Neue Möglichkeiten interaktiver 3-dimensionaler Modellierungen von Potentialfeldern und ihrer Ableitungen

Die hier dargestellten Methoden dienen der drei-dimensionalen, interaktiven Bearbeitung der Potentialfelder Gravimetrie und Magnetik, sowie ihrer Ableitungen (Schwere- und Magnetik-Tensor). Die Methodik ist sowohl für terrestrische, als auch Bohrloch- und Airborne-Verfahren einsetzbar. Um die Mehrdeutigkeit der interaktiven Bearbeitung bei der Vorwärtsrechnung und Inversion der Felder zu minimieren, beziehen die numerischen Verfahren verstärkt eine schnelle Computergraphik ein, sodass die Randbedingungen (meist aus der Reflexionsseismik) für die Berechnungen durch den Anwender stets sichtbar sind. Die Vorwärtsrechnungen basieren auf der Approximation geologischer Strukturen durch Polyeder, die Inversionsrechnungen für Geometrie und Gesteinsparameter (Dichte, remanente und induzierte Gesteinsmagnetisierung) werden mit Hilfe der CMA-ES (covariance-matrix-adoption evolution strategy) durchgeführt. CMA-ES ist die ideale Methode, um stark nicht-lineare und komplexe Probleme der Geophysik zu optimieren. Der Benutzer hat die Möglichkeit, die Inversion visuell zu steuern und zu beeinflussen. Die die Untergrundstrukturen approximierenden Polyeder sind durch konstante Gesteinsparameter charakterisiert; durch die Überlagerung eines Voxelmodells sind auch Strukturen mit hochgradig variabler Gesteinsparameterverteilung darstellbar. In vielen Anwendungen liegen häufig Daten vor, deren Auflösung für eine Potentialfelder-Modellierung nicht unbedingt erforderlich ist: Hier helfen neu entwickelte automatisierte Verfahren der gestalt-erhaltenden Datenreduktion. Für die Visualisierung von Potentialfeldern in Bohrlöchern werden Beispiele für eine nutzerfreundliche Visualisierung gezeigt.conferenc

INTEGRATE - Integrated 3D structural, thermal, gravity and rheological modeling of the Alps and their forelands

The aim of this project was to obtain a better understanding of the crust and the uppermost mantle beneath the Alpine orogen and its forelands and to test different hypotheses on the configuration of the subduction system as well as on the distribution of deformation and seismicity. Therefore, we have integrated the geoscientific observations publicly available so far on properties of the sediments and the crystalline crust (geometry, seismic velocities, and densities) with seismologically derived heterogeneities in the sub-crustal mantle into a consistent data-based 3D structural model that resolves the first-order contrasts in physical properties of the units composing the orogen and the forelands. The derived structural model was additionally constrained by 3D gravity modelling and used as input to derive a lithospheric temperature field based on petrological assumptions on the composition of the crust and mantle. This is done to study the effects of regional heat-flow into the Alps and their foreland basins. Starting from these 3D density thermal and lithology models, the integrated strength was derived and discussed in the context of stress and deformation fields. The project led to the successful completion of a dissertation by Cameron Spooner who obtained the highest possible grade (“summa cum laude”) from the University of Potsdam and published 4 high-level papers. Also, a Master thesis was successfully completed by Max Lowe at CAU Kiel that also led to a publication (Lowe et al. 2021). As members of the AAAGRG, the partners of CAU Kiel were significantly involved in the compilation of the new gravity maps for the Alps and their forelands (Zahorek 2021). The project contributed to “Theme 3: deformation of the crust and mantle during mountain building”, in providing the configuration of the different crustal units and of the lithospheric mantle. The project also contributed to “Theme 4: motion patterns and seismicity” in that it supported identifying spatial patterns of faulting and seismicity in relation to the rheological configuration. In response to its regional character, the project links with the different activity fields of the SPP and a continuous exchange of observations and modelling results with many working groups in the SPP and supported data processing and interpretation

DEFORM – Deformation patterns in relation to the deep configuration of the lithosphere of the Alps and their forelands

