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"Técnicas de geoprocessamento aplicadas à análise morfométrica" / GIS techniques applied to morphometric analysisCarlos Henrique Grohmann de Carvalho 05 May 2004 (has links)
Neste trabalho, buscou-se o desenvolvimento e adequação de técnicas de análise morfométrica em Sistemas de Informações Geográficas. Como base de trabalho, foram utilizados os programas livres GRASS-GIS e a linguagem estatística R. Os parâmetros morfométricos estudados foram hipsometria, declividade, orientação de vertentes, perfis em varredura, densidade de lineamentos e de drenagem, rugosidade de relevo, isobases e gradiente hidráulico. A área de estudo localiza-se na borda leste do Quadrilátero Ferrífero (MG), e possui unidades geomorfológicas distintas: um relevo montanhoso a oeste (Serra do Caraça), separado por uma escarpa de centenas de metros de terrenos caracterizados por dissecação fluvial, que abrigam em sua porção central, um planalto sustentado por conglomerados ferruginosos cenozóicos. O elemento principal da análise morfométrica é o Modelo Numérico de Terreno (MDT), que pode ser interpolado a partir de curvas de nível ou de pontos cotados. Há ainda a possibilidade de utilizar MDTs produzidos pela agência espacial americana (NASA), disponíveis gratuitamente via internet. A metodologia proposta envolve principalmente operações básicas de SIG, como conversão entre formatos vetorial e matricial, operações matemáticas simples em mapas raster e interpolação de valores pontuais em superfícies contínuas. Análise de superfícies de tendência foi realizada para verificar a possibilidade de uso do método em estudos de morfotectônica. Foram ajustadas superfícies polinomiais de 1º a 6º grau, e as significâncias estatísticas de cada polinômio e do incremento do grau polinomial foram verificadas com análise de variância. Os mapas morfométricos produzidos permitiram a identificação de estruturas provavelmente relacionadas com a configuração atual da paisagem. Os mapas de resíduos para as superfícies de tendência mais representativas possuem boa correlação com as estruturas inferidas. A metodologia proposta pode ser adaptada aos diversos pacotes SIG existentes no mercado. O uso de programas livres e de código aberto garante o acesso a todos, e sua crescente popularização abre novas perspectivas nesse campo. / This work aims on developing and adaptation of morphometric analysis in Geographic Information Systems. Free softwares GRASS-GIS and R statistical language were used as main applications. Studied morphometric parameters were hypsometry, slope, aspect, swath profiles, drainage and lineament density, surface roughness, isobase and hydraulic gradient. The study area is located in the eastern border of Quadrilátero Ferrífero (MG), and has distinct geomorphological units: a mountainous relief to west (Serra do Caraça), separated by a scarp with hundreds of meters of fall from fluvial dissected terrains, with a flat plateau in its central portion, the Chapada de Canga. The main element for morphometric analysis is the Digital Elevation Model (DEM), which can be interpolated form contours or scattered points. There is also the possibility of utilize NASA' s DEMs, freely available via internet. The proposed methodology deals mainly with basic GIS operations, like conversion between raster and vector, simple mathematic operations on raster maps and interpolation of discrete values into continuous surfaces. Trend-surface analysis was carried out o verify the possibility of use the method for morphotectonic studies. Polynomial surfaces from 1st to 6th degree were adjusted; the statistical significance of each surface and the significance of increasing polynomial degree were verified with analysis of variance. Produced morphometric maps allow identification of structures probably related with present-day landscape configuration. Residuals maps for most representative trend-surfaces keep good correlation with inferred structures. The proposed methodology can be adapted to the variety of GIS packages available in the market. The use of free and open-source softwares guarantees access to everyone, and its increasing popularization opens new perspectives in this field.
