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Geologic and Structural Characterization of Shallow Seismic Properties Along The San Jacinto Fault at Sage Brush Flat, Southern CaliforniaJanuary 2018 (has links)
abstract: The study of fault zones is a critical component to understanding earthquake mechanics and seismic hazard evaluations. Models or simulations of potential earthquakes, based on fault zone properties, are a first step in mitigating the hazard. Theoretical models of earthquake ruptures along a bi-material interface result in asymmetrical damage and preferred rupture propagation direction. Results include greater damage intensity within stiffer material and preferred slip in the direction of the more compliant side of the fault. Data from a dense seismic array along the Clark strand of the SJFZ at Sage Brush Flat (SGB) near Anza, CA, allows for analysis and characterization of shallow (<1km depth) seismic structure and fault zone properties. Results indicate potential asymmetric rock damage at SGB, similar to findings elsewhere along the SJFZ suggesting an NW preferred rupture propagation.
In this study, analysis of high resolution topography suggests asymmetric morphology of the SGB basin slopes are partially attributed to structural growth and fault zone damage. Spatial distributions of rock damage, from site mapping and fault perpendicular transects within SGB and Alkali Wash, are seemingly asymmetric with pulverization dominantly between fault strands or in the NE fault block. Remapping of the SJFZ through Alkali Wash indicates the fault is not isolated to a single strand along the main geologic boundary as previously mapped. Displacement measurements within SGB are analogous to those from the most recent large earthquake on the Clark fault. Geologic models from both a 3D shear wave velocity model (a product from the dense seismic array analysis) and lithologic and structural mapping from this study indicate surface observations and shallow seismic data compare well. A synthetic three-dimensional fault zone model illustrates the complexity of the structure at SGB for comparison with dense array seismic wave products. Results of this study generally agree with findings from seismic wave interpretations suggesting damage asymmetry is controlled by a NW preferred rupture propagation. / Dissertation/Thesis / Geologic Map of Sage Brush Flat / 3D fault zone model of the SJFZ at Sage Brush Flat / Masters Thesis Geological Sciences 2018
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Mapping and Kinematic Structural Analysis of the Deep Creek Fault Zone, South Flank of the Uinta Mountains, Near Vernal, UtahHaddox, David A. 11 May 2005 (has links) (PDF)
The geology along the southern flank of the Uinta Mountains, located north of Vernal, Utah, has been mapped at the 7.5' scale within two quadrangles: the Dry Fork and Steinaker Reservoir Quadrangles. Ambiguities dealing with stratigraphy, structural geology, and geohazards are currently being addressed as a result of this and other mapping projects in the vicinity. The geologic units in the area range in age from Mississippian to Late Cretaceous and include Uinta-sourced Tertiary units. Brief unit descriptions are provided for each of the units exposed in the map area. The main structural influence on the rocks within the area is that of the Uinta Uplift and its southern bounding fault, the Uinta Basin Boundary thrust. Locally, the Deep Creek fault zone overprints and dissects the southernmost flank of the broad Uinta Anticline. Other smaller structurally complex areas and folds exist east of the Deep Creek fault zone. The Deep Creek fault zone is made up of a series of NW-SE trending faults, likely related to the South Flank fault zone. Many authors have inferred dip-slip movement along the South Flank fault zone, but have not supported these claims using kinematic data. Detailed mapping and kinematic data collected within the study area has produced a better understanding of the deformation history along the fault zones in question. The faults within the Deep Creek fault zone have steep, linear traces upon which both vertical dip-slip and very nearly strike-slip (left-lateral oblique-slip, mainly) movement has occurred. The faults of the Deep Creek fault zone are likely Paleocene in age. The data suggest a bimodal history of deformation which the principal stress field does not seem to be influenced by typical east-northeast-west-southwest Laramide orogenic far-field stresses. The creation and early history of these faults may have been due to localized stress fields related to activity of the underlying Uinta Basin Boundary thrust, or a later period of uplift, a possible accommodation zone between the western and eastern domes of the Uinta Mountain Range, a transfer zone between the Uinta Basin Boundary thrust and the Asphalt Ridge fault, or a combination of these.
