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This thesis addresses a diverse range of topics in the area of probabilistic seismic risk analysis of engineering facilities. This intentional path of diversity has been followed primarily because of the relatively new and rapid development of this facet of earthquake engineering. As such this thesis focuses on the rigorous scrutinization of current, and in particular, simplified methods of seismic risk assessment; the development of novel aspects of a risk assessment methodology which provides easily communicated performance measures and explicit consideration for the many uncertainties in the entire earthquake problem; and the application of this methodology to case-study examples including structures supported on pile foundations embedded in liquefiable soils. The state-of-the-art in seismic risk and loss assessment is discussed via the case study of a 10 storey New Zealand office building. Particular attention is given to the quality and quantity of information that such assessment methodologies provide to engineers and stakeholders for rational decision-making. Two chapters are devoted to the investigation of the power-law model for representing the ground motion hazard. Based on the inaccuracy of the power-law model at representing the seismic hazard over a wide range of exceedance rates, an alternative, more accurate, parametric hazard model based on a hyperbola in log-log space is developed and applied to New Zealand peak ground acceleration and spectral acceleration hazard data. A semianalytical closed-form solution for the demand hazard is also developed using the hyperbolic hazard model and applied for a case-study performance assessment. The power-law hazard model is also commonly used to obtain a closed-form solution for the annual rate of structural collapse (collapse hazard). The magnitude of the error in this closed-form solution due to errors in the necessary functional forms of its constitutive relations is examined via a parametric study. A series of seven chapters are devoted to the further development of various aspects of a seismic risk assessment methodology. Intensity measures for use in the estimation of spatially distributed seismic demands and seismic risk assessment which are: easily predicted; can predict seismic response with little uncertainty; and are unbiased regarding additional properties of the input ground motions are examined. An efficient numerical integration algorithm which is specifically tailored for the solution of the governing risk assessment equations is developed and compared against other common methods of numerical integration. The efficacy of approximate uncertainty propagation in seismic risk assessment using the so-called First-Order Second-Moment method is investigated. Particular attention is given to the locations at which the approximate uncertainty propagation is used, the possible errors for various computed seismic risk measures, and the reductions in computational demands. Component correlations have to date been not rigorously considered in seismic loss assessments due to complications in their estimation and tractable methodologies to account for them. Rigorous and computationally efficient algorithms to account for component correlations are presented. Particular attention is also given to the determination of correlations in the case of limited empirical data, and the errors which may occur in seismic loss assessment computations neglecting proper treatment of correlations are examined. Trends in magnitude, distribution, and correlation of epistemic uncertainties in seismic hazard analyses for sites in the San Francisco bay area are examined. The characteristics of these epistemic uncertainties are then used to compare and contrast three methods which can be used to propagate such uncertainties to other seismic risk measures. Causes of epistemic uncertainties in component fragility functions, their evaluation, and combination are also examined. A series of three chapters address details regarding the seismic risk assessment of structures supported on pile foundations embedded in liquefiable soils. A ground motion prediction equation for spectrum intensity (found to be a desirable intensity measure for seismic response analysis in liquefiable soils) is developed based on ground motion prediction equations for spectral accelerations, which are available in abundance in literature. Determination of intensity measures for the seismic response of pile foundations, which are invariably located in soil deposits susceptible to liquefaction, is examined. Finally, a rigorous seismic performance and loss assessment of a case-study bridge structure is examined using rigorous ground motion selection, seismic effective stress analyses, and professional cost estimates. Both direct repair and loss of functionality consequences for the bridge structure are examined.

