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1. A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS$_4$ measured from stellar occultations

Author

Rommel, F. L., Braga-Ribas, F., Ortiz, J. L., Sicardy, B., Santos-Sanz, P., Desmars, J., Camargo, J. I. B., Vieira-Martins, R., Assafin, M., Morgado, B. E., Boufleur, R. C., Benedetti-Rossi, G., Gomes-Júnior, A. R., Fernández-Valenzuela, E., Holler, B. J., Souami, D., Duffard, R., Margoti, G., Vara-Lubiano, M., Lecacheux, J., Plouvier, J. L., Morales, N., Maury, A., Fabrega, J., Ceravolo, P., Jehin, E., Albanese, D., Mariey, H., Cikota, S., Ruždjak, D., Cikota, A., Szakáts, R., Aissa, D. Baba, Gringahcene, Z., Kashuba, V., Koshkin, N., Zhukov, V., Fişek, S., Çakır, O., Özer, S., Schnabel, C., Schnabel, M., Signoret, F., Morrone, L., Santana-Ros, T., Pereira, C. L., Emilio, M., Burdanov, A. Y., de Wit, J., Barkaoui, K., Gillon, M., Leto, G., Frasca, A., Catanzaro, G., Sanchez, R. Zanmar, Tagliaferri, U., Di Sora, M., Isopi, G., Krugly, Y., Slyusarev, I., Chiorny, V., Mikuž, H., Bacci, P., Maestripieri, M., Grazia, M. D., de la Cueva, I., Yuste-Moreno, M., Ciabattari, F., Kozhukhov, O. M., Serra-Ricart, M., Alarcon, M. R., Licandro, J., Masi, G., Bacci, R., Bosch, J. M., Behem, R., Prost, J. -P., Renner, S., Conjat, M., Bachini, M., Succi, G., Stoian, L., Juravle, A., Carosati, D., Gowe, B., Carrillo, J., Zheleznyak, A. P., Montigiani, N., Foster, C. R., Mannucci, M., Ruocco, N., Cuevas, F., Di Marcantonio, P., Coretti, I., Iafrate, G., Baldini, V., Collins, M., Pál, A., Csák, B., Fernández-Garcia, E., Castro-Tirado, A. J., Hudin, L., Madiedo, J. M., Anghel, R. M., Calvo-Fernández, J. F., Valvasori, A., Guido, E., Gherase, R. M., Kamoun, S., Fafet, R., Sánchez-González, M., Curelaru, L., Vîntdevară, C. D., Danescu, C. A., Gout, J. -F., Schmitz, C. J., Sota, A., Belskaya, I., Rodríguez-Marco, M., Kilic, Y., Frappa, E., Klotz, A., Lavayssière, M., Oliveira, J. Marques, Popescu, M., Mammana, L. A., Fernández-Lajús, E., Schmidt, M., Hopp, U., Komžík, R., Pribulla, T., Tomko, D., Husárik, M., Erece, O., Eryilmaz, S., Buzzi, L., Gährken, B., Nardiello, D., Hornoch, K., Sonbas, E., Er, H., Burwitz, V., Sybilski, P. Waldemar, Bykowski, W., Müller, T. G., Ogloza, W., Gonçalves, R., Ferreira, J. F., Ferreira, M., Bento, M., Meister, S., Bagiran, M. N., Tekeş, M., Marciniak, A., Moravec, Z., Delinčák, P., Gianni, G., Casalnuovo, G. B., Boutet, M., Sanchez, J., Klemt, B., Wuensche, N., Burzynski, W., Borkowski, M., Serrau, M., Dangl, G., Klös, O., Weber, C., Urbaník, M., Rousselot, L., Kubánek, J., André, P., Colazo, C., Spagnotto, J., Sickafoose, A. A., Hueso, R., Sánchez-Lavega, A., Fisher, R. S., Rengstorf, A. W., Perelló, C., Dascalu, M., Altan, M., Gazeas, K., de Santana, T., Sfair, R., Winter, O. C., Kalkan, S., Canales-Moreno, O., Trigo-Rodríguez, J. M., Tsamis, V., Tigani, K., Sioulas, N., Lekkas, G., Bertesteanu, D. N., Dumitrescu, V., Wilberger, A. J., Barnes, J. W., Fieber-Beyer, S. K., Swaney, R. L., Fuentes, C., Mendez, R. A., Dumitru, B. D., Flynn, R. L., and Wake, D. A.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

This work aims at constraining the size, shape, and geometric albedo of the dwarf planet candidate 2002 MS4 through the analysis of nine stellar occultation events. Using multichord detection, we also studied the object's topography by analyzing the obtained limb and the residuals between observed chords and the best-fitted ellipse. We predicted and organized the observational campaigns of nine stellar occultations by 2002 MS4 between 2019 and 2022, resulting in two single-chord events, four double-chord detections, and three events with three to up to sixty-one positive chords. Using 13 selected chords from the 8 August 2020 event, we determined the global elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the object's rotational information from the literature, constrains the object's size, shape, and albedo. Additionally, we developed a new method to characterize topography features on the object's limb. The global limb has a semi-major axis of 412 $\pm$ 10 km, a semi-minor axis of 385 $\pm$ 17 km, and the position angle of the minor axis is 121 $^\circ$ $\pm$ 16$^\circ$. From this instantaneous limb, we obtained 2002 MS4's geometric albedo and the projected area-equivalent diameter. Significant deviations from the fitted ellipse in the northernmost limb are detected from multiple sites highlighting three distinct topographic features: one 11 km depth depression followed by a 25$^{+4}_{-5}$ km height elevation next to a crater-like depression with an extension of 322 $\pm$ 39 km and 45.1 $\pm$ 1.5 km deep. Our results present an object that is $\approx$138 km smaller in diameter than derived from thermal data, possibly indicating the presence of a so-far unknown satellite. However, within the error bars, the geometric albedo in the V-band agrees with the results published in the literature, even with the radiometric-derived albedo.

Published
2023
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2. Stable SEI Formation on Al-Si-Mn Metallic Glass Li-Ion Anode

Author

Schnabel, M, Lin, TC, Arca, E, Yoon, I, Veith, GM, He, X, and Kostecki, R

Subjects
Energy, Macromolecular and Materials Chemistry, Physical Chemistry (incl. Structural), Materials Engineering
Abstract

Alloying anodes such as silicon are of great interest for lithium-ion batteries due to their high lithium-ion storage capacities, but have only seen minimal commercial deployment due to their limited calendar life. This has been attributed to an intrinsically unstable solid electrolyte interphase (SEI) that is aggravated by mechanical failure. An amorphous structure can mitigate lithiation strains, and amorphous alloys, or metallic glasses, often exhibit exceptional fracture toughness. Additional elements can be added to metallic glasses to improve passivation. Splat quenching was utilized to prepare an amorphous Al64Si25Mn11 Li-ion anode with a specific capacity >900 mAh g-1 that remains amorphous upon cycling. On this metallic glass electrode, parasitic electrolyte reduction is found to be much reduced in comparison to pure Si or Al, and comparable to that on Cu. The SEI is much thinner, more stable, and richer in fluorinated inorganic phases than the SEI formed on Si, while organic carbonate compounds such as lithium ethylene decarbonate (LiEDC) are notably absent. This study indicates that metallic glasses can become a viable new class of Li-ion anode materials with improved surface passivity.