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Quaternary Geology and Neotectonics of Southern Star Valley and the Southwest Flank of the Salt River Range, Western WyomingWarren, Gregory A. 01 May 1992 (has links)
Southern Star Valley is a structural and physiographic basin bounded on the east by the southern Star Valley fault, an active normal fault associated with Basin and Range extension. The southern Star Valley fault separates southern Star Valley from the Salt River Range and forms a dramatic north-south trending topographic escarpment. Statistical analysis of relative-age dating (RD) parameters taken from glacial deposits in the Salt River Range defined distinctive age groups for the deposits, and comparison of RD data allowed correlations with late Pleistocene and Holocene glacial deposits elsewhere in the Rocky Mountains. However, the sedimentary lithologies in the glacial deposits in the study area and inherent variability of RD data limited definitive regional correlations.
The southern Star Valley fault (SSVF) lies in a parabola-shaped zone of large, seismogenic normal faults. The zone trails to the west of the eastward-migrating Yellowstone hot spot. Basin-facing fault scarps up to 11 meters high created by recurrent late Quaternary faulting along the southern Star Valley fault are preserved in late-Pleistocene and Holocene alluvial fans along the Salt River Range front.
Radiocarbon ages from faulted deposits exposed in a trench provide age estimates of ca. 8,090 ± 80 and 5,540 ± 70 yrs. B. P. for the two most recent paleoearthquakes. The magnitudes of the paleoearthquakes, based on surface rupture height and length and estimates, were between Ms6.9 and Ms7.1. The tectonic geomorphology of river alluvium and alluvial fans near the SSVF suggests that recurrent faulting has downdropped the northern end of southern Star Valley more in relationship to the southern part of the valley and created a deep depocenter in the northern part.
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Neotectonics of the Mount Lofty Ranges (South Australia) / Victor Tokarev.Tokarev, Victor January 2005 (has links)
"February, 2005" / Bibliography: leaves 259-272. / ix, 272 leaves : ill. (some col.), maps (col.), plates (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / "The Mount Lofty Ranges and flanking St Vincent and Western Murray Basins preserve a rich record of Australian intraplate neotectonic movements and their effects of landscape evolution and sedimentary basin development in this region of South Australia." "The major goal of this study is to develop a new tectonic model that contributes to our fundamental understanding of how neotectonic motions and deformations operate within this sector of the southern Australian Earth crust. The other main aim of this thesis is to provide a better understanding of the effects those neotectonic movements imposed on landscape evolution and sedimentation." --Introd. / Thesis (Ph.D.)--University of Adelaide, Faculty of Science, School of Earth and Environmental Sciences, Discipline of Geology and Geophysics, 2005
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Late Neogene stratigraphy and sedimentation across the Murray Basin, southeastern AustraliaMiranda, J. A. January 2007 (has links)
The Late Neogene sedimentary sequence of the Murray Basin provides an excellent opportunity to examine paleoenvironmental change across southeastern Australia. A detailed stratigraphic analysis of sediments deposited within the basin in the last 10 Ma was undertaken to assess the influence of tectonic and eustatic processes on deposition. / Stratigraphic observations and radiogenic isotope analysis reveals the onset of deposition by 7.2 Ma with a transgressive episode that deposited the marine marls of the Bookpurnong Beds. Deposition was restricted to the central and eastern parts of the basin due to the Hamley Fault. In the west, subsurface elevation contours indicate the presence of incised paleodrainage channels above Miocene limestones, which facilitated the formation of a large estuary system at 5.3 Ma. The sediments of the Norwest Bend Formation were deposited within this western region, while further east, the Loxton-Parilla Sands strandplain deposited over 214 coastal ridges. The basal parts of this unit occur as lateral equivalents to the sediments of the Lower Norwest Bend Formation (in the west). Topographic