An Exploration of Ultimate Culture

Description
The sport of Ultimate, formerly known as Ultimate Frisbee™, spread around the world in the mid-seventies and was considered an alternative sport that embraced a more casual atmosphere than other traditional, competitive sports. Ultimate is now receiving national and international…

The sport of Ultimate, formerly known as Ultimate Frisbee™, spread around the world in the mid-seventies and was considered an alternative sport that embraced a more casual atmosphere than other traditional, competitive sports. Ultimate is now receiving national and international attention as a competitive sport, with broadcasts of games on networks such as ESPN. As it transitions into a mainstream sport while attempting to maintain its alternative roots, it is possible that there are contrasting opinions between those who want to bring it further into the mainstream and those who want to maintain as much as possible of the original, alternative culture. In this work, we surveyed members of the Ultimate community for their perspectives on the unique culture of Ultimate.
Because the Ultimate community considers itself to be progressive, despite its largely Caucasian makeup, one topic of exploration was the political landscape of the Ultimate community. A second unique aspect of ultimate is the system for enforcing rules used by the players on the field, known as the spirit of the game. This system replaces referees and creates an ethical dynamic both during play and within the community that is not found in other sports. The last major topic of study here is the self-perception of the players as athletes. Because Ultimate continues to maintain a reputation as an alternative sport, athletes may perceive themselves differently than in more established sports.
When asked if Ultimate players perceived the Ultimate community as accepting of athletes who are people of color (POC) or members of the lesbian, gay, bisexual, or transgender community (LGBT), the community reported being accepting of all minorities. However, acceptance of POC athletes was rated significantly lower than the acceptance of LGBT athletes. When asked about comradery, the respondents rated comradery higher within the Ultimate community than in other sports. When asked how impartial players were in Ultimate compared to other sports, players with more experience tended to report perceiving themselves as more impartial. All demographics reported being more impartial in Ultimate than in other athletics. When asked about the seriousness of Ultimate, those who had not played another sport considered Ultimate to be more serious than those who had played another sport. In addition, players with more years of Ultimate experience also considered it to be more serious than those with fewer years of experience. Overall, additional studies on Ultimate culture are needed in order to obtain more viewpoints, as there is a lack of research in this field for comparison.
Date Created
2019-05
Agent

Constraining Source Models, Underlying Mechanisms, and Hazards Associated with Slow Slip Events: Insight from Space-Borne Geodesy and Seismology

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Description
The movement between tectonic plates is accommodated through brittle (elastic) displacement on the plate boundary faults and ductile permanent deformation on the fault borderland. The elastic displacement along the fault can occur in the form of either large seismic events…

The movement between tectonic plates is accommodated through brittle (elastic) displacement on the plate boundary faults and ductile permanent deformation on the fault borderland. The elastic displacement along the fault can occur in the form of either large seismic events or aseismic slip, known as fault creep. Fault creep mainly occurs at the deep ductile portion of the crust, where the temperature is high. Nonetheless, aseismic creep can also occur on the shallow brittle portion of the fault segments that are characterized by frictionally weak material, elevated pore fluid pressure, or geometrical complexity. Creeping segments are assumed to safely release the accumulated strain(Kodaira et al., 2004; Rice, 1992)(Kodaira et al., 2004; Rice, 1992)(Kodaira et al., 2004; Rice, 1992)(Kodaira et al., 2004; Rice, 1992)(Kodaira et al., 2004; Rice, 1992) on the fault and also impede propagation of the seismic rupture. The rate of aseismic slip on creeping faults, however, might not be steady in time and instead consist of successive periods of acceleration and deceleration, known as slow slip events (SSEs). SSEs, which aseismically release the strain energy over a period of days to months, rather than the seconds to minutes characteristic of a typical earthquake, have been interpreted as earthquake precursors and as possible triggering factor for major earthquakes. Therefore, understanding the partitioning of seismic and aseismic fault slip and evolution of creep is fundamental to constraining the fault earthquake potential and improving operational seismic hazard models. Thanks to advances in tectonic geodesy, it is now possible to detect the fault movement in high spatiotemporal resolution and develop kinematic models of the creep evolution on the fault to determine the budget of seismic and aseismic slip.