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Seismic velocity contrasts and temporal changes of strike-slip faults in central CaliforniaZhao, Peng 27 August 2010 (has links)
The spatial patterns of bimaterial interfaces along the Parkfield section of the San Andreas Fault (SAF) and central section of the Calaveras Fault are systematically investigated with large data sets of near-fault waveforms. Different from the usage of direct P and S waves in traditional tomographic studies, a particular seismic phase named fault zone head wave (FZHW) is used to image the bimaterial fault interfaces. The results show clear variations of seismic velocities contrast both along-strike and along-depth directions in both regions, which is in general consistent with local geological setting at surface and existing 3D tomography results. In the Parkfield section of SAF, the result of velocity contrast is used to test the relationship between preferred rupture directions of M6 Parkfield earthquakes and bimaterial interface. Strong velocity contrast (~5-10%) near Middle Mountain (MM) could control the rupture directions of nearby earthquakes to SE, such as the case for 1966 M6 Parkfield earthquake. In comparison, weak velocity contrast (~0-2%) near the epicenter of the 2004 Parkfield M6 earthquake (i.e., Gold Hill) probably has no influence on controlling its rupture direction, which is consistent with the bilateral rupture of the 2004 Parkfield earthquake. In the central Calaveras Fault, a detailed analysis of the moveout between FZHWs and direct P waves revealed the existence of a complicated fault structure with velocity contrast increasing from NW to SE of station CCO. The high velocity contrast SE of station CCO could be caused by a low-velocity zone SE of station CCO.
The spatio-temporal variations of seismic velocity around the central Calaveras Fault and its nearby region are investigated based on the waveform analysis of 333 repeating clusters following the 1984 ML6.2 Morgan Hill earthquake. Clear reduction of seismic velocity is shown for all repeating clusters immediately after the mainshock, followed by a logarithmic recovery. The coseismic change mostly occurs at shallow layers (top few hundred meters) for the region away from the rupture area of the mainshock, but extends much deeper around the rupture zone of the Morgan Hill earthquake. The estimated depth of the damage zone is up to 6 km in the fault based on the repeating clusters directly beneath station CCO.
Finally, temporal changes around the Parkfield section of SAF are studied using recently developed ambient noise cross-correlation technique. The extracted daily empirical Green functions (EGFs) from 0.4-1.3 Hz noise records are used to estimate subtle temporal changes associated with large earthquakes from local to teleseismic distances. The results show clear coseismic reduction of seismic velocities after the 2004 M6 Parkfield earthquake, similar to the previous observation based on repeating earthquakes. However, no systematic changes have been detected for other four regional/teleseismic events that have triggered clear tremor activity in the same region. These results suggest that temporal changes associated with distance sources are very subtle or localized so that they could not be detected within the resolution of the current technique (~0.2%).
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Remote Sensing Study Of Surgu Fault ZoneKoc, Ayten 01 September 2005 (has links) (PDF)
The geometry, deformation mechanism and kinematics of the Sü / rgü / Fault Zone is investigated by using remotely sensed data including Landsat TM and ASTER imagery combined with SRTM, and stereo-aerial photographs. They are used to extract information related to regional lineaments and tectono-morphological characteristics of the SFZ. Various image processing and enhancement techniques including contrast enhancement, PCA, DS and color composites are applied on the imagery and three different approaches including manual, semi automatic and automatic lineament extraction methods are followed. Then the lineaments obtained from ASTER and Landsat imagery using manual and automatic methods are overlaid to produce a final lineaments map.
The results have indicated that, the total number and length of the lineaments obtained from automatic is more than other methods while the percentages of overlapping lineaments for the manual method is more than the automatic method which indicate that the lineaments from automatic method does not discriminate man made features which result more lineaments and less overlapping ratio with respect to final map.
