Lower Rhine Embayment Research Articles

Luminescence dating of the Lower Middle Terrace site at Brühl, southern Lower Rhine Embayment – a first dating approach

Luminescence dating of the Lower Middle Terrace site at Brühl, southern Lower Rhine Embayment – a first dating approach

Chemotaxonomy of fossil woods from the Lower Rhine Embayment, Germany

In the Lower Rhine Embayment (western Germany), the Neogene lignite bearing sequence is rich in large fossil wood trunks. Woods collected from sand-filled channels of a meandering river system (Pliocene: Reuver series) and from coal seams (Miocene: seams Garzweiler, Frimmersdorf and Morken) were investigated by Curie-point pyrolysis coupled with gas chromatography–mass spectrometry in order to determine their palaeobotanical classification. In comparison with reference data of individual pyrograms of modern woods, it became possible to classify 15 fossil wood trunks chemotaxonomically as follows: eleven samples were identified as Taxodioxylon sp. by reference Sequoia sempervirens, three samples were identified as Populoxylon sp. by reference Populus nigra and one sample was identified as Sciadopityoxylon sp. by two references of Sciadopitys verticillata. Microanatomical crosschecks describe the equivalent samples taxonomically as Taxodioxylon gypsaceum (GÖPPERT) KRÄUSEL, Taxodioxylon germanicum (GREGUSS) VAN DER BURGH, Populus nigra L. and Sciadopityoxylon wettsteinii JURASKY, and confirm the chemical classifications. For both fossil and reference woods, our relative quantifications of guaicyl and syringyl moieties are in precise accordance with discriminations of gymnosperms versus angiosperms. This means that not only unknown recent woods can chemotaxonomically accurately be determined by Curie-point pyrolysis gas chromatography–mass spectrometry and their equivalent modern wood reference from our data base, but also the taxonomy of botanically related wood types reaching back to the geological past up to a Miocene age at least.

Loess-paleosol sequences at the northern European loess belt in Germany: Distribution, geomorphology and stratigraphy

Abstract Pleistocene loess and loess derivates are distributed along the mountain front of the Central European Mountain Belt in northern and central Germany. Examples from two regions, the Lower Rhine Embayment (LRE) and the Northern foreland of the Harz Mountains (FHM) show that the distribution of loess and the development of loess-paleosol sequences (LPS) are controlled by relief, climate, tectonics, the distance to large river systems, the distance to the Scandinavian ice sheet and the distance to the shelf of the North Sea. In the oceanic LRE higher humidity enhanced the periglacial processes which increased erosion, but also led to preservation in accumulative positions. In contrast, in the more continental FHM the sediments were affected by less intensive periglacial processes and no solifluction can be detected. New loess distribution maps are presented for both key areas, and key sections, especially for the last glacial cycle, are compared and summarized. Both study regions are located in the west – east trending loess belt north of the Central European Mountain belt (in front of the Rhenish Shield = Ardennes-Eifel and Harz Mountains). Finally, a synthesis of typical sediment sequences for both regions is given as an example of paleoenvironmental (landscape) development in northern Central Europe.

A Multi-Proxy Analysis of two Loess-Paleosol Sequences in the Northern Harz Foreland, Germany

Two loess-paleosol-sequences from the northern Harz foreland, Hecklingen and Zilly, have been investigated. In general, loess-paleosol-sequences represent valuable terrestrial archives of regional environmental and climatic conditions during past glacial periods. The study area is part of the northern European loess belt and was in the vicinity of the Scandinavian ice sheet during the Weichselian. Aiming towards a better understanding of the paleoenvironmental conditions during the Weichselian in an area close to the Scandinavian ice sheet, results from grain-size, geochemical (XRF, CNS), color and magnetic susceptibility measurements are combined. The findings demonstrate an increased input of aeolian material during the last glacial maximum and the last cover loess period, which is in accordance to the theory of drier and colder conditions during this time frame. Further, data reveal a strong input not only of loess but also of coarser material coming from a shorter distance during the last glacial maximum in both profiles. Material of the last glacial maximum clearly indicates a shift of wind direction towards easterly winds. In Hecklingen, an enhancement of coarser material has been observed within the recent soil and MIS 3 soil material. Since soil material that dates back to the MIS 3 is present in the profile, it can be assumed that surface processes were less intrusive during the MIS 3 and 2 than in e.g. the Lower Rhine Embayment and Saxony.

