@phdthesis{Cherubini2013,
  author    = {Cherubini, Yvonne},
  title     = {Influence of faults on the 3D coupled fluid and heat transport},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-69755},
  school      = {Universit{\"a}t Potsdam},
  year      = {2013},
  abstract  = {Da geologische St{\"o}rungen k{\"o}nnen als Grundwasserleiter, -Barrieren oder als gemischte leitende /stauende Fluidsysteme wirken. Aufgrund dessen k{\"o}nnen St{\"o}rungen maßgeblich den Grundwasserfluss im Untergrund beeinflussen, welcher deutliche Ver{\"a}nderungen des tiefen thermischen Feldes bewirken kann. Grundwasserdynamik und Temperaturver{\"a}nderungen sind wiederum entscheidende Faktoren f{\"u}r die Exploration geothermischer Energie. Diese Studie untersuchte den Einfluss von St{\"o}rungen auf das Fluidsystem und das thermische Feld im Untergrund. Sie erforschte die physikalischen Prozesse, welche das Fluidverhalten und die Temperaturverteilung in St{\"o}rungen und in den umgebenden Gesteinen. Dazu wurden 3D Finite Elemente Simulationen des gekoppelten Fluid und W{\"a}rmetransports f{\"u}r synthetische sowie reale Modelszenarien auf unterschiedlichen Skalen durchgef{\"u}hrt. Um den Einfluss einer schr{\"a}g einfallenden St{\"o}rung systematisch durch die schrittweise Ver{\"a}nderung der hydraulischen {\"O}ffnungsweite und der Permeabilit{\"a}t, zu untersuchen, wurde ein klein-skaliges synthetisches Modell entwickelt. Ein inverser linearer Zusammenhang wurde festgestellt, welcher zeigt, dass sich die Fluidgeschwindigkeit in der St{\"o}rung jeweils um ~1e-01 m/s verringert, wenn die {\"O}ffnungsweite der St{\"o}rung um jeweils eine Magnitude vergr{\"o}ßert wird. Ein hoher Permeabilit{\"a}tskontrast zwischen St{\"o}rung und umgebender Matrix beg{\"u}nstigt die Fluidadvektion hin zur St{\"o}rung und f{\"u}hrt zu ausgepr{\"a}gten Druck- und Temperaturver{\"a}nderungen innerhalb und um die St{\"o}rung herum. Bei geringem Permeabilit{\"a}tskontrast zwischen St{\"o}rung und umgebendem Gestein findet hingegen kein Fluidfluss in der St{\"o}rung statt, wobei das hydrostatische Druck- sowie das Temperaturfeld unver{\"a}ndert bleiben. Auf Grundlage der synthetischen Modellierungsergebnisse wurde der Einfluss von St{\"o}rungen auf einer gr{\"o}ßeren Skala anhand eines komplexeren (realen) geologischen Systems analysiert. Dabei handelt es sich um ein 3D Modell des Geothermiestandortes Groß Sch{\"o}nebeck, der ca. 40 km n{\"o}rdlich von Berlin liegt. Die Integration von einer permeablen und drei impermeablen Hauptst{\"o}rungen, zeigte unterschiedlich starke Einfl{\"u}sse auf Fluidzirkulation, Temperatur - und Druckfeld. Die modellierte konvektive Zirkulation in der permeablen St{\"o}rung ver{\"a}ndert das thermische Feld stark (bis zu 15 K). In den gering durchl{\"a}ssigen St{\"o}rungen wird die W{\"a}rme ausschließlich durch Diffusion geleitet. Der konduktive W{\"a}rmetransport beeinflusst das thermische Feld nicht, bewirkt jedoch lokale Ver{\"a}nderungen des hydrostatischen Druckfeldes. Um den Einfluss großer St{\"o}rungszonen mit kilometerweitem vertikalen Versatz auf das geothermische Feld der Beckenskala zu untersuchen, wurden gekoppelte Fluid- und W{\"a}rmetransportsimulationen f{\"u}r ein 3D Strukturmodell des Gebietes Brandenburg durchgef{\"u}hrt (Noack et al. 2010; 2013). Bez{\"u}glich der St{\"o}rungspermeabilit{\"a}t wurden verschiedene geologische Szenarien modelliert, von denen zwei Endgliedermodelle ausgewertet wurden. Die Ergebnisse zeigten, dass die undurchl{\"a}ssigen St{\"o}rungen den Fluidfluss nur lokal beeinflussen. Da sie als hydraulische Barrieren wirken, wird der Fluidfluss mir sehr geringen Geschwindigkeiten entlang der St{\"o}rungen innerhalb eines Bereichs von ~ 1 km auf jeder Seite umgelenkt. Die modellierten lokalen Ver{\"a}nderungen des Grundwasserzirkulationssystems haben keinen beobachtbaren Effekt auf das Temperaturfeld. Hingegen erzeugen permeable St{\"o}rungszonen eine ausgepr{\"a}gte thermische Signatur innerhalb eines Einflussbereichs von ~ 2.4-8.8 km in -1000 m Tiefe und ~6-12 km in -3000 m Tiefe. Diese thermische Signatur, in der sich k{\"a}ltere und w{\"a}rmere Temperaturbereiche abwechseln, wird durch auf- und abw{\"a}rts gerichteten Fluidfluss innerhalb der St{\"o}rung verursacht, der grunds{\"a}tzlich durch existierende Gradienten in der hydraulischen Druckh{\"o}he angetrieben wird. Alle Studien haben gezeigt, dass St{\"o}rungen