To obtain the rupture history of the Parkfield, California, earthquake, we perform 12 kinematic inversions using elliptical sub-faults. The preferred model has a seismic moment of 1.21 x 10^18 Nm, distributed on two distinct ellipses. The average rupture speed is ~2.7 km/s. The good spatial agreement with previous large earthquakes and aftershocks in the region, suggests the presence of permanent asperities that break during large earthquakes. We investigate our inversion method with several tests. We demonstrate its capability to retrieve the rupture process. We show that the convergence of the inversion is controlled by the space-time location of the rupture front. Additional inversions show that our procedure is not highly influenced by high-frequency signal, while we observe high sensitivity to the waveforms duration. After considering kinematic inversion, we present a full dynamic inversion for the Parkfield earthquake using elliptical sub-faults. The best fitting model has a seismic moment of 1.18 x 10^18 Nm, distributed on one ellipse. The rupture speed is ~2.8 km/s. Inside the parameter-space, the models are distributed according the rupture speed and final seismic moment, defining a optimal region where models fit correctly the data. Furthermore, to make the preferred kinematic model both dynamically correct while fitting the data, we show it is necessary to connect the two ellipses. This is done by adopting a new approach that uses b-spline curves. Finally, we relocate earthquakes in the vicinity of the Darfield, New-Zealand earthquake. 40 years prior to the earthquake, where there is the possibility of earthquake migration towards its epicentral region. Once it triggers the 2010-2011 earthquake sequence, we observe earthquakes migrating inside regions of stress increase. We also observe a stress increase on a large seismic gap of the Alpine Fault, as well as on some portions of the Canterbury Plains that remain today seismically quiet.

The Ethiopian Plateau, situated in the northernmost part of the East African Rift System, has been uplifted and incised by the Blue Nile River, creating the 1.5 km-deep Blue Nile Canyon, the only extensive canyon within the Nile drainage basin. Much of this canyon incision is related to the Ethiopian Plateau uplift, which is due to a combined tectonic influence linked to the East African Rift System and the Afar Mantle Plumerelated upwelling since the Oligocene. The Blue Nile Canyon incision followed this plume-related upwelling, which resulted in extensive flood basalt emplacement around ~30 Ma. This study employs low-temperature apatite (U-Th)/He thermochronology to better understand the timeline and mode of the Blue Nile Canyon incision and the landscape geodynamics of the Ethiopian Plateau. Neoproterozoic basement rocks and Mesozoic sedimentary rock samples were collected in a vertical transect along the Blue Nile Canyon for AHe dating. Euhedral apatite grains that are inclusion-free and fractureless were selected for dating. The Australian Scientific Instrument (ASI) Alphachron and Inductively Coupled Plasma Mass Spectrometer (ICP-MS) measured the concentrations of radiogenic isotopes uranium (U), thorium (Th), and helium (He) to obtain apatite helium (AHe) dates, providing (U-Th)/He cooling ages ranging from 64 to 460 Ma. These AHe dates are much older than the 30 Ma flood basalt event, thus older than the canyon incision. In this study, a cooling/thermal history is suggested by explaining the data dispersion by the radiation damage effect in the dated apatite grains, which is related to He retention with time. The apatite suite has been subjected to protracted cooling, longer residence time in the He partial retention zone, and partial resetting due to Mesozoic rift-related burial and subsidence from deposition of ~1.2 kmthick sedimentary rocks, the extensive emplacement of ~1 km-thick flood basalt at 30 Ma, and differential incision. Radiation Damage Accumulation and Annealing Model (RDAAM) time-temperature thermal models indicate a rapid cooling event, suggesting rapid incision after 10 Ma, which is explained by an increase in uplift of the Ethiopian Plateau, likely due to mantle delamination.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2006. / Earthquakes and other seismic events are known to have catastrophic effects on people and property. These large-scale events are almost always preceded by smallerscale seismic events called precursors, such as tremors or other vibrations. The use of precursor data to predict the realization of seismic hazards has been a long-standing technical problem in different disciplines. For example, blasting or other mining activities have the potential to induce the collapse of rock surfaces, or the occurrence of other dangerous seismic events in large volumes of rock. In this study, seismic data (T4) obtained from a mining concern in South Africa were considered using a nonlinear time series approach. In particular, the method of surrogate analysis was used to characterize the deterministic structure in the data, prior to fitting a predictive model. The seismic data set (T4) is a set of seismic events for a small volume of rock in a mine observed over a period of 12 days. The surrogate data were generated to have structure similar to that of T4 according to some basic seismic laws. In particular, the surrogate data sets were generated to have the same autocorrelation structure and amplitude distributions of the underlying data set T4. The surrogate data derived from T4 allow for the assessment of some basic hypotheses regarding both types of data sets. The structure in both types of data (i.e. the relationship between the past behavior and the future realization of components) was investigated by means of three test statistics, each of which provided partial information on the structure in the data. The first is the average mutual information between the reconstructed past and futures states of T4. The second is a correlation dimension estimate, Dc which gives an indication of the deterministic structure (predictability) of the reconstructed states of T4. The final statistic is the correlation coefficients which gives an indication of the predictability of the future behavior of T4 based on the past states of T4. The past states of T4 was reconstructed by reducing the dimension of a delay coordinate embedding of the components of T4. The map from past states to future realization of T4 values was estimated using Long Short-Term Recurrent Memory (LSTM) neural networks. The application of LSTM Recurrent Neural Networks on point processes has not been reported before in literature. Comparison of the stochastic surrogate data with the measured structure in the T4 data set showed that the structure in T4 differed significantly from that of the surrogate data sets. However, the relationship between the past states and the future realization of components for both T4 and surrogate data did not appear to be deterministic. The application of LSTM in the modeling of T4 shows that the approach could model point processes at least as well or even better than previously reported applications on time series data.

