Earth Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

Receive updates for this collection

Two-dimensional waveform tomography of the Queen Charlotte Basin of Western Canada and the Seattle fault zone

Date created: 
2011-12-12
Abstract: 

Two-dimensional frequency domain visco-acoustic waveform tomography is applied to limited-offset marine seismic reflection data from the Queen Charlotte sedimentary Basin of western Canada, and from the Seattle Fault Zone in Puget Sound, Washington. It was possible to obtain high resolution P-wave velocity and attenuation images of the subsurface, and to practically evaluate the effectiveness of the visco-acoustic waveform tomography method. A specific data preconditioning and inversion strategy is developed to recover models to a depth of 1.2 to 1.3 km. The preconditioning of the data converts the field data to a form similar to that predicted by the acoustic waveform modelling algorithm. A multiscale inversion strategy was designed to mitigate non-linearity issues and to improve the estimation of attenuation. The starting velocity model is derived from first arrival traveltime tomography and the starting attenuation model is a homogeneous Q p -value. Four seismic lines in the Queen Charlotte Basin are imaged, and the recovered velocity models aid in interpreting shallow structures such as Quaternary strata and Pliocene faulting. The joint interpretation of the velocity and attenuation models enables the identification of siltstone, shales, the presence of hydrocarbons and seafloor pockmarks. The shallowmost basement rocks are interpreted to be volcanic. Using a section of the seismic data across the Seattle Fault Zone, synthetic visco-acoustic and visco-elastic modelling was used to verify the effectiveness of applying visco-acoustic waveform tomography to visco-elastic data. The results show that visco-acoustic waveform tomography of marine seismic reflection data is reliable when high velocity gradients are absent from the model. Finally, an interpretation is provided for the inversion results across the Seattle Fault Zone. The inverted velocity and attenuation models enable the identification of glacial and post-glacial Pleistocene, Tertiary sedimentary rocks, and Eocene volcanic rocks. Several north-dipping shallow thrust faults, anticlines and a syncline are identified across the Seattle uplift and the Seattle Fault Zone. The orientation of the faults are consistent with the interpretations of the Seattle Fault Zone as either a fault propagating fold with a forelimb breakthrough, or as the leading edge of a triangle zone within a passive roof duplex.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Andrew Calvert
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Characterizing volcanic behaviour using thermal remote sensing and other time series data, 2000-2009, Volcán de Colima, Mexico

Author: 
Date created: 
2011-11-16
Abstract: 

This thesis examines if a protocol can be created using satellite and existing ground-based time series data recorded at Mexico’s most active volcano, Volcán de Colima, over an extended time period (five years), to identify past patterns in the behaviour of the volcano. Thermally anomalous pixels due to volcanic activity are identified on MODIS and GOES satellite images by customizing thresholds in the hybrid approach algorithm to locate pixels with radiance values that exceed the normal background radiance and natural variance at Volcán de Colima. Visual comparison of the resulting thermal anomaly time series with RSEM, mean temperature, and precipitation time series data, and volcanic activity reports yield four common observation types. Furthermore, inspection and comparison of the data sets reveal that additional data requirements and advanced statistical analysis are required to fully characterize past volcanic behaviour for use as a tool to forecast future activity.

Document type: 
Thesis
Supervisor(s): 
Glyn Williams-Jones
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Study of non-volcanic tremors in the Cascadia subduction zone

Date created: 
2011-09-07
Abstract: 

I locate for the first time several episodic and minor tremor sequences along the Cascadia subduction zone from Vancouver Island to northern California between February 2003 and December 2005 using a single location method. My results suggest that Cascadia tremors occur within a distributed deformation zone surrounding the plate interface. I observe spatial and temporal correlations between the greatest magnitude of slow slip and the location of the first day of tremor activity for some episodic sequences in northern Cascadia. In addition to episodic events, minor tremors have also occurred in the region of slow slip, but during different time intervals. In northern California and Oregon, tremors are mainly located where the interplate thermal structure is 550°C–600°C, while the distribution of northern Cascadia tremor epicentres borders the downdip extension of the thermal transition zone in northern Puget Sound, and places the majority of tremors where the interplate thermal structure is 500°C–550°C. In Cascadia, microearthquakes are located much closer to tremor epicenters in comparison with the large earthquakes. A big percentage of tremors in northern and southern Cascadia occur when the b-value is close to an extremum, and this is more obvious for crustal earthquakes. The only clearly identified gap in tremor activity in northern Cascadia correlates with the lowest measured coda Q in the region.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Andrew Calvert
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Stability and mechanism of failure of The Barrier, southwest British Columbia