einen beachtlichen Einfluss auf den Fluid-, und W{\"a}rmefluss haben. Es stellte sich heraus, dass die Permeabilit{\"a}t in der St{\"o}rung und in den umgebenden geologischen Schichten so wie der spezifische geologische Rahmen entscheidende Faktoren in der Ausbildung verschiedener W{\"a}rmetransportmechanismen sind, die sich in St{\"o}rungen entwickeln k{\"o}nnen. Die von permeablen St{\"o}rungen verursachten Temperaturver{\"a}nderungen k{\"o}nnen lokal, jedoch groß sein, genauso wie die durch hydraulisch leitende und nichtleitende St{\"o}rungen hervorgerufenen Ver{\"a}nderungen des Fluidystems. Letztlich haben die Simulationen f{\"u}r die unterschiedlich skalierten Modelle gezeigt, dass die Ergebnisse sich nicht aufeinander {\"u}bertragen lassen und dass es notwendig ist, jeden geologischen Rahmen hinsichtlich Konfiguration und Gr{\"o}ßenskala gesondert zu betrachten. Abschließend hat diese Studie demonstriert, dass die Betrachtung von St{\"o}rungen in 3D Finiten Elementen Modellen f{\"u}r die Simulation von gekoppeltem Fluid- und W{\"a}rmetransport auf unterschiedlichen Skalen m{\"o}glich ist. Da diese Art von numerischen Simulationen sowohl die geologische Struktur des Untergrunds sowie die im Erdinnern ablaufenden physikalischen Prozesse integriert, k{\"o}nnen sie einen wertvollen Beitrag leisten, indem sie Feld- und Laborgest{\"u}tzte Untersuchungen vervollst{\"a}ndigen.},
  language  = {de}
}
@phdthesis{Ghani2019,
  author    = {Ghani, Humaad},
  title     = {Structural evolution of the Kohat and Potwar fold and thrust belts of Pakistan},
  doi       = {10.25932/publishup-44077},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-440775},
  school      = {Universit{\"a}t Potsdam},
  pages     = {viii, 121},
  year      = {2019},
  abstract  = {Fold and thrust belts are characteristic features of collisional orogen that grow laterally through time by deforming the upper crust in response to stresses caused by convergence. The deformation propagation in the upper crust is accommodated by shortening along major folds and thrusts. The formation of these structures is influenced by the mechanical strength of d{\´e}collements, basement architecture, presence of preexisting structures and taper of the wedge. These factors control not only the sequence of deformation but also cause differences in the structural style. The Himalayan fold and thrust belt exhibits significant differences in the structural style from east to west. The external zone of the Himalayan fold and thrust belt, also called the Subhimalaya, has been extensively studied to understand the temporal development and differences in the structural style in Bhutan, Nepal and India; however, the Subhimalaya in Pakistan remains poorly studied. The Kohat and Potwar fold and thrust belts (herein called Kohat and Potwar) represent the Subhimalaya in Pakistan. The Main Boundary Thrust (MBT) marks the northern boundary of both Kohat and Potwar, showing that these belts are genetically linked to foreland-vergent deformation within the Himalayan orogen, despite the pronounced contrast in structural style. This contrast becomes more pronounced toward south, where the active strike-slip Kalabagh Fault Zone links with the Kohat and Potwar range fronts, known as the Surghar Range and the Salt Range, respectively. The Surghar and Salt Ranges developed above the Surghar Thrust (SGT) and Main Frontal Thrust (MFT). In order to understand the structural style and spatiotemporal development of the major structures in Kohat and Potwar, I have used structural modeling and low temperature thermochronolgy methods in this study. The structural modeling is based on construction of balanced cross-sections by integrating surface geology, seismic reflection profiles and well data. In order to constrain the timing and magnitude of exhumation, I used apatite (U-Th-Sm)/He (AHe) and apatite fission track (AFT) dating. The results obtained from both methods are combined to document the Paleozoic to Recent history of Kohat and Potwar. The results of this research suggest two major events in the deformation history. The first major deformation event is related to Late Paleozoic rifting associated with the development of the Neo-Tethys Ocean. The second major deformation event is related to the Late Miocene to Pliocene development of the Himalayan fold and thrust belt in the Kohat and Potwar. The Late Paleozoic