and magnetic data reveal that tectonism was active during this period and resulted in the erosion and truncation of strandlines. / Tectonic evidence and an estimated minimum 28,037 year cyclicity between strandline sets, suggests that the Loxton-Parilla Sands strandlines do not represent an unbroken record of glacioeustatic change. The subaerial exposure of these sediments at approximately 3.0 Ma caused the formation of a calcareous karst above the Norwest Bend Formation and a ferruginous and/or silicious cap (the Karoonda Surface) above the Loxton-Parilla Sands. The stratigraphic position of these surfaces are indicative of a regional widespread unconformity. / The Douglas-Blackburn paleodrainage system in western Victoria was dammed during the Mid-Late Pliocene by uplift associated with the Padthaway High, which caused the formation of a 400,000 km2 lacustrine system, known as Lake Bungunnia. Topographic analysis indicates that Lake Bungunnia comprised at least four distinct sub-basins with water depths of up to 30 metres, with lake shorelines indicating that active tectonism occurred during this period. The resulting lack of sediment input to the coast caused the formation of the Kanawinka Escarpment, a large erosional scarp along the southern margin of the Padthaway High. / The geomorphology of the modern Murray Basin can be directly attributed to the demise of the Lake Bungunnia system. Movement along the Morgan Fault in the west at approximately 700 Ka, resulted in the draining and progressive drying of Lake Bungunnia as a breach was created along the Padthaway High. The Murray River gorge as observed today was incised following this episode. The modern Murray River (and playa lakes such as Lake Tyrell) occupy the lowest elevations along the former sub-basins of Lake Bungunnia. / The Late Neogene sedimentary sequence across the Murray Basin illustrates a complex interaction of eustatic and tectonic processes on deposition. Sedimentation within strandline, estuarine and lacustrine systems, particularly in the western Murray Basin, display evidence of significant tectonic control. This highlights the important role that neotectonic processes have played in shaping southeastern Australia.
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Neotectonics Of The Karamik Graben-afyon- (isparta Angle), Sw TurkeyCicek, Aydin 01 July 2009 (has links) (PDF)
ABSTRACT
NEOTECTONICS OF THE KARAMIK GRABEN-AFYON-(ISPARTA ANGLE), SW
TURKEY
Ç / iç / ek, Aydin
M.Sc., Department of Geological Engineering
Supervisor: Prof. Dr. Ali Koç / yigit
July 2009, 98 pages
The Karamik Graben (KG) is 6-17-km-wide, 29-km-long and NNE-SSWtrending
active depression located within the Isparta Angle of the Southwestern
Turkey extensional neotectonic domain. The KG is bounded by ENE-SSWtrending
Karacaö / ren fault zone to the south, the NNE-SSW-trending Koç / beyli-
Akkonak fault zone to the east, the WNW-ESE-trending AkSehir fault zone to the
north, and the NE-SW to NNE-SSW-trending Devederesi fault zone to the west.
The KG contains two graben infills separated by an angular unconformity:
(1) Middle Miocene-Middle Pliocene deformed infill, and (2) the Upper Pliocenerecent
non-deformed infill. Some geological structures reveal that the older infill
was accumulated under the control of an extensional tectonic regime (phase-I
extension). Analysis of NW-SE-trending folds and some strike-slip faults indicate
that the older infill deformed by a short-term NE-SW-directed compression. This
contractional event is the last record of the paleotectonic period. Some geological and geophysical evidence indicate that the younger infill has been deposited under the control of an extensional tectonic regime (phase-II extension). Analysis of some slickensides implies that the current tectonic regime
is being characterized by a multi-directional extension in predominantly N-S, E-W and NW-SE directions. This multi-directional extension dominates the Plio- Quaternary neotectonic period initiated Late Pliocene.
Total throw amounts accumulated along the margin boundary faults imply that subsidence rates are ~0.15 mm/yr and ~0.21 mm/yr since Late Pliocene.
Some of the northern margin-boundary faults of the KG reactivated during the neotectonic period as evidenced by 2002.02.02 Mw = 6.5 Ç / ay earthquake.
However, the rest of these faults are still active and they keep their nature of seismic gap.
