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 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 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 Fundamentals of Geophysical Data Processing written by Jon F. Claerbout and published by McGraw-Hill Companies. This book was released on 1976 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Experimental Investigation of Near field Effects on the SASW Dispersion Curve written by Sungmoon Hwang and published by . This book was released on 2014 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: When any method of surface wave testing that involves Rayleigh waves is performed, one important assumption is that plane Rayleigh waves are being measured. In the forward modeling or inversion procedure that is used to analyze the field dispersion curve to determine the field V[subscript s] profile, the analysis is based on the wave field consisting of plane Rayleigh waves. Therefore, field dispersion curves that contain near-field data could adversely distort the field V[subscript s] profile. To minimize the influence of near-field effects, several criteria have been recommended in the past. However, most of the criteria were based on empirical equations that implicitly assumed zones of influence, or numerical simulations. There is a lack of experimental investigation, particularly full-scale field investigations. Even, the numerical solutions have been based on simple soil profiles without significant velocity contrasts between soil layers and/or varying thicknesses of soil layers which can significantly influence near-field effects. Data from full-scale field test using the Spectral-Analysis-of-Surface-Waves (SASW) method was used in this thesis research. SASW tests performed at two stages in the construction of a deep, 90-ft thick backfill were studied. The V[subscript s] profiles were normally dispersive, with a substantial increase in the velocity of the layer beneath the backfill. The study shows the adverse distortions that can occur in the field dispersion curve from near-field effects when the spacing of the receiver pair is: (1) above the zone of rapidly increasing V[subscript s] near the surface and (2) less than the depth to the stiffer layer in deeper measurements. Other factors that affect the results are discussed and recommendations are presented to minimize the introduction of near-field effects, at least in these relatively simple V[subscript s] profiles.

Download or read book Advancements in Surface Wave Testing written by Siavash Mahvelati and published by . This book was released on 2019 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Multichannel Analysis of Surface Waves (MASW) method has been widely used to evaluate the subsurface in engineering applications since late 1990's. In MASW, surface waves are introduced into the subsurface and recorded by sensors along the ground surface. The characteristics of the propagating surface wave are influenced by the subsurface stratification, the manner in which the surface waves are input into the ground, and the survey parameters to acquire data. Rayleigh waves are typically generated by vertical strikes on a metallic plate which serves as a coupler between the active input source (e.g., a sledgehammer) and the ground surface. It has been suggested that plastic-type base plates can improve the low-frequency energy of Rayleigh waves and therefore, can increase the depth of investigation among other potential improvements. However, very little studies exist in the literature that evaluate the role of base plate material, especially plastic materials. In addition to Rayleigh surface waves, seismic surface waves can also be generated with horizontal impacts (i.e., Love waves) using specialized base plates. In this regard, much less is available in the literature regarding Love waves as sources in MASW testing which means that optimum field survey parameters, the effects of near-field, and the role of seismic source have not been thoroughly investigated yet for Love waves. Given the aforementioned gaps in the literature, two aspects of MASW have been investigated. First, the role of base plate material, specifically plastic-type plates, has been studied. Field data collected from six sites along with the data from laboratory experiments and numerical simulations of hammer-plate impact were studied. The results showed that softer base plates improve the energy transfer by as much 20% and lead to minor improvements, typically one-digit numbers in relative changes, in other signal characteristics such as signal bandwidth and signal-to-noise ratio. These results were corroborated with laboratory testing and numerical models of wave propagation with different base plate materials. The second goal was to improve understanding of Love wave propagation, particularly as related to resolution capabilities from survey parameters. Rayleigh and Love waveforms were collected with multiple active seismic sources at three sites and a systematic comparison was made between the two types of waves. Also, seismic wave propagation was simulated using the research community code SPECFEM2D to further investigate their differences. The results revealed critical new information about the depth of investigation, the effects of bedrock location on near-field effects, and the role of the different survey parameters on Rayleigh and Love wave data. The depth of investigation of Love wave MASW was deeper by about 2-9 m than that of Rayleigh MASW as a result of improved minimum frequency. The minimum source offset to avoid near-field effects was comparable for both Rayleigh and Love waves (0.3-0.4 of maximum wavelength). At closer source offset locations, Rayleigh waves were more affected by near-field effects and showed an additional 10% underestimation of planar phase velocities. Overall, the results from both parts of this study provides new practical insights about some of the unexplored aspects of surface wave testing using MASW.