In this dissertation, I measure the decades-long time evolution of fault-related crustal deformation along the San Andrea Fault in California and the northeast Japan subduction zone using space-borne geodetic techniques, such as Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR). The surface observation of deformation combined with seismic data set allow constraining the time series of creep distribution on the fault surface at seismogenic depth. The obtained time-dependent kinematic models reveal that creep in both study areas evolves through a series of SSEs, each lasting for several months. Using physics-based models informed by laboratory experiments, I show that the transient elevation of pore fluid pressure is the driving mechanism of SSEs. I further investigate the link between SSEs and evolution of seismicity on neighboring locked segments, which has implications for seismic hazard models and also provides insights into the pattern of microstructure on the fault surface. I conclude that while creeping segments act as seismic rupture barriers, SSEs on these zones might promote seismicity on adjacent seismogenic segments, thus change the short-term earthquake forecast.
Date Created
2018
Agent

Geologic and Structural Characterization of Shallow Seismic Properties Along The San Jacinto Fault at Sage Brush Flat, Southern California

Description
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…

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.
Date Created
2018
Agent

Field and Flume Investigations of Bedload Transport and Bedforms in Sand-Bedded Rivers

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Description
Worldwide, rivers and streams make up dense, interconnected conveyor belts of sediment– removing carved away earth and transporting it downstream. The propensity of alluvial river beds to self-organize into complex trains of bedforms (i.e. ripples and dunes) suggests that the…

Worldwide, rivers and streams make up dense, interconnected conveyor belts of sediment– removing carved away earth and transporting it downstream. The propensity of alluvial river beds to self-organize into complex trains of bedforms (i.e. ripples and dunes) suggests that the associated fluid and sediment dynamics over individual bedforms are an integral component of bedload transport (sediment rolled or bounced along the river bed) over larger scales. Generally speaking, asymmetric bedforms (such as alluvial ripples and dunes) migrate downstream via erosion on the stoss side of the bedform and deposition on the lee side of the bedform. Thus, the migration of bedforms is intrinsically linked to the downstream flux of bedload sediment. Accurate quantification of bedload transport is important for the management of waters, civil engineering, and river restoration efforts. Although important, accurate qualification of bedload transport is a difficult task that continues t elude researchers. This dissertation focuses on improving our understanding and quantification of bedload transport on the two spatial scales: the bedform scale and the reach (~100m) scale.

Despite a breadth of work investigating the spatiotemporal details of fluid dynamics over bedforms and bedload transport dynamics over flat beds, there remains a relative dearth of investigations into the spatiotemporal details of bedload transport over bedforms and on a sub-bedform scale. To address this, we conducted two sets of flume experiments focused on the two fundamental regions of flow associated with bedforms: flow separation/reattachment on the lee side of the bedform (Chapter 1; backward facing-step) and flow reacceleration up the stoss side of the next bedform (Chapter 2; two-dimensional bedform). Using Laser and Acoustic Doppler Velocimetry to record fluid turbulent events and manual particle tracking of high-speed imagery to record bedload transport dynamics, we identified the existence and importance of “permeable splat events” in the region proximal to flow reattachment.

These coupled turbulent and sediment transport events are integral to the spatiotemporal pattern of bedload transport over bedforms. Splat events are localized, high magnitude, intermittent flow features in which fluid impinges on the bed, infiltrates the top portion of bed, and then exfiltrates in all directions surrounding the point of impingement. This initiates bedload transport in a radial pattern. These turbulent structures are primarily associated with quadrant 1 and 4 turbulent structures (i.e. instantaneous fluid fluctuations in the streamwise direction that bring fluid down into the bed in the case of quadrant 1 events, or up away from the bed in the case of quadrant 4 events) and generate a distinct pattern of bedload transport compared to transport dynamics distal to flow reattachment. Distal to flow reattachment, bedload transport is characterized by relatively unidirectional transport. The dynamics of splat events, specifically their potential for inducing significant magnitudes of cross-stream transport, has important implications for the evolution of bedforms from simple, two dimensional features to complex, three-dimensional features.

