≥2.0 in the whole URG and use it for the determination of magnitude frequencies. The data processing results in a dataset with 274 Poisson distributed instrumentally recorded earthquakes within the URG between 01/1971 and 02/2012 and 34 historic events since the year 1250.Our analysis reveals significant b-value variations along the URG that allow us to differentiate four distinct sections (I–IV) with significant differences in earthquake magnitude distributions: I: Basel region in the Swiss–France–German border region (b=0.83), II: region between Mulhouse and Freiburg in the southern URG (b=1.42), III: central URG (b=0.93), and IV: northern URG (b=1.06). High b-values and thus a relatively low amount of high magnitude events in the Freiburg section are possibly a consequence of strongly segmented, small-scale structures that are not able to accumulate high stresses.We use the obtained magnitude–frequency distributions and representative source mechanisms for each section to determine coseismic displacement rates. A maximum horizontal displacement rate of 41μm/a around Basel is found whereas only 8μm/a are derived for the central and northern URG. A comparison with geodetic and geological constraints implies that the coseismic displacement rates cover less than 10% of the overall displacement rates, suggesting a high amount of aseismic deformation in the URG.

Possible natural fluid pathways from gravity pseudo-tomography in the geothermal fields of Northern Alsace (Upper Rhine Graben)

BackgroundThis study aims on investigating the regional flow field of the Soultz and adjacent geothermal fields located on the western side of the central Upper Rhine Graben and thus to provide insight into the origin of the 70% of the geothermal fluid coming from the regional inflow in the deep reservoir of the Soultz site. In an integrative approach, we consolidate conceptual models on fluid flow in the central Upper Rhine Graben.MethodsBased on a 3D geological model and a new 3D temperature interpolation, we tackle the relation between tectonic structures and the occurrence of advection/convection along favourably oriented fault zones. Using sequential Butterworth filters, we study the distribution of negative residual anomalies in a pseudo-tomography down to a depth of about 6 to 8 km.ResultsWe derived N-S-striking V-shaped negative anomalies that are consistent with the orientation of fault zones revealing major temperature anomalies to their east.ConclusionsFollowing the concept of negative anomalies revealing zones of increased fracture porosity, and in agreement with fluid-chemistry, our findings suggest infiltration of meteoric water through the graben boundary fault and along preferential flow pathways that merge at intermediate depth. Up-flow of thermal water mixed most likely with brine from the deeper eastern part of the graben occurs along W-dipping typically rather steep structures.

Hydraulic and hydrochemical properties of deep sedimentary reservoirs of the Upper Rhine Graben, Europe

AbstractHydraulic and hydrochemical data from several hundred wells mostly drilled by the oil and gas industry within the four deep carbonate and siliciclastic reservoirs of the Upper Rhine Graben area in France and Germany have been compiled, examined, validated and analysed with the aim to characterize fluids and reservoir properties. Due to enhanced temperatures in the subsurface of the Upper Rhine Graben, this study on hydraulic and hydrochemical properties has been motivated by an increasing interest in deep hydrogeothermal energy projects in the Rhine rift valley. The four examined geothermal reservoir formations are characterized by high hydraulic conductivity reflecting the active tectonic setting of the rift valley and its fractured and karstified reservoirs. The hydraulic conductivity decreases only marginally with depth in each of the reservoirs, because the Upper Rhine Graben is a young tectonically active structure. The generally high hydraulic conductivity of the reservoir rocks permits cross‐formation advective flow of thermal water. Water composition data reflect the origin and hydrochemical evolution of deep water. Shallow water to 500 m depth is, in general, weakly mineralized. The chemical signature of the water is controlled by fluid–rock geochemical interactions. With increasing depth, the total of dissolved solids (TDS) increases. In all reservoirs, the fluids evolve to a NaCl‐dominated brine. The high salinity of the reservoirs is partly derived from dissolution of halite in evaporitic Triassic and Cenozoic formations, and partly from the fluids residing in the crystalline basement. Water of all four reservoirs is saturated with respect to calcite and other minerals including quartz and barite.

Vertical displacement rates in the Upper Rhine Graben area derived from precise leveling

The recent vertical displacement field of the Upper Rhine Graben (URG) located in the tri-national region between Germany, France and Switzerland is investigated using repeatedly measured leveling data. We estimate vertical displacement rates at leveling benchmarks by applying a kinematic network adjustment on more than 40,000 height differences measured by German, French and Swiss surveying agencies. Focusing on an optimal solution for the adjusted rates in the URG area also historical data (measured before 1900) are used, significantly increasing the time span of available measurements and the number of transnational connections between the three countries. To account for inhomogeneities apparent in the database, we apply an iterative variance component estimation within the adjustment procedure, particularly revealing more realistic information on the accuracy of the estimated rates. A special focus within our analysis is put on the statistical testing of gross errors in the observations and model-related errors at benchmarks with non-linear movement. As some of the estimated vertical rates behave significantly different compared to the vertical rates of adjacent benchmarks, a filtering of outliers is applied after the adjustment procedure. The resulting map of linear height changes in an area of 280 km in N–S and 230 km in E–W direction provides detailed insight into the recent vertical displacements of the URG and neighboring regions. In the German part of the study area, it was possible for the first time to consistently constrain an average subsidence rate of 0.5 mm/a ( $$\pm $$ 0.2 mm/a) of the Graben interior w.r.t. the Black Forest. In addition to the tectonic displacements, some man-induced surface movements, e.g., caused by oil and groundwater extraction, are observed and discussed.