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The role of extension during the evolution of the NW Indian HimalayaHintersberger, Esther January 2013 (has links)
The evolution of most orogens typically records cogenetic shortening and extension. Pervasive normal faulting in an orogen, however, has been related to late syn- and post-collisional stages of mountain building with shortening focused along the peripheral sectors of the orogen. While extensional processes constitute an integral part of orogenic evolution, the spatiotemporal characteristics and the kinematic linkage of structures related to shortening and extension in the core regions of the orogen are often not well known. Related to the India-Eurasia collision, the Himalaya forms the southern margin of the Tibetan Plateau and constitutes the most prominent Cenozoic type example of a collisional orogen. While thrusting is presently observed along the foothills of the orogen, several generations of extensional structures have been detected in the internal, high-elevation regions, both oriented either parallel or perpendicular to the strike of the orogen. In the NW Indian Himalaya, earthquake focal mechanisms, seismites and ubiquitous normal faulting in Quaternary deposits, and regional GPS measurements reveal ongoing E-W extension. In contrast to other extensional structures observed in the Himalaya, this extension direction is neither parallel nor perpendicular to the NE-SW regional shortening direction.
In this study, I took advantage of this obliquity between the trend of the orogen and structures related to E-W oriented extension in order to address the question of the driving forces of different extension directions. Thus, extension might be triggered triggered by processes within the Tibetan Plateau or originates from the curvature of the Himalayan orogen. In order to elaborate on this topic, I present new fault-kinematic data based on systematic measurements of approximately 2000 outcrop-scale brittle fault planes with displacements of up to several centimeters that cover a large area of the NW Indian Himalaya. This new data set together with field observations relevant for relative chronology allows me to distinguish six different deformation styles. One of the main results are that the overall strain pattern derived from this data reflects the regionally important contractional deformation pattern very well, but also reveals significant extensional deformation. In total, I was able to identify six deformation styles, most of which are temporally and spatially linked and represent protracted shortening, but also significant extensional directions. For example, this is the first data set where a succession of both, arc-normal and E-W extension have been documented in the Himalaya.
My observations also furnish the basis for a detailed overview of the younger extensional deformation history in the NW Indian Himalaya. Field and remote-sensing based geomorphic analyses, and geochronologic 40Ar/39Ar data on synkinematic muscovites along normal faults help elucidate widespread E-W extension in the NW Indian Himalaya which must have started at approximately 14-16 Ma, if not earlier. In addition, I documented and mapped fault scarps in Quaternary sedimentary deposits using satellite imagery and field inspection. Furthermore, I made field observations of regional normal faults, compiled structures from geological maps and put them in a regional context. Finally, I documented seismites in lake sediments close to the currently most active normal fault in the study area in order to extend the (paleo) seismic record of this particular fault. Taken together, this data sets document that E-W extension is the dominant active deformation style in the internal parts of the orogen. In addition, the combined field, geomorphic and remote-sensing data sets prove that E-W extension occurs in a much more larger region toward the south and west than the seismicity data have suggested.
