Download or read book Influence of Local Site Conditions on the Reliability of Fundamental Mode Surface Wave Inversion Methods written by Brent L. Rosenblad and published by . This book was released on 2009 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of reliable shear wave velocity (VS) profiles from surface wave velocity measurements requires compatibility between the measured and theoretical dispersion curves used in the inversion procedure. The most common approach in geotechnical applications is to use a fundamental-mode theoretical dispersion curve based on the assumption that the measured dispersion curve is representative of the fundamental mode of surface wave propagation. Analyses of low-frequency surface wave measurements presented in this paper show that this widespread assumption is invalid at low frequencies (long wavelengths) for some profile conditions. Results are presented from measurements performed at two deep soil sites in the central United States where surface wave analyses were performed using both the common fundamental-mode approach as well as an "effective-velocity" approach. At one site these two methods produced essentially the same estimate of the VS profile, while at the second site the estimated VS values at depth differed by more than 40 %. Using soil profile information for these sites and simulations of surface wave propagation, it is shown that the shallower depth to a higher-velocity formation at the second site created dominant higher-mode energy at wavelengths of 300-600 m, resulting in an overestimation of deep VS values.

Download or read book Surface Wave Methods for Near Surface Site Characterization written by Sebastiano Foti and published by CRC Press. This book was released on 2014-08-21 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: Develop a Greater Understanding of How and Why Surface Wave Testing Works Using examples and case studies directly drawn from the authors’ experience, Surface Wave Methods for Near-Surface Site Characterization addresses both the experimental and theoretical aspects of surface wave propagation in both forward and inverse modeling. This book accents the key facets associated with surface wave testing for near-surface site characterization. It clearly outlines the basic principles, the theoretical framework and the practical implementation of surface wave analysis. In addition, it also describes in detail the equipment and measuring devices, acquisition techniques, signal processing, forward and inverse modeling theories, and testing protocols that form the basis of modern surface wave techniques. Review Examples of Typical Applications for This Geophysical Technique Divided into eight chapters, the book explains surface wave testing principles from data measurement to interpretation. It effectively integrates several examples and case studies illustrating how different ground conditions and geological settings may influence the interpretation of data measurements. The authors accurately describe each phase of testing in addition to the guidelines for correctly performing and interpreting results. They present variants of the test within a consistent framework to facilitate comparisons, and include an in-depth discussion of the uncertainties arising at each stage of surface wave testing. Provides a comprehensive and in-depth treatment of all the steps involved in surface wave testing Discusses surface wave methods and their applications in various geotechnical conditions and geological settings Explains how surface wave measurements can be used to estimate both stiffness and dissipative properties of the ground Addresses the issue of uncertainty, which is often an overlooked problem in surface wave testing Includes examples with comparative analysis using different processing techniques and inversion algorithms Outlines advanced applications of surface wave testing such as joint inversion, underwater investigation, and Love wave analysis Written for geotechnical engineers, engineering seismologists, geophysicists, and researchers, Surface Wave Methods for Near-Surface Site Characterization offers practical guidance, and presents a thorough understanding of the basic concepts.

