Download or read book A New Procedure for Estimation of Shear Wave Velocity Profiles Using Multi Station Spectral Analysis of Surface Waves Regression Line Slope and Genetic Algorithm Methods written by Morteza Zarrabi and published by . This book was released on 2006 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 774 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Shear Wave Velocity of Soils by the Spectral Analysis of Surface Waves SASW Method written by Seyed Mohammad Ali Zomorodian and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spectral analysis of surface waves (SASW) method is an in-situ seismic method used for determining the thickness and elastic properties of soil and pavement. The SASW method is fast and economical to perform since no boreholes are required. The method is suitable for sites where the use of large equipment is difficult or where sublayer conditions make it difficult to perform other seismic tests. The SASW method is also ideal for preliminary field investigations to be conducted prior to more detailed site investigation, and for quality control and monitoring of ground improvement. The purpose of this research was to improve the SASW method by incorporating multi-mode propagation in the backcalculation procedure. In order to facilitate the investigation carried out in this study, two computer programs were developed to simulate SASW tests (and also Steady-State surface wave tests) and to calculate theoretical dispersion curves. The program for calculating theoretical dispersion curves was based on the root-searching procedure used in existing backcalculation methods. The computer programs developed in this study were used in a case study to demonstrate difficulties encountered by existing methods in dealing with multi-mode situations. It was shown that: (i) wavelength filtering criteria used by existing methods yield inconsistent (i.e. erroneous) dispersion curves when more than one propagation mode participate in the wave field, and (ii) backcalculation procedures based on root-searching cannot identify predominant propagation modes and hence fail to yield accurate results in the case of multi-mode propagation. Two developments were made in the present study to overcome the above difficulties. First, a new wavelength filtering criterion was adopted. In this criterion, the dispersion data point for a particular frequency is rejected (i.e. filtered out) if the values of phase velocity obtained from two different receiver-to-receiver spacings are not in close agreement. In this manner, inconsistencies that might result in the dispersion due to multi-mode propagation are avoided. Second, a new procedure to calculate the theoretical dispersion curve was developed. This procedure is based on the maximum vertical flexibility coefficient (at each frequency) of the theoretical layered model. Unlike root-searching methods, the maximum vertical flexibility coefficient method easily identifies predominant propagation modes. A computer program was developed in this study for backcalculation of SASW data based on the flexibility coefficient method. Least-squares optimization using the down-hill simplex method was also implemented in this program to automate the backcalculation process. The accuracy of the above proposed procedures was demonstrated using SASW field tests. The shear wave velocity profiles obtained using the procedures developed in this study are in good agreement with those obtained from other in-situ seismic tests. (Abstract shortened by UMI.).
Download or read book Estimation of Shear Wave Velocity Profiles Employing Genetic Algorithms and the Diffuse Field Approach on Microtremors Array written by Walter Salazar and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book chapter explains the methodology to determine the shear wave velocity VS profile employing microtremors array data at Port of Spain, Trinidad, and its implication in the seismic amplification and liquefaction hazard in the city. We divide this study into five sections; firstly, we introduce a description of the spectral autocorrelation method and the genetic algorithm schemes to retrieve the Vs and thickness of soil layers. Secondly, we validate the soil profiles via inspection of the ellipticity pattern at such sites; we also compared the observed horizontal-to-vertical spectral ratios (H/V) with the synthetic ones derived by the Diffuse Field Approach and 1D theoretical SH wave amplification functions. Thirdly, we compute the shear wave velocity in the first 30 m obtained from our genetic inversion and compared with the ones estimated by the empirical formulas based on geomorphological conditions. Fourthly, we present a preliminary liquefaction hazard map based on the level of H/V microtremor ratios and the fundamental period of vibration. Finally, we conclude with further recommendations for planning purposes in the city of Port of Spain.
Download or read book Inversion Method for Spectral Analysis of Surface Waves SASW written by Maria Catalina Orozco and published by . This book was released on 2003 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research focuses on estimating the shear wave velocity (Vs) profile based on the dispersion curve obtained from SASW field test data (i.e., inversion of SASW data). It is common for the person performing the inversion to assume the prior information required to constrain the problem based on his/her own judgment. Additionally, the Vs profile is usually shown as unique without giving a range of possible solutions. For these reasons, this work focuses on: (i) studying the non-uniqueness of the solution to the inverse problem; (ii) implementing an inversion procedure that presents the estimated model parameters in a way that reflects their uncertainties; and (iii) evaluating tools that help choose the appropriate prior information. One global and one local search procedures were chosen to accomplish these purposes: a pure Monte Carlo method and the maximum likelihood method, respectively. The pure Monte Carlo method was chosen to study the non-uniqueness by looking at the range of acceptable solutions (i.e., Vs profiles) obtained with as few constraints as possible. The maximum likelihood method was chosen because it is a statistical approach, which enables us to estimate the uncertainties of the resulting model parameters and to apply tools such as the Bayesian criterion to help select the prior information objectively. The above inversion methods were implemented for synthetic data, which was produced with the same forward algorithm used during inversion. This implies that all uncertainties were caused by the nature of the SASW inversion problem (i.e., there were no uncertainties added by experimental errors in data collection, analysis of the data to create the dispersion curve, layered model to represent a real 3-D soil stratification, or wave propagation theory). At the end of the research, the maximum likelihood method of inversion and the tools for the selection of prior information were successfully used with real experimental data obtained in Memphis, Tennessee.