Published
2021

3. Formation of silicon nanocrystals in silicon carbide using flash lamp annealing

Author

Weiss, C., Schnabel, M., Prucnal, S., Hofmann, J., Reichert, A., Fehrenbach, T., Skorupa, W., and Janz, S.

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

During the formation of Si nanocrystals (Si NC) in Si$_x$C$_{1-x}$ layers via solid-phase crystallization, the unintended formation of nanocrystalline SiC reduces the minority carrier lifetime and therefore the performance of Si$_x$C$_{1-x}$ as an absorber layer in solar cells. A significant reduction in the annealing time may suppress the crystallization of the SiC matrix while maintaining the formation of Si NC. In this study, we investigated the crystallization of stoichiometric SiC and Si-rich SiC using conventional rapid thermal annealing (RTA) and nonequilibrium millisecond range flash lamp annealing (FLA). The investigated Si$_x$C$_{1-x}$ films were prepared by plasma-enhanced chemical vapor deposition and annealed at temperatures from 700${\deg}$C to 1100${\deg}$C for RTA and at flash energies between 34 J/cm$^2$ and 62 J/cm$^2$ for FLA. GIXRD and FTIR were conducted to investigate hydrogen effusion, Si and SiC NC growth, and SiC crystallinity. Both the Si content and the choice of the annealing process affect the crystallization behavior. It is shown that under certain conditions, FLA can be successfully utilized for the formation of Si NC in a SiC matrix, which closely resembles Si NC in a SiC matrix achieved by RTA. The samples must have excess Si, and the flash energy should not exceed 40 J/cm$^2$ and 47 J/cm$^2$ for Si$_{0.63}$C$_{0.37}$ and Si$_{0.77}$C$_{0.23}$ samples, respectively. Under these conditions, FLA succeeds in producing Si NC of a given size in less crystalline SiC than RTA does. This result is discussed in terms of nucleation and crystal growth using classical crystallization theory. For FLA and RTA samples, an opposite relationship between NC size and Si content was observed and attributed either to the dependence of H effusion on Si content or to the optical absorption properties of the materials, which also depend on the Si content.

Published
2020
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4. Structural and optical properties of silicon nanocrystals embedded in silicon carbide

Author

Weiss, C., Schnabel, M., Reichert, A., Löper, P., and Janz, S.

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

The outstanding demonstration of quantum confinement in Si nanocrystals (Si NC) in a SiC matrix requires the fabrication of Si NC with a narrow size distribution. It is understood without controversy that this fabrication is a difficult exercise and that a multilayer (ML) structure is suitable for such fabrication only in a narrow parameter range. This parameter range is sought by varying both the stoichiometric SiC barrier thickness and the Si-rich SiC well thickness between 3 and 9 nm and comparing them to single layers (SL). The samples processed for this investigation were deposited by plasma-enhanced chemical vapor deposition (PECVD) and subsequently subjected to thermal annealing at 1000-1100${\deg}$C for crystal formation. Bulk information about the entire sample area and depth were obtained by structural and optical characterization methods: information about the mean Si NC size was determined from grazing incidence X-ray diffraction (GIXRD) measurements. Fourier-transform infrared spectroscopy (FTIR) was applied to gain insight into the structure of the Si-C network, and spectrophotometry measurements were performed to investigate the absorption coefficient and to estimate the bandgap $E_{04}$. All measurements showed that the influence of the ML structure on the Si NC size, on the Si-C network and on the absorption properties is subordinate to the influence of the overall Si content in the samples, which we identified as the key parameter for the structural and optical properties. We attribute this behavior to interdiffusion of the barrier and well layers. Because the produced Si NC are within the target size range of 2-4 nm for all layer thickness variations, we propose to use the Si content to adjust the Si NC size in future experiments.

Published
2020
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5. Enhanced Interfacial Stability of Si Anodes for Li-Ion Batteries via Surface SiO2Coating

Author

Schnabel, M, Arca, E, Ha, Y, Stetson, C, Teeter, G, Han, SD, and Stradins, P

Subjects
silicon anode, silicon oxide, lithiation, lithium-ion battery, solid electrolyte interphase, carbonate electrolyte, interface, electrolyte reduction
Abstract

Silicon is a promising alloying anode for lithium-ion batteries because of its high capacity and low cost. However, its use has been hampered by mechanical failure arising from the large volume change upon cycling and by an insufficiently stable solid electrolyte interphase (SEI). SEI formation depends on the Si surface, which is often an oxide (SiOx). In this study we compare three different Si surfaces using Si wafers: 1.3 nm native SiOx, 1.4 nm thermally grown SiO2, and a SiOx-free surface. The oxide-free surface showed the worst electrochemical performance, never exceeding 94% Coulombic efficiency (CE). It also exhibited the thickest SEI and the highest overpotential for lithiation, which correlated with uninhibited electrolyte reduction and the incorporation of P-F species into the SEI. The oxide-coated surfaces performed significantly better, demonstrating a CE above 99% beyond the second cycle, low overpotential for lithiation, and a thinner and more stable SEI. The oxides lower the onset potential for electrolyte reduction and yield an SEI with fewer P-F species. However, it was found that the CE with the native oxide surface decays from the fifth cycle onward and correlates with a resurgence of electrolyte reduction. A 1-2 nm thermal SiO2 coating is optimum for achieving a stable SEI that minimizes side reactions and sustains efficient cycling.

Published
2020

6. Tectonic Quiescence in Actively Extending Back‐Arc Regions.

Author

Beniest, A., Dannowski, A., Schnabel, M., and Kopp, H.

Subjects
ISLAND arcs, PLATE tectonics, SUBDUCTION zones, PYROXENE, HYDROUS
Abstract