Download or read book Influence of Site Conditions on Near field Effects in Multi channel Surface Wave Measurements written by Cheng-Hsuan Li and published by . This book was released on 2011 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geophysical measurements using surface wave methods (SWM) are in widespread use as a means to non-destructively and non-intrusively characterize geotechnical site conditions for a variety of applications. Surface wave measurements are used to develop shear wave velocity (Vs) profiles which are directly related to the small-strain shear modulus (G) of the soil, an important parameter for dynamic and static geotechnical analysis. One of the potential sources of error in SWM is the underestimation of surface wave velocity due to inaccurate measurements in the near-field, where the receiver array is located too close to the source. These near-field effects have been studied extensively for the two-channel SASW method, but few cases have been studied using multi-channel arrays. A recent criteria developed by Yoon and Rix (2009) for multi-channel measurements suggested that the normalized array center (NAC) distance (i.e. the number of wavelengths between the source and array center) should be 2 or greater. However, this finding conflicts with recent experimental data collected in the Mississippi embayment by Rosenblad and Li (2011), which showed near-field effects occurring at NAC values of about 0.5. The objective of this research is to investigate and explain this contradiction and better understand the factors influencing near-field effects. It is hypothesized that the primary reason for the discrepancy is different conditions of saturation (and hence, Poisson's ratio) in the Yoon and Rix (2009) study and the Rosenblad and Li (2011) study. Numerical simulations of surface wave propagation were performed for five synthetic Vs profiles under different assumed saturation conditions. It was found that Poisson's ratio did have a significant influence on the required source offset distance to minimize near-field effects. However, the effect was complex and strongly influenced by the Vs profile. For the profiles considered, limiting NAC values ranged from about 2 to as low as 0.3. The lowest values were observed for cases of linearly increasing Vs with depth under saturated conditions. Simulation of surface wave measurements for a site in the Mississippi embayment produced results that were consistent with the experimental observations. The findings from this work have important implications on both the measurement procedures and inversion methods used in multi-channel surface wave methods.

Download or read book Surface Wave Analysis for Near Surface Applications written by Giancarlo Dal Moro and published by Elsevier. This book was released on 2014-11-04 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic Wave Analysis for Near Surface Applications presents the foundational tools necessary to properly analyze surface waves acquired according to both active and passive techniques. Applications range from seismic hazard studies, geotechnical surveys and the exploration of extra-terrestrial bodies. Surface waves have become critical to near-surface geophysics both for geotechnical goals and seismic-hazard studies. Included in this book are the related theories, approaches and applications which the lead editor has assembled from a range of authored contributions carefully selected from the latest developments in research. A unique blend of theory and practice, the book’s concepts are based on exhaustive field research conducted over the past decade from the world’s leading seismologists and geophysicists. Edited by a geophysicist with nearly 20 years of experience in research, consulting, and geoscience software development Nearly 100 figures, photographs, and examples aid in the understanding of fundamental concepts and techniques Presents the latest research in seismic wave characteristics and analysis, the fundamentals of signal processing, wave data acquisition and inversion, and the latest developments in horizontal-to-vertical spectral ratio (HVSR) Each chapter features a real-world case study—13 in all—to bring the book’s key principles to life

Download or read book Inverse Problem Theory and Methods for Model Parameter Estimation written by Albert Tarantola and published by SIAM. This book was released on 2005-01-01 with total page 349 pages. Available in PDF, EPUB and Kindle. Book excerpt: While the prediction of observations is a forward problem, the use of actual observations to infer the properties of a model is an inverse problem. Inverse problems are difficult because they may not have a unique solution. The description of uncertainties plays a central role in the theory, which is based on probability theory. This book proposes a general approach that is valid for linear as well as for nonlinear problems. The philosophy is essentially probabilistic and allows the reader to understand the basic difficulties appearing in the resolution of inverse problems. The book attempts to explain how a method of acquisition of information can be applied to actual real-world problems, and many of the arguments are heuristic.

