Large areas of the Earth are covered by intrusive and extrusive lavas, forming high velocity basalts, which are often opaque to cinventional seismicreflection surveys. On the North East Atlantic margin these basalts cover sediments in whose lateral extension away from the basalt cover proven hydrocarbon reservoirs and source rocks exist. To reveal the comparable structures that are expected to exist beneath the basalt cover novel seismic methods are required. The primary objectives of this thesis are to examine the effects of basalts on seismic wave propagation and the concequent implications for imaging sedimentary structures beneath them. From studies of basalt propertiesand borehole data in connection with foreward modelling and real data, I show that new acquisition methods, like low frequency set-ups and far-offset recordings, have to be used to image beneath basalt sequences.

This thesis presents a detailed 40 evolutionary model of the deepwater fold-and-thrust belt of the western Niger Delta using a 3D seismic reflection dataset. The geometries and kinematics of the fault-related folds interpreted in the study area have been compared to two series of 20 sandbox analogue models of a doubly-vergent wedge to understand the evolution of these structures. The regional interpretation of the 3D seismic dataset revealed the occurrence of four thrust domains separated by dextral tear faults. Each domain is characterised by differing deformational styles. Distinct structural styles have been interpreted in e~ch thrust domain. Section restoration of regional cross sections revealed different amounts of shortening, from 0.7 km to 2.7 km, within each domain, an overall break-forward propagation sequence, and a complex thrust interaction with reactivations and synchronous activity commonly observed. The detailed 3D interpretation and structural analysis of individual fault-related folds demonstrated ~hat these structures evolved initially as detachment folds which were subsequently faulted by break thrusts in their limbs, resulting in faulted detachment folds. At the Present Day, the structures show geometric similarities to shear fault bend folds but clearly have evolved in a non self similar way. Detailed analyses have revealed that folds are partitioned vertically with brittle duplex systems at the detachment level, , overlain by a region of pure shear homogeneous strain which itself is overlain by a pre-kinematic sequence representing the flexural lid of the folds. Fold growth is recorded by growth strata and shows an initial rapid rate of crestal uplift followed by a decrease in uplift with continued shortening. This is interpreted to be a result of fold growth by limb rotation. The above-described structural aspects are included in the new evolutionary models of fault-related folds proposed in this thesis. The 20 scaled analogue modelling of doubly-vergent wedge using high- resolution digital photography and Die analyses have clearly shown that the laboratory models also evolve in a similar fashion and develop in some way similar geometries to those in the deepwater fold belts.

This study derived and presented an analytical expression to estimate the collapse potential of a generic class of multi-storey, uniform, moment-resisting steel frames (MRSF). This expression was compared and validated with nonlinear pushover analysis (POA) and Incremental Dynamic Analysis (IDA) for a range of different heights of buildings which were designed according to Eurocodes. Moreover, the factors that influence the collapse potential, such as lateral load patterns, displaced shape and arrangement of plastic hinges formed were also investigated. From this study, two key parameters were introduced, the damage index (DI), %, or adjusted DI, i, and strength parameter, s. The results indicated that the analytical expression produced quite promising results compared to both static and dynamic nonlinear finite element analyses. This analytical expression shows that the design base shear suggested by Eurocode 8 is not a good estimate of the collapse load. Furthermore, from this piece of know ledge, % or i and s are the important parameters that are needed to calibrate and develop an equivalent Single-Degree-of- Freedom (SDOF) system. The SDOF model can be used as a precursor to Multi-Degree-of- Freedom (MDOF) analysis. It can play a useful role in accelerograms records selection because it requires less computational time in determining critical records for MDOF analysis. However, it is difficult to develop the SDOF system and replace the MD OF system because parameters such as elastic viscous damping, ~, and pseudo-yield, x~, are difficult to control. These two parameters are dependant on the type of the structural system and ground motion records. This is because every single earthquake has its own unique characteristics. Moreover, a new intensity measure (IM) called normalised peak ground acceleration (pGA) has been introduced. It produces strong correlation between IM and DM (i.e. inter-storey drift) for all events rather than conventional IM, i.e. PGA and Se (.7;).