We analyzed refraction and reflection seismic data covering the Central Lau Spreading Center (CLSC) and the Tonga volcanic arc at 18°S in the Pacific Ocean to investigate tectonic inactivity in actively extending back‐arc systems. Our P‐wave travel time tomography shows a characteristic 6–8 km thick back‐arc crust beneath and around the CLSC and a ∼13 km thick arc‐crust at the eastern end of our profile, which corresponds to the Tonga volcanic arc. Lower crustal velocities increase to 7.5 km/s toward the volcanic arc, marking the transition from back‐arc to arc crust. These high P‐wave velocities can be explained by a high pyroxene content in the lower crust originating from depleted melts. Our seismic reflection data show steep normal faults below the CLSC and volcanic structures closer to the volcanic arc, without a tectonically inactive zone (also knows as the "diffuse plate boundary") in between. Based on our results, we suggest that the Niuafo'ou and Tonga microplates should be treated as one tectonic plate with local zones of intra‐plate deformation that are separated by zones that are tectonically quiet. Plain Language Summary: In a subduction zone one tectonic plate sinks below another. A retreating downgoing plate causes tension in the overriding plate, which leads to thinning behind the volcanic arc: a back‐arc basin is born. We investigate the crustal structure of a seismically inactive region within a back‐arc basin in overall extension. Our aim is to understand why there is no seismic activity in this specific area. The Lau Basin is our case study, because it is a type‐example for back‐arc basin tectonics. We have acquired and interpreted seismic data to analyse the structure of the crust along a profile in the Lau Basin. We observe crustal thickness changes from typical back‐arc crust (6 and 7 km) to arc‐crust (13 km), and volcanic remnants in the crust with higher crustal velocities. Current tectonic activity only occurs at the Central Lau Spreading Center (CLSC), not in between the CLSC and the volcanic arc. We therefore reject the idea of a diffuse plate boundary, and propose that the Niuafo'ou and Tonga microplates should be treated as one tectonic plate that consists of localized zones that deform. In between those actively extending zones, there are areas that do not deform and that are tectonically quiet. Key Points: The crustal structure of the central Lau Basin at 18°S complies with typical back‐arc/arc crustal velocities and thicknessSouth of the FRSC no plate boundary is observed, suggesting one Niuafo'ou‐Tonga plate with zones of intraplate deformationHigh crustal P‐wave velocities result from the crystalisation of hydrous melts (upper crust) and pyroxene‐rich material (lower crust) [ABSTRACT FROM AUTHOR]

Published
2024
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7. Breaking boundaries: Exploring extended pembrolizumab in first-line treatment of renal cell carcinoma with axitinib-pembrolizumab combination

Author

Aydogdu, C., primary, Paffenholz, P., additional, Stelmach, R., additional, Schlack, K., additional, Roghmann, F., additional, Handke, A., additional, Mandal, S., additional, Schnabel, M., additional, Merseburger, A., additional, Ivanyi, P., additional, Tschäbitz, S., additional, Darr, C., additional, Grünwald, V., additional, Stief, C.G., additional, and Casuscelli, J., additional

Published
2024
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10. Treatment options and outcome of metastatic renal cell carcinoma patients with brain or bone metastases - a real world evidence

Author

Paffenholz, P, Ivanyi, P, Jozefina, C, Stelmach, R, Zschäbitz, S, Schostak, M, Gür, M, Schlack, K, Darr, C, Schnabel, M, Rinderknecht, E, Hilser, T, Flegar, L, Mandal, S, Klee, M, Daniel, S, Handke, A, Nestler, T, Mattigk, A, Augustin, M, Hijazi, S, Rehlinghaus, M, Heidenreich, A, Grünwald, V, Paffenholz, P, Ivanyi, P, Jozefina, C, Stelmach, R, Zschäbitz, S, Schostak, M, Gür, M, Schlack, K, Darr, C, Schnabel, M, Rinderknecht, E, Hilser, T, Flegar, L, Mandal, S, Klee, M, Daniel, S, Handke, A, Nestler, T, Mattigk, A, Augustin, M, Hijazi, S, Rehlinghaus, M, Heidenreich, A, and Grünwald, V

Published
2024

12. Tectonic Quiescence in Actively Extending Back‐Arc Regions

Author

Beniest, Anouk, Dannowski, Anke, Schnabel, M., Kopp, Heidrun, Beniest, Anouk, Dannowski, Anke, Schnabel, M., and Kopp, Heidrun

Abstract

We analyzed refraction and reflection seismic data covering the Central Lau Spreading Center (CLSC) and the Tonga volcanic arc at 18°S in the Pacific Ocean to investigate tectonic inactivity in actively extending back-arc systems. Our P-wave travel time tomography shows a characteristic 6–8 km thick back-arc crust beneath and around the CLSC and a ∼13 km thick arc-crust at the eastern end of our profile, which corresponds to the Tonga volcanic arc. Lower crustal velocities increase to 7.5 km/s toward the volcanic arc, marking the transition from back-arc to arc crust. These high P-wave velocities can be explained by a high pyroxene content in the lower crust originating from depleted melts. Our seismic reflection data show steep normal faults below the CLSC and volcanic structures closer to the volcanic arc, without a tectonically inactive zone (also knows as the “diffuse plate boundary”) in between. Based on our results, we suggest that the Niuafo'ou and Tonga microplates should be treated as one tectonic plate with local zones of intra-plate deformation that are separated by zones that are tectonically quiet. Key Points The crustal structure of the central Lau Basin at 18°S complies with typical back-arc/arc crustal velocities and thickness South of the FRSC no plate boundary is observed, suggesting one Niuafo'ou-Tonga plate with zones of intraplate deformation High crustal P-wave velocities result from the crystalisation of hydrous melts (upper crust) and pyroxene-rich material (lower crust) Plain Language Summary In a subduction zone one tectonic plate sinks below another. A retreating downgoing plate causes tension in the overriding plate, which leads to thinning behind the volcanic arc: a back-arc basin is born. We investigate the crustal structure of a seismically inactive region within a back-arc basin in overall extension. Our aim is to understand why there is no seismic activity in this specific area. The Lau Basin is our case study, because it is a type-e

Published
2024
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15. Essays on the economics of crime

Author

Schnabel, M.

Subjects
330
Abstract

This thesis considers public policy effects on crime in Sweden using extensive administrative register data on all convictions in Sweden between 1973-2010. First, it explores the impacts of the Swedish compulsory schooling reform that took place between 1949-1962 on individual crime of the generation directly targeted by the education reform. Then it considers the intergenerational effect of this education policy on crime. Policies are often evaluated on either short term outcomes or just in terms of their effect on individuals directly targeted. If such policies shift outcomes across generations their benefits may be much larger than originally thought. This study provides novel evidence on the intergenerational impact of policy by showing that educational reform in Sweden reduced crime rates of the targeted generation and their sons by comparable amounts. The second policy evaluated in this thesis is a liberalization of the opening hours of the Swedish alcohol monopoly outlet stores that took place between 2000- 2001. This study distinguishes itself from existing studies by mapping out an age-specific policy impact on crime for all ages and for a broad set of types of crimes. Whether and how alcohol policies shift criminal outcomes differently for different ages and type of crimes is not well established. The liberalized opening hours of outlet stores had very heterogeneous effects on crime by age and type of crimes. It reduced overall crime rates for male teenagers by 15-20 percent, mainly driven by reductions in drugs and property offences. Men in their mid-thirties also experience a substantial reduction of overall crime rates by 9 percent that comes from reductions in other crimes category and traffic crimes. While a strong increase of 10 percent in the crime rate for men in their early to mid-twenties can be mainly attributed towards a large increase in drug offences.

Published
2014

16. Is the Percolation Probability on $\mathbb{Z}^d$ with Long Range Connections Monotone?

Author

Atman, A. P. F., de Lima, B. N. B., and Schnabel, M.