Download or read book Study of Surface Wave Methods for Deep Shear Wave Velocity Profiling Applied in the Upper Mississippi Embayment written by Jianhua Li and published by . This book was released on 2008 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface wave methods have become an important tool for non-intrusively and inexpensively determining shear wave velocity (V [subscript-s]) profiles for many geotechnical earthquake engineering applications. The primary objectives of this study are to (1) compare active-source and passive (ambient vibration) surface wave methods for developing V [subscript-s] profiles to depths of 200 to 300 m at deep soil sites, and (2) identify the primary factors affecting the reliability and consistency of surface wave methods. This comparative study became possible with the advent of a unique low- frequency field vibrator developed as part of the National Science Foundation's (NSF) Network for Earthquake Engineering Simulation (NEES) program. This vibrator is able to actively excite surface wave energy down to frequencies of less than 1 Hz. Four surface wave methods (two active-source methods and two passive-source methods) were applied in this study, namely: (1) the Spectral-Analysis-of-Surface-Waves (SASW) method, (2) the active-source frequency- wavenumber ([function]-k) method, (3) the passive-source frequency-wavenumber ([function]-k) method and (4) the refraction microtremor (ReMi) method. The focus of this study is on two critical aspects of surface wave methods: (1) development of a reliable surface wave dispersion curve from field measurements, and (2) compatibility between the experimental dispersion curve and the theoretical model used in the inversion procedure to develop the final V [subscript-s] profile. Measurements were performed at eleven sites distributed over a distance of about 180 km in the upper Mississippi Embayment in the central United States, where soil deposits are hundreds of meters deep. Limitations associated with each of the four methods were identified in this study. With respect to the SASW method it was found that potential phase unwrapping problems could cause an erroneous estimate of the dispersion curve. These errors were found to be associated with an abrupt mode transition caused by a strong velocity contrast at a shallow depth. With respect to the active-source [function]-k approach, it was demonstrated that near-field effects caused by a short near- source offset produced an underprediction of the surface wave dispersion curve at long wavelengths. Recommendations for acceptable source offset distances were developed based on the results from this study. The performance of the passive approaches (passive [function]-k method and ReMi method) was shown to be strongly dependent on the local ambient wavefield characteristics. Results from a study of the ambient wavefield characteristics at the 11 sites showed high ambient vibration levels at all sites in the frequency range of 1 to 4 Hz. Passive measurements using a circular array provided good comparisons with the active-source methods out to wavelengths of 500 m (2.5 times the array aperture) in most cases. Poor performance at one site was shown to be due to a multi-source wavefield at low frequencies. An improved comparison at this site was achieved by applying high-resolution processing methods. The ReMi method was found to provide good results down to frequencies of 3 to 4 Hz (wavelengths of 100 to 150 m) but very poor performance at lower frequencies (

Download or read book The Microtremor Survey Method written by Hiroshi Okada and published by SEG Books. This book was released on 2003 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes the nature of the microtremor noise field, the use of appropriate surface arrays of geophones, and the two principal classes of array-processing techniques, high-resolution beamforming and the spatial autocorrelation method (SPAC). This is the first comprehensive textbook of the microtremor survey method written in English.

Download or read book Pre failure Deformation Characteristics of Geomaterials written by Jamiolkowski and published by CRC Press. This book was released on 2001 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second of two volumes from the 1999 conference (v.1 was published in 1999) makes available the opening lecture on pre-failure behavior of soils as construction materials, as well as 24 contributions on various themes of the conference, laboratory tests, in situ tests, stress-strain behavior, applications and case histories. Some specific topics include time-dependent deformation characteristics of stiff geomaterials, boundary value problems in geotechnical engineering, and the effect of reinforcement due to choice of geogrid. There is no subject index. c. Book News Inc.

Download or read book Encyclopedia of Solid Earth Geophysics written by D.E. James and published by Springer Science & Business Media. This book was released on 1989-11-30 with total page 1299 pages. Available in PDF, EPUB and Kindle. Book excerpt: Consisting of more than 150 articles written by leading experts, this authoritative reference encompasses the entire field of solid-earth geophysics. It describes in detail the state of current knowledge, including advanced instrumentation and techniques, and focuses on important areas of exploration geophysics. It also offers clear and complete coverage of seismology, geodesy, gravimetry, magnetotellurics and related areas in the adjacent disciplines of physics, geology, oceanography and space science.