The Canadian Shield is one of the largest exposures of Precambrian geology on the Earth, and is underlain by a deep (>250 km) and laterally extensive cratonic root. The processes which formed the crust during this period of Earth history remain a matter of considerable debate, as do the events which led to the creation and stabilisation of the sub-continental lithospheric mantle. The thermal effect that these cold, refractory roots have on the underlying asthenosphere and mantle transition zone is also unclear. The Hudson Bay intracratonic basin lies at the core of stable continental North America with several hypotheses, including crustal thinning through extension or a surface-coupled mantle downwelling, being postulated for its existence. The reason for several of these problems being unanswered is due to the regions inaccesiblilty and harsh climate. However, recent seismic deployments across the Hudson Bay region have allowed these hypotheses to be tested through a teleseisrnic receiver function study. Bulk crustal properties (thickness, Vp/Vs) determined using the H-}( stacking method (Zhu and Kanamori, 2000) indicate that the Meso- to Paleoarchean crust of the Rae domain is strikingly simple with uniform thickness (~37 km), a sharp Moho and low Vp/Ys ratio « 1.73) indicative of a felsic-to-intermediate composition. There is little evidence from the geological record of the central Rae domain for collisional processes, and the spatial extent of felsic crust is more consistent with models of crustal formation involving vertical tectonic processes. The thickest crust observed lies on southern Baffin Island (~43 km), coincident with the Paleoproterozoic Trans-Hudson Orogen. The results suggest that crusta I thicknesses could have been originally in excess of 65 km, similar to what is seen in modern collisional environments. The results point toward secular crusta I evolution. from non-plate tectonic prior to 3.0Ga through to fully developed Wilson cycle style plate tectonics by the Paleoproterozoic. Heterogeneous (dipping and/or anisotropic) structure within the shallow lithospheric mantle is observed on both the radial and tangential RF components beneath the Melville Peninsula and northern Baffin Island. The pattern of periodicity on the tangential component suggests either an interface or anisotropic layer dipping towards at 240°/60°, agreeing well with dike swarms located on central Baffin Island, believed to be emplaced during localised intrabasinal rifting during the Paleopro- terozoic. This makes extensional processes a prime candidate for the structure primarily observed in the lithospheric mantle, possibly favouring this type of deformation as a mechanism for subsidence of the Hudson Bay intracratonic basin. Pds arrival times and differential times (P660s-P4lOs, indicative of transition zone thickness) from the 41 O-km (the '410') and 660-km (the '660') seismic discontinuities are analysed for stations located across the entire Canadian Shield. 1-0 time migrations and 3-~ depth migrations show that the transition zone discontinuities are unperturbed beneath one of the largest and deepest cratonic roots on the Earth, with the implication that the root has little «SO K) or no thermal effect at transition zone depths. The internal discontinuity structure is also simple, meaning the observations can be reconciled with phase changes in the olivine system alone. Frequency dependence of amplitude from the '410' show that the pattern with frequency is indicative of a gradational increase in velocity with depth across the '410'. Comparing these observations to synthetic RFs suggests that the sharpness of the '410' is in the region of 20-34 km, depending on the nature of the velocity increase. This sharpness estimate is consistent with water contents of 550 pprn to greater than 1200 ppm. These values lie above the saturation point of peridotite at these depths meaning a region containing dehydration melting, and hence a seismic low velocity layer, should be present above the '410'. This is inconsistent with much of the migrated data, and other avenues for broadening may need to be explored. Velocity jumps constrained by the modelling are 5-7%, above that of the ak 135 model (4.4%). The higher velocity jump appears to be consistent with a mantle of pyrolitic composition. Collectively, the results provide new fundamental constraints on the processes that were occurring during the Precambrian from a previously unstudied region. The study has also highlighted the simplicity of the mantle transition zone beneath a vast cratonic root, raising questions regarding the presence of small-scale convection beneath continents and their affect on the Earth's heat budget.

The discovery of double and triple seismic planes at subduction intermediate depths has attracted the interest of the scientific community but the exact cause for this earthquake layering remains elusive. In order to investigate the origins of the observed seismic planes the work described in this thesis examines the effects of slab bending and unbending at intermediate depths along with the input of thermal stresses, the basalt transition into eclogite and slab pull, on the stress distributions of a modelled slab.

In low to moderate seismicity intraplate regions, earthquake engineers and engineering seismologists face challenges dealing with the considerable level of uncertainty in the estimation of magnitude recurrence parameters and maximum magnitude estimation for probabilistic seismic hazard assessment (PSHA). This is largely due to the lack of strong ground motion records, short and incomplete earthquake catalogue, and extremely long recurrence intervals between large magnitude events. This puts additional importance of finding reliable estimates of earthquake source parameters for historical and early instrumental records which often have greater impact on hazard results than short span of instrumental records. This thesis explores the presence of regional differences within stable continental regions (SCRs) as well as a degree of regional variability with respect to the global average SCR using isoseismal area data. This is accomplished by careful collection and processing of isoseismal areas from the global stable continental regions, and by developing felt area-to-magnitude relationships through a uniform regression framework of Johnston (1996b). By comparing with existing relationships, the applicability of the newly developed felt area-to-magnitude relationships is evaluated. Analyses of focal depth distribution, and their correspondence with the Moho depth and the surface heat flow are investigated for the Korean peninsula, as a case study region. Macroseismic attenuation parameters for the Kövesligethy (1906) attenuation model are derived from a newly compiled, comprehensive macroseismic intensity database in order to determine macroseismic focal depths. The influence of using different types of macroseismic data and regional earthquake data on the macroseismic attenuation parameters is also investigated. Finally, a suite of three intensity attenuation models, each using a different functional form, is derived for the Korean peninsula, and the sensitivity of the model results to different regression techniques and functional regression forms is evaluated. The newly derived intensity attenuation model is used to estimate earthquake magnitude and epicentral location through the bootstrap resampling technique of Bakun and Wentworth (1997).