Late Oligocene macrofloras from fluviatile siliciclastic facies of the Köln Formation at the south-eastern border of the Lower Rhine Embayment (North Rhine-Westphalia, Germany)

Abstract The leaf remains described herein came from the oldest sites of the Cainozoic deposits in the Lower Rhine Embayment, located in the Siebengebirge Volcanic Field at the south-eastern border of this basin, in the area of Siebengebirge and vicinity. These revisited floras are bound to pre-volcanic siliciclastic facies of the Siebengebirge Mts., interpreted as marginal facies of the Köln Formation. Chronostratigraphically they are assigned to the late Oligocene (Chattian). The described leaf remains are partially compressions with preserved epidermal anatomy, and therefore highly useful for systematic determination of leaf impressions recovered from other localities of siliciclastic facies. On account of the epidermal characteristics of leaf compressions varying in gross morphology, the previously determined taxa Quercus goepperti, Laurus phoeboides, and Persea speciosa all fall into the abundantly represented Eotrigonobalanus furcinervis. The siliciclastic deposits originated in coastal and flood plain areas within fluviatile environments of variable deposition energy. Remains of Taxodium dubium, Eotrigonobalanus furcinervis, Populus germanica, and Daphnogene cinnamomifolia dominate among the recovered fossils. The general aspects of this plant assemblage correspond, together with their sedimentary settings, to riparian forest vegetation with mesophytic elements.

Loess-paleosol sequences at the northern European loess belt in Germany: Examples from the Lower Rhine embayment and the northern foreland of the Harz Mountains

Loess-paleosol sequences at the northern European loess belt in Germany: Examples from the Lower Rhine embayment and the northern foreland of the Harz Mountains

Die Niederrheinische Bucht – Braunkohlegewinnung im Tagebau Hambach (Exkursion E am 31. März 2016)

Die Niederrheinische Bucht – Braunkohlegewinnung im Tagebau Hambach (Exkursion E am 31. März 2016)

Geologische Traverse von der Wurm-Mulde in die Niederrheinische Bucht (Exkursion G am 1. April 2016)

This field trip crosses the coal-bearing Upper Carboniferous Wurm syncline NW of the Variscan front and ends at the Cenozoic sediments of the Lower Rhine embayment. It covers the NE–SW striking Variscan fold- and thrust belt, the unconformably overlying Upper Cretaceous sands and carbonate rocks of the Lousberg, the Tertiary coastal sands of the regressing North Sea basin and the Quaternary gravels of the East-Maas terraces. Meanwhile the history of mining, documented 1353 AD and thus one of the world’s oldest hard coal mine districts, is discussed.

Analysis of a Burglargram

The Seismological Station of Cologne University (BNS) was founded in 1951 on the outskirts of Bensberg, Germany, at that time an independent city and which now is a part of Bergisch Gladbach, some 15 km east from downtown Cologne. The station building is a small (120 m2) typical 1950s family home (Fig. 1). In the early years it served two functions: as a seismological station with a Wiechert‐type 1.3 t seismometer in the basement and as the home of Professor Martin Schwarzbach, the station’s founder and his wife. Schwarzbach, a pioneer of climate research using geological methods (Schwarzbach, 1950), moved out after he became an emeritus, and the building was dedicated to maintaining the rapidly expanding seismic network in the Lower Rhine embayment, which now consists of over 40 stations. Figure 1. (a) Bensberg seismic station of Cologne University, seen from the northwest. On top of the garage is a patio with a door opening toward the engineer’s office. An iron gate secures the door at night. (b) Perspective view using a laser scan of the engineer’s office. The dashed line labeled LE3D points to the location of the seismometer. The arrows indicate the size of the room and the distance from the seismometer to the adjacent walls; all measures are in meters. In the more than 60 years of history of the BNS, numerous natural and anthropogenic threats had to be dealt with, including ground water in the seismometer vault, a car crashing through the garden fence, and lightning exploding a tree on the compound (Hinzen, 2012). On Friday, 14 August 2015, a new anthropogenic threat was …