It is revealed from the detail analysis that, the SFZ displays characteristic deformation patterns of strike-slip faults, such as pressure ridges, linear fault controlled valleys, deflected stream courses, rotated blocks and juxtaposition of stratigraphical horizons in macroscopic scale. In addition to these, kinematic analyses carried out using fault slip data indicated that the Sü / rgü / Fault Zone is dextral strike-slip fault zone with a reverse component of slip and cumulative displacement along the fault is more than 2 km.
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The Progressive Evolution of the Champlain Thrust Fault Zone: Insights from a Structural Analysis of its ArchitectureMerson, Matthew 01 January 2018 (has links)
Near Burlington, Vermont, the Champlain Thrust fault placed massive Cambrian dolostones over calcareous shales of Ordovician age during the Ordovician Taconic Orogeny. Although the Champlain Thrust has been studied previously throughout the Champlain Valley, the architecture and structural evolution of its fault zone have never been systematically defined. To document these fault zone characteristics, a detailed structural analysis of multiple outcrops was completed along a 51 km transect between South Hero and Ferrisburgh, Vermont.
The Champlain Thrust fault zone is predominately within the footwall and preserves at least four distinct events that are heterogeneous is both style and slip direction. The oldest stage of structures—stage 1—are bedding parallel thrust faults that record a slip direction of top-to-the-W and generated localized fault propagation folds of bedding and discontinuous cleavages. This stage defines the protolith zone and has a maximum upper boundary of 205 meters below the Champlain Thrust fault surface. Stage 2 structures define the damage zone and form two sets of subsidiary faults form thrust duplexes that truncate older recumbent folds of bedding planes and early bedding-parallel thrusts. Slickenlines along stage 2 faults record a change in slip direction from top-to-the-W to top-to-the-NW. The damage zone is ~197 meters thick with its upper boundary marking the lower boundary of the fault core. The core, which is ~8 meters thick, is marked by the appearance of mylonite, phyllitic shales, fault gouge, fault breccia, and cataclastic lined faults. In addition, stage 3 sheath folds of bedding and cleavage are preserved as well as tight folds of stage 2 faults. Stage 3 faults include thrusts that record slip as top-to-the-NW and -SW and coeval normal faults that record slip as top-to-the-N and -S. The Champlain Thrust surface is the youngest event as it cuts all previous structures, and records fault reactivation with any top-to-the-W slip direction and a later top-to-the-S slip. Axes of mullions on this surface trend to the SE and do not parallel slickenlines.
The Champlain Thrust fault zone evolved asymmetrically across its principal slip surface through the process of strain localization and fault reactivation. Strain localization is characterized by the changes in relative age, motion direction along faults, and style of structures preserved within the fault zone. Reactivation of the Champlain Thrust surface and the corresponding change in slip direction was due to the influence of pre-existing structures at depth. This study defines the architecture of the Champlain Thrust fault zone and documents the importance of comparing the structural architecture of the fault zone core, damage zone, and protolith to determine the comprehensive fault zone evolution.
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Geometry and Physical Properties of the Chelungpu Fault, Taiwan, and Their Effect on Fault RuptureHeermance, Richard V. 01 May 2002 (has links)
Rupture of the Chelungpu fault during the September 21, 1999, 7.6 Mwearthquake in Taiwan caused a 90-Jr,m-long surface rupture with variable displacement along strike. Analysis of core from two holes drilled through the fault zone, combined with geologic mapping and detailed investigation from three outcrops, define the fault geometry and physical properties of the Chelungpu fault in its northern and southern regions. In the northern region, the fault dips 45-60° east parallel to bedding and consists of a narrow (1-20 cm) core of dark-gray, sheared clay gouge at the base of a 30-50 m zone of increased fracture density that is confined asymmetrically to the hanging wall. Microstructural analysis of the fault gouge indicates the presence of extremely narrow clay zones (50-300 μm thick) that are interpreted as the fault rupture surfaces. Few shear indicators are observed outside of the fault gouge, which implies that slip was localized in the gouge in the northern region. Slip localization along a bed-parallel surface resulted in less high-frequency ground motion and larger displacements during the earthquake than in the southern region. Observations from the southern region indicate that the fault dips 20-30° at the surface and consists of a wide (20- 70 m-thick) zone of sheared, foliated shale with numerous gouge zones. A footwall-ramp geometry juxtaposes 2000-3000 m of flat-lying Quaternary Toukoshan Formation in the footwall with Pliocene and Miocene, east-dipping siltstone and muds tone in the hanging wall. The wide, diffuse fault zone contributed to the lower displacement and higher frequency ground motion in the southern region during the 1999 earthquake. The structure in the northern region is the result of the fault being a very young (<50 >ka) fault segment in the hanging wall of an older segment of the Chelungpu fault, buried in the Taichung basin. The fault in the southern region is located on an older (~1 Ma) fault trace. The contrasting fault properties in the different regions are responsible for the variability in strong-motion and displacement observed during the 1999 earthquake.