Planet earth is restless and one cannot control its inside activities and vibrations those leading to natural hazards. Earthquake is one of such natural hazards that have affected the mankind most. Most of the causalities due to earthquakes happened not because of earthquakes as such, but because of poorly designed structures which could not withstand the earthquake forces. The improper building construction techniques adopted and the high population density are the major causes of the heavy damage due to earthquakes. The damage due to earthquakes can be reduced by following proper construction techniques, taking into consideration of appropriate forces on the structure that can be caused due to future earthquakes. The steps towards seismic hazard evaluation are very essential to estimate an optimal and reliable value of possible earthquake ground motion during a specific time period. These predicted values can be an input to assess the seismic vulnerability of an area based on which new construction and the restoration works of existing structures can be carried out. A large number of devastating earthquakes have occurred in India in the past. The northern region of India, which is along the plate boundary of the Indian plate with the Eurasian plate, is seismically very active. The north eastern movement of Indian plate has caused deformation in the Himalayan region, Tibet and the North Eastern India. Along the Himalayan belt, the Indian and Eurasian plates converge at the rate of about 50 mm/year (Bilham 2004; Jade 2004). The North East Indian (NEI) region is known as one of the most seismically active regions in the world. However the peninsular India, which is far away from the plate boundary, is a stable continental region, which is considered to be of moderate seismic activity. Even though, the activity is considered to be moderate in the Peninsular India, world’s deadliest earthquake occurred in this region (Bhuj earthquake 2001). The rapid drifting of Indian plate towards Himalayas in the north east direction with a high velocity along with its low plate thickness might be the cause of high seismicity of the Indian region. Bureau of Indian Standard has published a seismic zonation map in 1962 and revised it in 1966, 1970, 1984 and 2002. The latest version of the seismic zoning map of India assigns four levels of seismicity for the entire Country in terms of different zone factors. The main drawback of the seismic zonation code of India (BIS-1893, 2002) is that, it is based on the past seismic activity and not based on a scientific seismic hazard analysis. Several seismic hazard studies, which were taken up in the recent years, have shown that the hazard values given by BIS-1893 (2002) need to be revised (Raghu Kanth and Iyengar 2006; Vipin et al. 2009; Mahajan et al. 2009 etc.). These facts necessitate a comprehensive study for evaluating the seismic hazard of India and development of a seismic zonation map of India based on the Peak Ground Acceleration (PGA) values. The objective of this thesis is to estimate the seismic hazard of entire India using updated seismicity data based on the latest and different methodologies. The major outcomes of the thesis can be summarized as follows. An updated earthquake catalog that is uniform in moment magnitude, has been prepared for India and adjoining areas for the period till 2010. Region specific magnitude scaling relations have been established for the study region, which facilitated the generation of a homogenous earthquake catalog. By carefully converting the original magnitudes to unified MW magnitudes, we have removed a major obstacle for consistent assessment of seismic hazards in India. The earthquake catalog was declustered to remove the aftershocks and foreshocks. Out of 203448 events in the raw catalog, 75.3% were found to be dependent events and remaining 50317 events were identified as main shocks of which 27146 events were of MW ≥ 4. The completeness analysis of the catalog was carried out to estimate completeness periods of different magnitude ranges. The earthquake catalog containing the details of the earthquake events until 2010 is uploaded in the website the catalog was carried out to estimate completeness periods of different magnitude ranges. The earthquake catalog containing the details of the earthquake events until 2010 is uploaded in the website the catalog was carried out to estimate completeness periods of different magnitude ranges. The earthquake catalog containing the details of the earthquake events until 2010 is uploaded in the website A quantitative study of the spatial distribution of the seismicity rate across India and its vicinity has been performed. The lower b values obtained in shield regions imply that the energy released in these regions is mostly from large magnitude events. The b value of northeast India and Andaman Nicobar region is around unity which implies that the energy released is compatible for both smaller and larger events. The effect of aftershocks in the seismicity parameters was also studied. Maximum likelihood estimations of the b value from the raw and declustered earthquake catalogs show significant changes leading to a larger proportion of low magnitude events as foreshocks and aftershocks. The inclusions of dependent events in the catalog affect the relative abundance of low and high magnitude earthquakes. Thus, greater inclusion of dependent events leads to higher b values and higher activity rate. Hence, the seismicity parameters obtained from the declustered catalog is valid as they tend to follow a Poisson distribution. Mmax does not significantly change, since it depends on the largest observed magnitude rather than the inclusion of dependent events (foreshocks and aftershocks). The spatial variation of the seismicity parameters can be used as a base to identify regions of similar characteristics and to delineate regional seismic source zones. Further, Regions of similar seismicity characteristics were identified based on fault alignment, earthquake event distribution and spatial variation of seismicity parameters. 