Flow dynamics, sedimentation and erosion of glacial lake outburst floods along the Middle Pleistocene Scandinavian Ice Sheet (northern central Europe)

During the Middle Pleistocene late Saalian glaciation of northern central Europe numerous pro‐glacial lakes formed along the southwestern margin of the Scandinavian Ice Sheet. Little is known about the drainage history of these lakes, the pathways of glacial lake outburst floods and their impacts on erosion, sedimentation and landscape evolution. This study investigated the impact of the late Saalian Weser and Münsterland Lake (Germany) outburst floods. In particular, we reconstructed the routing and flow dynamics of the lake outburst flood and analysed the flood related sediments. We employed one‐dimensional hydraulic modelling to calculate glacial lake outburst flood hydrographs. We modelled the flow pathway and local flow conditions along the pathway based on the boundary conditions of two different hydrographs and two different ice‐margin positions. The modelling results were compared with geomorphological and sedimentological field data in order to estimate the magnitude and impact of the flood on erosion and sedimentation. Two major lake drainage events are reconstructed for the study area, during which approximately 90–50 km3 of water was released. Modelling results indicate that the lake outburst floods created a high‐energy flood wave with a height of 35–50 m in confined valley areas that rapidly spread out into the Lower Rhine Embayment eventually flowing into the North Sea basin. The sedimentary record of the outburst floods comprises poorly sorted coarse‐grained gravel bars, long‐wavelength bedforms and sandy bedforms deposited by supercritical and subcritical flows. Some parts of the sandy flood deposits are rich in reworked mammoth bones or mammoth and horse teeth, pointing to reworking of older fluvial sediments, hydraulic concentration and subsequent re‐sedimentation of vertebrate remains. These deposits are preserved in sheltered areas or at high elevations, well above the influence of postglacial fluvial erosion. The flood‐related erosional features include up to 80‐m‐deep scour pools, alluvial channels and streamlined hills.

Dissolved noble gases and stable isotopes as tracers of preferential fluid flow along faults in the Lower Rhine Embayment, Germany

Groundwater in shallow unconsolidated sedimen- tary aquifers close to the Bornheim fault in the Lower Rhine Embayment (LRE), Germany, has relatively low δ 2 Ha nd δ 18 Ov alues in comparison to regional modern groundwater recharge, and 4 He concentrations up to 1.7×10 −4 cm 3 (STP) g -1 ±2.2 % which is approximately four orders of magnitude higher than expected due to solubility equilibrium with the atmosphere. Groundwater age dating based on estimated in situ production and terrigenic flux of helium provides a groundwater residence time of ∼10 7 years. Although fluid exchangebetweenthedeepbasalaquifersystemandtheupper aquifer layers is generally impeded by confining clay layers and lignite, this study's geochemical data suggest, for the first time, that deep circulating fluids penetrate shallow aquifers in the locality of fault zones, implying that sub-vertical fluid flow occurs along faults in the LRE. However, large hydraulic-head gradients observed across many faults suggest that they act as barriers to lateral groundwater flow. Therefore, thegeochemicaldatareportedherealsosubstantiateaconduit- barrier model of fault-zone hydrogeology in unconsolidated sedimentarydeposits,aswell ascorroboratingtheconceptthat faults in unconsolidated aquifer systems can act as loci for hydraulic connectivity between deep and shallow aquifers. The implications of fluid flow along faults in sedimentary basins worldwide are far reaching and of particular concern for carboncapture and storage (CCS) programmes, impacts of deepshale gasrecoveryforshallowgroundwateraquifers,and nuclear waste storage sites where fault zones could act as potential leakage pathways for hazardous fluids.

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.