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Structural and Geochemical Analyses of Disseminated-Gold Deposits, Bald Mountain-Alligator Ridge District, Nevada: Insights into Fault-Zone Architecture and Its Effect on MineralizationHammond, K. Jill 01 May 2001 (has links)
Structural and geochemical analyses of the Top and Casino deposits, Bald Mountain-Alligator Ridge district, Nevada, were conducted to determine how structures affected gold deposition in Carlin-type deposit s. We also examined how permeability changed over time in a fault that cuts siltstone-dominated sedimentary rocks. The association of gold and related arsenic with faults at the margins of a Jurassic pluton and sedimentary rocks suggests that ore fluids migrated along faults and fracture s. Permeability of the faults changed over time within the Casino deposit, where the ore-controlling fault was a distributed conduit in the early stages of mineralization but a barrier and a localized conduit a t opposite ends of the deposit during later stages. Results indicate that faults may significantly influence patterns of ore deposition and change character over deposit-scale distances, and continued slip along faults may create clay-rich low-permeability faults that are mineralized during early stages of development.
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Subsurface Structure Of The Central Thrace Basin From 3d Seismic Reflection DataTaikulakov, Yerlan Yengelsbekovich 01 January 2011 (has links) (PDF)
The Thrace Basin located in northwest Turkey displays attractive prospective traps for hydrocarbon and has received much attention from the petroleum industry. Despite the extensive exploration efforts, there are only few studies which address the fault kinematics and deformation mechanism of the
region in connection with structural development. In this study, 3D raw seismic data set collected around Temrez High near Babaeski fault zone will be processed and interpreted along with the available borehole data to reveal the subsurface structure of the region that will contribute towards understanding the Neogene tectonic evolution of the central Thrace basin, origin of the transcurrent tectonics and possible role of the North Anatolian Fault Zone.
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Fault zone damage, nonlinear site response, and dynamic triggering associated with seismic wavesWu, Chunquan 05 July 2011 (has links)
My dissertation focuses primarily on the following three aspects associated with passing seismic waves in the field of earthquake seismology: temporal changes of fault zone properties, nonlinear site response, and dynamic triggering.
Quantifying the temporal changes of material properties within and around active fault zones (FZ) is important for better understanding of rock rheology and estimating the strong ground motion that can be generated by large earthquakes. As high-amplitude seismic waves propagate through damaged FZ rocks and/or shallow surface layers, they may produce additional damage leading to nonlinear wave propagation effects and temporal changes of material properties (e.g., seismic velocity, attenuation). Previous studies have found several types of temporal changes in material properties with time scales of tens of seconds to several years. Here I systematically analyze temporal changes of fault zone (FZ) site response along the Karadere-Düzce branch of the North Anatolian fault that ruptured during the 1999 İzmit and Düzce earthquake sequences. The coseismic changes are on the order of 20-40%, and are followed by a logarithmic recovery over an apparent time scale of ~1 day. These results provide a bridge between the large-amplitude near-instantaneous changes and the lower-amplitude longer-duration variations observed in previous studies. The temporal changes measured from this high-resolution spectral ratio analysis also provide a refinement for the beginning of the longer more gradual process typically observed by analyzing repeating earthquakes.
