Predictability and Repeatability of Non-Ergodic Site Response for Diverse Geological Conditions

Predictability and Repeatability of Non-Ergodic Site Response for Diverse Geological Conditions
Author: Pengfei Wang
Publisher:
Total Pages: 209
Release: 2020
Genre:
ISBN:


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Ground motion models (GMMs) are used to predict ground motion intensity measures given parameters descriptive of source, path, and site conditions. These GMMs incorporate source, path, and site response models that represent approximately the average conditions in the database from which the GMMs were derived. In the case of NGA-type models, global data is used, potentially with path and site adjustments for large regions with ample data (e.g., California), so the predictions represent either global or regional averages. In contrast, when GMMs are applied for a specific engineering project, the source, path, and site response attributes of interest are those local to the site, which may depart from the global or regional averages represented by the GMM. In this context, I refer to the source, path, and site models in the GMM as ergodic. Alternative models that consider local, or site-specific features, are considered non-ergodic, and have the potential to significantly reduce the ground motion variability that is considered in probabilistic seismic hazard analysis. My thesis work is concerned principally with the site response component of GMMs, and in particular, with evaluating the effectiveness of predictive models available for non-ergodic site response analysis. The ergodic site amplification within a GMM represents the global or regional average for the site's value of time-averaged upper 30 meters shear wave velocity and basin depth. Many local effects may introduce departures in site response from the ergodic model, including strong impedance contrasts within the shear wave velocity profile, an unfavorable location relative to a basin edge, complexity of local terrain, and perhaps other factors. Therefore, the ergodic site response model has two drawbacks: (1) potential for a biased estimate of mean site response and (2) because the ergodic model averages over a diverse array of conditions having many different site responses, the model carries a relatively large standard deviation. The alternative of non-ergodic site response takes into account the particular geologic conditions at a site that control site response. If applied properly, non-ergodic site response can produce unbiased estimates of site response and remove site-to-site variability from the total standard deviation, which is a significant contributor. One method of evaluating non- ergodic site response in practice is to utilize recordings at the site to evaluate misfits from a GMM, and then use this information to construct a median site response model. However, when on-site recordings are not available, site-specific analysis requires the application of various predictive models. The questions addressed in this research relate to the effectiveness of different predictive models for estimation of site response. The general approach followed in this research was to develop a database of available recordings for sites in a study region, analyze the data to develop non-ergodic site responses, and then either 1) apply existing predictive models to the sites with "measured" (i.e., non- ergodic) site responses and then evaluate their effectiveness over the population of sites or; 2) develop a new predictive model where existing models cannot be reasonably applied. The first approach of evaluating existing tools is applied to a population of 159 sites in California. The second approach of developing a new model is applied to 7 sites in Obihiro (Japan), where soft soil conditions (VS30 = 102 to 211 m/s) require the development of a novel modeling framework. For the California sites, the predictive models considered are ground response analysis (GRA; one-dimensional shear wave propagation through a soil column), square-root impedance method (SRI), and models conditioned on horizontal-to-vertical spectral ratio (HVSR) vs frequency plots. The GRA and SRI methods require a shear wave velocity (VS) profile for the site and models for material damping for each soil horizon in the profile. Among the 159 sites, the profile depth range is 30 to 255 m (profile period range is 0.06 to 1.02 sec). The HVSR model requires HVSR data, which can be derived from microtremors or earthquake recordings. A challenge that was encountered in the application of GRA and SRI methods was the lack of soil profiles to accompany VS profiles. I developed protocols for estimation of soil type parameters that allow geotechnical damping models to be applied. Additional damping models were also considered, including one that is informed by high-frequency spectral decay of site ground motions ( 0). Despite the depth of the profiles considered in this work being relatively modest, ground response analyses (or square-root-impedance analyses) are able to improve site response predictions relative to ergodic models for approximately 36% of sites (for periods less than or equal to the site period). The inability of site-specific methods to improve prediction accuracy for the 64% sites could stem from three potential sources: (1) simulations of one-dimension wave propagation do not accurately characterize the physics of site response; (2) the measured VS profile from the site does not accurately represent site conditions, either because of strong site heterogeneity or inaccurate measurements; (3) portions of the site profile beneath the profile depth significantly impact the site response in the frequency range of the measured profile. These problems are common to some extent in virtually all site response simulations, so understanding their collective impact is of practical importance. The unknown influence of these factors introduces epistemic uncertainties, which we quantify. Lacking any knowledge of whether a given site is well represented with one-dimensional simulations, this epistemic uncertainty is only slightly reduced from that of the site-to-site variability in ergodic models within soil column period range. For the subset of sites where this modeling is effective, the epistemic uncertainty is more substantially reduced by amounts ranging from 0.05-0.10 in natural log units. The HVSR model considered in this work (adapted from a model in literature) uses the frequency and amplitude of peaks in HVSR spectra. I identify three populations of sites based on microtremor data - those for which a clear HVSR peak is evident (40%), those for which no peak occurs (40%), and intermediate/ambiguous cases (20%). When the ergodic model is used, sites with a peak are observed to have higher bias and site-to-site variability than sites without peaks; as a result, commonly used models for site-to-site variability represent a blending of these condition because the occurrence of peaks is not accounted for. Use of the HVSR model for sites with peaks does not appreciably change the bias but reduces dispersion at long periods (> 1 sec) relative to what is obtained with an ergodic model. The lack of improvement at short period could be caused by false positives (peaks in HVSR that do not appear in site response) and not well-aligned peak positions between HVSR and site response, and may also be influenced by the model used in our analyses having been derived for conditions in Japan. I recommend a California-specific bias correction for sites without a peak. For the Obihiro (Japan) sites, I developed a region-specific site amplification model applicable to the peaty organic soils in this region. The analysis of site response from regional data required removal of source-specific biases and careful consideration of source-to-site path effects. These considerations were essential to avoid mapping source- or path-related model misfits into estimates of site response. I considered two subduction ground motion models as reference models. By paying special attention to the conditions for which the path models are effective, and making adjustments for between-island path misfits (Hokkaido to Honshu and vice-versa), I found the proposed approach effectively identifies site effects, and that the results are insensitive to the selected ground motion model. Observed site responses are characterized by strong resonances at first-mode site frequencies as derived from HVSR measurements.