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 Study of Laboratory and Field Techniques to Measure Shear Wave Parameters Frequency Effects written by Hassan Ali and published by . This book was released on 2015 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last decade, significance of correctly evaluating the dynamic properties of soil has been widely recognized by the research community. Among various parameters, shear wave velocity and damping ratio has been recognized as the key parameter for the soils subjected to dynamic loading. The shear wave velocity is used in the geotechnical assessments for site characterization, ground response analysis, and liquefaction potential. The dynamic properties of the soils can be attained in the lab or in-situ. The dynamic soil properties are dependent on different state parameters, such as, void ratio, confining stress, water content, strain levels, and drainage conditions. Apart from the influence of the above parameters, the dynamic soil parameters are also affected by the frequency and the amplitude of the dynamic load applied to the soil. The in-situ tests compliments the laboratory testing in the evaluation of the dynamic soil parameters. Although, correlations can be used to estimate the in-situ parameters but a direct measurement is necessary. To develop a greater confidence of the results of the in-situ tests, it is helpful to compare the field results to conventional laboratory tests. In the RC testing, the effect of base stiffness has a significant effect on shear modulus and damping values. In literature, only two studies have shown the effect of base fixidity. In this thesis, the issue is addressed by testing sand and clay sample on traditional bench and isolation table. In addition to base fixidity, coupling between the specimen and base platen is also very critical. Radial blades in top and bottom platen are introduced along with porous stone fixed underneath the blades. Aluminum probes are recommended for the calibration of the RC device, however, the effect on shear modulus and damping as function of shear strain is not well studied. Therefore, the stiff probe is tested from low to large strains and effect on damping ratio is studied. Finally, a new BE method is proposed to understand the estimation of shear wave velocity at higher frequencies. Due to the large variation in the interpretation of the BE tests results, there is no standard method for the estimation of the shear wave velocity. In this thesis, a new calibration procedure using state of the art laser vibrometer is used to understand the bending behavior of benders in air and in tip to tip configuration. Shear wave velocity comparison between RC and BE tests is done in usual practice, however, the frequency effects from these two tests are not well stated. In this study, the frequency effects are studied and a new methodology, modified frequency domain method, is introduced and tested on dry specimen. The results of the BE tests match well with the RC test values. MASW is a practiced field test to evaluate the shear wave velocity profile for geomaterials, however, the effect of frequency in the case of an anomaly has not been well understood. Therefore, this study uses numerical simulations and a lab scale model to study these effects. In addition, the effect of actual accelerometers on the measurements is studied for the first time using a high frequency laser vibrometer. The frequency effects in field theory of the MASW and SCPT is also studied to address the actual limitations in the analysis of SCPT data without the consideration of frequency effects. Based on the objective, this research focuses on: (1) the study of the laboratory resonant column and bender element tests, (2) numerical simulations and laboratory surface waves testing, and (3) field testing using surface waves and seismic cone penetration method for the estimation of shear wave parameters with emphasis on the frequency effects. An important aspect of the laboratory testing is the calibration of the equipment. Standard procedures are available for the calibration of the resonant column (RC) device, however, the same is not true for the bender element (BE). In this study, the bender elements are calibrated using three different configurations, tip-to-tip, aluminum rods, and using state-of-art laser vibrometer. The State of art laser vibrometer is used to characterize the bending behavior of the bender elements showing the resonance frequency of 12 kHz and damping of 2 % when vibrating in air. The top and bottom platen of RC device were modified to allow better coupling between the specimen and benders. Radial blades were introduced to account for coupling of stiff clay specimens. Four different soils (sand, stiff clay, mine paste, and leda clay) were tested in this study. The results of the tests, from the RC and the BE tests, were analyzed in the time and the frequency domains. Comparison of the results show, a maximum of 45 $\%$ difference in the velocity obtained from the RC and BE tests. Leda clay tests were done on the modified base platens and the difference in the Vs between the RC and BE is 6% compared to the stiff clay specimen where the difference is 28% To study the difference in the