An improved knowledge on nonlinear site response is critical for better understanding strong ground motions and predicting shaking induced damages. I use the same sliding-window spectral ratio technique to analyze temporal changes in site response associated with the strong ground motion of the Mw6.6 2004 Mid-Niigata earthquake sequence recorded by the borehole stations in Japanese Digital Strong-Motion Seismograph Network (KiK-Net). The coseismic peak frequency drop, peak spectral ratio drop, and the postseismic recovery time roughly scale with the input ground motions when the peak ground velocity (PGV) is larger than ~5 cm/s, or the peak ground acceleration (PGA) is larger than ~100 Gal. The results suggest that at a given site the input ground motion plays an important role in controlling both the coseismic change and postseismic recovery in site response.
In a follow-up study, I apply the same sliding-window spectral ratio technique to surface and borehole strong motion records at 6 KiK-Net sites, and stack results associated with different earthquakes that produce similar PGAs. In some cases I observe a weak coseismic drop in the peak frequency when the PGA is as small as ~20-30 Gal, and near instantaneous recovery after the passage of the direct S waves. The percentage of drop in the peak frequency starts to increase with increasing PGA values. A coseismic drop in the peak spectral ratio is also observed at 2 sites. When the PGA is larger than ~60 Gal to more than 100 Gal, considerably stronger coseismic drops of the peak frequencies are observed, followed by a logarithmic recovery with time. The observed weak reductions of peak frequencies with near instantaneous recovery likely reflect nonlinear response with essentially fixed level of damage, while the larger drops followed by logarithmic recovery reflect the generation (and then recovery) of additional rock damage. The results indicate clearly that nonlinear site response may occur during medium-size earthquakes, and that the PGA threshold for in situ nonlinear site response is lower than the previously thought value of ~100-200 Gal.
The recent Mw9.0 off the Pacific coast of Tohoku earthquake and its aftershocks generated widespread strong shakings as large as ~3000 Gal along the east coast of Japan. I systematically analyze temporal changes of material properties and nonlinear site response in the shallow crust associated with the Tohoku main shock, using seismic data recorded by the Japanese Strong Motion Network KIK-Net. I compute the spectral ratios of windowed records from a pair of surface and borehole stations, and then use the sliding-window spectral ratios to track the temporal changes in the site response of various sites at different levels of PGA The preliminary results show clear drop of resonant frequency of up to 70% during the Tohoku main shock at 6 sites with PGA from 600 to 1300 Gal. In the site MYGH04 where two distinct groups of strong ground motions were recorded, the resonant frequency briefly recovers in between, and then followed by an apparent logarithmic recovery. I investigate the percentage drop of peak frequency and peak spectral ratio during the Tohoku main shock at different PGA levels, and find that at most sites they are correlated.
The third part of my thesis mostly focuses on how seismic waves trigger additional earthquakes at long-range distance, also known as dynamic triggering. Previous studies have shown that dynamic triggering in intraplate regions is typically not as common as at plate-boundary regions. Here I perform a comprehensive analysis of dynamic triggering around the Babaoshan and Huangzhuang-Gaoliying faults southwest of Beijing, China. The triggered earthquakes are identified as impulsive seismic arrivals with clear P- and S-waves in 5 Hz high-pass-filtered three-component velocity seismograms during the passage of large amplitude body and surface waves of large teleseismic earthquakes. I find that this region was repeatedly triggered by at least four earthquakes in East Asia, including the 2001 Mw7.8 Kunlun, 2003 Mw8.3 Tokachi-oki, 2004 Mw9.2 Sumatra, and 2008 Mw7.9 Wenchuan earthquakes. In most instances, the microearthquakes coincide with the first few cycles of the Love waves, and more are triggered during the large-amplitude Rayleigh waves. Such an instantaneous triggering by both the Love and Rayleigh waves is similar to recent observations of remotely triggered 'non-volcanic' tremor along major plate-boundary faults, and can be explained by a simple Coulomb failure criterion. Five earthquakes triggered by the Kunlun and Tokachi-oki earthquakes were recorded by multiple stations and could be located. These events occurred at shallow depth (< 5 km) above the background seismicity near the boundary between NW-striking Babaoshan and Huangzhuang-Gaoliying faults and the Fangshan Pluton. These results suggest that triggered earthquakes in this region likely occur near the transition between the velocity strengthening and weakening zones in the top few kms of the crust, and are likely driven by relatively large dynamic stresses on the order of few tens of KPa.
