Das 6. Hannes-Meyer-Seminar am Bauhaus Dessau

Wissenschaftliches Kolloquium vom 24. bis 26. Juni 1986 in Weimar an der Hochschule für Architektur und Bauwesen zum Thema: 'Der wissenschaftlich-technische Fortschritt und die sozial-kulturellen Funktionen von Architektur und industrieller Formgestaltung in unserer Epoche

Scaling behavior in the β\beta-relaxation regime of a supercooled Lennard-Jones mixture

We report the results of a molecular dynamics simulation of a supercooled binary Lennard-Jones mixture. By plotting the self intermediate scattering functions vs. rescaled time, we find a master curve in the $\beta$-relaxation regime. This master curve can be fitted well by a power-law for almost three decades in rescaled time and the scaling time, or relaxation time, has a power-law dependence on temperature. Thus the predictions of mode-coupling-theory on the existence of a von Schweidler law are found to hold for this system; moreover, the exponents in these two power-laws are very close to satisfying the exponent relationship predicted by the mode-coupling-theory. At low temperatures, the diffusion constants also show a power-law behavior with the same critical temperature. However, the exponent for diffusion differs from that of the relaxation time, a result that is in disagreement with the theory.Comment: 8 pages, RevTex, four postscript figures available on request, MZ-Physics-10

Identification of uppercrustal discontinuities using dip curvature analysis of isostatic residual gravity: examples from the central Andes

Structural analysts are often faced with the problem of identifying prominent structural discontinuities covered by post-tectonic sedimentary or volcanic rocks. Gravity fields are often used to delineate the trace of buried discontinuities but are frequently found to be too crude to localize discontinuities adequately. Here, we introduce the importance of dip curvature of the isostatic residual gravity for identifying upper-crustal discontinuities. The relationship between Bouguer gravity, isostatic residual gravity and its dip curvature, first-order structural elements and distribution of Neogene volcanic rocks was examined in the central Andean plateau, more specifically, the southern Altiplano and the Puna...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

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

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