Subjects
Condensed Matter - Statistical Mechanics, Physics - Computational Physics
Abstract

We present a numerical study for the threshold percolation probability, $p_c$, in the bond percolation model with multiple ranges, in the square lattice. A recent Theorem demonstrated by de Lima {\it et al.} [B. N. B. de Lima, R. P. Sanchis, R. W. C. Silva, STOCHASTIC PROC APPL {\bf 121}, 2043-2048 (2011)] states that the limit value of $p_c$ when the long ranges go to infinity converges to the bond percolation threshold in the hypercubic lattice, $\mathbb{Z}^d$, for some appropriate dimension $d$. We present the first numerical estimations for the percolation threshold considering two-range and three-range versions of the model. Applying a finite size analysis to the simulation data, we sketch the dependence of $p_c$ in function of the range of the largest bond. We shown that, for the two-range model, the percolation threshold is a non decreasing function, as conjectured in the cited work, and converges to the predicted value. However, the results to the three-range case exhibit a surprising non-monotonic behavior for specific combinations of the long range lengths, and the convergence to the predicted value is less evident, raising new questionings on this fascinating problem., Comment: 9 pages, figures

Published
2012

17. A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS4 measured from stellar occultations

Author

Rommel, F. L., primary, Braga-Ribas, F., additional, Ortiz, J. L., additional, Sicardy, B., additional, Santos-Sanz, P., additional, Desmars, J., additional, Camargo, J. I. B., additional, Vieira-Martins, R., additional, Assafin, M., additional, Morgado, B. E., additional, Boufleur, R. C., additional, Benedetti-Rossi, G., additional, Gomes-Júnior, A. R., additional, Fernández-Valenzuela, E., additional, Holler, B. J., additional, Souami, D., additional, Duffard, R., additional, Margoti, G., additional, Vara-Lubiano, M., additional, Lecacheux, J., additional, Plouvier, J. L., additional, Morales, N., additional, Maury, A., additional, Fabrega, J., additional, Ceravolo, P., additional, Jehin, E., additional, Albanese, D., additional, Mariey, H., additional, Cikota, S., additional, Ruždjak, D., additional, Cikota, A., additional, Szakáts, R., additional, Baba Aissa, D., additional, Gringahcene, Z., additional, Kashuba, V., additional, Koshkin, N., additional, Zhukov, V., additional, Fişek, S., additional, Çakir, O., additional, Özer, S., additional, Schnabel, C., additional, Schnabel, M., additional, Signoret, F., additional, Morrone, L., additional, Santana-Ros, T., additional, Pereira, C. L., additional, Emilio, M., additional, Burdanov, A. Y., additional, de Wit, J., additional, Barkaoui, K., additional, Gillon, M., additional, Leto, G., additional, Frasca, A., additional, Catanzaro, G., additional, Sanchez, R. Zanmar, additional, Tagliaferri, U., additional, Di Sora, M., additional, Isopi, G., additional, Krugly, Y., additional, Slyusarev, I., additional, Chiorny, V., additional, Mikuž, H., additional, Bacci, P., additional, Maestripieri, M., additional, Grazia, M. D., additional, de la Cueva, I., additional, Yuste-Moreno, M., additional, Ciabattari, F., additional, Kozhukhov, O. M., additional, Serra-Ricart, M., additional, Alarcon, M. R., additional, Licandro, J., additional, Masi, G., additional, Bacci, R., additional, Bosch, J. M., additional, Behem, R., additional, Prost, J.-P., additional, Renner, S., additional, Conjat, M., additional, Bachini, M., additional, Succi, G., additional, Stoian, L., additional, Juravle, A., additional, Carosati, D., additional, Gowe, B., additional, Carrillo, J., additional, Zheleznyak, A. P., additional, Montigiani, N., additional, Foster, C. R., additional, Mannucci, M., additional, Ruocco, N., additional, Cuevas, F., additional, Di Marcantonio, P., additional, Coretti, I., additional, Iafrate, G., additional, Baldini, V., additional, Collins, M., additional, Pál, A., additional, Csák, B., additional, Fernández-Garcia, E., additional, Castro-Tirado, A. J., additional, Hudin, L., additional, Madiedo, J. M., additional, Anghel, R. M., additional, Calvo-Fernández, J. F., additional, Valvasori, A., additional, Guido, E., additional, Gherase, R. M., additional, Kamoun, S., additional, Fafet, R., additional, Sánchez-González, M., additional, Curelaru, L., additional, Vîntdevară, C. D., additional, Danescu, C. A., additional, Gout, J.-F., additional, Schmitz, C. J., additional, Sota, A., additional, Belskaya, I., additional, Rodríguez-Marco, M., additional, Kilic, Y., additional, Frappa, E., additional, Klotz, A., additional, Lavayssière, M., additional, Oliveira, J. Marques, additional, Popescu, M., additional, Mammana, L. A., additional, Fernández-Lajús, E., additional, Schmidt, M., additional, Hopp, U., additional, Komžík, R., additional, Pribulla, T., additional, Tomko, D., additional, Husárik, M., additional, Erece, O., additional, Eryilmaz, S., additional, Buzzi, L., additional, Gährken, B., additional, Nardiello, D., additional, Hornoch, K., additional, Sonbas, E., additional, Er, H., additional, Burwitz, V., additional, Sybilski, P. Waldemar, additional, Bykowski, W., additional, Müller, T. G., additional, Ogloza, W., additional, Gonçalves, R., additional, Ferreira, J. F., additional, Ferreira, M., additional, Bento, M., additional, Meister, S., additional, Bagiran, M. N., additional, Tekeş, M., additional, Marciniak, A., additional, Moravec, Z., additional, Delinčák, P., additional, Gianni, G., additional, Casalnuovo, G. B., additional, Boutet, M., additional, Sanchez, J., additional, Klemt, B., additional, Wuensche, N., additional, Burzynski, W., additional, Borkowski, M., additional, Serrau, M., additional, Dangl, G., additional, Klös, O., additional, Weber, C., additional, Urbaník, M., additional, Rousselot, L., additional, Kubánek, J., additional, André, P., additional, Colazo, C., additional, Spagnotto, J., additional, Sickafoose, A. A., additional, Hueso, R., additional, Sánchez-Lavega, A., additional, Fisher, R. S., additional, Rengstorf, A. W., additional, Perelló, C., additional, Dascalu, M., additional, Altan, M., additional, Gazeas, K., additional, de Santana, T., additional, Sfair, R., additional, Winter, O. C., additional, Kalkan, S., additional, Canales-Moreno, O., additional, Trigo-Rodríguez, J. M., additional, Tsamis, V., additional, Tigani, K., additional, Sioulas, N., additional, Lekkas, G., additional, Bertesteanu, D. N., additional, Dumitrescu, V., additional, Wilberger, A. J., additional, Barnes, J. W., additional, Fieber-Beyer, S. K., additional, Swaney, R. L., additional, Fuentes, C., additional, Mendez, R. A., additional, Dumitru, B. D., additional, Flynn, R. L., additional, and Wake, D. A., additional

Published
2023
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18. Fake symmetry transitions in lattice Dirac spectra

Author

Schnabel, M. and Wettig, T.