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Outcrop analogue studies of rocks from the Northwest German Basin for geothermal exploration and exploitation / Fault zone structure, heterogeneous rock properties, and application to reservoir conditionsReyer, Dorothea 24 October 2013 (has links)
Schichtung und Störungszonen sind typische Phänomene in Sedimentbecken wie dem Nordwestdeutschen Becken. Diese Gesteinsheterogenitäten können großen Einfluss auf viele verschiedene Fragestellungen im Zusammenhang mit der Exploration, dem Bohren und der hydraulischen Stimulation des geothermischen Reservoirs haben. Diese Doktorarbeit liefert Aussagen und Ansätze, wie hoch aufgelöste Daten, die in Aufschlüssen erhoben wurden, für eine verbesserte Vorhersage des Störungszonenaufbaus und der gesteinsmechanischen Eigenschaften in größeren Tiefen verwendet werden können.
Um den Aufbau von Störungszonen und assoziierten Bruchsystemen in Sedimentgesteinen besser zu verstehen, wurden 58 Abschiebungen im Aufschlussmaßstab detailliert analysiert. Der Schwerpunkt lag dabei auf der Analyse von Bruchorientierung, -dichte, -öffnungsweite und -länge – jeweils getrennt betrachtet für Bruchzone und Nebengestein – sowie auf den strukturellen Indizes. Es konnten deutliche Unterschiede zwischen karbonatischen und klastischen Gesteinen festgestellt werden: in karbonatischen Gesteinen treten häufig ausgeprägte Bruchzonen mit erhöhten Bruchdichten auf. Während die maximale Öffnungsweite für beide Einheiten ähnlich ist, ist der Anteil an Brüchen mit großen Öffnungsweiten in der Bruchzone deutlich größer als im Nebengestein. In Karbonatgesteinen kann die Bruchorientierung in der Bruchzone stark von der im Nebengestein abweichen. In klastischen Gesteinen dagegen sind in beiden Einheiten ähnliche Bruchorientierungen zu finden. Die Auswertung der strukturellen Indizes zeigt, dass Abschiebungen in Karbonatgesteinen eher bruchzonen-dominiert sind als solche in klastischen Gesteinen und folglich größeren positiven Einfluss auf die Reservoirpermeabilität haben. Auf Basis der bestimmten Bruchdichtenverteilungen und Elastizitätsmoduli wurden effektive Steifigkeiten Ee innerhalb der Abschiebungen berechnet. Dabei zeigen Bruchzonen in klastischen Gesteinen eine deutlich geringere Abnahme der Steifigkeiten als solche in Karbonatgesteinen.