Paleoecological and climatic implications of stable isotope results from late Pleistocene bone collagen, Ziegeleigrube Coenen, Germany

Climatic and ecological conditions during Marine Oxygen Isotope Stage (MIS) 3 are complex and the impact of cold spells on the ecosystems in Central Europe still needs to be investigated thoroughly. Ziegeleigrube Coenen (ZC) is a late Pleistocene MIS 3 locality in the Lower Rhine Embayment of Germany, radiocarbon-dated to >3414Cka BP. The site yielded a broad spectrum of mammal species. We investigated the carbon (δ13C), nitrogen (δ15N) and sulfur (δ34S) isotope signatures of bone collagen, since these are valuable tools in characterizing ecological niches, environmental conditions and aspects of climate and mobility. By comparison with pre- and post-Last Glacial Maximum (LGM) sites in Central Europe we show that ZC belongs in a cold event of MIS 3 and was climatically more similar to post-LGM sites than to pre-LGM sites. However, the trophic structure resembled that of typical pre-LGM sites in Belgium. This cold event in MIS 3 changed the bottom of the foodweb, but do not seem to have had a direct impact on the occurrence of the mammalian species and their ecological distribution. Apparently the (mega-) faunal community could adapt also to harsher environmental conditions during MIS 3.

The Fossil-Lagerstätte Enspel — a crater lake in a volcanic-influenced terrestrial environment of the Westerwald Basin (late Oligocene, Western Germany)

The Westerwald region belongs to the Central European Volcanic Province (CEVP). As seen here, theWesterwald Basin is an aggregation of small basins (the smallest ones cover an area as little as 10,000 m), mainly situated within the Variscan Mosel, Lahn and Dill Synclines. Sedimentation started in the middle Eocene (Hottenrott 2002). A pre-existing landscape was filled first by coarse sediments, followed by clays and brown coal (Schafer et al. 2011). Tectonic activity seems to have increased during the middle late Oligocene, resulting in an increasing relief, displayed by sandy sediments (Butz and Vortisch 1987). Two watersheds separate the Westerwald Basin from the Lower Rhine Embayment (Schindler and Wuttke 2013) (Fig. 1). In the late Oligocene, volcanic activity commenced with trachytic intrusions, phreatomagmatic maar eruptions (Enspel) and pyroclastic eruptions. They were followed by basic shallow intrusions, lava flows, and continued maar formation (Elbtal, ?Elz) and the deposition of thick pyroclastics (Schreiber 1996; Haase et al. 2004). Locally, the eruptions and minor intercalated sediments covered the landscape up to 50 m high (Schafer et al. 2011). Reischmann (2011) relates the Oligocene volcanism to the Alpine orogeny and North Atlantic rifting; the main reason is extension and thinning of the lithosphere, resulting in a passive uplift of the asthenosphere; partial melting was caused by pressure release, which resulted in the eruptions in the CEVP. The volcanic activity led to changes in the local drainage systems, e.g. dammed valleys with subsequent lake formation. Caused by contemporaneous temporarily high Chattian sea level, palustrine facies became widespread, so that thick lignite seams were formed along with laminated lake sediments (e.g. Lake Norken, Uhl et al. 2011; fossil site Breitscheid, Schindler and Kolb 2010). Hygrophilous plant communities covered the lowlands. The macroflora of this riparian vegetation is dominated by leaves of Acer cf. tricuspidatum BRONN, twigs of Glyptostrobus europaeus (BRONGNIART) UNGER and charcoalified wood of Cupressaceae (Taxodiaceae s.l.), as seen in the lacustrine to swampy sediments of Lake Norken (Uhl et al. 2011). Upland or dryland floras and faunas were also influenced by volcanic activity. Forests died under heavy ash load, and their remnants were washed into the lowlands and partly preserved as silicified trunks. Isolated reptile and mammal bones and teeth (e.g. Teike and Tobien 1950) can be found within coarse volcanic ash (personal field observation, and unprepared material of the collections of the Museums of Breitscheid, Hachenburg, Wiesbaden and the Hessisches Landesamt fur Umwelt und Geologie, Wiesbaden, all Germany), demonstrating the influence of pyroclastic and/or lahar events on the biota. Floral recovery starts with pioneering plants like Cyperaceae, Poaceae and Betulaceae. This pioneering flora was succeeded by zonal assemblages of a mesophytic forest with strong East Asian influence (Herrmann et al. 2003, 2010; Kohler and Uhl 2014). This article is a contribution to the special issue “The Fossil-Lagerstatte Enspel reconstructing the palaeoenvironment with new data on fossils and geology” M. Wuttke (*) : T. Schindler Direktion Landesarchaologie, Referat Erdgeschichte, Generaldirektion Kulturelles Erbe Rheinland-Pfalz, Grose Langgasse 29, 55116 Mainz, Germany e-mail: michael.wuttke@gdke.rlp.de