Subjects
High Energy Physics - Lattice
Abstract

In a recent lattice investigation of Ginsparg-Wilson-type Dirac operators in the Schwinger model, it was found that the symmetry class of the random matrix theory describing the small Dirac eigenvalues appeared to change from the unitary to the symplectic case as a function of lattice size and coupling constant. We present a natural explanation for this observation in the framework of a random matrix model, showing that the apparent change is caused by the onset of chiral symmetry restoration in a finite volume. A transition from unitary to symplectic symmetry does not occur., Comment: 6 pages, 3 figures, REVTeX

Published
1999
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20. A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS4 measured from stellar occultations

Author

Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Rommel, F.L., Braga-Ribas, F., Ortiz Moreno, José Luis, Sicardy, B., Santos Sanz, Pablo, Desmars, Josselin, Camargo, J.I.B., Vieira-Martins, R., Assafin, M., Morgado, B.E., Boufleur, R.C., Burwitz, V., Waldemar Sybilski, P., Bykowski, W., Müller, Thomas G., Ogloza, W., Gonçalves, R., Ferreira, J.F., Ferreira, M., Bento, M., Urbaník, M., Di Sora, M., Souami, Damya, Canales-Moreno, O., Meister, S., Bagiran, M.N., Tekeş, M., Marciniak, Anna, Moravec, Z., Delinčák, P., Gianni, G., Casalnuovo, G.B., Isopi, G., Tsamis, V., Boutet, M., Sanchez, J., Trigo-Rodríguez, Josep M., Duffard, René, Renner, S., Rousselot, L., Margoti, G., Kubánek, J., André, P., Krugly, Yurij, Colazo, C., Spagnotto, J., Sickafoose, A.A., Hueso, R., Sánchez-Lavega, A., Fisher, R.S., Conjat, M., Lecacheux, J., Rengstorf, A.W., Perelló, C., Slyusarev, I., Vara-Lubiano, M., Dascalu, M., Castro-Tirado, Alberto J., Tigani, K., Sioulas, Nick, Lekkas, G., Bertesteanu, D.N., Bachini, M., Dumitrescu, V., Wilberger, A.J., Chiorny, V., Barnes, J.W., Fieber-Beyer, S.K., Swaney, R.L., Fuentes, C., Hudin, L., Plouvier, J.L., Mendez, R.A., Dumitru, B.D., Succi, G., Flynn, R.L., Mikuz, H., Wake, D.A., Morales, Nicolás, Maury, Alain, Fabrega, J., Ceravolo, P., Jehin, Emmanuel, Madiedo, J.M., Albanese, D., Mariey, H., Stoian, L., Bacci, P., Cikota, S., Ruždjak, D., Cikota, A., Szakáts, Róbert, Baba Aissa, D., Gringahcene, Z., Kashuba, V., Koshkin, N., Anghel, R.M., Zhukov, V., Maestripieri, M., Juravle, A., Fişek, S., Çakir, O., Özer, S., Schnabel, C., Schnabel, M., Signoret, F., Morrone, L., Santana-Ros, Toni, Pereira, C.L., Grazia, M.D., Calvo-Fernández, J.F., Carosati, D., Emilio, M., Burdanov, A.Y., de Wit, J., Barkaoui, K., Gillon, M., Leto, G., Frasca, A., Catanzaro, G., Carrillo, J., Zanmar Sanchez, R., Tagliaferri, U., Gowe, B., Valvasori, A., Klemt, B., de la Cueva, I., Guido, E., Yuste-Moreno, M., Ciabattari, F., Kozhukhov, O.M., Serra-Ricart, M., Alarcon, Miguel R., Licandro, Javier, Masi, G., Bacci, Roberto, Wuensche, N., Kamoun, S., Bosch, Josep M., Behem, R., Gherase, R.M., Prost, J.-P., Altan, M., Zheleznyak, A.P., Montigiani, N., Foster, C.R., Mannucci, M., Burzynski, W., Ruocco, Nello, Cuevas, F., Di Marcantonio, P., Coretti, I., Iafrate, G., Baldini, V., Gazeas, K., Fafet, R., Collins, M., Pál, András, Borkowski, M., Csák, B., Fernández-García, Emilio, Benedetti-Rossi, G., Sánchez-González, M., Curelaru, L., Vîntdevară, C.D., Danescu, C.A., de Santana, T., Gout, J.-F., Schmitz, C.J., Serrau, M., Sota, Alfredo, Belskaya, Irina, Rodríguez-Marco, M., Kilic, Y., Gomes-Júnior, A.R., Frappa, E., Klotz, A., Lavayssière, M., Sfair, R., Marques Oliveira, J., Dangl, G., Popescu, Marcel, Mammana, L.A., Fernández-Lajús, E., Schmidt, M., Hopp, U., Komžík, R., Fernández-Valenzuela, Estela, Pribulla, T., Tomko, D., Winter, O.C., Klös, O., Husárik, Marek, Erece, O., Eryilmaz, S., Buzzi, Luca, Gährken, B., Nardiello, D., Hornoch, Kamil, Sonbas, E., Holler, B.J., Er, H., Weber, C., Kalkan, S., Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Rommel, F.L., Braga-Ribas, F., Ortiz Moreno, José Luis, Sicardy, B., Santos Sanz, Pablo, Desmars, Josselin, Camargo, J.I.B., Vieira-Martins, R., Assafin, M., Morgado, B.E., Boufleur, R.C., Burwitz, V., Waldemar Sybilski, P., Bykowski, W., Müller, Thomas G., Ogloza, W., Gonçalves, R., Ferreira, J.F., Ferreira, M., Bento, M., Urbaník, M., Di Sora, M., Souami, Damya, Canales-Moreno, O., Meister, S., Bagiran, M.N., Tekeş, M., Marciniak, Anna, Moravec, Z., Delinčák, P., Gianni, G., Casalnuovo, G.B., Isopi, G., Tsamis, V., Boutet, M., Sanchez, J., Trigo-Rodríguez, Josep M., Duffard, René, Renner, S., Rousselot, L., Margoti, G., Kubánek, J., André, P., Krugly, Yurij, Colazo, C., Spagnotto, J., Sickafoose, A.A., Hueso, R., Sánchez-Lavega, A., Fisher, R.S., Conjat, M., Lecacheux, J., Rengstorf, A.W., Perelló, C., Slyusarev, I., Vara-Lubiano, M., Dascalu, M., Castro-Tirado, Alberto J., Tigani, K., Sioulas, Nick, Lekkas, G., Bertesteanu, D.N., Bachini, M., Dumitrescu, V., Wilberger, A.J., Chiorny, V., Barnes, J.W., Fieber-Beyer, S.K., Swaney, R.L., Fuentes, C., Hudin, L., Plouvier, J.L., Mendez, R.A., Dumitru, B.D., Succi, G., Flynn, R.L., Mikuz, H., Wake, D.A., Morales, Nicolás, Maury, Alain, Fabrega, J., Ceravolo, P., Jehin, Emmanuel, Madiedo, J.M., Albanese, D., Mariey, H., Stoian, L., Bacci, P., Cikota, S., Ruždjak, D., Cikota, A., Szakáts, Róbert, Baba Aissa, D., Gringahcene, Z., Kashuba, V., Koshkin, N., Anghel, R.M., Zhukov, V., Maestripieri, M., Juravle, A., Fişek, S., Çakir, O., Özer, S., Schnabel, C., Schnabel, M., Signoret, F., Morrone, L., Santana-Ros, Toni, Pereira, C.L., Grazia, M.D., Calvo-Fernández, J.F., Carosati, D., Emilio, M., Burdanov, A.Y., de Wit, J., Barkaoui, K., Gillon, M., Leto, G., Frasca, A., Catanzaro, G., Carrillo, J., Zanmar Sanchez, R., Tagliaferri, U., Gowe, B., Valvasori, A., Klemt, B., de la Cueva, I., Guido, E., Yuste-Moreno, M., Ciabattari, F., Kozhukhov, O.M., Serra-Ricart, M., Alarcon, Miguel R., Licandro, Javier, Masi, G., Bacci, Roberto, Wuensche, N., Kamoun, S., Bosch, Josep M., Behem, R., Gherase, R.M., Prost, J.-P., Altan, M., Zheleznyak, A.P., Montigiani, N., Foster, C.R., Mannucci, M., Burzynski, W., Ruocco, Nello, Cuevas, F., Di Marcantonio, P., Coretti, I., Iafrate, G., Baldini, V., Gazeas, K., Fafet, R., Collins, M., Pál, András, Borkowski, M., Csák, B., Fernández-García, Emilio, Benedetti-Rossi, G., Sánchez-González, M., Curelaru, L., Vîntdevară, C.D., Danescu, C.A., de Santana, T., Gout, J.-F., Schmitz, C.J., Serrau, M., Sota, Alfredo, Belskaya, Irina, Rodríguez-Marco, M., Kilic, Y., Gomes-Júnior, A.R., Frappa, E., Klotz, A., Lavayssière, M., Sfair, R., Marques Oliveira, J., Dangl, G., Popescu, Marcel, Mammana, L.A., Fernández-Lajús, E., Schmidt, M., Hopp, U., Komžík, R., Fernández-Valenzuela, Estela, Pribulla, T., Tomko, D., Winter, O.C., Klös, O., Husárik, Marek, Erece, O., Eryilmaz, S., Buzzi, Luca, Gährken, B., Nardiello, D., Hornoch, Kamil, Sonbas, E., Holler, B.J., Er, H., Weber, C., and Kalkan, S.

