Oceanic strike-slip earthquakes occur on transform faults and fracture zones that cut across thousands of kilometers of seafloor. The largest of these events often rupture a considerable portion of their associated fault and can provide a comprehensive look at seismic slip across the entire fault plane as well as constraints on the depth extent of seismic slip. It is generally accepted that seismic and aseismic slip along oceanic transform faults is thermally controlled, however composition and geometry have been proposed as significant controls on some faults. High strain rates are a mechanism to achieve greater rupture depths, such as the unusually deep centroids reported for the largest strike-slip earthquake recorded to date, the 2012 MW 8.6 Indian Ocean earthquake. Detailed studies of notable earthquakes and a scattering of well-known faults have been of great use in elucidating oceanic strike-slip rupture. Determining if observed behavior is characteristic of all oceanic strike-slip faults requires a different approach. To resolve how seismic and aseismic slip are controlled with depth and along strike, well-constrained depths of many earthquakes along oceanic strike-slip faults are determined by modeling teleseismic body waves. Finite-fault slip inversions are calculated for the largest, most recent, and best-recorded oceanic strike-slip events. The constrained depth and along-strike location of slip for numerous oceanic earthquakes on strike-slip faults illuminates the distribution of seismic rupture on these faults in detail, as well as in unprecedented breadth through the examination of oceanic faults in a range of spreading rates and lithosphere ages. These well-constrained depths are within the expected limit to brittle failure (600-800ºC) and show that seismic rupture extends throughout the upper mantle to the crust. Observations of seismic rupture along an oceanic strike-slip fault also provide a comparison to the behavior of continental strike-slip faults that pose a far greater hazard to population centers, such as the San Andreas Fault in the Western United States and the North Anatolian Fault in Turkey.

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Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on Mar. 4, 2009). Includes bibliographical references (p. 50-59).

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No description available.

Inläckage av grundvatten är ofrånkomligt i en bergtunnel, men måste vanligen begränsas för att inte medföra skador på både omgivning och den egna anläggningen. Denna begränsning uppnås genom tätning av tunneln och kontrolleras med mätningar av inläckaget. Vilka begränsningsvärden för inläckaget som är möjliga att uppnå, baseras på prediktioner av inläckaget och fastslås i tillståndet som ges för denna vattenverksamhet. Syftet med det här arbetet är att få förståelse för orsakerna till avvikelser mellan det faktiska inläckage som mätningarna visar (utfallet) och det predikterade inläckaget. För att göra detta kommer en fallstudie att genomföras på anläggningen av två ramptunnlar, Solhems- och Kälvestatunneln, i infrastrukturprojektet E4 Förbifart Stockholm. Baserat på fallstudien skapas en ny konceptuell modell av de två ramptunnlarna som inkluderar information om jord-, berg- och grundvattenförhållanden som framkommit till och med i byggskedet. Utifrån denna konceptuella modell görs nya prediktioner av inläckaget med en analytisk formel. Detta jämförs med den konceptuella modell i systemhandlingsskedet från vilken de ursprungliga prediktionerna gjordes. De nya beräkningarna predikterar genomgående ett högre inläckage än de ursprungliga och avviker mindre från utfallet på flertalet delsträckor. Orsakerna till avvikelserna utvärderas, framförallt med avseende på ansatt hydraulisk konduktivitet då detta visat sig ha stor effekt på prediktionerna. Utvärderingen visade att den hydrauliska konduktiviteten i berget generellt var för lågt ansatt, något som hade kunnat förutsägas med annorlunda datainsamling i ett tidigare skede. Mer specifikt orsakade en svaghetszon, som borttagits i tidigare skeden men som observerats i byggskedet, stora avvikelser mellan prediktion och utfall på åtminstone en delsträcka i Solhemstunneln. Om informationen om svaghetszoner tolkats annorlunda i ett tidigare skede hade även detta kunnat förutsägas. / Groundwater inflow to a rock tunnel is inevitable, but nonetheless important to limit. Otherwise both the surroundings and the tunnel itself risk becoming subject to damage. To prevent this, legal limitations are set for the inflow. Measurements are then made to ensure that the inflow does not exceed these limitations. When constructing a tunnel in hard rock, the limit objectives are hopefully met through the filling of rock fractures through grouting. Inflow predictions are made at an early stage of a tunnel project, both in order to establish the legal requirements but also as basis for grouting design. The aim of the work reported is to understand why these predictions in some cases deviate from the measured inflow. To accomplish this, a case study on two road tunnels in one of Sweden's most comprehensive infrastructure projects of all time, the construction of a motorway bypass around the capital Stockholm, is presented and assessed. Several causes of deviations between inflow predictions and observations in these two tunnels are suggested, most of them related to the hydraulic conductivity of the rock. Overall the rock quality seems to be worse than predicted. In one tunnel segment in particular, one cause of major deviations from inflow predictions is due to a fracture zone which has not been accounted for. These identified causes of increased inflow could have been foreseen in an early stage of the project, either through more extensive investigations or different interpretations of existing data. New inflow predictions have been made based on the suggested corrections. The result is consistently higher than the predictions made earlier and mostly less deviant from observations. This indicates that the real inflow is probably higher than initially predicted.