104 regional seismic source zones were delineated which are inevitable input to seismic hazard analysis. Separate subsets of the catalog were created for each of these zones and seismicity analysis was done for each zone after estimating the cutoff magnitude. The frequency magnitude distribution plots of all the source zones can be found at http://civil.iisc.ernet.in/~sitharam . There is considerable variation in seismicity parameters and magnitude of completeness across the study area. The b values for various regions vary from a lower value of 0.5 to a higher value of 1.5. The a value for different zones vary from a lower value of 2 to a higher value of 10. The analysis of seismicity parameters shows that there is considerable difference in the earthquake recurrence rate and Mmax in India. The coordinates of these source zones and the seismicity parameters a, b & Mmax estimated can be directly input into the Probabilistic seismic hazard analysis. The seismic hazard evaluation of the Indian landmass based on a state-of-the art Probabilistic Seismic Hazard Analysis (PSHA) study has been performed using the classical Cornell–McGuire approach with different source models and attenuation relations. The most recent knowledge of seismic activity in the region has been used to evaluate the hazard incorporating uncertainty associated with different modeling parameters as well as spatial and temporal uncertainties. The PSHA has been performed with currently available data and their best possible scientific interpretation using an appropriate instrument such as the logic tree to explicitly account for epistemic uncertainty by considering alternative models (source models, maximum magnitude in hazard computations, and ground-motion attenuation relationships). The hazard maps have been produced for horizontal ground motion at bedrock level (Shear wave velocity ≥ 3.6 km/s) and compared with the earlier studies like Bhatia et al., 1999 (India and adjoining areas); Seeber et al, 1999 (Maharashtra state); Jaiswal and Sinha, 2007 (Peninsular India); Sitharam and Vipin, 2011 (South India); Menon et al., 2010 (Tamilnadu). It was observed that the seismic hazard is moderate in Peninsular shield (except the Kutch region of Gujarat), but the hazard in the North and Northeast India and Andaman-Nicobar region is very high. The ground motion predicted from the present study will not only give hazard values for design of structures, but also will help in deciding the locations of important structures such as nuclear power plants. The evaluation of surface level PGA values is of very high importance in the engineering design. The surface level PGA values were evaluated for the entire study area for four NEHRP site classes using appropriate amplification factors. If the site class at any location in the study area is known, then the ground level PGA values can be obtained from the respective map. In the absence of VS30 values, the site classes can be identified based on local geological conditions. Thus this method provides a simplified methodology for evaluating the surface level PGA values. The evaluation of PGA values for different site classes were evaluated based on the PGA values obtained from the DSHA and PSHA. This thesis also presents VS30 characterization of entire country based on the topographic gradient using existing correlations. Further, surface level PGA contour map was developed based on the same. Liquefaction is the conversion of formally stable cohesionless soils to a fluid mass, due to increase in pore pressure and is prominent in areas that have groundwater near the surface and sandy soil. Soil liquefaction has been observed during the earthquakes because of the sudden dynamic earthquake load, which in turn increases the pore pressure. The evaluation of liquefaction potential involves evaluation of earthquake loading and evaluation of soil resistance to liquefaction. In the present work, the spatial variation of the SPT value required to prevent liquefaction has been estimated using a probabilistic methodology, for entire India. To summarize, the major contribution of this thesis are the development of region specific magnitude correlations suitable for Indian subcontinent and an updated homogeneous earthquake catalog for India that is uniform in moment magnitude scale. The delineation and characterization of regional seismic source zones for a vast country like India is a unique contribution, which requires reasonable observation and engineering judgement. Considering complex seismotectonic set up of the country, the present work employed numerous methodologies (DSHA and PSHA) in analyzing the seismic hazard using appropriate instrument such as the logic tree to explicitly account for epistemic uncertainties considering alternative models (For Source model, Mmax estimation and Ground motion prediction equations) to estimate the PGA value at bedrock level. Further, VS30 characterization of India was done based on the topographic gradient, as a first level approach, which facilitated the development of surface level PGA map for entire country using appropriate amplification factors. Above factors make the present work very unique and comprehensive touching various aspects of seismic hazard. It is hoped that the methodology and outcomes presented in this thesis will be beneficial to practicing engineers and researchers working in the area of seismology and geotechnical engineering in particular and to the society as a whole.

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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.

Seven and a half kilometers of high-resolution SH-wave seismic reflection profiles were collected across the Mt. Vernon graben, a 35 km by 3 km graben (bounded by the Wabash Island (WIF) and Hovey Lake faults (HLF)) in the southern Wabash Valley fault system (WVFS) of southern Indiana. Forty-six discrete faults were imaged that displaced Quaternary horizons in the vicinity of the WIF and HLF. The structural styles associated with faults include: 1) normal displacement, 2) reverse displacement and other compressional features, 3) varying magnitudes of slip along fault planes, and 4) different senses of slip along individual fault planes. Carbon 14 dating of displaced horizons suggests movement between approximately 26,000 and 42,000 YBP. The style and timing of Quaternary deformation within the WVFS, the close association of soil faults to documented post-Pennsylvanian bedrock faults (HLF and WIF), and focal mechanism studies of current seismicity in the Wabash Valley seismic zone are all direct evidence that the extensionally-formed faults of the WVFS are being transpressionally reactivated: a manner consistent with the current east-northeast westsouthwest regional compressive stress field.