Multiple geophysical and geological data sets were compiled, reprocessed, and interpreted using state-of-the-art signal processing and modeling algorithms to characterize the complex post-Paleozoic geology that overlies the southwestern projection of the Fluorspar Area Fault Complex (FAFC) in western Kentucky. Specific data included 21.5 km of SH-wave seismic reflection, 1.5 km of P-wave seismic reflection, 2 km of electrical resistivity, vertical seismic profiles, Vp and Vs sonic-suspension logs, and 930 lithologic borehole logs. The resultant model indicates three general northeast–southwest-oriented fault zones pass through the study area as southwestern extensions of parts of the FAFC. These fault zones form two significant subparallel grabens with ancillary substructures. The geometry of the interpreted fault zones indicates that they have undergone episodic tectonic deformation since their first formation. Evidence of thickening and steeply dipping reflectors within Tertiary and Quaternary sediment in the downthrown blocks indicate syndepositional movement. Subtle thickening and lack of steeply dipping intraformational reflectors in the Cretaceous suggest a more quiescent period, with sediment deposition unconformably draping and filling the earlier Paleozoic structural surface. There is also evidence that the Tertiary and early Quaternary reactivation was associated with an extensional to compressional regional stress reversal, as manifested by the antiformal folds seen in the hanging wall reflectors and the potential small-amplitude force folds in the Quaternary alluvium, as well as a clear displacement inversion along the Metropolis-loess seismic horizon in two high-resolution reflection images. A surface shear-wave splitting experiment proved to be an efficient and effective tool for characterizing shallow subsurface azimuthally anisotropic geologic inclusions in low-impedance water-saturated sediment environments. The measured azimuthal anisotropy across a well-constrained N60ºE-striking fault exhibited a natural coordinate system that had a fast direction coincident with the fault strike and an orthogonal slow direction. This is also one indicator that faults inactive during significant geologic intervals (i.e., Holocene) do not "heal". Integrated shear-wave velocity models and electrical resistivity tomography profiles across the fault zones exhibit lower shear-wave velocities and resistivities within the deformation zones compared with values outside the boundaries. This is additional evidence that the deformed sediment does not reconsolidate or heal, but that the sediment particle configuration remains more loosely packed, providing an increase in the overall porosity (i.e., hydraulic conductivity). This can wholly or in large part explain the anomalous contaminant plume migration path that is coincident with the deformed zones of the regional gravel groundwater aquifer.

