@misc{NaliboffGlerumBruneetal.2020, author = {Naliboff, John B. and Glerum, Anne and Brune, Sascha and P{\´e}ron-Pinvidic, G. and Wrona, Thilo}, title = {Development of 3-D rift heterogeneity through fault network evolution}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {13}, issn = {1866-8372}, doi = {10.25932/publishup-52466}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-524661}, pages = {13}, year = {2020}, abstract = {Observations of rift and rifted margin architecture suggest that significant spatial and temporal structural heterogeneity develops during the multiphase evolution of continental rifting. Inheritance is often invoked to explain this heterogeneity, such as preexisting anisotropies in rock composition, rheology, and deformation. Here, we use high-resolution 3-D thermal-mechanical numerical models of continental extension to demonstrate that rift-parallel heterogeneity may develop solely through fault network evolution during the transition from distributed to localized deformation. In our models, the initial phase of distributed normal faulting is seeded through randomized initial strength perturbations in an otherwise laterally homogeneous lithosphere extending at a constant rate. Continued extension localizes deformation onto lithosphere-scale faults, which are laterally offset by tens of km and discontinuous along-strike. These results demonstrate that rift- and margin-parallel heterogeneity of large-scale fault patterns may in-part be a natural byproduct of fault network coalescence.}, language = {en} } @misc{BaesSobolevGeryaetal.2020, author = {Baes, Marzieh and Sobolev, Stephan Vladimir and Gerya, Taras V. and Brune, Sascha}, title = {Plume-induced subduction initiation}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {2}, issn = {1866-8372}, doi = {10.25932/publishup-52274}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-522742}, pages = {21}, year = {2020}, abstract = {Initiation of subduction following the impingement of a hot buoyant mantle plume is one of the few scenarios that allow breaking the lithosphere and recycling a stagnant lid without requiring any preexisting weak zones. Here, we investigate factors controlling the number and shape of retreating subducting slabs formed by plume-lithosphere interaction. Using 3-D thermomechanical models we show that the deformation regime, which defines formation of single-slab or multi-slab subduction, depends on several parameters such as age of oceanic lithosphere, thickness of the crust and large-scale lithospheric extension rate. Our model results indicate that on present-day Earth multi-slab plume-induced subduction is initiated only if the oceanic lithosphere is relatively young (<30-40 Myr, but >10 Myr), and the crust has a typical thickness of 8 km. In turn, development of single-slab subduction is facilitated by older lithosphere and pre-imposed extensional stresses. In early Earth, plume-lithosphere interaction could have led to formation of either episodic short-lived circular subduction when the oceanic lithosphere was young or to multi-slab subduction when the lithosphere was old.}, language = {en} } @phdthesis{Brune2018, author = {Brune, Sascha}, title = {Modelling continental rift dynamics}, doi = {10.25932/publishup-43236}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-432364}, school = {Universit{\"a}t Potsdam}, pages = {192}, year = {2018}, abstract = {Continental rift systems open up unique possibilities to study the geodynamic system of our planet: geodynamic localization processes are imprinted in the morphology of the rift by governing the time-dependent activity of faults, the topographic evolution of the rift or by controlling whether a rift is symmetric or asymmetric. Since lithospheric necking localizes strain towards the rift centre, deformation structures of previous rift phases are often well preserved and passive margins, the end product of continental rifting, retain key information about the tectonic history from rift inception to continental rupture. Current understanding of continental rift evolution is based on combining observations from active rifts with data collected at rifted margins. Connecting these isolated data sets is often accomplished in a conceptual way and leaves room for subjective interpretation. Geodynamic forward models, however, have the potential to link individual data sets in a quantitative manner, using additional constraints from rock mechanics and rheology, which allows to transcend previous conceptual models of rift evolution. By quantifying geodynamic processes within continental rifts, numerical modelling allows key insight to tectonic processes that operate also in other plate boundary settings, such as mid ocean ridges, collisional mountain chains or subduction zones. In this thesis, I combine numerical, plate-tectonic, analytical, and analogue modelling approaches, whereas numerical thermomechanical modelling constitutes the primary tool. This method advanced rapidly during the last two decades owing to dedicated software development and the availability of massively parallel computer facilities. Nevertheless, only recently the geodynamical modelling community was able to capture 3D lithospheric-scale rift dynamics from onset of extension to final continental rupture. The first chapter of this thesis provides a broad introduction to continental rifting, a summary of the applied rift modelling methods and a short overview of previews studies. The following chapters, which constitute the main part of this thesis feature studies on plate boundary dynamics in two and three dimension followed by global scale analyses (Fig. 1). Chapter II focuses on 2D geodynamic modelling of rifted margin formation. It highlights the formation of wide areas of hyperextended crustal slivers via rift migration as a key process that affected many rifted margins worldwide. This chapter also contains a study of rift velocity evolution, showing that rift strength loss and extension velocity are linked through a dynamic feed-back. This process results in abrupt accelerations of the involved plates during rifting illustrating for the first time that rift dynamics plays a role in changing global-scale plate motions. Since rift velocity affects key processes like faulting, melting and lower crustal flow, this study also implies that the slow-fast velocity evolution should be imprinted in rifted margin structures. Chapter III relies on 3D Cartesian rift models in order to investigate various aspects of rift obliquity. Oblique rifting occurs if the extension direction is not orthogonal to the rift trend. Using 3D lithospheric-scale models from rift initialisation to breakup I could isolate a characteristic evolution of dominant fault orientations. Further work in Chapter III addresses the impact of rift obliquity on the strength of the rift system. We illustrate that oblique rifting is mechanically preferred over orthogonal rifting, because the brittle yielding requires a