Naturally fractured reservoirs are playing an important role in exploration geophysics. As fractures can control the permeability and pore pressure of the reservoir, it is crucial to study the fracture characterisation. The thesis is mainly including the estimated seismic anisotropy from shear-wave splitting (SWS) observations and the study of the S-wave scattering characteristics of fractured media as well. A suite of synthetic fractured media with a broad range of fracture parameters is generated. The range of fracture parameters was chosen based on the numerical simulation and also where there is a lack of research in the literature. An automated approach of SWS analysis is performed which is suitable to cope with large volume of SWS measurements. The SWS analysis was automatically performed using cross-correlation and eigenvalue minimisation methods by using a cluster analysis technique. The automated quality measuring is obtained from the misfit calculation of both methods to estimate SWS measurements. This method leads to detect 7% and 4% high quality SWS of 6624 SWS measurements for the single and the double fracture sets models, respectively. This method is crucially beneficial as it reduces the number of inspection of SWS measurements. The SWS measurements are obtained from the receivers distribution at near-surface as well as four boreholes. The parametrisation study of SWS shows that the number of models with good SWS decreases with increasing fracture length size. Moreover, by increasing normal and tangential compliance by one order of magnitude while keeping compliance ratio constant leads to models with good SWS in most cases. The simulation of synthetic microseismic event provides suitable S-wave sources that result in SWS measurements to image fracture parameters (i.e., fracture density and orientation). The δVS, the difference between the fast and slow shear-waves velocities along the raypath, varied between 0% and 14% which is influenced by the fracture density. As the discrete fractures are superimposed in an isotropic medium, so the anisotropy is interpreted in terms of the fracture strike and fracture density by implementing an inversion method based on the effective medium theory (EMT). The inversion was performed for a single fracture set (i.e., HTI) and double orthogonal fracture sets (i.e., orthorhombic symmetry system). The fracture strike inversion is more constrained than the fracture density due to the limited ray coverage and inversion algorithm assumptions. In the subsequent part of the thesis, I confirm the general scale-dependence of seismic anisotropy and provide new results specific to SWS. I find that SWS develops under conditions when the ratio of wavelength to fracture size (λS /d) is greater than 3, where Rayleigh scattering from coherent fractures leads to an effective anisotropy such that effective medium model (EMM) theory is qualitatively valid. When 1 < λS /d < 3 there is a transition from Rayleigh to Mie scattering, where no effective anisotropy develops and hence the SWS measurements are unstable. When λS /d < 1 I observe geometric scattering and begin to see behaviour similar to transverse isotropy. I find that seismic anisotropy is more sensitive to fracture density than fracture compliance ratio. More importantly, I observe that the transition from scattering to an effective anisotropic regime occurs over a propagation distance between 1 to 2 wavelengths depending on the fracture density and compliance ratio. Finally, I use different methods including the RMS envelope analysis, shear-wave polarisation distortion, differential attenuation analysis and peak frequency shifting to assess the scattering behaviour of parametrised models in which the propagation direction is either normal or parallel to the fracture surfaces. The quantitative measures show strong observable deviations for fractures size on the order of or greater than the dominant seismic wavelength within the Mie and geometric scattering regime for both propagation normal and parallel to fracture strike. The results suggest that strong scattering is symptomatic of fractures having size on the same order of the probing seismic wave.