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.

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. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The Charleston earthquake of 1886 was one of the largest shocks to occur on the eastern coast of North America. The geological cause has long been a controversial issue and a variety of source models have been proposed. Previous potential field modeling and reinterpretation of seismic reflection and well data collected in the early 1980s indicate that the crust between approximately 1 and 4.5 km depth is comprised primarily of Mesozoic mafic rocks, with extensive faulting that is spatially coincident with modern seismicity in the epicentral area (Chapman and Beale, 2010). This thesis proposes a new and testable hypothesis concerning the fault source of the 1886 shock that is very different from all previous interpretations. It is based on data collected during 2011-2012 from a local seismic network deployment in the immediate epicentral area. The 8-station temporary network was designed to better constrain earthquake hypocenter locations and focal mechanisms. Hypocenter locations of 134 earthquakes indicate a south-striking, west-dipping seismogenic zone in the upper 12 km of the crust. Over 40% of the 66 well-constrained focal mechanisms show reverse faulting on approximately north-south trending nodal planes, consistent with the orientation of the tabular hypocenter distribution. I offer the following hypothesis: The 1886 shock occurred by compressional reactivation of a major, south-striking, west-dipping early Mesozoic extensional fault. The modern seismicity can be regarded as a long-term aftershock sequence that is outlining the 1886 damage zone. Variability of shallow focal mechanisms is due to the complex early Mesozoic fault structure in the upper 4-5 km. / Master of Science

Southern Vancouver Island, situated on Canada’s West Coast, is exposed to many natural and human-made threats due to its physical geography and demography. Perceptions of these disaster risks and of seismic hazard, in particular, were surveyed through locally-administered questionnaires conducted with 105 members of the general public and 13 emergency managers living and working on southern Vancouver Island, specifically in the Cowichan Valley Regional District (CVRD) and the Capital Regional District (CRD). Perhaps the greatest risk to the region, and that, which is perceived by both the general public and practitioners as the greatest risk, is low frequency, high consequence earthquake events. The region is exposed to earthquakes from many sources, but has not experienced a damaging quake in several decades, begging questions as to whether residents consider earthquake a prominent threat and whether they have an accurate appreciation for the earthquake hazard (likelihood) in the region. While researchers have scientifically quantified the earthquake hazard in the region for over 50 years, only in the past 10 years has this hazard information been presented in a format that is comprehensible by the general public. In order for individuals and communities to make informed decisions, this information must ultimately reach the public and be interpretable and actionable. This research describes and analyzes disaster risk and seismic hazard perception on Southern Vancouver Island, and identifies whether there are gaps in communication between the scientists who create the knowledge, the emergency managers who disseminate the information, and the general public who ultimately needs to act on the information to increase their resilience. Results reveal that earthquakes are perceived as the highest disaster risk among both the general public and emergency managers on southern Vancouver Island, and that a large majority of participants know that their community is at risk from an earthquake. In addition, while emergency managers consider mostly natural threats to be significant risks, the general public more commonly identify human-made intentional threats as significant risks. The study also found that gender and location influence how individuals prefer to receive hazard information. In addition, household income and time spent living on Vancouver Island are key variables for how likely members of the general public are to be prepared. Findings suggest that while both emergency managers and the general public overestimate the earthquake hazard on southern Vancouver Island, on average emergency managers perceive the earthquake hazard to be greater than the general public does. Interestingly, general public respondents in the CVRD perceive seismic hazard to be higher than respondents in the CRD, while the calculated hazard is actually higher in the CRD. In addition, emergency managers underestimate residents’ perceptions of earthquake hazard. In other words, they feel that the public underestimates the hazard when actually both emergency managers and the general public overestimate it. These misperceptions have implications for future seismic hazard and disaster risk communication. Prior to this study, disaster risk perception has not been explored in detail in this region, and while limitations to this research are outlined, the study provides a useful descriptive analysis and baseline information for emergency managers and academic researchers to build upon. The findings of this research have specific relevance for emergency managers to inform their public education and outreach efforts around preparation, response and resilience to disasters on southern Vancouver Island. / Graduate / 2018-09-08