Download or read book Theoretical Global Seismology written by F. A. Dahlen and published by Princeton University Press. This book was released on 2020-08-04 with total page 1040 pages. Available in PDF, EPUB and Kindle. Book excerpt: After every major earthquake, the Earth rings like a bell for several days. These free oscillations of the Earth and the related propagating body and surface waves are routinely detected at broad-band seismographic stations around the world. In this book, F. A. Dahlen and Jeroen Tromp present an advanced theoretical treatment of global seismology, describing the normal-mode, body-wave, and surface-wave methods employed in the determination of the Earth's three-dimensional internal structure and the source mechanisms of earthquakes. The authors provide a survey of both the history of global seismological research and the major theoretical and observational advances made in the past decade. The book is divided into three parts. In the first, "Foundations," Dahlen and Tromp give an extensive introduction to continuum mechanics and discuss the representation of seismic sources and the free oscillations of a completely general Earth model. The resulting theory should provide the basis for future scientific discussions of the elastic-gravitational deformation of the Earth. The second part, "The Spherical Earth," is devoted to the free oscillations of a spherically symmetric Earth. In the third part, "The Aspherical Earth," the authors discuss methods of dealing with the Earth's three-dimensional heterogeneity. The book is concerned primarily with the forward problem of global seismology--detailing how synthetic seismograms and spectra may be calculated and interpreted. As a long-needed unification of theories in global seismology, the book will be important to graduate students and to professional seismologists, geodynamicists, and geomagnetists, as well as to astronomers who study the free oscillations of the Sun and other stars.

Download or read book Time Series Analysis and Inverse Theory for Geophysicists written by David Gubbins and published by Cambridge University Press. This book was released on 2004-03-18 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique textbook provides the foundation for understanding and applying techniques commonly used in geophysics to process and interpret modern digital data. The geophysicist's toolkit contains a range of techniques which may be divided into two main groups: processing, which concerns time series analysis and is used to separate the signal of interest from background noise; and inversion, which involves generating some map or physical model from the data. These two groups of techniques are normally taught separately, but are here presented together as parts I and II of the book. Part III describes some real applications and includes case studies in seismology, geomagnetism, and gravity. This textbook gives students and practitioners the theoretical background and practical experience, through case studies, computer examples and exercises, to understand and apply new processing methods to modern geophysical datasets. Solutions to the exercises are available on a website at http://publishing.cambridge.org/resources/0521819652

Download or read book An Introduction to Seismology Earthquakes and Earth Structure written by Seth Stein and published by John Wiley & Sons. This book was released on 2013-05-30 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: An Introduction to Seismology, Earthquakes and Earth Structures is an introduction to seismology and its role in the earth sciences, and is written for advanced undergraduate and beginning graduate students. The fundamentals of seismic wave propagation are developed using a physical approach and then applied to show how refraction, reflection, and teleseismic techniques are used to study the structure and thus the composition and evolution of the earth. The book shows how seismic waves are used to study earthquakes and are integrated with other data to investigate the plate tectonic processes that cause earthquakes. Figures, examples, problems, and computer exercises teach students about seismology in a creative and intuitive manner. Necessary mathematical tools including vector and tensor analysis, matrix algebra, Fourier analysis, statistics of errors, signal processing, and data inversion are introduced with many relevant examples. The text also addresses the fundamentals of seismometry and applications of seismology to societal issues. Special attention is paid to help students visualize connections between different topics and view seismology as an integrated science. An Introduction to Seismology, Earthquakes, and Earth Structure gives an excellent overview for students of geophysics and tectonics, and provides a strong foundation for further studies in seismology. Multidisciplinary examples throughout the text - catering to students in varied disciplines (geology, mineralogy, petrology, physics, etc.). Most up to date book on the market - includes recent seismic events such as the 1999 Earthquakes in Turkey, Greece, and Taiwan). Chapter outlines - each chapter begins with an outline and a list of learning objectives to help students focus and study. Essential math review - an entire section reviews the essential math needed to understand seismology. This can be covered in class or left to students to review as needed. End of chapter problem sets - homework problems that cover the material presented in the chapter. Solutions to all odd numbered problem sets are listed in the back so that students can track their progress. Extensive References - classic references and more current references are listed at the end of each chapter. A set of instructor's resources containing downloadable versions of all the figures in the book, errata and answers to homework problems is available at: http://levee.wustl.edu/seismology/book/. Also available on this website are PowerPoint lecture slides corresponding to the first 5 chapters of the book.