Present-day surface deformation in the Alps in terms of uplift and crustal seismicity has been attributed to surface (i.e., climatic) and tectonic processes (i.e., subduction, slab detachment/break-off, mantle flow). Quantifying the relative contribution of these forces and their interplay is fundamental to understand their role in mountain building. The present-day 3D configuration of the lithosphere and upper-mantle is a prerequisite to assess the contribution of tectonic processes. In the first phase of 4D-MB, INTEGRATE project produced a multidisciplinary data-integrated crustal model of the Alps and its forelands (Spooner et al., 2019, 2020, 2022). In the follow-up project DEFORM, we use these results to quantify how the active forces originating from the internal heterogeneity in the lithosphere and upper-mantle (i.e., lithospheric thickness and slabs in the asthenosphere) can provide some insights into the present-day mechanical set-up of the study area. To objectively interpret the upper-mantle configuration, we convert the results of regional shear-wave tomography models to temperature using an in-house developed tool (Kumar, 2022) based on Gibbs-free energy minimization algorithm (Connolly, 2005). Our results showcase a shallow/attached slab in the Northern Apennines as a common feature in the different tomography models, as also consistent with recent AlpArray seismic data-derived tomography models. They also highlight some differences among the different tomography models beneath the Alps. We quantitatively address these differences by statistically clustering tomography models into three end-members corresponding to the mean and 67% confidence intervals. These end-member models represent scenarios ranging from shallow/attached slabs to almost no slabs in the northern Apennines and Alps. End-member scenarios of the mantle configuration are tested with the new pan-Alpine gravity anomaly by 3D density modelling (IGMAS+, Götze et al., 2023), surface uplift from GNSS, AlpArray seismicity catalogue, mantle flow inferred from the shear-wave splitting measurements of the AlpArray seismic experiment, and resulting topography. As a first step, we model topography and deformation velocities as resulting from buoyancy-forces driven by a quasi-instantaneous flow resulting from the first-order rheological structure of the lithosphere-asthenosphere system using the open-source geodynamic simulator LaMEM (Kaus et al., 2016). We found that detached slab beneath the Alps, but attached beneath the Northern Apennines captures first-order patterns in topography, vertical surface velocities, and mantle flow (Kumar et al., 2022). The presence of an attached slab beneath the northern Apennines can also explain the observed sub-crustal seismicity compared to the upper-crustal seismicity in the Alps. Data-derived scenario-based modelling approach allowed us to capture the first-order characteristics of the lithosphere and upper-mantle configuration in the Alps and corresponding forelands. Although we have been able to explain first-order observations with respect to the end member variations in viscosity and density contrasts, we additionally carried out a global sensitivity analysis to quantify associated uncertainties as well as the degree of parameter correlation within a solid density-effective viscosity phase space. This was done using physics-preserving surrogate models (model order reduction via reduced basis, Degen et al., 2022) to effectively run ensemble models of the dynamic state of the system (Denise et al., 2023). Using surrogate models, we explore deformation velocities and stresses, guiding boundary conditions to reconstruct the loading/unloading history of the last glacial cycle

A Constrained 3D Density Model of the Upper Crust from Gravity Data Interpretation for Central Costa Rica

Copyright © 2010 Oscar H. Lücke et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.The map of complete Bouguer anomaly of Costa Rica shows an elongated NW-SE trending gravity low in the central region. This gravity low coincides with the geographical region known as the Cordillera Volcánica Central. It is built by geologic and morpho-tectonic units which consist of Quaternary volcanic edifices. For quantitative interpretation of the sources of the anomaly and the characterization of fluid pathways and reservoirs of arc magmatism, a constrained 3D density model of the upper crust was designed by means of forward modeling. The density model is constrained by simplified surface geology, previously published seismic tomography and P-wave velocity models, which stem from wide-angle refraction seismic, as well as results from methods of direct interpretation of the gravity field obtained for this work. The model takes into account the effects and influence of subduction-related Neogene through Quaternary arc magmatism on the upper crust.Special Priority Program 1257 ‘Mass Transport and Mass Distribution in the Earth System’Collaborative Research Centre/[SFB574]//AlemaniaGerman Academic Exchange Service//DAAD/AlemaniaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela Centroamericana de Geologí

Casting manufacturing of cylindrical preforms made of low alloy steels

The manufacturing of complex drivetrain components made of steel requires multi-stage manufacturing processes, resulting in long processing times and high costs. Forged parts get their final geometry after multi-stage forming operations. One approach to shorten such process chains is close contour casting of steel preforms and a single subsequent forming step to achieve high strength properties similar to those of multi-stage forged parts. Since the application of precision forging using cast steel preforms has been studied insufficiently up to now, the manufacturing of cylindrical preforms made of the low-alloy heat-treatable steel G42CrMo4 by sand casting was investigated. Using casting simulations, suitable casting parameters for the finished casting systems were identified and nearly pore-free preforms were achieved. Depending on the casting system, metallographic investigations revealed different fractions of bainite in the microstructure of the casted preforms. Subsequently, the cylinders were deformed in upsetting experiments by which the remaining porosity could be eliminated. The numerical casting simulation was combined with a forming simulation to model the reduction in porosity and to allow the prediction of the densification behavior in further research employing more complex geometries

Colorado Basin 3D structure and evolution, Argentine passive margin

International audienceThis 3D structural model of the Colorado Basin provides new insights into the crustal geometry of the basin and its evolution in relation with the Argentine passive margin. Three NW-SE segments (oblique to the N30°E-trending margin) structure the basin. The oldest infill is generally thought to be coeval with the rifting of the South Atlantic margins in Late Jurassic-Early Cretaceous. This coeval development of the Colorado Basin and of the passive margin is still under debate and gives rise to several hypotheses that we investigate in the light of our observations. We propose that reactivation of inherited structures is predominant in the evolution of the Colorado Basin: (1) the Western segment follows the continental continuation of the Colorado transfer zone; (2) the Central segment consists in the continental continuation of the Tona deformation zone; (3) the Eastern segment is superimposed over the Palaeozoic Claromecó Basin. In addition to the 3 segments, the Central High, separating the Central segment to the Eastern segment, corresponds to the Palaeozoic Sierras Australes Fold Belt. The direction of extension responsible for the South Atlantic opening cannot explain the syn-rift infill and thinning of the basin. The structural analysis shows two phases of syn-rift deformation with different directions. Thus, we suggest that the Colorado Basin and the South Atlantic margin are not coeval but that a first extensional event, probably oblique, predates the extension responsible for the South Atlantic opening. This event is then followed by the formation of the N30°-trending distal margin and the reactivation of Palaeozoic N70°-trending faults occurs under the NW-SE opening of the South Atlantic. This two-phase evolution is consistent with the fault chronology and the two directions of thinned crust observed in the distal margin