Seismic reflectivity inversion is an important step in both signal processing and quantitative interpretation since reflectivity contains the information of impedance and other elastic parameters. Conventional methods assume stratified media and perform deconvolution on seismic data trace by trace. However, when using these single-channel methods, the lateral coherency of the result may be affected when the input seismic traces have low signal-to-noise ratios (SNRs) or complex structures. In this thesis, the development of multichannel inversion algorithms will be investigated to improve the continuity of the reflectivity profiles and suppress the noise. An example of a widely-used seismic reflectivity inversion method that is applied to single-channel seismic trace is the basis pursuit method. In this thesis, an FX prediction filter is incorporated with the conventional BP method, to investigate the potential benefit of multichannel implementation. Since the dictionary used in BP is huge in size, the matrix operations are very time consuming, yielding a long overall computational time. To improve the efficiency, a GPU-accelerated basis pursuit method is further implemented under CUDA architecture. Numerical results with the same accuracy are obtained and a speedup factor up to 145 for the whole process has been achieved. To implement a multichannel reflectivity inversion, the curvelet transform is employed. A comparative study on the performance of the curvelet deconvolution with two other widely used methods, the least-squares method and Lp-norm deconvolution, is further conducted. Since the deconvolution based on the curvelet transform offers a good trade-off between the lateral continuity and sparseness, the curvelet deconvolution result is used as the initial model to enhance the Lp-norm deconvolution. Numerical results show that the lateral continuity of the spiky reflectivity profile can be further improved. Moreover, I develop a proper multichannel deconvolution method based on the Cauchy constraint. In this algorithm, a multichannel prediction operator is integrated into the iteration process. In this way, the information of the adjacent traces is exploited during the inversion procedure. This method can provide results with improved lateral coherency, better structure characterisation ability and lower residual energy ratio. I also develop two modified processes based on the original Cauchy constrained multichannel method. These two modifications can give better quality for the reflectivity inversion results, when compared with the original algorithm. Finally, using a similar concept as the multichannel deconvolution method with the Cauchy constraint, I apply the multichannel inversion algorithm to seismic impedance inversion, with the input reflectivity series obtained from the previous inversion steps. Numerical results show impedance profiles with better structure identification and lateral continuity.

Shale typically has a low but non-negligible permeability of the order of nanodarcys (recognized an appreciated in production of unconventional resources), which could affect the magnitude and pattern of the pressure in conventional reservoirs over the lifetime of a producing field. The implications of this phenomenon for reservoir monitoring by 4D seismic can be significant, but depend on the geology of the field, the time-lines for production and recovery, and the timing of the seismic surveys. In this PhD thesis I developed an integrated workflow to assess the process of shale pressure diffusion and its elastic implications in the 4D seismic interpretation of four conventional reservoirs (three North Sea case studies and one from West Africa), with different geological settings (shallow marine and turbidites) and production mechanisms. To accomplish that, first, a detailed petrophysical evaluation was performed to characterize the overburden, intra-reservoir and underburden shales. Next, the simulation models were adjusted to activate the shale-related contributions, and then, applying simulator to seismic workflows, 3D and 4D synthetic seismic modelling were performed, for comparison with the observed seismic data and to establish the impact of the shale pressure diffusion in the elastic dynamic behaviour of the reservoir. This work also includes a case study where evaluation of shale pressure diffusion was integrated with geomechanical simulations to assess the propagation of time shifts and time strain in the overburden of a high pressure/high temperature reservoir under compaction, improving the understanding of the distribution and polarity of the observed seismic time strain. Fluid flow simulation results of this work indicate that activation of the shale improves the overall reservoir connectivity, enhancing model prediction (production history matched data). The fit to observed 4D seismic data was improved in all the field applications with a noticeable reduction (up to 6%) in the mismatch (hardening and softening signal distribution) for the models with active shales. In reservoirs where the saturation was very sensitive to changes in pressure, shale activation proved to impact strongly on the breakout and distribution of gas liberated from solution. Overall, this work found that inclusion of shale in the 3D and 4D reservoir seismic modelling can provide valuable insights for the interpretation of the reservoir’s dynamic behaviour and that, under particular conditions such as strong reservoir compartmentalization, shale pressure diffusion could be a significant process in the interpretation of the 4D seismic signature.

The response of Earth materials to seismic wave propagation is the most commonly used geophysical method for studying the Earth’s crust. Rocks making up the Earth’s crust are porous, with fluids occupying the pore space. The saturation of the pore space can be multiphase, for example, in gas reservoirs and gas bearing oil reservoirs where gas and liquid occupy the pore space. Additional voids such as aligned fractures are common in the Earth’s crust and are known to cause seismic anisotropy. Knowledge of the effects of pore fluids and of aligned fractures on seismic wave propagation is needed for the interpretation of seismic data in terms of these physical properties. This information is particularly useful for the hydrocarbon industry as the presence of either natural or artificially induced fractures can play a major role in the safe and efficient exploration and production of hydrocarbons. Therefore, it is important to be able to remotely characterise fractures in fluid-filled reservoir rocks. Theoretical models are used to relate seismic measurements to the physical properties of rocks such as porosity, saturation, and fracture properties. Previous studies have either focused on multiphase saturation effects in non-fractured isotropic rocks or on single fluid phase saturation effects in fractured anisotropic rocks. Therefore, the combined effect of multiphase saturation and aligned fractures is still poorly understood. This thesis focuses on improving the understanding of the effect of saturation on fracture-induced seismic anisotropy.