Download or read book Seismic Wave Propagation in Stratified Media written by Brian Kennett and published by ANU E Press. This book was released on 2009-05-01 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic Wave Propagation in Stratified Media presents a systematic treatment of the interaction of seismic waves with Earth structure. The theoretical development is physically based and is closely tied to the nature of the seismograms observed across a wide range of distance scales - from a few kilometres as in shallow reflection work for geophysical prospecting, to many thousands of kilometres for major earthquakes. A unified framework is presented for all classes of seismic phenomena, for both body waves and surface waves. Since its first publication in 1983 this book has been an important resource for understanding the way in which seismic waves can be understood in terms of reflection and transmission properties of Earth models, and how complete theoretical seismograms can be calculated. The methods allow the development of specific approximations that allow concentration on different seismic arrivals and hence provide a direct tie to seismic observations.

Download or read book A Study on the Benefits of Including Near field Effects in Active source Surface Wave Data Collection and Interpretation written by Thompson McCaskill and published by . This book was released on 2014 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geotechnical analyses for earthquake engineering and other applications are often predicated on the accurate determination of shear wave velocity (VS) profiles. Surface wave methods (SWM) are a noninvasive approach to developing VS profiles that involve measurement of Rayleigh wave propagation between a wave-generating source and a receiver array placed on the ground surface. There are several variations of SWM, but all utilize the same three-step process for developing a VS profile, namely: (1) data collection -- measuring ground surface vibrations emanating from a source; (2) data processing -- developing an experimental dispersion curve relating wave velocity to wavelength or frequency; and (3) inversion -- finding the VS profile that produces a theoretical dispersion curve matching the experimental dispersion curve. In current practice, the theoretical model used to fit the experimental data is a far-field model that only simulates motions from planar Rayleigh waves. Therefore, the receiver array used to collect the data in step 1 must be located far from the source (or "far-field"), where body waves have largely dissipated (due to greater damping) and Rayleigh wavefronts are nearly planar. Closer to the source -- in the so-called "nearfield" -- the ground motion includes coupled interactions of body waves and non-planar Rayleigh waves and is inconsistent with a far-field theoretical model. The primary objective of this study was to investigate the effectiveness and potential benefits of including near-field contributions in both the surface wave data collection and modeling. First, it was hypothesized that source offset distance criteria currently used to mitigate near-field effects could be greatly reduced without affecting the quality of surface wave results.Second, it was hypothesized that additional information about the soil profile could be determined if the near-field portion of the dispersion curve was included in both the data collection and theoretical modeling. Three different studies were performed for this research, namely: (1) a preliminary sensitivity study, to study the sensitivity of the near-field portion of the dispersion curve to changes in various profile parameters, (2) surface wave analysis using simulated experimental data, to assess both profile recovery effectiveness and the possibility of inferring additional profile parameters (specifically, Poisson's ratio), and (3) surface wave analysis with real data, to validate the profile findings from the study using simulated data. Experimental data were collected and/or simulated using both the Spectral-Analysis-of-Surface-Waves (SASW) method and multi-channel surface wave methods, but the primary focus of this study was on the SASW method. The results from the study showed that surface wave analyses that included near-field contributions in both data collection and theoretical modeling were as effective or more effective at recovering the VS profile as conventional far-field approaches, with the benefit of shorter arrays and smaller sources. This study also showed that surface wave measurements that included near-field data were sensitive to changes in Poisson's ratio of the profile, as compared with the known insensitivity of conventional far-field surface wave methods. The results from the limited experimental study were less conclusive, but generally confirmed the findings from the study performed using simulated data.