Author: 
Date created: 
2011-04-21
Abstract: 

The Barrier is a steep, 250 m-high escarpment of dacite in Garibaldi Provincial Park, British Columbia. The lava flow comprises four lobes, two of which (Lobes 3 and 4) came into contact with the late Pleistocene Cordilleran ice sheet. Lobe 3 was the source of a major landslide in 1855-1856 and a smaller event in 1977. This thesis investigates potential mechanisms responsible for landslides from The Barrier. Methods that I applied include magnetic surveys to determine the three-dimensional character of lava flows forming The Barrier, long-range photogrammetry to map the structure of the escarpment in digital terrain models, field mapping, distinct element modelling, and passive seismic landslide monitoring. Of particular importance to the stability of The Barrier are ice-contact structures in the volcanic rocks, which provide clues about emplacement environments. Results show that The Barrier should be considered potentially unstable and that past instability is intimately linked to structures produced by emplacement of the lavas against glacier ice. My work also provides new geophysical and geomechanical data for The Barrier.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Dr. John J. Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Rock avalanches on glaciers

Author: 
Date created: 
2011-04-14
Abstract: 

This thesis examines relations between rock avalanches and the glaciers on which they are deposited. I have attempted to understand a geophysical phenomenon from two viewpoints: sedimentology and glaciology. The contributions are both methodological, and practical. I have used a GIS to quantify debris sheet geomorphology. A thorough characterization of rock avalanche debris is a necessary step in understanding the flow mechanics of large landslide. I have also developed a technique for solving radar interferometry phase unwrapping problems. A digital elevation model created using this technique is used to quantify the velocity of a glacier prior to its disturbance by landslides. Three debris sheets on Black Rapids Glacier, Alaska, have coarse blocky rims. Longitudinal flowbands in these debris sheets, as well as in a debris sheet deposited on Sherman Glacier, Alaska, separate bands of different block size. Elongated blocks are parallel to flow, except at the perimeter of the debris sheets, where they are aligned nearly perpendicular to flow. Blocks on Sherman Glacier have been reoriented by glacier flow since the landslide in 1964. The matrix of all four debris sheets does not systematically change with depth or distance from the source. However, Sherman Glacier debris has become coarser due to weathering. Black Rapids Glacier surged in 1936-1937. Between 1949 and 1995, the glacier gradually returned to a pre-surge hypsometry. Maximum elevation changes along the glacier centerline in the ablation and accumulation areas, are, respectively, -249 m (-5.4 m a-1) and +63 m (+1.4 m a-1). Centerline thickening of +62 m (+1.4 m a-1), just above the Loket tributary in the upper part of the ablation zone, indicates dynamic thickening following the surge. The response of Black Rapids Glacier to the rock avalanches is spatially and temporally complex. Increases in measured and modelled surface velocity across the debris sheets are much greater than velocities observed higher on the glacier. The velocity recorded at the downglacier margin of the debris doubled between 2002 and 2004, resulting in a reversed velocity gradient. The changes in ice dynamics are related to the landslides through the effect of debris insulation on mass balance.

Document type: 
Thesis
File(s): 
Supervisor(s): 
John J. Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Quaternary geology of Bluegoose Prairie, Baffin Island, Nunavut

Date created: 
2011-04-13
Abstract: 

The surficial geology and glacial history of Bluegoose Prairie (NTS 36H/1-8) are described, and the first surficial geology map of the area is presented. Four phases of ice flow occurred in Bluegoose Prairie since the Last Glacial Maximum. Collapse of the Foxe Dome ca. 6.2 - 6.5 14C ka BP initiated deglaciation of Foxe Basin. Deglaciation of Bluegoose Prairie and subsequent isostatic rebound were rapid, as evidenced by a relative sea level curve constructed using marine mollusc 14C ages. Diverse macrofossil assemblages show deglacial climate was as warmer or warmer than today. Contemporaneous pairs of terrestrial and marine macrofossils allow for the measurement of deglacial marine reservoir age for Bluegoose Prairie. This new value of 985 ± 10 14C years, 265 14C years older than previously thought, can be applied to deglacial marine 14C ages in Foxe Basin and Hudson Strait. Application of this value allows more accurate palaeogeographic reconstructions.