Abstract

Context. The physical characterization of trans-Neptunian objects is essential for improving our understanding of the formation and evolution of our Solar System. Stellar occultation is a ground-based technique that can be successfully used to determine some of the TNOs’ fundamental physical properties with high precision, such as size and shape. Aims. This work is aimed at constraining the size, shape, and geometric albedo of the dwarf planet candidate (307261) 2002 MS4 through the analysis of nine stellar occultation events. Using multichord detection, we also study the object’s topography by analyzing the obtained limb and residuals between the observed chords and the best-fit ellipse. Metods. We predicted and organized the observational campaigns of nine stellar occultations by 2002 MS4 between 2019 and 2022, resulting in two single-chord events, four double-chord detections, and three events with between 3 and 61 positive chords. We derived the occultation light curves using differential aperture photometry, from which the star ingress and egress instants were calculated. Using 13 selected chords from the 8 August 2020 event, we determined the global elliptical limb of 2002 MS4. The best-fit ellipse, combined with the object’s rotational information from the literature, sets constraints on the object’s size, shape, and albedo. Additionally, we developed a new method to characterize the topography features on the object’s limb. Results. The global limb has a semi-major axis of a′ = 412 ± 10 km, a semi-minor axis of b′= 385 ± 17 km, and the position angle of the minor axis is 121° ± 16°. From this instantaneous limb, we obtained 2002 MS4’s geometric albedo of pV = 0.1 ± 0.025, using HV = 3.63 ± 0.05 mag and a projected area-equivalent diameter of 796 ± 24 km. Significant deviations from the fitted ellipse in the northernmost limb were detected from multiple sites, highlighting three distinct topographic features: one 11 km depth depression, followed by a 25−5+4 k

Published
2023

21. Extension Dynamics of the Northern Fonualei Rift and Spreading Center and the Southern Mangatolu Triple Junction in the Lau Basin at 16°S

Author

Jegen, Anna Margarethe, Dannowski, Anke, Schnabel, M., Barckhausen, U., Brandl, Philipp A., Riedel, Michael, Beniest, A., Heyde, I., Hannington, Mark D., Sandhu, Avrinder, Werner, Reinhard, Kopp, Heidrun, Jegen, Anna Margarethe, Dannowski, Anke, Schnabel, M., Barckhausen, U., Brandl, Philipp A., Riedel, Michael, Beniest, A., Heyde, I., Hannington, Mark D., Sandhu, Avrinder, Werner, Reinhard, and Kopp, Heidrun

Abstract

Due to the complexity of 2D magnetic anomaly maps north of 18°S and the sparsity of seismic data, the tectonic evolution of the northern Lau Basin has not yet been unraveled. We use a multi-method approach to reconstruct the formation of the basin at ∼16°S by compiling seismic, magnetic, gravimetric and geochemical data along a 185 km-long crustal transect. We identified a crustal zonation which preserves the level of subduction input at the time of the crust's formation. Paired with the seafloor magnetization, the crustal zonation enabled us to qualitatively approximate the dynamic spreading history of the region. Further assessment of the recent tectonic activity and the degree of tectonic overprinting visible in the crust both suggest a complex tectonic history including a dynamically moving spreading center and the reorganizing of the local magma supply. Comparing the compiled data sets has revealed substantial differences in the opening mechanisms of the two arms of the Overlapping Spreading Center (OSC) that is made up by the northernmost tip of the Fonualei Rift and Spreading Center in the east and the southernmost segment of the Mangatolu Triple Junction in the west. The observed transition from a predominantly tectonic opening mechanism at the eastern OSC arm to a magmatic opening mechanism at the western OSC arm coincides with an equally sharp transition from and strongly subduction influenced crust to a crust with virtually no subduction input. The degree of subduction input alters the geochemical composition, as well as the lithospheric stress response. Key Points Oceanic crust in the north-eastern Lau Basin formed at the now reorganized FRSC-MTJ system The position and the opening mechanisms of back-arc basin spreading center's change more dynamically at mid-ocean ridges Different opening mechanisms at the southern Mangatolu Triple Junction and northern Fonualei Rift Spreading Center despite their proximity

Published
2023
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24. Besonderheiten bei geriatrischen Patienten mit Verdacht auf symptomatischen Harnwegsinfekt

Author

Manseck, S., Otto, W., Schnabel, M. J., Denzinger, S., Burger, M., and Spachmann, P. J.

Subjects
ddc: 610, Medicine and health, 610 Medical sciences, Medicine
Abstract

Einleitung: Geriatrische Patienten mit symptomatischen Harnwegsbeschwerden sind aufgrund des demographischen Wandels, der steigenden Lebenserwartung und der zunehmenden Komorbiditäten ein überproportional wachsender Teil des urologischen Patientenkollektivs. Material und Methoden: Anhand[zum vollständigen Text gelangen Sie über die oben angegebene URL], 46. Gemeinsame Tagung der Bayerischen Urologenvereinigung und der Österreichischen Gesellschaft für Urologie und Andrologie

Published
2022

25. Häufigkeit von Überbehandlungen bei symptomatischen Harnwegsinfektionen von Frauen im gebärfähigen Alter

Author

Manseck, S., Otto, W., Schnabel, M. J., Denzinger, S., Burger, M., and Spachmann, P. J.