New advancements in sonar technology have enabled more detailed quantification of bedload transport on the reach scale, a process paramount to the effective management of rivers with sand or gravel-dominated bed material. However, a practical and scalable field methodology for reliably estimating bedload remains elusive. A popular approach involves calculating transport from the geometry and celerity of migrating bedforms, extracted from time-series of bed elevation profiles (BEPs) acquired using echosounders. Using two sets of repeat multibeam sonar surveys from the Diamond Creek USGS gage station in Grand Canyon National Park with large spatio-temporal resolution and coverage, we compute bedload using three field techniques for acquiring BEPs: repeat multi-, single-, and multiple single-beam sonar. Significant differences in flux arise between repeat multibeam and single beam sonar. Mulitbeam and multiple single beam sonar systems can potentially yield comparable results, but the latter relies on knowledge of bedform geometries and flow that collectively inform optimal beam spacing and sampling rate. These results serve to guide design of optimal sampling, and for comparing transport estimates from different sonar configurations.
Date Created
2018
Agent

The Hominin Sites and Paleolakes Drilling Project: Inferring the Environmental Context of Human Evolution From Eastern African Rift Lake Deposits

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Description

The role that climate and environmental history may have played in influencing human evolution has been the focus of considerable interest and controversy among paleoanthropologists for decades. Prior attempts to understand the environmental history side of this equation have centered…

The role that climate and environmental history may have played in influencing human evolution has been the focus of considerable interest and controversy among paleoanthropologists for decades. Prior attempts to understand the environmental history side of this equation have centered around the study of outcrop sediments and fossils adjacent to where fossil hominins (ancestors or close relatives of modern humans) are found, or from the study of deep sea drill cores. However, outcrop sediments are often highly weathered and thus are unsuitable for some types of paleoclimatic records, and deep sea core records come from long distances away from the actual fossil and stone tool remains. The Hominin Sites and Paleolakes Drilling Project (HSPDP) was developed to address these issues. The project has focused its efforts on the eastern African Rift Valley, where much of the evidence for early hominins has been recovered. We have collected about 2 km of sediment drill core from six basins in Kenya and Ethiopia, in lake deposits immediately adjacent to important fossil hominin and archaeological sites. Collectively these cores cover in time many of the key transitions and critical intervals in human evolutionary history over the last 4 Ma, such as the earliest stone tools, the origin of our own genus Homo, and the earliest anatomically modern Homo sapiens. Here we document the initial field, physical property, and core description results of the 2012–2014 HSPDP coring campaign.

Date Created
2016-02-19
Agent

Spatio-Temporal Mapping of Plate Boundary Faults in California Using Geodetic Imaging

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Description

The Pacific–North American plate boundary in California is composed of a 400-km-wide network of faults and zones of distributed deformation. Earthquakes, even large ones, can occur along individual or combinations of faults within the larger plate boundary system. While research…

The Pacific–North American plate boundary in California is composed of a 400-km-wide network of faults and zones of distributed deformation. Earthquakes, even large ones, can occur along individual or combinations of faults within the larger plate boundary system. While research often focuses on the primary and secondary faults, holistic study of the plate boundary is required to answer several fundamental questions. How do plate boundary motions partition across California faults? How do faults within the plate boundary interact during earthquakes? What fraction of strain accumulation is relieved aseismically and does this provide limits on fault rupture propagation? Geodetic imaging, broadly defined as measurement of crustal deformation and topography of the Earth’s surface, enables assessment of topographic characteristics and the spatio-temporal behavior of the Earth’s crust.

We focus here on crustal deformation observed with continuous Global Positioning System (GPS) data and Interferometric Synthetic Aperture Radar (InSAR) from NASA’s airborne UAVSAR platform, and on high-resolution topography acquired from lidar and Structure from Motion (SfM) methods. Combined, these measurements are used to identify active structures, past ruptures, transient motions, and distribution of deformation. The observations inform estimates of the mechanical and geometric properties of faults. We discuss five areas in California as examples of different fault behavior, fault maturity and times within the earthquake cycle: the M6.0 2014 South Napa earthquake rupture, the San Jacinto fault, the creeping and locked Carrizo sections of the San Andreas fault, the Landers rupture in the Eastern California Shear Zone, and the convergence of the Eastern California Shear Zone and San Andreas fault in southern California. These examples indicate that distribution of crustal deformation can be measured using interferometric synthetic aperture radar (InSAR), Global Navigation Satellite System (GNSS), and high-resolution topography and can improve our understanding of tectonic deformation and rupture characteristics within the broad plate boundary zone.