In conclusion, the data presented here reveal the importance of extension in a region, which is still dominated by ongoing collision and shortening. The regional fault distribution and cross-cutting relationships suggest that extension parallel and perpendicular to the strike of the orogen are an integral part of the southward propagation of the active thrust front and the associated lateral growth of the Himalayan arc. In the light of a wide range of models proposed for extension in the Himalaya and the Tibetan plateau, I propose that E-W extension in the NW Indian Himalaya is transferred from the Tibetan Plateau due the inability of the Karakorum fault (KF) to adequately accommodate ongoing E-W extension on the Tibetan Plateau. Furthermore, in line with other observations from Tibet, the onset of E-W normal faulting in the NW Himalaya may also reflect the attainment of high topography in this region, which generated crustal stresses conducive to spatially extensive extension. / Die Hauptaufgabe von MHC-kodierten Proteinen ist die Erkennung von körperfremden Molekülen sowie das Einleiten einer adäquaten Immunantwort, womit sie eine Schlüsselrolle im Immunsystem der Wirbeltiere einnehmen. Man nimmt an, dass ihre außergewöhnliche Vielfalt eine Antwort auf die sich ständig anpassenden Parasiten und Krankheitserreger ist, durch adaptive Selektion erhalten wird und dass die individuelle Allelausstattung einen Großteil der Parasitenbelastung erklärt, wofür bereits zahlreiche MHC-Studien Hinweise gefunden haben. Trotzdem ist unser Verständnis über die wirkenden Mechanismen teilweise noch lückenhaft. Ein stark vernachlässigter Aspekt hierbei sind z.B. eventuelle Unterschiede in der Genexpression der MHC-Allele und eine geringere Expression wäre gleichbedeutend mit einer geringeren Aktivierung des Immunsystems. Ich habe hierzu zwei frei lebende Kleinsäugerarten (Delomys sublineatus, Apodemus flavicollis) unter natürlichen Selektionsbedingungen untersucht. Dabei habe ich neben der genotypischen Diversität von MHC-Genen auch deren Expression, sowie die Genexpression immunregulativer Zytokine mit in Betracht gezogen und in Relation zur individuellen Belastung mit gastrointestinalen Helminthen Das gleichzeitige Auftreten von Verkürzung und Dehnung (Extension) ist ein charakteristisches Kennzeichen bei der Bildung von Kollisionsgebirgen. Eine bis heute gängige These beinhaltet ein weit verbreitetes Auftreten von bschiebungen jedoch erst in späteren Stadien der Gebirgsbildung, bzw. nach deren Abschluÿ. Verkürzung ist hingegen während der gesamten Gebirgsbildung zu beobachten. Auch wenn Extensionsprozesse einen wesentlichen Bestandteil der Gebirgsbildung darstellen, ist deren räumlichen und zeitlichen Abfolge sowie ihre kinematische Kopplung zu Verkürzungstrukturen nur wenig gesichert. Der Himalaja, durch die Kollision von Indien und Eurasien entstanden, bildet den südlichen Rand des tibetischen Hochplateaus und stellt ein typisches aktives Kollisionsgebilde dar.
Während heutzutage an der Gebirgsfront Überschiebungen beobachtet werden, können mehrere Generationen an Extensionsstrukturen in den hochgelegenen Regionen des Himalajas dokumentiert werden, die sowohl parallel als auch senkrecht zur Gebirgsfront verlaufen. Im NW Indiens zeugen Erdbebendaten
sowie regionale GPS-Daten von andauernder E-W-Extension. Im Gegensatz zu anderen im Himalaja beschriebenen Extensionsstrukturen ist diese Extensionsrichtung jedoch weder parallel noch senkrecht zur NE-SW orientierten regionalen Verkürzungsrichtung.
In der vorliegenden Arbeit nutze ich diesen schiefen Winkel zwischen der Ausrichtung des Gebirges einerseits und den mit E-W-Extension assoziierten Strukturen andererseits, um mögliche Ursachen für verschiedene Extensionsarten differenzieren zu können. So könnte Extension entweder durch Prozesse innerhalb des tibetischen Hochplateaus gesteuert werden, oder durch die Krümmung des Himalajas, der bogenförmig verläuft. Um dies zu untersuchen, verwende ich einen neuen störungskinematischen Datensatz aus systematischen Messungen von ca. 2000 spröden Störungsflächen im Aufschlussmaßstab über den gesamten Bereich des Himalajas in NW Indien. Zusammen mit Geländebeobachtungen, aus denen eine relative Altersabfolge abgeleitet werden konnte, ermöglicht mir dieser Datensatz zwischen sechs einzelnen Deformationsarten zu differenzieren. Die meisten dieser Deformationsarten sind zeitlich und räumlich verbunden und zeigen fortschreitende Verkürzung an, gleichzeitig werden auch signifikante Extensionsrichtungen dokumentiert. Unter anderem kann ich hier zum ersten Mal eine separierte Abfolge von Extension parallel zum Himalaja-Bogen bzw. E-W-Extension dokumentieren.
