The number of subsea production systems placed in deepwater locations in the Gulf of Mexico (GOM) has increased significantly in the last ten to fifteen years. Currently, API-RP2A (2000 a,b) designates the GOM as a low seismic zone, and thus does not require seismic effects to be considered during the design process. However, there have been a number of seismic events with Richter magnitudes between 3.0 and 4.9 that have occurred in this region. As a result, questions have been raised regarding the seismic performance of deepwater subsea systems. This thesis presents an analytical parametric study where a prototype subsea structure was selected based on a survey of subsea systems. The baseline analytical model consisted of a single casing embedded in soft clay soils, which supported a lumped mass at a cantilevered height above the soil. A number of the model characteristics were varied in the parametric study to simulate the structural response of a range of subsea structures. This thesis discusses the impact of API-RP2A Zone 1 and 2 design seismic demands for the performance of subsea structures. The results from the subsequent analyses show that the stresses and deflections produced by the Zone 1 and 2 peak ground accelerations fall within the allowable limits.

In this paper, we turn the interpolation problem of coarsely-sampled data into a denoising problem. From this point of view, we illustrate the benefit of random sampling at sub-Nyquist rate over regular sampling at the same rate. We show that, using nonlinear sparsity promoting optimization, coarse random sampling may actually lead to significantly better wavefield reconstruction than equivalent regularly sampled data.

Performance-based earthquake engineering is an emerging field of study that complements the prescriptive methods that the design codes provide to ensure adequate seismic performance of structures. Accounting for uncertainties in the performance assessments forms an important component in this area. In this context, the present study focuses on two broad themes; first, treatment of uncertainties and the application of the first-order reliability method (FORM) in finite-element reliability analysis, and second, the seismic risk assessment of reinforced concrete structures for performance states such as, collapse and monetary loss. In the first area, the uncertainties arising from inherent randomness (“aleatory uncertainty”) and due to the lack of knowledge (“epistemic uncertainty”) are identified. A framework for the separation of these uncertainties is proposed. Following this, the applicability of FORM to the linear and nonlinear finite-element structural models under static and dynamic loading is investigated. The case studies indicate that FORM is applicable for linear and nonlinear static problems. Strategies are proposed to circumvent and remedy potential challenges to FORM. In the case of dynamic problems, the application of FORM is studied with an emphasis on cumulative response measures. The limit-state surface is shown to have a closed and nonlinear geometric shape. Solution methods are proposed to obtain probability bounds based on the FORM results. In the application-oriented second area of research, at first, the probability of collapse of a reinforced concrete frame is assessed with nonlinear static analysis. By modelling the post-failure behaviour of individual structural members, the global response of the structure is estimated beyond the component failures. The final application is the probabilistic assessment of monetary loss for a high-rise shear wall building due to the seismic hazard in the Cascadia subduction zone. A 3-dimensional finite-element model of the structure with nonlinear material models is subjected to stochastic ground motions in the reliability analysis. The parameters for the stochastic ground motion model are developed for Vancouver, Canada. Monetary losses due to the damage of structural and non-structural components are included.

During the last decade, archaeologists have widely accepted the use of geophysical exploration techniques, including magnetic, resistivity and electromagnetic methods, for pre-excavation site assessment. Although researchers were quick to recognize the potential of seismic techniques to provide cross-sectional images of the subsurface, early feasibility studies concluded that seismic methods were inappropriate due to restricted resolving power and the relatively small-scale nature of archaeological features. Unfortunately, this self-fulfilling prophesy endures and has largely discouraged subsequent attempts to exploit seismic methods for archaeological reconnaissance. Meanwhile, however, seismic technology has been revolutionized in connection with engineering, groundwater and environmental applications. Attention to detail in developing both instrumentation and data acquisition techniques has yielded a many-fold improvement in seismic resolving power. In light of these advances, this dissertation re-examines the potential of reflection seismology for archaeological remote sensing. It is not the objective of this dissertation to deliver an unequivocal pronouncement on the ultimate utility of reflection seismology for the investigation of archaeological sites. Rather, the goal has been to establish a sound theoretical foundation for objective evaluation of the method's potential and future development. In particular, a thorough theoretical analysis of seismic detection and resolution yields practical performance and identifies frequency response characteristics associated with optimum resolution. Findings have guided subsequent adaptation, development and integration of seismic instrumentation, resulting in a prototype system for high-resolution seismic imaging of the shallow subsurface. Finally, to assess system performance and the suitability of optimum offset data acquisition techniques, a full-scale subsurface model has been constructed, allowing direct comparison between experimental soundings and known subsurface structure. Results demonstrate the potential of reflection seismology to resolve near-surface features on the scale of archaeological interest. Moreover, despite conventional wisdom that the groundpenetrating radar method possesses vastly superior resolving power, acquisition of coincident radar soundings demonstrates that the two techniques provide comparable resolution.

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