Subjects
ddc: 610, Medicine and health, 610 Medical sciences, Medicine
Abstract

Einleitung: Die Notfallambulanzen von großen Versorgungskrankenhäusern werden zunehmend von Patientinnen mit Harnwegsinfekten in Anspruch genommen. Aspekte der Sicherheitsmedizin mit der Sorge des Behandlers vor juristischen Konsequenzen einer konservativ ausgerichteten Therapie führen[zum vollständigen Text gelangen Sie über die oben angegebene URL], 46. Gemeinsame Tagung der Bayerischen Urologenvereinigung und der Österreichischen Gesellschaft für Urologie und Andrologie

Published
2022

39. Crustal Structure of the Niuafo'ou Microplate and Fonualei Rift and Spreading Center in the Northeastern Lau Basin, Southwestern Pacific

Author

Schmid, F., Kopp, H., Schnabel, M., Dannowski, A., Heyde, I., Riedel, M., Hannington, M. D., Engels, M., Beniest, A., Klaucke, I., Augustin, N., Brandl, P. A., Devey, C., Geology and Geochemistry, Kopp, H., 1 GEOMAR, Helmholtz Centre for Ocean Research Kiel Germany, Schnabel, M., 3 BGR, Federal Institute for Geosciences and Natural Resources Hanover Germany, Dannowski, A., Heyde, I., Riedel, M., Hannington, M. D., Engels, M., Beniest, A., 5 Department of Earth Sciences Vrije Universiteit Amsterdam Amsterdam The Netherlands, Klaucke, I., Augustin, N., Brandl, P. A., and Devey, C.

Subjects
back-arc basin, 551.8, back‐arc basin, Lau Basin, SDG 14 - Life Below Water
Abstract

The northeastern Lau Basin is one of the fastest opening and magmatically most active back‐arc regions on Earth. Although the current pattern of plate boundaries and motions in this complex mosaic of microplates is reasonably understood, the internal structure and evolution of the back‐arc crust are not. We present new geophysical data from a 290 km long east‐west oriented transect crossing the Niuafo'ou Microplate (back‐arc), the Fonualei Rift and Spreading Center (FRSC) and the Tofua Volcanic Arc at 17°20′S. Our P wave tomography model and density modeling suggest that past crustal accretion inside the southern FRSC was accommodated by a combination of arc crustal extension and magmatic activity. The absence of magnetic reversals inside the FRSC supports this and suggests that focused seafloor spreading has until now not contributed to crustal accretion. The back‐arc crust constituting the southern Niuafo'ou Microplate reveals a heterogeneous structure comprising several crustal blocks. Some regions of the back‐arc show a crustal structure similar to typical oceanic crust, suggesting they originate from seafloor spreading. Other crustal blocks resemble a structure that is similar to volcanic arc crust or a “hydrous” type of oceanic crust that has been created at a spreading center influenced by slab‐derived water at distances, Key Points: First insights into the crustal structure of the northeastern Lau Basin, along a 290 km transect at 17°20′S. Crust in southern Fonualei Rift and Spreading Center was created by extension of arc crust and variable amount of magmatism. Magmatic underplating is present in some parts of the southern Niuafo'ou Microplate., Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347

Published
2020

41. Feng-shui and computational fluid dynamics (CFD): Analyzing natural ventilation and human comfort

Author

bin li, Guo, W., Schnabel, M. A., and Moleta, T.

Subjects
Uncategorized
Abstract

The paper explores the analogies between Computational Fluid Dynamics (CFD) and Feng-Shui by undertaking an analysis of natural ventilation in Jiangmen city, Southern China. Feng-Shui has been used to inform the orientation, layout, and design of buildings in China for thousands of years. The research questions if these concepts are still valid for contemporary building design. Noting that computational simulation methods such as CFD allow architects to analyse the natural ventilation of buildings, this paper provides a novel study that examines if Feng-Shui principles can be reconciled against contemporary design processes. The research simulates 'community', 'block', and 'single courtyard' via CFD study to confirm the scientifically measurable concepts of Feng-Shui have concerning natural ventilation. We conclude that Feng-Shui concepts enhance natural ventilation and subsequently makes a positive contribution to sustainable building and design.

Published
2021
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42. Virtual world16: Virtual design collaboration for the intersection of academia and industry

Author

Schnabel, M. A., Kobayashi, Y., Pencreach, Y., Bennadji, A., Choi, D., Fiamma, P., Fukuda, T., Tian Tian Sky LO, Narahara, T., Novak, M., Ron, R., Swarts, M., Terzidis, K., Tucker, T., and Vital, R.

Subjects
Uncategorized
Abstract

Overthe past 13 years, the 'Worldl6'-group has collaborated face-to-face on various challenges that architectural design faces within VR, architecture, urban design, and its delivery to the professional industries. The focus of the collaboration is to foster pathways of academic research and developments to industries and professions. In 2020, due to the restrictions of the pandemic, the group had to rethink and redevelop how to collaborate meaningfully and become resilient: the Worldl6 collaborated akin to the Virtual Design Studios (VDS) of the Nineties for the first time exclusively virtually becoming the 'Virtual Worldl6'. The paper presents the group's various projects that are transformative to the praxis in VR architecture, design and urban design, and critically reflects on the lessons learned from VDS-paradigm.

Published
2021
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43. A Subducting Seamount Imaged in the Rupture Zone of the 1994 Java Earthquake, and Its Implication on Co-seismic Slip Propagation and Tsunami Generation

Author

Xia, Yueyang, Geersen, Jacob, Kläschen, Dirk, Ma, Bo, Lange, Dietrich, Riedel, Michael, Schnabel, M., Kopp, Heidrun, Xia, Yueyang, Geersen, Jacob, Kläschen, Dirk, Ma, Bo, Lange, Dietrich, Riedel, Michael, Schnabel, M., and Kopp, Heidrun

Abstract

The 2 June 1994 Java (Indonesia) tsunami earthquake ruptured in a seismically quiet subduction zone and generated a larger-than-expected tsunami. Since the peak of the co-seismic slip occurred underneath a local bathymetric high, the 1994 event was previously interpreted as being caused by a subducting seamount. Combining a re-processed seismic reflection line across the rupture area with a refraction tomography P-wave velocity model, multibeam bathymetry, and gravity data suggests that rupture over a subducted seamount is unlikely to explain the seismo-tectonic genesis of the event. The forearc high is rather related to the enhanced back-thrusting activity and an island arc crust backstop in the upper plate. We newly resolve a shallow subducting seamount seaward of the forearc high and up-dip of the rupture area. We propose that this seamount acted as a seismic barrier and may have diverted the co-seismic rupture into the overlying splay faults, which may have contributed to the larger-than-expected tsunami

Published
2021

44. A multimethodical approach to decipher extensional processes in the northern Lau Basin at 16 ºS

Author

Jegen, Anna Margarethe, Dannowski, Anke, Kopp, Heidrun, Barckhausen, U., Heyde, I., Schnabel, M., Schmid, Florian, Beniest, Anouk, Hannington, Mark D., Jegen, Anna Margarethe, Dannowski, Anke, Kopp, Heidrun, Barckhausen, U., Heyde, I., Schnabel, M., Schmid, Florian, Beniest, Anouk, and Hannington, Mark D.