Ein weiteres Ziel dieser Studie ist es, einen detaillierten Überblick über die E-W-Extension im NW indischen Himalaja zu erhalten. Basierend auf Kartierung von jungen Bruchstufen sowie geomorphologische Auswertungen, 40Ar/39Ar-daten von synkinematisch gewachsenen Muskoviten auf Abschiebungen, sowie einer Kompilierung von eigene Geländebeobachtungen gröÿerer Abschiebungen mit schon
publizierten Strukturen, konnte ich die räumliche Ausdehnung der E-W-Extension sowie deren zeitliche Einordnung als jüngstes Deformationsereignis belegen. Schlussendlich konnte ich anhand von Deformation in Seeablagerungen in der Nähe der momentan aktivsten Abschiebung im Untersuchungsgebiet den Nachweis an paläoseismologischen Ereignissen entlang dieser Störung ausweiten. Mit diesem Datensatz kann ich nachweisen, dass E-W-Extension in einem wesentlich ausgedehnteren Gebiet nach Süden und Westen hin auftritt, als bisher vorhandene Daten dies vermuten lassen, und dass E-W-Extension vor 14-16 Ma begann, wenn nicht sogar noch früher.
Zusammenfassend bezeugen die hier präsentierten Daten die Relevanz von Extension in einer von Verkürzung geprägten Region. Die räumliche Verteilung von Störungen sowie Überschneidungskriterien lassen vermuten, dass Extension sowohl parallel wie auch senkrecht zum Himalaja-Bogen ein essentieller Teil des südwärts gerichteten Wanderns der aktiven Überschiebungsfront und des damit assoziierten lateralen Wachstums des Gebirges ist. Nach Abwägung der groÿen Bandbreite an Modellen für Extension im Himalaja und im tibetischen Hochplateau, bin ich der Meinung, dass E-W-Extension im NW indischen Himalaja ihren Ursprung im tibetischen Hochplateau hat. Grund dafür ist, dass die Bewegung entlang der Karakorum-Störung nicht ausreichend ist, um die fortdauernde E-W-Extension im tibetischen Hochplateau zu kompensieren. In Übereinstimmung mit anderen Beobachtungen in Tibet ist es auÿerdem möglich, dass das Einsetzen von E-W-Extension im NW Himalaja ebenfalls Erreichen der hohen Topographie in dieser Gegend widerspiegelt, durch die krustale Prozesse in Gang gesetzt werden, die wiederum zu räumlich ausgedehnten Extensionsprozessen führen können.. Anhand von Leber und Milzproben beider Arten habe ich die Methode der ‚real-time PCR‘ zur relativen Quantifizierung von mRNA im Labor etabliert. Bereits für die Labormaus etablierte PCR-Primersysteme wurden an beiden Arten getestet und so konnten stabile Referenzgene gefunden werden, die Grundvoraussetzung für zuverlässige Genexpressionsmessungen. Für D. sublineatus konnte gezeigt werden, dass Helminthenbefall eine typische Th2 Immunantwort induziert, und dass der Zytokin Il4 Gehalt mit Befallsintensität strongyler Nematoden zunimmt. Es wurde für D. sublineatus kein signifikanter Zusammenhang zwischen MHC Expression oder anderen Zytokinen mit Helminthenbefall gefunden. In A. flavicollis wurde ein negativer Zusammenhang zwischen haptischer MHC-Expression und dem parasitären Nematoden Heligmosomoides polygyrus festgestellt, was auf eine Immunvermeidungsstrategie des Nematoden hindeutet. Ich fand typische positive und negative Assoziationen zwischen MHC-Allelen und anderen Helminthenarten, sowie Zeichen eines positiven Selektionsdruckes auf den MHC-Sequenzen, was sich durch eine erhöhte Rate aminosäureverändernder Mutationen zeigte. Diese nicht-synonymen Veränderungen waren auf Positionen innerhalb des zweiten Exons des DRB-Genes beschränkt, wohingegen die untersuchten Bereiche des ersten und dritten Exons stark konserviert vorlagen. Diese variablen Positionen kodieren Schlüsselstellen im Bereich der Antigenbindungsstelle im MHC Molekül. Zusammenfassend zeigt diese Arbeit, dass Genexpressionsstudien auch an Wildtieren durchgeführt und verlässliche Daten erzeugt werden können. Zusätzlich zur strukturellen Vielfalt sollten zukünftig auch mögliche Genexpressionsunterschiede bei MHC-Studien berücksichtigt werden, um ein kompletteres Bild der koevolutiven Wirt-Parasiten-Beziehungen zeichnen zu können. Dies ist vor allem dann von evolutiver Bedeutung, wenn die Parasiten in der Lage sind die MHC Expression aktiv zu beeinflussen. Die Studien konnten nicht die exakte Bedeutung von MHC-Genexpression in der antagonistischen Koevolution definieren, aber sie konnten zeigen dass diese Bedeutung stark von den jeweils beteiligten Partnern abzuhängen vermag.