lower tectonic force. This mechanism elucidates rift competition during South Atlantic rifting, where the more oblique Equatorial Atlantic Rift proceeded to breakup while the simultaneously active but less oblique West African rift system became a failed rift. Finally this Chapter also investigates the impact of a previous rift phase on current tectonic activity in the linkage area of the Kenyan with Ethiopian rift. We show that the along strike changes in rift style are not caused by changes in crustal rheology. Instead the rift linkage pattern in this area can be explained when accounting for the thinned crust and lithosphere of a Mesozoic rift event. Chapter IV investigates rifting from the global perspective. A first study extends the oblique rift topic of the previous chapter to global scale by investigating the frequency of oblique rifting during the last 230 million years. We find that approximately 70\% of all ocean-forming rift segments involved an oblique component of extension where obliquities exceed 20°. This highlights the relevance of 3D approaches in modelling, surveying, and interpretation of many rifted margins. In a final study, we propose a link between continental rift activity, diffuse CO2 degassing and Mesozoic/Cenozoic climate changes. We used recent CO2 flux measurements in continental rifts to estimate worldwide rift-related CO2 release, which we based on the global extent of rifts through time. The first-order correlation to paleo-atmospheric CO2 proxy data suggests that rifts constitute a major element of the global carbon cycle.}, language = {en} } @misc{RubeyBruneHeineetal.2017, author = {Rubey, Michael and Brune, Sascha and Heine, Christian and Davies, D. Rhodri and Williams, Simon E. and M{\"u}ller, R. Dietmar}, title = {Global patterns in Earth's dynamic topography since the Jurassic}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {623}, issn = {1866-8372}, doi = {10.25932/publishup-41824}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418241}, pages = {899 -- 919}, year = {2017}, abstract = {We evaluate the spatial and temporal evolution of Earth's long-wavelength surface dynamic topography since the Jurassic using a series of high-resolution global mantle convection models. These models are Earth-like in terms of convective vigour, thermal structure, surface heat-flux and the geographic distribution of heterogeneity. The models generate a degree-2-dominated spectrum of dynamic topography with negative amplitudes above subducted slabs (i.e. circum-Pacific regions and southern Eurasia) and positive amplitudes elsewhere (i.e. Africa, north-western Eurasia and the central Pacific). Model predictions are compared with published observations and subsidence patterns from well data, both globally and for the Australian and southern African regions. We find that our models reproduce the long-wavelength component of these observations, although observed smaller-scale variations are not reproduced. We subsequently define "geodynamic rules" for how different surface tectonic settings are affected by mantle processes: (i) locations in the vicinity of a subduction zone show large negative dynamic topography amplitudes; (ii) regions far away from convergent margins feature long-term positive dynamic topography; and (iii) rapid variations in dynamic support occur along the margins of overriding plates (e.g. the western US) and at points located on a plate that rapidly approaches a subduction zone (e.g. India and the Arabia Peninsula). Our models provide a predictive quantitative framework linking mantle convection with plate tectonics and sedimentary basin evolution, thus improving our understanding of how subduction and mantle convection affect the spatio-temporal evolution of basin architecture.}, language = {en} } @phdthesis{Brune2009, author = {Brune, Sascha}, title = {Landslide generated tsunamis : numerical modeling and real-time prediction}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-32986}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {Submarine landslides can generate local tsunamis posing a hazard to human lives and coastal facilities. Two major related problems are: (i) quantitative estimation of tsunami hazard and (ii) early detection of the most dangerous landslides. This thesis focuses on both those issues by providing numerical modeling of landslide-induced tsunamis and by suggesting and justifying a new method for fast detection of tsunamigenic landslides by means of tiltmeters. Due to the proximity to the Sunda subduction zone, Indonesian coasts are prone to earthquake, but also landslide tsunamis. The aim of the GITEWS-project (German-Indonesian Tsunami Early Warning System) is to provide fast and reliable tsunami warnings, but also to deepen the knowledge about tsunami hazards. New bathymetric data at the Sunda Arc provide the opportunity to evaluate the hazard potential of landslide tsunamis for the adjacent Indonesian islands. I present nine large mass movements in proximity to Sumatra, Java, Sumbawa and Sumba, whereof the largest event displaced 20 km³ of sediments. Using numerical modeling, I compute the generated tsunami of each event, its propagation and runup at the coast. Moreover, I investigate the age of the largest slope failures by relating them to the Great 1977 Sumba earthquake. Continental slopes off northwest Europe are well known for their history of huge underwater landslides. The current geological situation west of Spitsbergen is comparable to the continental margin off Norway after the last glaciation, when the large tsunamigenic Storegga slide took place. The influence of Arctic warming on the stability of the Svalbard glacial margin is discussed. Based on new geophysical data, I present four possible landslide scenarios and compute the generated tsunamis. Waves of 6 m height would be capable of reaching northwest Europe threatening coastal areas. I present a novel technique to detect large submarine landslides using an array of tiltmeters, as a possible tool in future tsunami early warning systems. The dislocation of a large amount of sediment during a landslide produces a permanent elastic response of the earth. I analyze this response with a mathematical model and calculate the theoretical tilt signal. Applications to the hypothetical Spitsbergen event and the historical Storegga slide show tilt signals exceeding 1000 nrad. The amplitude of landslide tsunamis is controlled by the product of slide volume and maximal velocity (slide tsunamigenic potential). I introduce an inversion routine that provides slide location and tsunamigenic potential, based on tiltmeter measurements. The accuracy of the inversion and of the estimated tsunami height near the coast depends on the noise level of tiltmeter measurements, the distance of tiltmeters from the slide, and the slide tsunamigenic potential. Finally, I estimate the applicability scope of this method by employing it to known landslide events worldwide.}, language = {en} }