Um die Kenntnisse über Eigenschaften typischer Gesteine im Nordwestdeutschen Becken zu erweitern, wurden physikalische (Vp-Geschwindigkeit, Porosität, Rohdichte und Korndichte) und gesteinsmechanische Parameter (Einaxiale Druckfestigkeit [UCS], Elastizitätsmodul, Zerstörungsarbeit und Zugfestigkeit; jeweils parallel und senkrecht zur sedimentären Schichtung) an 35 Gesteinsproben aus Aufschlüssen und 14 Bohrkernproben bestimmt. Für einen Teil dieser Proben (eine Vulkanit- sowie jeweils drei Sandstein- und Kalksteinproben) wurden Triaxialmessungen durchgeführt. Da Bohrkernmaterial selten ist, war es Ziel dieser Arbeit, die in-situ-Gesteinseigenschaften anhand von Aufschlussproben vorherzusagen. Die Eigenschaften von Proben aus größeren Tiefen werden dann mit denen äquivalenter Proben verglichen, d.h. Bohrkern und äquivalente Aufschlussprobe haben das gleiche stratigraphische Alter und eine vergleichbare sedimentäre Fazies. Die Äquivalenz der Proben wurde anhand von Dünnschliffen sichergestellt. Empirische Beziehungen bzw. Korrelationen zwischen UCS und allen physikalischen und geomechanischen Parametern wurden mit Regressionsanalysen bestimmt, jeweils lithologisch getrennt für alle Proben (inkl. Bohrkerne) und nur für Aufschlussproben. Die meisten Korrelationen haben ein hohes Bestimmtheitsmaß; die Ergebnisse der Bohrkerne liegen meist innerhalb der 90% Prognosebänder der Korrelationen, die für Aufschlussproben berechnet wurden. Auf ähnliche Weise wurden anhand von mehreren Triaxialmessungen pro Probe linearisierte Mohr-Coulomb Versagenskriterien bestimmt, die sowohl in Hauptnormalspannungen als auch in Normal- und Scherspannungen angegeben werden. Ein Vergleich zeigt, dass es zwar für Klastika und Vulkanite aus Aufschlüssen möglich ist, Versagenskriterien, die in Hauptnormalspannungen ausgedrückt werden, auf Bohrkernproben anzuwenden, aber nicht für Karbonate. Sind die Versagenskriterien allerdings in Normal- und Scherspannungen angegeben, ist die Anwendbarkeit für alle Gesteinsarten gut. Eine Übertragbarkeit der empirischen Beziehungen auf die Tiefe wird abgeleitet. Die wichtigsten Parameter, um die Anwendbarkeit der Aufschlussdaten zu gewährleisten, sind eine vergleichbare Textur und eine ähnliche Porosität von Äquivalenzproben aus Steinbrüchen und Bohrkernproben.
Die Bruchausbreitung infolge einer hydraulischen Stimulation von heterogenen Gesteinen wurde mit dem Programm FRACOD analysiert. Es wurden numerische Modelle erstellt, die für das NWGB charakteristisch sind und die sowohl geschichtete Abfolgen als auch bereits existierende Brüche berücksichtigen. Die Ergebnisse der Untersuchung von Bruchsystemen in Störungszonen und die gemessenen gesteinsmechanischen Eigenschaften werden als Eingangsparameter verwendet. Die Modellierung zeigt, dass ein großer mechanischer Kontrast zwischen einzelnen Schichten bezüglich Elastizitätsmodul und Poissonkoeffizient geringeren Einfluss auf die Ausbreitungsrichtung des Bruches hat, als stark unterschiedliche Bruchzähigkeiten. Werden bereits existierende Brüche in das Modell eingebaut, zeigt sich eine starke Wechselwirkung mit dem induzierten Hydrobruch.
Die Ergebnisse dieser Doktorarbeit sind von vielfältigem Nutzen. Erstens helfen die Daten bei der Exploration von geothermischen Reservoiren in Störungszonen mit hohen natürlichen Permeabilitäten. Zweitens liefern die Ergebnisse der Labormessungen Aussagen und Ansätze, wie man die mechanischen Gesteinseigenschaften in größeren Tiefen anhand von Aufschlussproben vorhersagen und sie als Eingangsparameter für zukünftige numerische Modellierungen zu geothermischen Fragestellungen heranziehen kann. Außerdem liefert die numerische Modellierung der Bruchausbreitung infolge einer hydraulischen Stimulation in heterogenen Gesteinen Einblicke in die relevanten Parameter, die Einfluss auf die Ausbreitungsrichtung des induzierten Bruches haben. Dieses Wissen wird dabei helfen, die hydraulische Stimulation an die jeweiligen Reservoirbedingungen anzupassen.
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