In Chapter 2, we consider the hydrostatic equilibrium figure of a rotating earth model with arbitrary radial density profile. We derive an exact non-linear partial differential equation describing the equilibrium figure. Perturbation theory is used to obtain approximate forms of this equation, and we show that the first-order theory is equivalent to Clairaut's equation. In Chapter 3, a method for parametrizing the possible equilibrium stress fields of a laterally heterogeneous earth model is described. In this method a solution of the equilibrium equations is first found that satisfies some desirable physical property. All other solutions can be written as the sum of this equilibrium stress field and a divergence-free stress tensor field whose boundary tractions vanish. In Chapter 4, we consider the minor vector method for the stable numerical solution of systems of linear ordinary differential equations. Results are presented for the application of the method to the calculation of seismic displacement fields in spherically symmetric, self-gravitating earth models. In Chapter 5, we present a new implementation of the direct solution method for calculating normal mode spectra in laterally heterogeneous earth models. Numerical tests are presented to demonstrate the validity and effectiveness of this method for performing large mode coupling calculations. In Chapter 6, we consider the theoretical basis for the viscoelastic normal mode method which is used in studies of seismic wave propagation, post-glacial rebound, and post-seismic deformation. We show how the time-domain solution to the viscoelastodynamic equation can be written as a normal mode sum in a rigorous manner.

Over the past decade, patterns of horizontal crustal motion observed along the Cascadia subduction zone (CSZ) from Global Positioning System (GPS) measurements have been used to derive locked subduction zone models with varying geometry and coupling factors. Although vertical crustal deformation estimates have been less abundant and less accurate than horizontal component observations, they provide key constraints to the models for estimating the extent of rupture for the next subduction thrust earthquake. In order to provide updated model constraint estimates, the contemporary vertical deformation pattern across the northern Cascadia margin was investigated through the combined application of GPS, repeated leveling, precise gravity, and monthly mean sea level measurements across southern Vancouver Island and repeated leveling on the mainland. To the first order, these estimates are consistent with across-margin tilt predictions from current dislocation models for the region. In their details, however, they reflect a more complex system than suggested by the simple models. Minor landward tilt across the margin at Tofino determined from the re-analyses of -8 years of continuous vertical GPS positions, -40 years of monthly mean sea levels and long-term time (decadal) intervals of repeat leveling surveys is distinctly different than the -3 mm yr'l of landward tilt observed at Neah Bay. While this difference may be minimized by allowing for a small amount of tilt induced at the southern stations from northward migration of the Cascadia forearc, differences in tilting of 3-4 mm yr'l between short- and long-term estimates of repeat leveling at Bamfield are attributed to transients. To a lesser degree, elevation changes across the margin at Tofino may also illustrate transients. As well, distinct differences in the magnitude of vertical deformation for stations to the north and south of Barkley Sound suggest that differential deformation may be occurring along the margin. Similarly, while repeat relative gravity measurements across the margin at Tofino indicate 3-7 mm yr-' of seaward tilt (at odds with results from all other methods), a temporal dependence of vertical deformation might also be evident from the long-term versus short-term tilt rates. However, although repeat absolute gravity estimates between 1995 and 2002 indicate little across-margin tilt, consistent with continuous GPS results, differences between the time series at the Ucluelet absolute gravity and GPS stations indicate that gravity observations could be influenced by episodic mass redistribution beneath western Vancouver Island. This suggests that gravity results might not be directly comparable to estimates from other geodetic methods in determining uplift rates. Extension of the vertical deformation profile eastward into the backarc using repeat leveling surveys indicates a broad region of uplift in the Pemberton area with respect to the coast, which is consistent with the vertical component at the continuous GPS station WSLR. Current dislocation models cannot account for the observed deformation. Therefore, modification of one model was attempted in which a weaker crustal zone, coincident with high heat flow near the Garibaldi Volcanic Arc, was included. A poor fit to the observed deformation rates indicates that further refinements must be made to such a model. Nonetheless, these results suggest a complex system of strain accumulation in the northern CSZ, which may result from a greater 3- dimensionality of the tectonic controls than current dislocation models of the region employ.

Research has demonstrated that equivalent temperature (TE), which incorporates both the surface air temperature (T) and moist heat content associated with atmospheric moisture, is a better indicator of overall heat content. This thesis follows up on a study that used TE to determine the impacts of land use/land cover and air masses on the atmospheric heat content over Kentucky during the growing season (April-September). The study, which used data from the Kentucky Mesonet, reveals that moist weather types dominate the growing season and, as expected, differences between T and TE are smaller under dry atmospheric conditions but larger under moist conditions. For example, the lowest TE-T difference was 10.04 °C on a dry weather day on the 18th of April, 2010 (T = 8.91 °C and TE = 18.95 °C). On the other hand, the highest estimated difference for a day of moist tropical weather was 46.54 °C on the 11th of August, 2010 (T = 26.54 °C and TE = 73.08 °C). Since land cover type influences both moisture availability and temperature in the lower atmosphere, the research shows that TE is larger in areas with higher physical evaporation and transpiration rates. Results support the hypothesis that the influence of different weather types over a region is a likely cause of interannual variation in TE.