Living on an Active Earth

Living on an Active Earth
Author: National Research Council
Publisher: National Academies Press
Total Pages: 431
Release: 2003-09-22
Genre: Science
ISBN: 0309065623


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The destructive force of earthquakes has stimulated human inquiry since ancient times, yet the scientific study of earthquakes is a surprisingly recent endeavor. Instrumental recordings of earthquakes were not made until the second half of the 19th century, and the primary mechanism for generating seismic waves was not identified until the beginning of the 20th century. From this recent start, a range of laboratory, field, and theoretical investigations have developed into a vigorous new discipline: the science of earthquakes. As a basic science, it provides a comprehensive understanding of earthquake behavior and related phenomena in the Earth and other terrestrial planets. As an applied science, it provides a knowledge base of great practical value for a global society whose infrastructure is built on the Earth's active crust. This book describes the growth and origins of earthquake science and identifies research and data collection efforts that will strengthen the scientific and social contributions of this exciting new discipline.

Spaces Speak, Are You Listening?

Spaces Speak, Are You Listening?
Author: Barry Blesser
Publisher: MIT Press
Total Pages: 453
Release: 2009-09-18
Genre: Architecture
ISBN: 026251317X


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How we experience space by listening: the concepts of aural architecture, with examples ranging from Gothic cathedrals to surround sound home theater. We experience spaces not only by seeing but also by listening. We can navigate a room in the dark, and "hear" the emptiness of a house without furniture. Our experience of music in a concert hall depends on whether we sit in the front row or under the balcony. The unique acoustics of religious spaces acquire symbolic meaning. Social relationships are strongly influenced by the way that space changes sound. In Spaces Speak, Are You Listening?, Barry Blesser and Linda-Ruth Salter examine auditory spatial awareness: experiencing space by attentive listening. Every environment has an aural architecture.The audible attributes of physical space have always contributed to the fabric of human culture, as demonstrated by prehistoric multimedia cave paintings, classical Greek open-air theaters, Gothic cathedrals, acoustic geography of French villages, modern music reproduction, and virtual spaces in home theaters. Auditory spatial awareness is a prism that reveals a culture's attitudes toward hearing and space. Some listeners can learn to "see" objects with their ears, but even without training, we can all hear spatial geometry such as an open door or low ceiling. Integrating contributions from a wide range of disciplines—including architecture, music, acoustics, evolution, anthropology, cognitive psychology, audio engineering, and many others—Spaces Speak, Are You Listening? establishes the concepts and language of aural architecture. These concepts provide an interdisciplinary guide for anyone interested in gaining a better understanding of how space enhances our well-being. Aural architecture is not the exclusive domain of specialists. Accidentally or intentionally, we all function as aural architects.