Document type: 
Thesis
Supervisor(s): 
Dr. Brent Ward
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

An integrated approach to estimating groundwater recharge and storage variability in southern Mali, Africa

Author: 
Date created: 
2011-06-10
Abstract: 

Groundwater recharge in southern Mali is investigated using a variety of methods. The aquifer system comprises a surficial unconfined aquifer in laterite that is hydraulically connected by vertical fractures through a sedimentary rock layer to a deep fractured semi-confined aquifer. Observed groundwater storage fluctuations from historical water level data correlate with GRACE satellite terrestrial water storage (TWS) variations, with peaks in September and lows in May; however, soil-moisture corrected GRACE data peaked in November due to the GLDAS model poorly predicting the timing of soil-water storage changes. Recharge modeling using HELP gave an average annual net recharge of 132.2 mm (12.6% of rainfall), comparing well with estimates from historical water level (149.1 mm; 16.4%) and GRACE (149.7 mm; 14.8%) data. Major ion chemistry suggests groundwater is fresh (average TDS of 205 mg/L) and rapidly recharged. 18O and 2H concentrations in groundwater and precipitation indicate July-September rainfall as the recharge source.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Diana Allen
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Characterizing highwall slopes at the Line Creek Mine, British Columbia using terrestrial photogrammetry

Author: 
Date created: 
2011-06-13
Abstract: 

Characterization of pit wall stability requires an understanding of the role of structural geology (folds, faults and jointing) in both providing information on kinematic release and as a control on rock mass quality. This thesis discusses the application of digital photogrammetry in the mapping of highwall structures within two pits at the Line Creek Coal Mine. The photogrammetric data are used to characterize fold type, geometry and attitude using classical structural geology techniques. Detailed discontinuity mapping using digital terrain models created from photogrammetric software allows measurement of orientation, trace length and spacing for different discontinuity sets. Kinematic and limit equilibrium analyses indicate that bench-scale failures and rockfall are mainly structurally controlled at Line Creek. The variation of debris height on benches, loss of bench width and variation in rockfall size can all be determined from digital terrain models and used to assess pit wall stability.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Doug Stead
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Hydrogeochemical evolution and arsenic mobilization in confined aquifers formed within glaciomarine sediments

Date created: 
2011-06-06
Abstract: 

The hydrogeochemical evolution and arsenic mobilization mechanisms in groundwater occurring in confined aquifers formed within glaciomarine sediments in the Lower Fraser Valley, British Columbia, are addressed. Methodology includes analysis of chemical and isotopic composition of groundwater, and mineralogical and chemical analysis of sediment samples sourced from core. Groundwater in confined aquifers is Na-HCO3 or Na-Cl type, basic and reduced; whereas groundwater in unconfined aquifers is Ca-Mg-HCO3 type, near neutral and oxidized. The chemistry of groundwater in confined aquifers is controlled by cation exchange, dissolution of carbonate minerals, silicate mineral weathering, and mixing with saline connate water suggesting freshening conditions. Arsenic release occurs as groundwater flows through glaciomarine sediments; its mobility is favoured by basic pH and reducing groundwater conditions. Possible arsenic release mechanisms are iron oxides reduction and sulphides oxidation. A method of spatially representing likelihood of arsenic occurrence in groundwater based on geochemical interpretation and available data is presented.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Dirk Kirste
Diana Allen
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

An integrated study of deep-seated gravitational slope deformations at Handcar Peak, southwestern British Columbia

Date created: 
2011-03-24
Abstract: 

I propose an integrated methodology for the study of deep-seated gravitational slope deformation (DSGSD) and apply the methodology to a gravitationally deforming slope at Handcar Peak in southwestern British Columbia. I mapped DSGSD-related geomorphologic features such as antislope scarps, trenches, ponds, rockslides, and rockfalls on aerial photographs and in the field, and conducted an investigation of sediments deposited behind an antislope scarp to determine the history of movement of the feature. I also characterized the structure and strength properties of the deforming rock mass through engineering geological mapping and investigated the mechanics of movement by kinematic analysis and distinct element numerical modelling. Results suggest that the current episode of movement at Handcar Peak began during or shortly after deglaciation and is continuing. Gravitational lineaments are the surface expression of displacement on weak fault planes. Deformation in numerical models is driven by slip on these faults and on downhill-dipping joints.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Doug Stead
John Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.