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Analogue modelling of strike-slip surface ruptures: Implications for Greendale Fault mechanics and paleoseismologySasnett, Peri Jordan January 2013 (has links)
Analogue modelling of strike-slip faulting provides insight into the development and behaviour of surface ruptures with accumulated slip, with relevance for understanding how information recorded in paleoseismic trenches relates to the earthquake behaviour of active faults. Patterns of surface deformation were investigated in analogue experiments using cohesive and non-cohesive granular materials above planar strike-slip basement faults. Surface deformation during the experiments was monitored by 3D PIV (particle image velocimetry) and 2D time lapse photography. Analysis focused on fault zone morphology and development, as well as the relationship of the models to surface deformation observed at the Greendale Fault that resulted from the 2010 Darfield earthquake.
Complex rupture patterns with similar characteristics to the Greendale Fault (e.g. en echelon fractures, Riedel shears, pop-up structures, etc.) can be generated by a simple fault plane of uniform dip, slip, and frictional properties. The specific structures and the style of their development are determined by the properties of the overburden and the nature of the material surface. The width of the zone of distributed deformation correlates closely with sediment thickness, while the width of discrete fracturing is controlled by the material properties as well as the thickness of the overburden. The overall deformation zone width increases with the growth of initial, oblique fractures and subsequently narrows with time as strain localizes onto discrete fractures parallel to the underlying basement fault.
Mapping the evolution of fracture patterns with progressive strain reveals that Riedel shears, striking at 90-120° (underlying fault strike = 90°) are more frequently reactivated during multiple earthquake cycles, and are thus most likely to provide reliable paleoseismic records. This will help identify suitable locations for paleoseismic trenches and interpret trench records on the Greendale Fault and other active, strike-slip faults in analogous geologic settings. These results also highlight the tendency of trenching studies on faults of this type to underestimate the number and displacement of previous ruptures, which potentially leads to an underestimate of the magnitude potential and recurrence interval of paleoearthquakes.
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INTEGRATED GEOPHYSICAL IMAGING OF SUBSURFACE GEOLOGIC CONDITIONS ACROSS A CONTAMINANT PLUME, MCCRACKEN COUNTY, KENTUCKYBlits, Cora A. 01 January 2008 (has links)
Over 7.8 km of seismic reflection data and 2 km of electrical resistivity data were acquired, processed, and interpreted during this multi-method geophysical study. Objectives included the definition of geologic conditions underlying a contaminant plume in McCracken County, western Kentucky, and the determination of the potential for structural control on the rate and direction of plume migration. Both geophysical methods indicate the presence of multiple high-angle normal faults outlining a series of asymmetric grabens ranging in width from 160 m to almost 300 m and striking between N40°E and N45°E. There was agreement between the two methods on fault location and degree of near-surface offset, with offsets of 1 to 2 m observed at 10 to 20 m below ground surface and 3 to 8 m observed at 20 to 30 m depth. Bedrock displacement was generally 2 to 3 times larger, with offsets of 10 to 26 m observed. The faults appear to have originated in the Paleozoic with predominantly normal reactivation occurring as recently as the Pleistocene. The fault strikes generally approximate the orientation of the northwestern contaminant plume. Observed offset of the Regional Gravel Aquifer may form a preferential flow path for contaminant migration.