Groundwater is one of the main natural resources worldwide. Groundwater exists in aquifers below the earth surface and provides quantities of water for various purposes such as supply to households and businesses, public supply, drinking water supply, irrigation and agriculture. Sweden is also highly dependent on groundwater. As mentioned in the list of 16 Environmental Quality Objectives, that the Swedish Parliament established, "groundwater must assure a safe and sustainable supply of drinking water, as well as promoting viable habitats for plants and animals in lakes and watercourses". However, the protection of groundwater and generally the aquifer resources is prone to various human activities that are harmful in terms of volume and quality. The present thesis aims to investigate the behavior of groundwater towards such human activities of large scales, like a tunnel construction, and small scale, like a construction of a geothermal plant. The area under study is investigated through spatial analysis, using ArcGIS; the groundwater levels are monitored and further statistically analyzed by implementing a Modified Double Mass Statistical Analysis; and further on a 3D numerical model is built in COMSOL Multiphysics in order to simulate possible drawdown caused by human intervention to the natural environment. The created 3D model was used in order to evaluate the drawdown and different scenarios were implemented with the aim to determine the degree of sensitivity the model has towards fracture parameters. Since the occurrence of fractures in the rock mass is often connected to extended investigation and time/cost consuming techniques, the model contains an overall uncertainty concerning the location and properties of the fracture formations in the area. The different scenarios involve variation of fracture zone width and thus the behavior of the top soil layer is investigated in terms of recovery after drawdown. The results indicated connection to human activities, with the statistical analysis to support this. Also, the numerical model showed that the fracture properties are connected to the recovery time of the groundwater levels after a drawdown is noticed. Wider fracture zone width implied more time needed for the groundwater levels to get to their initial values, under the perception that the source of recharge is precipitation. On the other hand, narrow fracture zone width was connected with greater drawdown, compared to the wider width scenario, and also earlier in time recovery of the groundwater levels. The type of the soil layer and its vulnerability to human activities can vary greatly in terms of volume loss which can prove a hazard to existing infrastructure on the ground surface. The present study can prove useful in cases of prestudy of drilling projects of any scale. There is strong connection between fracture formations and recovery of groundwater levels and thus such kind of models can generate innovative techniques of planning before a project begins. / Grundvatten är en av de viktigaste naturresurserna världen över. Grundvatten finns i akviferer under jordytan och ger vatten för olika ändamål så som tillförsel till hushåll och företag, kommunalt bruk, dricksvattenförsörjning, bevattning och jordbruk. Även Sverige är mycket beroende av grundvatten. I en sammanställning av 16 nationella miljökvalitetsmål fastställde riksdagen bland annat att "grundvatten måste säkerställa ett säkert och hållbart utbud av dricksvatten samt att främja livskraftiga livsmiljöer för växter och djur i sjöar och vattendrag". Skyddet av grundvatten och de allmänna vattenresursresurserna är framtaget för att begränsa påverkan från olika mänskliga aktiviteter som är skadliga när det gäller volym och kvalitet. Föreliggande uppsats syftar till att undersöka grundvattnets beteende till följd av storskaliga mänskliga aktiviteter, till exempel en tunnelkonstruktion, och mindre aktiviteter, till exempel byggnation av en geotermisk anläggning. Det område som studeras undersöks genom rumslig analys, med hjälp av ArcGIS; grundvattennivån övervakas och analyseras vidare statistiskt genom implementering av en statistisk analys av Modified Double Mass Statistical Analysis; en numerisk 3D-modell byggs i mjukvaran COMSOL Multiphysics för att simulera möjlig grundvattennivåsänkning orsakad av mänsklig påverkan i den naturliga miljön. 3D-modellen användes för att utvärdera eventuell grundvattensänkning och olika scenarier implementerades med syfte att bestämma graden av känslighet med avseende på sprickparameterar i modellen. Eftersom förekomst av sprickor i bergmassan ofta innebär ett behov av utökad undersökning och tid/kostnadskrävande tekniker innehåller modellen en övergripande osäkerhet om platsen samt egenskaper hos sprickorna i området. De olika scenarierna involverar variation av sprickzonsbredd och det övre jordskiktets beteende betraktas i termer av återhämtning efter avsänkt grundvattennivå. Resultaten indikerade koppling till mänskliga aktiviteter, den statistiska analysen stödjer detta. Den numeriska modellen visade också att sprickornas egenskaper är kopplade till grundvattennivåernas återhämtningstid efter det att en grundvattennivåsänkning noterats. Bredare sprickzonsbredd innebar längre återhämtningstid för grundvattennivåerna att stiga till deras ursprungliga värden, under förutsättning att källan till återhämtning är nederbörd. Å andra sidan var en smalare sprickzonsbredd förenad med större grundvattenavsänkning samt snabbare återhämtning av grundvattennivån jämfört med scenariot för bredare sprickzoner. Jordlagrets typ och dess känslighet för påverkan från mänskliga aktiviteter kan variera kraftigt i fråga om volymförlust vilket kan utgöra en fara för befintlig infrastruktur på markytan. Den aktuella studien kan vara användbar i förstudier till borrprojekt av vilken skala som helst. Det finns stark koppling mellan sprickbildning och återhämtning av grundvattennivån, och sålunda denna typ av modeller generera innovativa planeringstekniker innan ett projekt börjar.