Vs values between the RC and BE, a new modified frequency domain method for BE testing is presented. The method was applied to the sand specimen. The sample is excited with a frequency sweep ranging from 0 to 52 kHz and change in unwrapped phase, between the input excitation and output response, is evaluated outside the range of resonant peaks of the specimen. The Vs values from the two tests match well for the frequency range between 29 and 23 kHz, with overall less than 10 % error for the range of confinement range studied in this thesis. Numerical simulations on homogeneous and non-homogeneous medium showed the change in the phase velocity of the Rayleigh waves (R-waves) due to the presence of a void. To introduce non-homogeneity, voids of various size and depth were used. Nine numerical models were analyzed, change in the phase velocity as a function of frequency was observed. A new methodology was introduced in which the receivers were divided into three sections, before, on-top, and after the void. Results from the dispersion curves show that the change in the phase velocity (function of frequency) is between 3% to 50% for different void width and depth. Multichannel analysis of surface waves (MASW) test method was used as the geophysical testing method. The laboratory tests were conducted using three different configurations on sandbox. Two tests involved use of accelerometers as receivers, however, the input source was different. While the third test consisted of using state of art laser vibrometer as receiver. Using the laser vibrometer, 96 surface responses were recorded compared to 12 using accelerometers. The results from the laboratory MASW test showed the frequency effect on the measurements due to the source used in this method. Coupling of the geophone/transducer in surface wave testing is an important issue. Results from the lab test using laser vibrometer showed that the mass loading effect of accelerometer affects the frequency content of the signal. The field MASW and the SCPT tests were done at the University of Waterloo Columbia Lake Test Site (UW-CLTS). The comparison of shear wave velocity from the field MASW and the SCPT shows the average shear wave velocity profile from the two tests, however, importance in not paid to the frequency of the input signal and main frequency difference between the MASW and SCPT tests. In this study, the frequency spectrum from the MASW and the SCPT tests data were analyzed to understand the change in the shear wave velocity at different depths. From the analysis, the percentage change in shear wave velocity between MASW line 1 and SCPT 1 and 2 is more than 90 % for depths between 0 and 2 m, while it reduces to 10 % for depths between 7 and 13 m.
Download or read book Vertical Shear wave Velocity Profiles Generated from Spectral Analysis of Surface Waves written by Dr. Neil Anderson and published by . This book was released on 2003 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface wave (Rayleigh wave) seismic data were acquired at six separate bridge sites in southeast Missouri. Each acquired surface wave data set was processed [spectral analysis of surface waves (SASW)] and transformed into a site-specific vertical shear-wave velocity profile (SASW shear-wave velocity profile). The SASW shear-wave velocity profiles generated for each bridge site were compared to other geotechnical data including seismic cone penetrometer shear-wave velocity profiles, cross-borehole shear-wave velocity profiles, and borehole lithology logs. The geotechnical data presented herein indicate the SASW shear-wave velocity profiles correlate well with subsurface lithology logs and available cross-borehole shear-wave velocity control. More specifically, clays, silts and sands exhibit relatively characteristic SASW shear-wave velocities, which increase incrementally with increasing depth of burial. The authors believe these correlations demonstrate that SASW shear-wave velocities are reliable.
Download or read book Determination of in Situ Shear Wave Velocities from Spectral Analysis of Surface Waves written by J. Scott Heisey and published by . This book was released on 1981 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A 2 D MASW Shear wave Velocity Profile Along a Test Segment of Interstate I 70 St Louis Missouri written by N. Anderson and published by . This book was released on 2004 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: The University of Missouri-Rolla acquired multi-channel surface wave (Rayleigh wave) seismic data along a 6400 ft segment of Interstate I-70 in downtown St. Louis, Missouri. The acquired surface wave data set was processed [multi-channel analysis of surface waves (MASW)] and transformed into a 2-D MASW shear-wave velocity profile with a station-spacing of 40 ft. The interpreted depth to bedrock along the length of the 2-D profile varies between 20 ft and 44 ft. Geotechnical data provided by the Missouri Department of Transportation and presented herein indicates the interpreted 2-D MASW shear-wave velocity profile correlates well with available bedrock (borehole) and seismic cone penetrometer control, supporting the conclusion that the MASW technique can be used to generate reliable 2-D shear-wave velocity profiles.