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PALEOSEISMIC AND STRUCTURAL CHARACTERIZATION OF THE HINES CREEK FAULT: DENALI NATIONAL PARK AND PRESERVE, ALASKAFederschmidt, Sara E 01 January 2014 (has links)
The Hines Creek fault (HCF) is a Holocene-active fault in central Alaska. Its trace has been mapped several times, but data on the history of fault displacement is scarce. As a major crustal-scale geologic boundary with uncertain Quaternary tectonic activity, it is a priority for more to be known about the activity of this fault to better understand the hazards it presents to the Denali National Park and Preserve and Alaskan infrastructure. This study characterizes the late Quaternary activity of the HCF through surficial geologic mapping and paleoseismic investigations. Mapping revealed a very steep (~84°-88° apparent dip), north dipping fault plane and measurements from offset Pleistocene outwash terraces revealed south side-down vertical offsets of up to 12 m, indicating a steeply dipping reverse fault. Three paleoseismic trenches excavated across the fault trace provided a record of seismic activity and hold evidence for at least four prehistoric earthquakes in the last 2 ka. Slip rate calculations estimate movement on the HCF to be between 0.6mm yr-1 and1.2 mm yr-1. The active trace of the HCF follows the southern margin of the tectonically active Mount Healy anticline, suggesting a kinematic linkage between the fault that underlies this anticline and the HCF.
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Late Neogene stratigraphy and sedimentation across the Murray Basin, southeastern AustraliaMiranda, J. A. January 2007 (has links)
The Late Neogene sedimentary sequence of the Murray Basin provides an excellent opportunity to examine paleoenvironmental change across southeastern Australia. A detailed stratigraphic analysis of sediments deposited within the basin in the last 10 Ma was undertaken to assess the influence of tectonic and eustatic processes on deposition. / Stratigraphic observations and radiogenic isotope analysis reveals the onset of deposition by 7.2 Ma with a transgressive episode that deposited the marine marls of the Bookpurnong Beds. Deposition was restricted to the central and eastern parts of the basin due to the Hamley Fault. In the west, subsurface elevation contours indicate the presence of incised paleodrainage channels above Miocene limestones, which facilitated the formation of a large estuary system at 5.3 Ma. The sediments of the Norwest Bend Formation were deposited within this western region, while further east, the Loxton-Parilla Sands strandplain deposited over 214 coastal ridges. The basal parts of this unit occur as lateral equivalents to the sediments of the Lower Norwest Bend Formation (in the west). Topographic and magnetic data reveal that tectonism was active during this period and resulted in the erosion and truncation of strandlines. / Tectonic evidence and an estimated minimum 28,037 year cyclicity between strandline sets, suggests that the Loxton-Parilla Sands strandlines do not represent an unbroken record of glacioeustatic change. The subaerial exposure of these sediments at approximately 3.0 Ma caused the formation of a calcareous karst above the Norwest Bend Formation and a ferruginous and/or silicious cap (the Karoonda Surface) above the Loxton-Parilla Sands. The stratigraphic position of these surfaces are indicative of a regional widespread unconformity. / The Douglas-Blackburn paleodrainage system in western Victoria was dammed during the Mid-Late Pliocene by uplift associated with the Padthaway High, which caused the formation of a 400,000 km2 lacustrine system, known as Lake Bungunnia. Topographic analysis indicates that Lake Bungunnia comprised at least four distinct sub-basins with water depths of up to 30 metres, with lake shorelines indicating that active tectonism occurred during this period. The resulting lack of sediment input to the coast caused the formation of the Kanawinka Escarpment, a large erosional scarp along the southern margin of the Padthaway High. / The geomorphology of the modern Murray Basin can be directly attributed to the demise of the Lake Bungunnia system. Movement along the Morgan Fault in the west at approximately 700 Ka, resulted in the draining and progressive drying of Lake Bungunnia as a breach was created along the Padthaway High. The Murray River gorge as observed today was incised following this episode. The modern Murray River (and playa lakes such as Lake Tyrell) occupy the lowest elevations along the former sub-basins of Lake Bungunnia. / The Late Neogene sedimentary sequence across the Murray Basin illustrates a complex interaction of eustatic and tectonic processes on deposition. Sedimentation within strandline, estuarine and lacustrine systems, particularly in the western Murray Basin, display evidence of significant tectonic control. This highlights the important role that neotectonic processes have played in shaping southeastern Australia.
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