Date Created
2017-03-21
Agent

Lateral Offset Quality Rating Along Low Slip Rate Faults: Application to the Alhama de Murcia Fault (SE Iberian Peninsula)

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Description

Seismic hazard assessment of strike-slip faults is based partly on the identification and mapping of landforms laterally offset due to fault activity. The characterization of these features affected by slow-moving faults is challenging relative to studies emphasizing rapidly slipping faults.…

Seismic hazard assessment of strike-slip faults is based partly on the identification and mapping of landforms laterally offset due to fault activity. The characterization of these features affected by slow-moving faults is challenging relative to studies emphasizing rapidly slipping faults. We propose a methodology for scoring fault offsets based on subjective and objective qualities. We apply this methodology to the Alhama de Murcia fault (SE Iberian Peninsula) where we identify 138 offset features that we mapped on a high-resolution (0.5 × 0.5 m pixel size) Digital Elevation Model (DEM). The amount of offset, the uncertainty of the measurement, the subjective and objective qualities, and the parameters that affect objective quality are independent variables, suggesting that our methodological scoring approach is good. Based on the offset measurements and qualifications we calculate the Cumulative Offset Probability Density (COPD) for the entire fault and for each fault segment. The COPD for the segments differ from each other. Tentative interpretation of the COPDs implies that the slip rate varies from one segment to the other (we assume that channels with the same amount of offset were incised synchronously). We compare the COPD with climate proxy curves (aligning using the very limited age control) to test if entrenchment events are coincident with climatic changes. Channel incision along one of the traces in Lorca-Totana segment may be related to transitions from glacial to interglacial periods.

Date Created
2015-11-06
Agent

Combining tectonic geomorphology and paleoseismology for understanding of earthquake recurrence

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Description
There is a need to understand spatio-temporal variation of slip in active fault zones, both for the advancement of physics-based earthquake simulation and for improved probabilistic seismic hazard assessments. One challenge in the study of seismic hazards is producing a…

There is a need to understand spatio-temporal variation of slip in active fault zones, both for the advancement of physics-based earthquake simulation and for improved probabilistic seismic hazard assessments. One challenge in the study of seismic hazards is producing a viable earthquake rupture forecast—a model that specifies the expected frequency and magnitude of events for a fault system. Time-independent earthquake forecasts can produce a mismatch among observed earthquake recurrence intervals, slip-per-event estimates, and implied slip rates. In this thesis, I developed an approach to refine several key geologic inputs to rupture forecasts by focusing on the San Andreas Fault in the Carrizo Plain, California. I use topographic forms, sub-surface excavations, and high-precision geochronology to understand the generation and preservation of slip markers at several spatial and temporal scales—from offset in a single earthquake to offset accumulated over thousands of years. This work results in a comparison of slip rate estimates in the Carrizo Plain for the last ~15 kyr that reduces ambiguity and enriches rupture forecast parameters. I analyzed a catalog of slip measurements and surveyed earth scientists with varying amounts of experience to validate high-resolution topography as a supplement to field-based active fault studies. The investigation revealed that (for both field and remote studies) epistemic uncertainties associated with measuring offset landforms can present greater limitations than the aleatoric limitations of the measurement process itself. I pursued the age and origin of small-scale fault-offset fluvial features at Van Matre Ranch, where topographic depressions were previously interpreted as single-event tectonic offsets. I provide new estimates of slip in the most recent earthquake, refine the centennial-scale fault slip rate, and formulate a new understanding of the formation of small-scale fault-offset fluvial channels from small catchments (<7,000 m2). At Phelan Creeks, I confirm the constancy of strain release for the ~15,000 years in the Carrizo Plain by reconstructing a multistage offset landform evolutionary history. I update and explicate a simplified model to interpret the geomorphic response of stream channels to strike-slip faulting. Lastly, I re-excavate and re-interpret paleoseismic catalogs along an intra-continental strike-slip fault (Altyn Tagh, China) to assess consistency of earthquake recurrence.
Date Created
2016
Agent

The roles of erosion rate and rock strength in the evolution of canyons along the Colorado River

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Description
For this dissertation, three separate papers explore the study areas of the western Grand Canyon, the Grand Staircase (as related to Grand Canyon) and Desolation Canyon on the Green River in Utah.