Statistically reliable petrophysical properties of potential reservoir rocks for geothermal energy use and their relation to lithostratigraphy and rock composition: The NE Rhenish Massif and the Lower Rhine Embayment (Germany)

We present a comprehensive statistical analysis of petrophysical properties of rocks of the northeastern Rhenish Massif and the Lower Rhine Embayment in Germany. Properties measured comprise thermal conductivity, specific heat capacity density, porosity, hydraulic permeability, and compressional wave velocity. This robust and statistically reliable data is generally useful for numerical modeling of heat transport processes and helps, in particular, reducing the risk of failure in projects of geothermal energy use. We measured the thermophysical properties of rocks from two geological settings: (1) predominantly little consolidated Tertiary rocks forming the young sedimentary cover of the Lower Rhine Embayment in the condition they arrived in the laboratory; (2) well consolidated Paleozoic rocks from the northeastern Rhenish Massif in both dry and saturated condition. We tested a total of 476 samples from different lithologies in both settings in a comprehensive laboratory program consisting of mineralogical analyses and various petro- and thermophysical measurements at ambient and elevated p-T-conditions. This yields relations between composition and thermophysical properties of different sedimentary rock types and allows distinguishing between effects due to rock matrix and structure. The results are used to prove petrophysical rock models and allow predicting thermal properties of distinct rock types for greater depth. The results show that the thermophysical properties of Paleozoic rocks are mainly controlled by their mineralogical compositions, while thermophysical characteristics of Tertiary rocks are the result of a superposition of properties of their mineral content and the water-filled pore volume.

Seismic Analysis of the Accidental WWII Bomb Explosion in Euskirchen, Germany, on 3 January 2014

Besides the well‐known forensics in law enforcement, forensic techniques are used in many scientific fields, including archaeology, biology, geology, and seismology. In seismology, the discrimination between earthquakes and chemical and nuclear explosions is by far the most important and extensively studied area (e.g., Thirlaway, 1973; Stump et al. , 1999, 2002; Douglas, 2007; Bowers and Selby, 2009). However, over the past decades, very diverse sources of seismic energy have been studied, and often astonishing source process details could be revealed by the analysis of seismograms. The sources include explosions, both intentional (e.g., Willmore, 1947, 1949; Holzer et al. , 1996; Koper et al. , 1999) and accidental (e.g., Koper et al. , 2003; Hinzen, 2007), sinking of ships (e.g., Koper et al. , 1999; Koper et al. , 2001; Mucciarelli, 2012), aircraft crashes (e.g., Kim et al. , 2001; McCormack, 2003), meteor approaches and sonic booms (e.g., Kanamori et al. , 1992; Qamar, 1995; Edwards et al. , 2008; Incorporated Research Institutions for Seismology, 2013; Heimann et al. , 2013; Roelofse and Saunders, 2013), and lightning strikes (Hinzen, 2012). On 3 January 2014, the air‐pressure wave of an explosion was widely felt in the eastern part of the Lower Rhine embayment, Germany. At 13:30 local time, the author noticed the wave and sound arriving at the seismic station in Bensberg (BNS) and immediately checked the data of the 40‐station local network of Cologne University. Using the arrivals of the air blast at 330 m/s for five stations and a standard velocity model for explosions, the event was located east of Euskirchen, a city of 55,000 inhabitants at the southern limit of the Lower Rhine embayment. During the data processing, police from the city of Bonn asked about the cause of the boom, which had …