Download or read book Seismic Surface Waves in a Laterally Inhomogeneous Earth written by V.I. Keilis-Borok and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface waves form the longest and strongest portion of a seismic record excited by explosions and shallow earthquakes. Traversing areas with diverse geologic structures, they 'absorb' information on the properties of these areas which is best retlected in dispersion, the dependence of velocity on frequency. The other prop erties of these waves - polarization, frequency content, attenuation, azimuthal variation of the amplitude and phase - arc also controlled by the medium between the source and the recording station; some of these are affected by the properties of the source itself and by the conditions around it. In recent years surface wave seismology has become an indispensable part of seismological practice. The maximum amplitude in the surface wave train of virtually every earthquake or major explosion is being measured and used by all national and international seismological surveys in the determination of the most important energy parameter of a seismic source, namely, the magnitude M,. The relationship between M, and the body wave magnitude fI1t, is routinely employed in identification of underground nuclear explosions. Surface waves of hundreds of earthquakes recorded every year are being analysed to estimate the seismic moment tensor of earthquake sources, to determine the periods of free oscillations of the Earth, to construct regional dispersion curves from which in turn the crustal and upper mantle structure in various areas is derived, and to evaluate the dissipative parameters of the mantle material.

Download or read book Addressing Surface Wave Inversion Non uniqueness and the Implications for Seismic Site Response Analyses written by David Paul Teague and published by . This book was released on 2017 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface ground motions predicted from a seismic site response analysis are strongly dependent on the shear wave velocity (Vs) profile used to represent the small-strain shearing stiffness of subsurface materials as a function of depth. Moreover, uncertainties are present in the input Vs profile and this uncertainty leads to uncertainty in the predicted site response. When Vs profiles are obtained from surface wave inversion, the final derived Vs profiles are non-unique, with many different interpretations of the subsurface shearing stiffness that are consistent with the measured surface wave field data. This non-uniqueness is exacerbated by the ambiguous interpretation of surface wave modes and the subjectivity of defining the inversion parameterization (trial number of layers and ranges in their respective Vs, compression wave velocities, and mass densities). Thus, it is necessary to develop strategies to systematically address these issues in order to develop Vs profiles with realistic estimates of uncertainty for use in site response analyses. First, a-priori information should be sought to aid in interpreting modes and to develop a realistic parameterization to guide the surface wave inversion. In complex geologic settings, it can be extremely challenging or even impossible to obtain geologically-realistic Vs profiles without this a-priori information. However, there are many situations when a-priori information is scarce or nonexistent. In such cases, alternative mode interpretations and/or parameterizations must be considered. Even with abundant a-prior information, the non-uniqueness issue generally cannot be eliminated and the variation in seismic site response associated with non-unique Vs profiles derived from the same surface wave dataset is of interest. At the two sites considered in this study, very different Vs profiles derived from surface wave inversion of the same dataset produced very similar site response estimates, provided that the experimental surface wave dispersion data was well-fit. Furthermore, the site response estimates associated with these Vs profiles were more accurate and less variable than those associated with Vs profiles that were developed using common strategies of accounting for Vs uncertainty. Thus, despite the non-uniqueness issue, Vs profiles derived from a rigorous surface wave inversion can yield robust site response estimates.

Download or read book Characterization of Modern and Historical Seismic Tsunamic Events and Their Global Societal Impacts written by Y. Dilek and published by Geological Society of London. This book was released on 2021-06-22 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: Earthquakes and tsunamis are devastating geohazards with significant societal impacts. Most recent occurrences have shown that their impact on the stability of nations–societies and the world geopolitics is immense, potentially triggering a tipping point for a major downturn in the global economy. This Special Publication presents the most current information on the causes and effects of some of the modern and historical earthquake–tsunami events, and effective practices of risk assessment–disaster management, implemented by various governments, international organizations and intergovernmental agencies. Findings reported here show that the magnitude of human casualties and property loss resulting from earthquakes–tsunamis are highly variable around the globe, and that increased community, national and global resilience is significant to empower societal preparedness for such geohazards. It is clear that all stakeholders, including scientists, policymakers, governments, media and world organizations must work together to disseminate accurate, objective and timely information on geohazards, and to develop effective legislation for risk reduction and realistic hazard mitigation–management measures in our globally connected world of today.