The Nepalese Himalaya, one of the most active regions within the Himalayan Mountain belt, is characterized by a thick succession of Miocene age Siwalik sedimentary rocks deposited at its foreland basin. To date, much of its tectonic evolution, including exhumation in the Nepalese Siwalik, is poorly understood. This study of a quantitative analysis of the bedrock river parameters should provide crucial information regarding tectonic activities in the area. The study investigated geomorphic parameters of river longitudinal profiles from 54 watersheds within the Siwalik section of the Nepalese Himalaya, for the first time. A total of 140 bedrock rivers from these watersheds were selected using stream power-law function and 30-meter resolution ASTER DEM. The quantitative data from the river longitudinal profiles were integrated with published exhumation ages. Results of this study show, first, a presence of major and minor knickpoints, with a total of 305 knickpoints identified, of which 180 were major knickpoints and the rest were minor knickpoints. Further classifications of knickpoints were based on structures (lineaments extracted from SRTM DEM), lithology, and possible uplift. Second, the Normalized Steepness index (ksn) values exhibited a range from 5.3 to 140.6. Third, the concavity index of streams in the study area ranged from as low as -12.1 to as high as 31.1 and the values were consistently higher upstream of the knickpoints. Finally, integration of the river profile data with the published exhumation ages show that the regions with a high ksn value correspond to the regions with higher incision and, therefore, are likely to have high uplift. The presence of a break in ksn in the eastern section of the study area suggests that the incision is likely accelerated by Main Frontal Thrust (MFT) movements. Erosion of the thrust sheet could have influenced the rapid uplift of the Siwalik due to isostatic processes. Thus, the timing of the source-region exhumation and its rate suggests that MFT-related tectonics, and/or climate processes, likely influenced the landscape evolution of the study area. The results of this study should help in comprehending the neo-tectonic deformation of the Nepalese Himalaya.

The western portion of the Mississippi/Atwater fold belt in the Gulf of Mexico contains what is known as The Green Knoll Salt Dome. The creation and growth of this salt diapir is punctuated by salt deposition, salt migration, sediment loading, and is linked to the “Frampton” fold belt. An indicator of these growth periods is exhibited in an angular unconformity (halo-kinetic sequence boundary) that flanks the diapir. This unconformity developed during the Miocene-Pliocene chronostratigraphic boundary. The “Redwood” (Green Canyon 1001) prospect was drilled after the discovery of middle Miocene sands containing hydrocarbons in the Mad Dog field (GC 826). The objective Miocene sand in the “Redwood” borehole was thin due to this angular unconformity causing the sand to pinch out. An evaluation of seismic and well log data provided by Bureau of Ocean Energy Management indicated that the unconformity might not provide the seal needed to trap hydrocarbons on the flank of the salt dome, or it did not allow enough sand to be deposited. A palinspastic structural restoration of the Green Knoll Salt Dome revealed that the growth of the Green Knoll and Frampton are connected. It is still possible that if a well were to be drilled further down dip from where The “Redwood” prospect was drilled, one may find a potential hydrocarbon reservoir.

Beneath Keathley Canyon (KC) off the Southern Coast of Louisiana and Texas, allochthonous salt bodies have attained thicknesses of over 7620 m (25000 feet), providing excellent seals and migration pathways for hydrocarbons produced by post-rift sedimentary deposition. This study analyzes a small portion of the KC area, utilizing Petrel Seismic software and well information from the KC102 (Tiber) well. An intra-Miocene wedge, expressed beneath salt, may provide information about movement of allochthonous salt over Wilcox sands, sediment compaction, and hydrocarbon pathways. Progradational sedimentation is the driving force which leads to faulting in the early Miocene, allowing Jurassic salt to rise, spreading laterally and upwards towards the surface, scarring the sediments beneath it in glacier-like form. This intrusion helped to create the proper conditions for formation of a petroleum play system, maintain reservoir quality sands and temperatures, and create a four way closure in the Eocene for prospective well location.