Download or read book Earthquake Geotechnical Engineering for Protection and Development of Environment and Constructions written by Francesco Silvestri and published by CRC Press. This book was released on 2019-07-19 with total page 8083 pages. Available in PDF, EPUB and Kindle. Book excerpt: Earthquake Geotechnical Engineering for Protection and Development of Environment and Constructions contains invited, keynote and theme lectures and regular papers presented at the 7th International Conference on Earthquake Geotechnical Engineering (Rome, Italy, 17-20 June 2019. The contributions deal with recent developments and advancements as well as case histories, field monitoring, experimental characterization, physical and analytical modelling, and applications related to the variety of environmental phenomena induced by earthquakes in soils and their effects on engineered systems interacting with them. The book is divided in the sections below: Invited papers Keynote papers Theme lectures Special Session on Large Scale Testing Special Session on Liquefact Projects Special Session on Lessons learned from recent earthquakes Special Session on the Central Italy earthquake Regular papers Earthquake Geotechnical Engineering for Protection and Development of Environment and Constructions provides a significant up-to-date collection of recent experiences and developments, and aims at engineers, geologists and seismologists, consultants, public and private contractors, local national and international authorities, and to all those involved in research and practice related to Earthquake Geotechnical Engineering.

Download or read book Monitoring the Comprehensive Nuclear Test Ban Treaty Surface Waves written by Anatoli L. Levshin and published by Springer Science & Business Media. This book was released on 2001-09-01 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: On September 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting nuclear explosions worldwide, in all environments. The treaty calls for a global verification system, including a network of 321 monitoring stations distributed around the globe, a data communications network, an international data center (IDC), and on-site inspections to verify compliance. Seismic methods play the lead role in monitoring the CTBT. This volume concentrates on the measurement and use of surface waves in monitoring the CTBT. Surface waves have three principal applications in CTBT monitoring: to help discriminate nuclear explosions from other sources of seismic energy, to provide mathematical characterizations of the seismic energy that emanates from seismic sources, and to be used as data in inversion for the seismic velocity structure of the crust and uppermost mantle for locating small seismic events regionally. The papers in this volume fall into two general categories: the development and/or application of methods to summarize information in surface waves, and the use of these summaries to advance the art of surface-wave identification, measurement, and source characterization. These papers cut across essentially all of the major applications of surface waves to monitoring the CTBT. This volume therefore provides a general introduction to the state of research in this area and should be useful as a guide for further exploration.

Download or read book Geotechnical Site Characterization Using Multi channel Analysis of Rayleigh and Love Waves written by James David Lane and published by . This book was released on 2009 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Multi-Channel Analysis of Surface Waves (MASW) is a technique in which surface waves can be analyzed to determine soil shear wave velocity profiles with depth. The shear wave velocity of soil can be used to calculate the shear modulus, which is an important geotechnical engineering parameter. Site surveys were conducted and analyzed located at a location on the flood plain of the Tennessee River. The flood plain consists of a thin layer of soil above rigid (Knox Dolomite) bedrock and exhibited strong stratification. Three different aspects of MASW data acquisition and analysis are presented in the study. The first aspect is the response correction of the classical horizontal and vertical component geophone and its effects on surface wave dispersion; the second aspect is the effect of Rayleigh wave MASW data acquisition, analysis, and modeling as influenced by Rayleigh wave guides; the third aspect is the use of MASW and Love wave data acquisition, analysis, and modeling. MASW is performed using a seismic source and geophones (velocity sensor) without correcting the amplitude and phase errors induced by the equivalent single degree of freedom response function representing the mechanical response of a given velocity sensor. Geophones were experimentally tested in the laboratory to determine their natural frequency, damping ratio, and transduction constants. The results from these tests were mathematically corrected for their mechanical response and compared to uncorrected and corrected field data. Several seismic sources and various sourceoffset distances were evaluated to determine their effects on Rayleigh wave dispersion. Rayleigh waves, guided in a layer, were interpreted to have a profound influence on the Rayleigh wave dispersion data obtained using different seismic sources and source-offset distances. Results from Love wave data analysis produced superior dispersion data in comparison to the dispersion data obtained from Rayleigh wave data, making interpretation much more certain.

Download or read book Array based Measurements of Surface Wave Dispersion and Attenuation Using Frequency wavenumber Analysis written by Sungsoo Yoon and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface wave methods have been used to determine dynamic properties of near-surface soils in geotechnical engineering for the past 50 years. Although the capabilities of engineering surface wave methods have improved in recent years due to several advances, several issues including (1) near-field effects, (2) combined active and passive measurements, and (3) accurate measurements of surface wave attenuation still require study to further improve the capabilities of modern surface wave methods. Near-field effects have been studied for traditional surface wave methods with two receivers and several filtering criteria to mitigate the effects have been recommended. However, these filtering criteria are not applicable to surface wave methods with multiple receivers. Moreover, the criteria are not quantitatively based and do not account for different types of soil profiles, which strongly influence near-field effects. A new study of near-field effects on surface wave methods with multiple receivers was conducted with numerical and experimental methods. Two normalized parameters were developed to capture near-field effects. Quantitatively based near-field effect criteria for an ideal homogeneous half-space and three typical soil profiles are presented. Combining active and passive surface wave measurements allows developing a shear wave velocity profile to greater depth without sacrificing the near-surface resolution offered by active measurements. Generally, active and passive measurements overlap in the frequency range from approximately 4 to 10 Hz, and there are often systematic differences between the two measurements. The systematic errors in active and passive surface wave methods were explored to explain and resolve the differences, allowing for a more accurate composite dispersion curve. The accuracy of measured surface wave attenuation is improved by properly accounting for (1) geometric spreading, (2) near-field effects, and (3) ambient noise. In this study, a traditional estimation method and a frequency-wavenumber method utilizing sub-arrays were investigated using displacement data from numerical simulations, focusing on near-field and ambient noise effects. Detailed procedures for the frequency-wavenumber estimation method are developed based on a study of the primary factors affecting attenuation estimates. The two methods are also evaluated using experimental displacement data obtained from surface wave field measurements with three different arrays.

