Master of Engineering

New Insights on the Uncertainties in Finite-Fault Earthquake Source Inversion Hoby Njara Tendrisoa Razafindrakoto Earthquake source inversion is a non-linear problem that leads to non-unique solutions. The aim of this dissertation is to understand the uncertainty and reliability in earthquake source inversion, as well as to quantify variability in earthquake rupture models. The source inversion is performed using a Bayesian inference. This technique augments optimization approaches through its ability to image the entire solution space which is consistent with the data and prior information. In this study, the uncertainty related to the choice of source-time function and crustal structure is investigated. Three predefined analytical source-time functions are analyzed; isosceles triangle, Yoffe with acceleration time of 0.1 and 0.3 s. The use of the isosceles triangle as source-time function is found to bias the finite-fault source inversion results. It accelerates the rupture to propagate faster compared to that of the Yoffe function. Moreover, it generates an artificial linear correlation between parameters that does not exist for the Yoffe source-time functions. The effect of inadequate knowledge of Earth’s crustal structure in earthquake rupture models is subsequently investigated. The results show that one-dimensional structure variability leads to parameters resolution changes, with a broadening of the posterior 5 PDFs and shifts in the peak location. These changes in the PDFs of kinematic parameters are associated with the blurring effect of using incorrect Earth structure. As an application to real earthquake, finite-fault source models for the 2009 L’Aquila earthquake are examined using one- and three-dimensional crustal structures. One- dimensional structure is found to degrade the data fitting. However, there is no significant effect on the rupture parameters aside from differences in the spatial slip extension. Stable features are maintained for both structures. In the last part of this work, a multidimensional scaling method is presented to compare and classify earthquake slip distributions. A similarity scale to rank them are thus formulated. Dissimilarities among slip models (from various parameterizations) are computed using two different distance metrics, normalized squared and gray-scale metrics. Multidimensional scaling is then used to visualize the differences among the models. The analyzes are done for 2 case studies; one based on artificial scenarios with a known answer and another one based on the published rupture models of the 2011 Tohoku earthquake.

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Faults have a controlling influence on a variety of geologic processes includingfluid flow, the mechanical behavior of the crust, and seismicity. The geologic sciences have long recognized that faults generate earthquakes; however, few indicators of ancient earthquakes exist in fault-zones. This dissertation documents several indicators for the preservation of ancient earthquakes in fault-zones including frictional melt (pseudotachylyte), highly-polished fault slip surfaces, and hydrothermal alteration. These deformation products result from rapid generation of frictional heat during earthquakes.This dissertation also focuses on the seismic potential of continental low-angle normal faults (LANF). We document the preservation of voluminous pseudotachylyte along a LANF suggesting that the fault repeatedly nucleated large earthquakes. Additionally, a synthesis of reported occurrences of LANF pseudotachylyte indicates that LANF seismicity is common during extension. This has important implication for the mechanics and evolution of LANFs and for the assessment of seismic hazards.We also present a little used, high resolution, and low-cost 3D range camera for use in geolgy. The KinectTM is a 3D infrared range camera that can be used to collect high- resolution (± 1 mm), 3D data in both field and laboratory settings. We describe the use of the KinectTM in geologic appications and recommend more widespread use.

京都大学 / 0048 / 新制・論文博士 / 博士(地球環境学) / 乙第12836号 / 論地環博第9号 / 新制||地環||25(附属図書館) / 31374 / (主査)教授 ショウ ラジブ, 教授 岡﨑 健二, 准教授 古川 愛子 / 学位規則第4条第2項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

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This research investigates the interaction between heavy precast cladding units attached to steel framed buildings. Cladding systems are designed as non-structural components and are not expected to contribute to the energy absorption of the primary structure. However, research has indicated that the cladding system may be designed to reduce the response of the primary structure under seismic excitations. The use of flexible connections between the cladding and primary structural frames may be able to provide beneficial effects to the entire structural response. In this study, a series of earthquake engineering simulations were conducted in OPENSEES to analyze the effects of the flexible connections of the cladding on both a 3 story and 9 story prototype structures. The research focus is on the 3 story structure. The results from 3 story and 9 story structures indicate that the flexible cladding connections have the ability to transfer hysteretic energy from the primary structure to the flexible cladding connections.

New methods for calculating the stochastic and seismic design response of linear and nonlinear structures are presented. For linear structures, two approaches are developed: (1) the modified mode displacement approach for classically as well as non-classically damped structures, and (2) the generalized force derivative approach for classically damped structures. Both techniques improve the calculation of the pseudostatic contribution of the truncated modes without including them in the analysis. In particular, the modified mode displacement approach is a useful tool for the calculation of seismic design responses affected by the contributions or higher modes. It properly considers the modal correlations as well as the correlation between retained and truncated modes. It is as fast as the mode acceleration method of structural dynamics and it only requires the commonly used ground response spectra employed by the classical mode displacement approach. On the other hand, the generalized force derivative approach requires the input to be defined in terms of its power spectral density function, but it improves even further the estimation of the missing mass effect due to the trucation of modes. For nonlinear structures, the stochastic equivalent linearization technique is employed to develop response spectrum approaches for hysteretic shear buildings and for two dimensional frames with plastic hinges. For this purpose, a generalized modal analysis technique is successfully employed. The proposed response spectrum approaches require the input be defined in terms of the response spectrum of first order oscillators as well as in terms of the commonly used ground response spectra. For shear buildings, the work is extended to include the calculation of floor response spectra. A simulation study is performed to compare the results obtained by the proposed approach. / Ph. D.

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