Electrochemical study of the corrosion of different alloys exposed to deaerated 80 °C geothermal brines containing CO2

Corrosion of metallic engineering materials accounts for problems during geothermal operation in the Upper Rhine Graben (URG). Herein, we study the electrochemical behaviour of various metal alloys in an 80°C simulated geothermal environment by using potentiodynamic polarisation and open-circuit potential measurements. Two different natural geothermal waters from URG geothermal sites were used for the experiments. The measurements reveal spontaneous passivation to be a key process for all alloys. This ennoblement protects more noble alloys from significant corrosion (e.g. titanium gr. 2, alloy 625) and brings less noble alloys to failure, mostly due to pitting corrosion (e.g. 316L).

Climatology of precipitation in the Vosges mountain range area

The aim of this work is to study the climatology of atmospheric precipitation in the study area situated in north-eastern France. It is shown that the Vosges mountain range, due to its position almost perpendicular to the prevailing western airflow, affects the spatial and temporal distribution (and thus the seasonality) of precipitation at a regional scale. This is carried out by computing the daily rainfall at 14 meteorological stations over the period 1950–2011. Different levels of rainfall resolution were examined – at first the annual rainfall which varies greatly between the windward side and the highest part of the Vosges mountain range and the Upper Rhine Plain (the difference is as large as 1700 mm per average year), then the monthly rainfall and distribution of recipitation within the year and finally the daily rainfall variability. Three categories of stations were determined according to their annual precipitation distribution: (i) mountain stations with a winter precipitation maximum, (ii) leeward slope stations with two precipitation maxima, i.e. in winter and summer and (iii) leeward stations located in the Upper Rhine Plain eastward of the Vosges with a summer precipitation maximum. Quantitative methods of ombric kontinentality demonstrate that the Vosges represent a limit between oceanic and a more continental climate. However, the empirical formulas are not satisfying and further research is required.

Food offerings in graves from the Danubian Neolithic (5500–4900 B.C.) in the upper Rhine valley

ABSTRACT Ranging from the valves of exotic marine shells (Spondylus) to anthropomorphic figurines fashioned on metapodials, and from carnivore tooth beads to the deposition of partial carcasses, the representation of fauna in the graves of the early Neolithic in northern France and in the upper Rhine valley takes very diverse forms. This contribution focuses on those remains which can be associated with the practice of food deposits in order to better define the modalities of this type of such finds (choice of species and body parts, preparation, arrangement and position in the grave), understand their meaning and outline their characteristics in relation to other categories of animal bone items (ornaments, tools…) which form part of the grave assemblage.

Determination of Site Factor in and Around Rhine Graben, France in the 1–11 Hz Frequency Band by Non-Reference Network Average Technique

The greatest challenge in estimating site response from instrumental recordings of seismic events is removing the source and path effects. Several methods have been suggested in the past in that direction which may be divided into two main categories, depending on whether or not they need a reference site, with respect to which the particular effects at other sites can be estimated. An alternative approach is to determine the site response relative to the network average. In the present paper we propose one such technique for estimating the site factor in the Rhine graben and its surrounding provinces. Judging the higher signal thresh-hold level (≥3 times the background) only sixteen earthquake events with local magnitude varying between 3 and 4.5 are used from the catalogue of 8 years during 1988–1995 recorded by the Fosse Rhenan network using short period single component seismometers belonging to the Ecole et Observatoire des Sciences de la Terre, Strasbourg, Prance and Survey Baden-Wurttenberg, Freiburg, Germany. Sixteen stations in and around Rhine graben are considered for the site factor computation in the 1–11 Hz frequency band. The contour maps prepared from the spatial distribution of non-reference network average site factor estimates at 1, 3, 5, 7, 9 and 11 Hz exhibit high values along the major faults and the minor tectonic features to the western (Vosges) and eastern (Foret-Noire) provinces. Irrespective of the magnitude of the earthquake, the Rhine graben is comparatively stable with low site factors at all the frequencies. As is expected from Coda site amplification studies, the network average contour patterns remained unchanged showing minor or no variation at all with frequencies.

A review of methods for determining stress fields from earthquakes focal mechanisms; Application to the Sierentz 1980 seismic crisis (Upper Rhine graben)

AbstractThe inversion of earthquake focal mechanisms is one of the few tools available for determining principal stress directions at seismogenic depths. Various methods have been proposed for performing such inversions. For three of the most commonly used methods, including one that has been proposed by Jacques Angelier, we discuss the physical assumptions and the error determination and then we propose an extension for one of the methods. All four methods are then applied for evaluating the stress field in the Upper Rhine graben. They are applied to seismic data recorded with a temporary monitoring network that was deployed 12 hours after the magnitude Mw = 4.4 Sierentz earthquake, which occurred on July 15, 1980. While differences in principal stress directions can be as much as 28° depending on the method used for the principal stress direction determination (orientation of the minimum principal stress has been found to range from N051°E with a 27° plunge to N090° E with a 20° plunge), the 90% confidence level associated with each method varies from 11° to 27°. Moreover, these various methods yield fairly diverse values for the R factor that characterizes relative differences between principal stress magnitudes (from R = 0.7 with a 0.2 90% confidence level to R = 0.3 with a 0.2 90% confidence level). Furthermore all three methods leave some focal mechanisms unexplained. These are then declared to be the result of heterogeneity and are not considered for the inversion. It is concluded that earthquake focal mechanisms inversions lack resolution for stress field evaluation at depth if no proper attention is given to the event independence hypothesis. When proper attention is given to this hypothesis, a resolution of the order of 15° may be achieved. The minimum principal stress orientation derived with these various focal mechanisms inversions differs by 4 to 36° from the orientation determined from borehole breakouts observed in Basel, in a 5 km deep well (N054°E ± 14°), located some 20 km from Sierentz. The solution that fits best borehole breakout observations is that which satisfies the minimum number (three) of prerequisite physical assumptions.