rifting is deciphered by inverse thermal modelling of detrital AFT and AHe ages from the Salt Range. The process of rifting in this area created normal faulting that resulted in the exhumation/erosion of Early to Middle Paleozoic strata, forming a major unconformity between Cambrian and Permian strata that is exposed today in the Salt Range. The normal faults formed in Late Paleozoic time played an important role in localizing the Miocene-Pliocene deformation in this area. The combination of structural reconstructions and thermochronologic data suggest that deformation initiated at 15±2 Ma on the SGT ramp in the southern part of Kohat. The early movement on the SGT accreted the foreland into the Kohat deforming wedge, forming the range front. The development of the MBT at 12±2 Ma formed the northern boundary of Kohat and Potwar. Deformation propagated south of the MBT in the Kohat on double d{\´e}collements and in the Potwar on a single basal d{\´e}collement. The double d{\´e}collement in the Kohat adopted an active roof-thrust deformation style that resulted in the disharmonic structural style in the upper and lower parts of the stratigraphic section. Incremental shortening resulted in the development of duplexes in the subsurface between two d{\´e}collements and imbrication above the roof thrust. Tectonic thickening caused by duplexes resulted in cooling and exhumation above the roof thrust by removal of a thick sequence of molasse strata. The structural modelling shows that the ramps on which duplexes formed in Kohat continue as tip lines of fault propagation folds in the Potwar. The absence of a double d{\´e}collement in the Potwar resulted in the preservation of a thick sequence of molasse strata there. The temporal data suggest that deformation propagated in-sequence from ~ 8 to 3 Ma in the northern part of Kohat and Potwar; however, internal deformation in the Kohat was more intense, probably required for maintaining a critical taper after a significant load was removed above the upper d{\´e}collement. In the southern part of Potwar, a steeper basement slope (β≥3°) and the presence of salt at the base of the stratigraphic section allowed for the complete preservation of the stratigraphic wedge, showcased by very little internal deformation. Activation of the MFT at ~4 Ma allowed the Salt Range to become the range front of the Potwar. The removal of a large amount of molasse strata above the MFT ramp enhanced the role of salt in shaping the structural style of the Salt Range and Kalabagh Fault Zone. Salt accumulation and migration resulted in the formation of normal faults in both areas. Salt migration in the Kalabagh fault zone has triggered out-of-sequence movement on ramps in the Kohat. The amount of shortening calculated between the MBT and the SGT in Kohat is 75±5 km and between the MBT and the MFT in Potwar is 65±5 km. A comparable amount of shortening is accommodated in the Kohat and Potwar despite their different widths: 70 km Kohat and 150 km Potwar. In summary, this research suggests that deformation switched between different structures during the last ~15 Ma through different modes of fault propagation, resulting in different structural styles and the out-of-sequence development of Kohat and Potwar.},
  language  = {en}
}
@phdthesis{Schuck2020,
  author    = {Schuck, Bernhard},
  title     = {Geomechanical and petrological characterisation of exposed slip zones, Alpine Fault, New Zealand},
  doi       = {10.25932/publishup-44612},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-446129},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XVII, 143},
  year      = {2020},
  abstract  = {The Alpine Fault is a large, plate-bounding, strike-slip fault extending along the north-western edge of the Southern Alps, South Island, New Zealand. It regularly accommodates large (MW > 8) earthquakes and has a high statistical probability of failure in the near future, i.e., is late in its seismic cycle. This pending earthquake and associated co-seismic landslides are expected to cause severe infrastructural damage that would affect thousands of people, so it presents a substantial geohazard. The interdisciplinary study presented here aims to characterise the fault zone's 4D (space and time) architecture, because this provides information about its rheological properties that will enable better assessment of the hazard the fault poses. The