In western Grand Canyon, I use comparative geomorphology between…

For this dissertation, three separate papers explore the study areas of the western Grand Canyon, the Grand Staircase (as related to Grand Canyon) and Desolation Canyon on the Green River in Utah.

In western Grand Canyon, I use comparative geomorphology between the Grand Canyon and the Grand Wash Cliffs (GWC). We propose the onset of erosion of the GWC is caused by slip on the Grand Wash Fault that formed between 18 and 12 million years ago. Hillslope angle and channel steepness are higher in Grand Canyon than along the Grand Wash Cliffs despite similar rock types, climate and base level fall magnitude. These experimental controls allow inference that the Grand Canyon is younger and eroding at a faster rate than the Grand Wash Cliffs.

The Grand Staircase is the headwaters of some of the streams that flow into Grand Canyon. A space-for-time substitution of erosion rates, supported by landscape simulations, implies that the Grand Canyon is the result of an increase in base level fall rate, with the older, slower base level fall rate preserved in the Grand Staircase. Our data and analyses also support a younger, ~6-million-year estimate of the age of Grand Canyon that is likely related to the integration of the Colorado River from the Colorado Plateau to the Basin and Range. Complicated cliff-band erosion and its effect on cosmogenic erosion rates are also explored, guiding interpretation of isotopic data in landscapes with stratigraphic variation in quartz and rock strength.

Several hypotheses for the erosion of Desolation Canyon are tested and refuted, leaving one plausible conclusion. I infer that the Uinta Basin north of Desolation Canyon is eroding slowly and that its form represents a slow, stable base level fall rate. Downstream of Desolation Canyon, the Colorado River is inferred to have established itself in the exhumed region of Canyonlands and to have incised to near modern depths prior to the integration of the Green River and the production of relief in Desolation Canyon. Analysis of incision and erosion rates in the region suggests integration is relatively recent.
Date Created
2016
Agent

Transitions in eruption style at silicic volcanoes: from stable domes to pyroclastic flows and explosive plumes

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Description
Silicic volcanoes produce many styles of activity over a range of timescales. Eruptions vary from slow effusion of viscous lava over many years to violent explosions lasting several hours. Hazards from these eruptions can be far-reaching and persistent, and are…

Silicic volcanoes produce many styles of activity over a range of timescales. Eruptions vary from slow effusion of viscous lava over many years to violent explosions lasting several hours. Hazards from these eruptions can be far-reaching and persistent, and are compounded by the dense populations often surrounding active volcanoes. I apply and develop satellite and ground-based remote sensing techniques to document eruptions at Merapi and Sinabung Volcanoes in Indonesia. I use numerical models of volcanic activity in combination with my observational data to describe the processes driving different eruption styles, including lava dome growth and collapse, lava flow emplacement, and transitions between effusive and explosive activity.

Both effusive and explosive eruptions have occurred recently at Merapi volcano. I use satellite thermal images to identify variations during the 2006 effusive eruption and a numerical model of magma ascent to explain the mechanisms that controlled those variations. I show that a nearby tectonic earthquake may have triggered the peak phase of the eruption by increasing the overpressure and bubble content of the magma and that the frequency of pyroclastic flows is correlated with eruption rate. In 2010, Merapi erupted explosively but also shifted between rapid dome-building and explosive phases. I explain these variations by the heterogeneous addition of CO2 to the melt from bedrock under conditions favorable to transitions between effusive and explosive styles.

At Sinabung, I use photogrammetry and satellite images to describe the emplacement of a viscous lava flow. I calculate the flow volume (0.1 km3) and average effusion rate (4.4 m3 s-1) and identify active regions of collapse and advance. Advance rate was controlled by the effusion rate and the flow’s yield strength. Pyroclastic flow activity was initially correlated to the decreasing flow advance rate, but was later affected by the underlying topography as the flow inflated and collapsed near the vent, leading to renewed pyroclastic flow activity.

This work describes previously poorly understood mechanisms of silicic lava emplacement, including multiple causes of pyroclastic flows, and improves the understanding, monitoring capability, and hazard assessment of silicic volcanic eruptions.
Date Created
2016
Agent
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