Abstract

The Lau Basin is a young back-arc basin steadily forming at the Indo-Australian-Pacific plate boundary, where the Pacific plate is subducting underneath the Australian plate along the Tonga-Kermadec island arc. As a result of the asymmetric roll back of the Pacific plate, the Lau basin’s divergence rates decline southwards hence dictating an asymmetric, V-shaped basin opening. Further, the decentralisation of the extensional motion over 11 distinct spreading centres and zones of active rifting has led to the formation of a composite crust formed of a microplate mosaic. One of these centres of extensional motion, and the subject of this study, are two overlapping spreading centres (OLSC), the southern tip of the eastern axis of the Mangatolu Triple Junction (MTJ-S) and the northern tip of the Fonualei Rift spreading centre (FRSC).In 2018, the research vessel Sonne (cruise SO267) set out to conduct seismic refraction and wide-angle reflection data along a 185 km long transect crossing the Lau Basinat ~16 °S from the Tonga arc in the east, the overlapping spreading centres, FRSC1 and MTJ-S2, and extending as far as a volcanic ridge in the west. Additionally, 2D MCS reflection seismic data as well as magnetic and gravimetric data were acquired.The results of our Monte-Carlo P-wave traveltime tomography show a crust that varies between 4.5-6 km in thickness. Underneath the OLSC the upper crust is 2-2.5 km thick and the lower crust 2-2.5 km thick. The velocity gradients of the upper and lower crust differ significantly from tomographic models of magmatically dominated oceanic ridges. Compared to such magmatically dominated ridges, our final P-wave velocity model displays a decreased velocity gradient in the upper crust and an increased velocity gradientin the lower crust more comparable to tectonically dominated rifts with a sparse magmatic budget.The dominance of crustal stretching in the regional rifting process leads to a tectonical stretching, thus thinning of the cru

Published
2021

45. Imaging the crustal structure of the southern plate boundary of the Niuafo’ou microplate, Lau Basin, southwest Pacific, with reflection and refractions seismic data

Author

Beniest, Anouk, Dannowski, Anke, Schnabel, M., Schmid, Florian, Werner, Reinhard, Kopp, Heidrun, Riedel, Michael, Heyde, I., Barckhausen, U., Petersen, Florian, Schramm, Bettina, Hannington, Mark D., Beniest, Anouk, Dannowski, Anke, Schnabel, M., Schmid, Florian, Werner, Reinhard, Kopp, Heidrun, Riedel, Michael, Heyde, I., Barckhausen, U., Petersen, Florian, Schramm, Bettina, and Hannington, Mark D.

Abstract

At the Australian-Pacific plate boundary, the northern Lau Basin is one of the fastest opening back-arc basins on earth. The current configuration of micro-plates, plate boundaries and motions within the northern Lau Basin is quite well understood, but in the southern part of the Lau Basin questions remain about the crustal structure. Here, the Central Lau Spreading Center (CLSC) and the southern tip of the Fonualei Rift and Spreading Center (FRSC) define the diffuse southern boundary of the Niuafo’ou microplate. It remains unclear where the southern plate boundary is located and what kind of boundary it is.We present 1) seismic refraction data of a 200-km long, E-W transect acquired in the transition zone from the eastern side of the CLSC to the southern tip of the FRSC and 2) seismic reflection data of four E-W profiles of varying length, acquired in both the southern part of the Niuafo’ou microplate and the transition in between the CLSC and the FRSC. The seismic data acquisition was accompanied by parametric sediment echosounder, gravimetric and magnetic measurements and was complemented by heat flow probes and dredged samples of the seafloor in the vicinity of the profile.Our travel time tomography reveals a pronounced lateral variation in seismic P-wave velocities from west to east, within the 7-8 km thick back-arc crust. Towards the east, the crust gradually thickens to 13 km of arc crust. The reflection seismic data reveals sediment pockets, varying between 300m to 1000m depth, located on both the thinner back-arc crust and thicker arc crust. In the abyssal regions, faults that cross-cut the basement, but do not reach the surface, are observed on all reflection seismic profiles and are considered inactive today. Towards the west of the profiles, faults reach the surface and are considered active. Rock sampling from this area retrieved predominantly massive aphyric basalts from the back-arc crust in the west. Olivine-rich basalts, andesites, and a broad spect

Published
2021

50. Crustal structure of the Niuafo’ou Microplate and Fonualei Rift and Spreading Center in the northeastern Lau Basin, Southwestern Pacific

Author

Schmid, Florian, Kopp, Heidrun, Schnabel, M., Dannowski, Anke, Heyde, I., Riedel, Michael, Hannington, Mark D., Engels, M., Beniest, Anouk, Klaucke, Ingo, Augustin, Nico, Brandl, Philipp A., Devey, Colin, Schmid, Florian, Kopp, Heidrun, Schnabel, M., Dannowski, Anke, Heyde, I., Riedel, Michael, Hannington, Mark D., Engels, M., Beniest, Anouk, Klaucke, Ingo, Augustin, Nico, Brandl, Philipp A., and Devey, Colin

Abstract

Key points:  First insights into the crustal structure of the northeastern Lau Basin, along a 290 km transect at 17°20’S.  Crust in southern Fonualei Rift and Spreading Center was created by extension of arc crust and variable amount of magmatism.  Magmatic underplating is present in some parts of the southern Niuafo’ou Microplate The northeastern Lau Basin is one of the fastest opening and magmatically most active back‐arc regions on Earth. Although the current pattern of plate boundaries and motions in this complex mosaic of microplates is reasonably understood, the internal structure and evolution of the back‐arc crust are not. We present new geophysical data from a 290 km long east‐west oriented transect crossing the Niuafo’ou Microplate (back‐arc), the Fonualei Rift and Spreading Centre (FRSC) and the Tofua Volcanic Arc at 17°20’S. Our P‐wave tomography model and density modelling suggests that past crustal accretion inside the southern FRSC was accommodated by a combination of arc crustal extension and magmatic activity. The absence of magnetic reversals inside the FRSC supports this and suggests that focused seafloor spreading has until now not contributed to crustal accretion. The back‐arc crust constituting the southern Niuafo’ou Microplate reveals a heterogeneous structure comprising several crustal blocks. Some regions of the back‐arc show a crustal structure similar to typical oceanic crust, suggesting they originate from seafloor spreading. Other crustal blocks resemble a structure that is similar to volcanic arc crust or a ‘hydrous’ type of oceanic crust that has been created at a spreading center influenced by slab‐derived water at distances < 50 km to the arc. Throughout the back‐arc region we observe a high‐velocity (Vp 7.2‐7.5 km s‐1) lower crust, which is an indication for magmatic underplating, which is likely sustained by elevated upper mantle temperatures in this region.

Published
2020
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