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 Development of Deep Site Specific and Reference Shear Wave Velocity Profiles in the Canterbury Plains New Zealand written by Michael Ryan Deschenes and published by . This book was released on 2017 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Deep (typically >1000 m) shear wave velocity profiles were developed across the Canterbury basin at nine strong motion stations using a combination of active and passive surface wave methods and horizontal to vertical spectral ratio measurements. A multi-mode, multi-method joint inversion process, which included Rayleigh and Love wave dispersion and horizontal to vertical spectral ratio data, was used to estimate the shear wave velocity profiles at each site. A-priori geologic information was utilized in defining preliminary constraints on the complex geologic layering of the Canterbury basin. At sites where interbedded layers were present, velocity reversals were considered in the inversion. Shear wave velocity profiles developed as part of this study were combined with the median profiles from 14 Christchurch sites detailed in a separate study, to develop a suite of region and soil specific reference shear wave velocity profiles for the Canterbury basin. Site specific and reference shear wave velocity profiles developed as part of this study can be used for back-analysis of earthquake ground motions, forward analysis of future ground motions, full 3D physics based simulations, or to refine 3D velocity models for the region. 1000 m) shear wave velocity profiles were developed across the Canterbury basin at nine strong motion stations using a combination of active and passive surface wave methods and horizontal to vertical spectral ratio measurements. A multi-mode, multi-method joint inversion process, which included Rayleigh and Love wave dispersion and horizontal to vertical spectral ratio data, was used to estimate the shear wave velocity profiles at each site. A-priori geologic information was utilized in defining preliminary constraints on the complex geologic layering of the Canterbury basin. At sites where interbedded layers were present, velocity reversals were considered in the inversion. Shear wave velocity profiles developed as part of this study were combined with the median profiles from 14 Christchurch sites detailed in a separate study, to develop a suite of region and soil specific reference shear wave velocity profiles for the Canterbury basin. Site specific and reference shear wave velocity profiles developed as part of this study can be used for back-analysis of earthquake ground motions, forward analysis of future ground motions, full 3D physics based simulations, or to refine 3D velocity models for the region.
Download or read book Shear Wave Velocity of the Ground Near Southern California TRINET Sites Using the Spectral Analysis of Surface Waves Method SASW and Parallel arrayed Harmonic wave Sources written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of Shear Wave Velocity Profiles in the Deep Sediments of the Mississippi Embayment Using Surface Wave and Spectral Ratio Methods written by Jonathan Pqul Bailey and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The deep soils of the Mississippi Embayment in the central United States will have a significant influence on earthquake ground motions generated by the New Madrid Seismic Zone. The seismic properties of these soils, which extend to depths of over 1000 meters in some areas, are poorly characterized at depths below 60 to 100 meters. This study presents shear wave velocity (Vs) profiles determined from Spectral-Analysis-of-Surface-Waves (SASW) measurements performed at eleven sites in Arkansas, Tennessee, and Missouri. These measurements were performed using the low-frequency field vibrator developed as part of the NSF Network for Earthquake Engineering Simulation (NEES) program. Shear wave velocity profiles were developed to depths of approximately 220 meters at eleven sites located throughout the Mississippi Embayment. In addition to the SASW measurements, ambient noise measurements of horizontal and vertical ground motions were performed to estimate the average Vs over the full profile depth using the H/V spectral ratio method. The Vs profiles derived from the SASW measurements compared well with Vs reference profiles that have been developed for the Mississippi Embayment and used in recent site response studies of the region. The observed variability of the profiles was found to be in general agreement with past assumptions used for the deep soil and correlated with changes in soil lithology. Relationships between the soil formations and Vs were consistent with past studies and provided information to greater depths. Lastly the H/V spectral ratio measurements were successfully applied at each of the eleven sites, but appeared to overestimate the average Vs.
Download or read book In Situ Measurement of Stiffness Profiles in the Seafloor Using the Spectral analysis of surface waves SASW Method written by Barbara Aileen Luke and published by . This book was released on 1995 with total page 424 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 Analytical Study of the Spectral analysis of surface waves Method at Complex Geotechnical Sites written by Jeffrey D. Bertel and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Spectral-Analysis-of-Surface-Waves (SASW) method is an accepted means of measuring shear wave velocity (VS). In some settings, SASW measurements have produced results that were inconsistent with results from other methods of measurement. The effectiveness of the SASW methodology at complex geotechnical sites was investigated to identify site conditions where the SASW approach may produce erroneous results. Analytical simulations of surface wave measurements were performed. A traditional SASW methodology (global analysis), and a more rigorous approach (array analysis) were used to generate experimental dispersion curves. The effectiveness of these approaches was evaluated by comparing the experimental results to the true dispersion curve. The global analysis yielded dispersion curves that tend to underestimate surface wave velocities at long wavelengths. The array approach worked well for both simple, gradually increasing VS profiles as well as for some complex profiles with large VS contrasts. In some cases both the global and array analysis produce an experimental dispersion curve that is not consistent with the theoretical dispersion curve, especially for soft-over-stiff profiles, a common profile encountered in the field. These results have implications for earthquake site response analysis.