Hilbert-huang Transform And Its Applications (2nd Edition)

Hilbert-huang Transform And Its Applications (2nd Edition)
Author: Norden E Huang
Publisher: World Scientific
Total Pages: 399
Release: 2014-04-22
Genre: Mathematics
ISBN: 981450825X


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This book is written for scientists and engineers who use HHT (Hilbert-Huang Transform) to analyze data from nonlinear and non-stationary processes. It can be treated as a HHT user manual and a source of reference for HHT applications. The book contains the basic principle and method of HHT and various application examples, ranging from the correction of satellite orbit drifting to detection of failure of highway bridges.The thirteen chapters of the first edition are based on the presentations made at a mini-symposium at the Society for Industrial and Applied Mathematics in 2003. Some outstanding mathematical research problems regarding HHT development are discussed in the first three chapters. The three new chapters of the second edition reflect the latest HHT development, including ensemble empirical mode decomposition (EEMD) and modified EMD.The book also provides a platform for researchers to develop the HHT method further and to identify more applications.

The Allure of Machinic Life

The Allure of Machinic Life
Author: John Johnston
Publisher: MIT Press
Total Pages: 477
Release: 2008
Genre: Artificial intelligence
ISBN: 0262101262


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An account of the creation of new forms of life and intelligence in cybernetics, artificial life, and artificial intelligence that analyzes both the similarities and the differences among these sciences in actualizing life.The Allure of Machinic Life

Field Sampling for Environmental Science and Management

Field Sampling for Environmental Science and Management
Author: Richard Webster
Publisher: Routledge
Total Pages: 202
Release: 2013
Genre: Business & Economics
ISBN: 1849713677


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It also describes the effects of bulking on errors and the use of ancillary information and regression to improve estimates.

Hydrogeophysics

Hydrogeophysics
Author: Yorum Rubin
Publisher: Springer Science & Business Media
Total Pages: 518
Release: 2006-05-06
Genre: Science
ISBN: 1402031025


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This ground-breaking work is the first to cover the fundamentals of hydrogeophysics from both the hydrogeological and geophysical perspectives. Authored by leading experts and expert groups, the book starts out by explaining the fundamentals of hydrological characterization, with focus on hydrological data acquisition and measurement analysis as well as geostatistical approaches. The fundamentals of geophysical characterization are then at length, including the geophysical techniques that are often used for hydrogeological characterization. Unlike other books, the geophysical methods and petrophysical discussions presented here emphasize the theory, assumptions, approaches, and interpretations that are particularly important for hydrogeological applications. A series of hydrogeophysical case studies illustrate hydrogeophysical approaches for mapping hydrological units, estimation of hydrogeological parameters, and monitoring of hydrogeological processes. Finally, the book concludes with hydrogeophysical frontiers, i.e. on emerging technologies and stochastic hydrogeophysical inversion approaches.

Mining goes Digital

Mining goes Digital
Author: Christoph Mueller
Publisher: CRC Press
Total Pages: 782
Release: 2019-05-22
Genre: Technology & Engineering
ISBN: 1000439062


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The conferences on ‘Applications for Computers and Operations Research in the Minerals Industry’ (APCOM) initially focused on the optimization of geostatistics and resource estimation. Several standard methods used in these fields were presented in the early days of APCOM. While geostatistics remains an important part, information technology has emerged, and nowadays APCOM not only focuses on geostatistics and resource estimation, but has broadened its horizon to Information and Communication Technology (ICT) in the mineral industry. Mining Goes Digital is a collection of 90 high quality, peer reviewed papers covering recent ICT-related developments in: - Geostatistics and Resource Estimation - Mine Planning - Scheduling and Dispatch - Mine Safety and Mine Operation - Internet of Things, Robotics - Emerging Technologies - Synergies from other industries - General aspects of Digital Transformation in Mining Mining Goes Digital will be of interest to professionals and academics involved or interested in the above-mentioned areas.

Applied Mining Geology

Applied Mining Geology
Author: Marat Abzalov
Publisher: Springer
Total Pages: 441
Release: 2016-08-10
Genre: Science
ISBN: 3319392646


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This book provides a detailed overview of the operational principles of modern mining geology, which are presented as a good mix of theory and practice, allowing use by a broad range of specialists, from students to lecturers and experienced geologists. The book includes comprehensive descriptions of mining geology techniques, including conventional methods and new approaches. The attributes presented in the book can be used as a reference and as a guide by mining industry specialists developing mining projects and for optimizing mining geology procedures. Applications of the methods are explained using case studies and are facilitated by the computer scripts added to the book as Electronic Supplementary Material.