Two-thirds of submarine volcanism in the Earth's ocean basins is manifested along mid-ocean ridges and the remaining one-third is revealed along intraoceanic arcs and seamounts. Hydrothermal systems and the circulation patterns associated with these volcanic settings remove heat from the solid Earth into the deep ocean. Hydrothermal circulation continues to remove and redistribute heat in the crust as it ages. The heat and mass fluxes added to the deep ocean influence mixing in the abyssal ocean thereby affecting global thermohaline circulation. In addition to removing heat, hydrothermal processes extract chemical components from the oceanic and carry it to the surface of the ocean floor, while also removing certain elements from seawater. The resulting geochemical cycling has ramifications on the localized mineral deposits and also the biota that utilize these chemical fluxes as nutrients. In this dissertation, I analyze observed conductive heat flow measurements in the Panama Basin and borehole thermal measurements in Brothers Volcano and use mathematical models to estimate advective heat and mass fluxes, and crustal permeability. In the first manuscript, I use a well-mixed aquifer model to explain the heat transport in a sediment pond in the inactive part of the Ecuador Fracture Zone. This model yields mass fluxes and permeabilities similar to estimates at young upper oceanic crust suggesting vigorous convection beneath the sediment layer. In the second manuscript, I analyze the conductive heat flow measurements made in oceanic between 1.5 and 5.7 Ma on the southern flank of the Costa Rica Rift. These data show a mean conductive heat deficit of 70%, and this deficit is explained by various hydrothermal advective transport mechanisms, including outcrop to outcrop circulation, transport through faults, and redistribution of heat by flow of hydrothermal fluids in the basement. In the third manuscript, I analyze the borehole temperature logs for two sites representative of recharge and discharge areas of hydrothermal systems in the Brothers Volcano. I develop upflow and downflow models for fluids in the borehole and formation resulting in estimated of flow rates and permeabilities. All three independent research works are connected by the common thread of utilizing relatively simple mathematical concepts to get new insights into hydrothermal processes in oceanic crust. / PHD / Two-thirds of underwater volcanic activity in the Earth’s ocean basins is exhibited in areas where new material for Earth’s outer shell is created and the remaining one-third is displayed along areas where the outer shell is destroyed. In these areas, hot springs that are under water and their water movement patterns remove heat from the solid outer shell and puts it into the deepest parts of the ocean. Hot water circulation continues to remove and redistribute heat and various chemical elements in the shell as it grows old. This heat and chemical elements, which get added to the deep ocean water, influences the way water mixes and forms layers in the world oceans. This also affects the movement of ocean currents. The chemical elements removed from the shell by hot water gets deposited as minerals on the ocean floor in places where hot springs arise. This variety of minerals provides nutrients for different marine organisms. In this work done during my PhD studies, I examine the heat and temperature that was measured in the Panama Basin and Brothers Volcano. I utilize these examinations to build simple math models to find out how much heat and chemical components are being added to the deep ocean water. I also find out the methods in which the hot water springs appear on the ocean floor and the patterns in which the hot water circulates in the Earth’s outer shell. All of these estimates will help the scientists who are studying the patterns and changes in ocean currents by giving them a number on how much heat is released from the inside of the Earth.