Download or read book Mechanics of Coastal Sediment Transport written by J?rgen Freds?e and published by World Scientific. This book was released on 1992 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book treats the subject of sediment transport in the marine environment, covering transport of non-cohesive sediment by waves and current in- and outside the surf zone. It can be read independently, but a background in hydraulics and basic wave mechanics is required. It is intended for M.Sc. and Ph.D. students. The primary aim of the book is to describe the physical processes of sediment transport and how to represent them in mathematical models. It does not present a large number of different formulae for the sediment transport rates under various conditions. The book can be divided in two main parts; in the first, the relevant hydrodynamic theory is described; in the second, sediment transport and morphological development are treated. The hydrodynamic part contains a review of elementary theory for water waves, chapters on the turbulent wave boundary layer and the turbulent interaction between waves and currents, and finally, surf zone hydrodynamics and wave driven currents. The part on sediment transport introduces the basic concepts (critical bed shear stress, bed load, suspended load and sheet layer, near-bed concentration, effect of sloping bed); it treats suspended sediment in waves and current and in the surf zone, and current and wave-generated bed forms. Finally, the modelling of cross-shore and long-shore sediment transport is described together with the development, of coastal profiles and coastlines.

Download or read book Proceedings of 17th Symposium on Earthquake Engineering Vol 4 written by Manish Shrikhande and published by Springer Nature. This book was released on 2023-06-30 with total page 679 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents select proceedings of the 17th Symposium on Earthquake Engineering organized by the Department of Earthquake Engineering, Indian Institute of Technology Roorkee. The topics covered in the proceedings include engineering seismology and seismotectonics, earthquake hazard assessment, seismic microzonation and urban planning, dynamic properties of soils and ground response, ground improvement techniques for seismic hazards, computational soil dynamics, dynamic soil–structure interaction, codal provisions on earthquake-resistant design, seismic evaluation and retrofitting of structures, earthquake disaster mitigation and management, and many more. This book also discusses relevant issues related to earthquakes, such as human response and socioeconomic matters, post-earthquake rehabilitation, earthquake engineering education, public awareness, participation and enforcement of building safety laws, and earthquake prediction and early warning system. This book is a valuable reference for researchers and professionals working in the area of earthquake engineering.

Download or read book Resistivity and Induced Polarization written by Andrew Binley and published by Cambridge University Press. This book was released on 2020-12-17 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive text on resistivity and induced polarization covering theory and practice for the near-surface Earth supported by modelling software.

Download or read book The Interaction of Ocean Waves and Wind written by Peter Janssen and published by Cambridge University Press. This book was released on 2004-10-28 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book was published in 2004. The Interaction of Ocean Waves and Wind describes in detail the two-way interaction between wind and ocean waves and shows how ocean waves affect weather forecasting on timescales of 5 to 90 days. Winds generate ocean waves, but at the same time airflow is modified due to the loss of energy and momentum to the waves; thus, momentum loss from the atmosphere to the ocean depends on the state of the waves. This volume discusses ocean wave evolution according to the energy balance equation. An extensive overview of nonlinear transfer is given, and as a by-product the role of four-wave interactions in the generation of extreme events, such as freak waves, is discussed. Effects on ocean circulation are described. Coupled ocean-wave, atmosphere modelling gives improved weather and wave forecasts. This volume will interest ocean wave modellers, physicists and applied mathematicians, and engineers interested in shipping and coastal protection.

Download or read book Seismic Refraction Prospecting written by Society of Exploration Geophysicists and published by . This book was released on 1967 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is a compilation of the newer techniques of refraction seismic surveying. It contains a series of articles written principally by members of SEG who are specialist in refraction techniques. The volume contains only new materials with a bibliography of references to other refraction materials available. The majority of the papers are of a "technique type" which describe some particular interpretation technique that may be used for better interpretation of special refraction data.