studies undertaken include field investigations of principal slip zone fault gouges exposed along strike of the fault, and subsequent laboratory analyses of these outcrop and additional borehole samples. These observations have provided new information on (I) characteristic microstructures down to the nanoscale that indicate which deformation mechanisms operated within the rocks, (II) mineralogical information that constrains the fault's geomechanical behaviour and (III) geochemical compositional information that allows the influence of fluid- related alteration processes on material properties to be unraveled. Results show that along-strike variations of fault rock properties such as microstructures and mineralogical composition are minor and / or do not substantially influence fault zone architecture. They furthermore provide evidence that the architecture of the fault zone, particularly its fault core, is more complex than previously considered, and also more complex than expected for this sort of mature fault cutting quartzofeldspathic rocks. In particular our results strongly suggest that the fault has more than one principal slip zone, and that these form an anastomosing network extending into the basement below the cover of Quaternary sediments. The observations detailed in this thesis highlight that two major processes, (I) cataclasis and (II) authigenic mineral formation, are the major controls on the rheology of the Alpine Fault. The velocity-weakening behaviour of its fault gouge is favoured by abundant nanoparticles promoting powder lubrication and grain rolling rather than frictional sliding. Wall-rock fragmentation is accompanied by co-seismic, fluid-assisted dilatancy that is recorded by calcite cementation. This mineralisation, along with authigenic formation of phyllosilicates, quickly alters the petrophysical fault zone properties after each rupture, restoring fault competency. Dense networks of anastomosing and mutually cross-cutting calcite veins and intensively reworked gouge matrix demonstrate that strain repeatedly localised within the narrow fault gouge. Abundantly undeformed euhedral chlorite crystallites and calcite veins cross-cutting both fault gouge and gravels that overlie basement on the fault's footwall provide evidence that the processes of authigenic phyllosilicate growth, fluid-assisted dilatancy and associated fault healing are processes active particularly close to the Earth's surface in this fault zone. Exposed Alpine Fault rocks are subject to intense weathering as direct consequence of abundant orogenic rainfall associated with the fault's location at the base of the Southern Alps. Furthermore, fault rock rheology is substantially affected by shallow-depth conditions such as the juxtaposition of competent hanging wall fault rocks on poorly consolidated footwall sediments. This means microstructural, mineralogical and geochemical properties of the exposed fault rocks may differ substantially from those at deeper levels, and thus are not characteristic of the majority of the fault rocks' history. Examples are (I) frictionally weak smectites found within the fault gouges being artefacts formed at temperature conditions, and imparting petrophysical properties that are not typical for most of fault rocks of the Alpine Fault, (II) grain-scale dissolution resulting from subaerial weathering rather than deformation by pressure-solution processes and (III) fault gouge geometries being more complex than expected for deeper counterparts. The methodological approaches deployed in analyses of this, and other fault zones, and the major results of this study are finally discussed in order to contextualize slip zone investigations of fault zones and landslides. Like faults, landslides are major geohazards, which highlights the importance of characterising their geomechanical properties. Similarities between faults, especially those exposed to subaerial processes, and landslides, include mineralogical composition and geomechanical behaviour. Together, this ensures failure occurs predominantly by cataclastic processes, although aseismic creep promoted by weak phyllosilicates is not uncommon. Consequently, the multidisciplinary approach commonly used to investigate fault zones may contribute to increase the understanding of landslide faulting processes and the assessment of their hazard potential.},
  language  = {en}
}