Les rides de Barracuda et de Tiburon sont deux reliefs sous-marins situés dans la partie ouest de l'océan Atlantique, là où la lithosphère océanique des plaques Amérique du Nord (NAM) et Amérique du Sud (SAM) est entraînée par subduction sous la plaque Caraïbe, formant l'arc volcanique des Petites Antilles et le prisme d’accrétion de Barbade. Le processus et la période de soulèvement conduisant au relief actuel de ces rides (qui semblent être un marqueur important dans l'histoire géodynamique de la région) sont sujets à débat depuis des décennies.L’interprétation de nouvelles données de sismique réflexion et de bathymétrie multifaisceaux acquises à travers les rides de Barracuda et de Tiburon (campagne Antiplac, 2007 ) a permis de dater les périodes de soulèvements des rides et réaliser des reconstructions paléogéographiques incluant les flux sédimentaires majeurs, depuis le Crétacé jusqu’ à l’Actuel.L’analyse structurale révèle des phases de réactivations tardives d’anciennes zones de fractures dans un contexte transpressif, conduisant aux surrections des rides de Tiburon et de Barracuda.Les processus géologiques possibles impliqués dans la formation des rides de Barracuda et de Tiburon coïncident avec les modèles cinématiques récents décrivant les mouvements relatifs entre les plaques NAM et SAM, le long de la limite de plaque diffuse.Ces résultats permettent de mieux définir la limite de plaque entre NAM et SAM. Elle est nécessairement hétérogène exploitant les zones de faiblesses dans la lithosphère que sont les zones de fracture. Au sein de cette limite de plaque la lithosphère serait donc fragmentée. / The Barracuda Ridge and the Tiburon Rise, two oceanic-basement ridges, lie in the western Atlantic Ocean, where oceanic lithosphere of the North American (NAM) and South American (SAM) plates is subducted beneath the Caribbean plate, creating the Lesser Antilles volcanic arc and the Barbados Ridge accretionary complex. The process and the timing of the uplift leading to the present day morphologies of the Tiburon and Barracuda ridges, that seem to be key markers in the geodynamic history of the region, has remained a matter of debate for decades.From the analysis of new multibeam and seismic reflection profiles acquired in 2007 (Antiplac crusie) DSDP-ODP boreholes available, we provide new information on the timing of the formation of the Barracuda Ridge and Tiburon Rise in their present-day configurations. We propose paleogeographic reconstructions with the main sediments fluxes deposited in the area of the Barracuda and Tiburon ridges from the Late Cretaceous to present. Structural analysis shows reactivation of fracture zones in a transpressive setting leading to the uplifts of the Barracuda and Tiburon Ridges.The location of the Barracuda Ridge and the Tiburon Rise and the timing of the uplift fit well with recent global plate kinematic models describing the movements of NAM relative to SAM along a diffuse plate boundaryThis NAM-SAM plate boundary zone, therefore must most certainly be heterogeneous in nature, exploiting weaknesses in the lithosphere provided by fracture zones where mechanically advantageous, but forming new boundary segments elsewhere, to transfer motion between reactivated segments of the fracture zones.

An integrated use of radio magnetotelluric (RMT) and controlled source tensor magnetotelluric (CSTMT) measurements, the so-called CSRMT method, has been employed in environmental and resource exploration studies. A number of case histories, including a groundwater investigation in glacial deposits, a study of fracture zones for geotechnical purposes and a mining exploration study of a copper deposit, are presented in this thesis in order to illustrate the usefulness and capability of the CSRMT method. The resolutions of the estimated models using various types of data are studied. Magnetotelluric transfer functions are used to analyze the dimensionality, the near surface resistivity distortions and the near field effects in the case of CSTMT data analysis. The near field effects in CSTMT data have also been identified by performing 2½D forward modelling. Data analysis, dimensionality tests and forward modelling show that at the lowest frequencies used the CSTMT transfer functions are generally distorted by source effects, except when the source-receiver distances are sufficient large compared with the penetration depth. Regarding CSTMT transfer functions, apparent resistivities are generally less distorted than phases. TM mode transfer functions are more affected by the sources than TE mode, while tipper vectors generally contain source signatures at all frequencies. Based on the analysis of dimensionality and source effects 2D inverse modelling of CSTMT and RMT data, as well as their combination, have been performed under the plane wave assumption. The RMT method proved to be a powerful tool for imaging the upper 50 m near-surface, but their penetration depth reduces as a conductive layer structures cover the targets at depth. The penetration depth can be increased by including the CSTMT data in the modelling if the measurements are in the far field range. The resolution of the deeper parts of the models may be improved by performing a joint inversion of TE and TM modes, if the strike direction is well-defined. Alternatively, inversion of determinant data can be performed, since the determinant data are less affected by 3D structures and source effects. However the resolution of the determinant models is somewhat degraded compared to the models inverted from combined TE and TM modes.