Subway-Induced Vibrations in Cologne Cathedral

The Cologne Cathedral, the largest Gothic church in northern Europe and a World Heritage Site since 1996, is located in the heart of Cologne, a city of one million inhabitants in western Germany. Some 150 m from the Cologne central train station and 350 m from the Rhine River, one of the busiest waterways in Europe, and right next to a busy street and a high‐use parking garage, it receives manifold ground motions of anthropogenic origin. However, when the constant daily stream of tourists, about six million annually, ceases in the evening hours after the church is closed to the public or during church services, the building becomes an oasis of silence despite its location right in the city center. Since 2006, the cathedral is equipped with five permanent strong‐motion stations which are part of a strong‐motion network covering the Lower Rhine Embayment (Hinzen and Fleischer, 2007). All stations use Epi sensor accelerometers and record continuously at 250 samples per second. Set up of stations and measurement examples from the cathedral have been given in detail by Hinzen et al. (2012). On 9 December 2012, a new subway line of the Kolner Verkehrsbetriebe (KVB) went into operation. It utilizes a tube that runs in proximity to the cathedral and, right from the start of its operation, vibrations and solid‐borne sound became sensible, mainly in the northeastern part of the large building (ground floor 7914 m2) and in the choir. In early January 2013 this fact became public and caused a media storm including reporting in the German evening news and newspaper articles in Russia and China before any countermeasures could be taken. This negative publicity was extreme. One reason was that during the construction of a new subway line in 2004 the 44 m tall tower of the St. Johann Baptist church, 1.38 km …

Comparison of deterministic and stochastic earthquake simulators for fault interactions in the Lower Rhine Embayment, Germany

Time-dependent probabilistic seismic hazard assessment requires a stochastic description of earthquake occurrences. While short-term seismicity models are well-constrained by observations, the recurrences of characteristic on-fault earthquakes are only derived from theoretical considerations, uncertain palaeo-events or proxy data. Despite the involved uncertainties and complexity, simple statistical models for a quasi-period recurrence of on-fault events are implemented in seismic hazard assessments. To test the applicability of statistical models, such as the Brownian relaxation oscillator or the stress release model, we perform a systematic comparison with deterministic simulations based on rate- and state-dependent friction, high-resolution representations of fault systems and quasi-dynamic rupture propagation. For the specific fault network of the Lower Rhine Embayment, Germany, we run both stochastic and deterministic model simulations based on the same fault geometries and stress interactions. Our results indicate that the stochastic simulators are able to reproduce the first-order characteristics of the major earthquakes on isolated faults as well as for coupled faults with moderate stress interactions. However, we find that all tested statistical models fail to reproduce the characteristics of strongly coupled faults, because multisegment rupturing resulting from a spatiotemporally correlated stress field is underestimated in the stochastic simulators. Our results suggest that stochastic models have to be extended by multirupture probability distributions to provide more reliable results.

The Maximum Earthquake Magnitude in a Time Horizon: Theory and Case Studies

We show how the maximum magnitude within a predefined future time horizon may be estimated from an earthquake catalog within the context of Gutenberg–Richter statistics. The aim is to carry out a rigorous uncertainty assessment, and calculate precise confidence intervals based on an imposed level of confidence α . In detail, we present a model for the estimation of the maximum magnitude to occur in a time interval T f in the future, given a complete earthquake catalog for a time period T in the past and, if available, paleoseismic events. For this goal, we solely assume that earthquakes follow a stationary Poisson process in time with unknown productivity Λ and obey the Gutenberg–Richter law in magnitude domain with unknown b ‐value. The random variables Λ and b are estimated by means of Bayes theorem with noninformative prior distributions. Results based on synthetic catalogs and on retrospective calculations of historic catalogs from the highly active area of Japan and the low‐seismicity, but high‐risk region lower Rhine embayment (LRE) in Germany indicate that the estimated magnitudes are close to the true values. Finally, we discuss whether the techniques can be extended to meet the safety requirements for critical facilities such as nuclear power plants. For this aim, the maximum magnitude for all times has to be considered. In agreement with earlier work, we find that this parameter is not a useful quantity from the viewpoint of statistical inference.

The Rurrand fault and the 1756 Düren earthquakes - Paleoseismological studies in the Lower Rhine Embayment

The Rurrand fault and the 1756 Düren earthquakes - Paleoseismological studies in the Lower Rhine Embayment