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 Natural Hazards written by John P. Tiefenbacher and published by BoD – Books on Demand. This book was released on 2019-08-28 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: Natural Hazards - Risk, Exposure, Response, and Resilience demonstrates advanced techniques to measure risks, exposures, responses, and solutions to hazards in an array of communities. Eleven original research reports by international scholars on hazard assessment and management are organized into four sections: studies assessing risk using in-depth modeling and technological detection to provide insight into problems associated with earthquakes, torrential rains, and nuclear power plant safety; studies revealing the spatial distributions of exposure and impacts from an assortment of hazards; studies examining human response to increased awareness of the patterns of hazard; and a study demonstrating assessment of resilience of sociotechnological systems to natural hazards. This volume contributes new conceptual and practical commentaries to assess, mitigate, and plan for disasters.
Download or read book Measuring Modeling and Predicting the Seismic Site Effect written by Yefei Ren and published by Frontiers Media SA. This book was released on 2024-01-25 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: As recognized universally by both seismology and earthquake engineering communities, the amplitude and frequency content of ground motions are influenced by local site effects, including the effects of near-surface geologic materials, surface topographic and basin effects, and so on. Strong linkage between seismic site effect and earthquake damage has been commonly demonstrated from many past earthquakes. Therefore, quantitative and reliable evaluation of the seismic site effect is one of the crucial aspects in seismic hazard assessment and risk mitigation. With the significant advancement of modern seismic monitoring networks and arrays, huge amounts of high-quality seismic records are now being accumulated. This encourages us to measure the site responses and its associated uncertainty for selected seismic stations by some record-dependent approaches, such as horizontal-to-vertical spectral ratio (HVSR) measurements, generalized spectral inversion (GIT) methods, etc. Machine learning techniques also show significant promise in characterization of the near-surface geologic properties and prediction of site response. These data-driven approaches help us to better understand the physics of spatial and temporal variabilities of ground motions. Due to more and more site-specific data being captured, invoking non-ergodic assumptions in seismic response analysis has recently been a topic of great interest in the community. For specific site response analysis, numerical simulations are carried out to model the dynamic process of seismic waves propagating and scattering in the subsurface strata. With development of modeling capacity, great efforts have been taken to evaluate quantitatively the complex 2D and 3D effects on seismic site response.
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 Guidelines for Estimation of Shear Wave Velocity Profiles written by Bernard R. Wair and published by . This book was released on 2012 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Cuttings and Extracts from Various Periodicals Pamphlets and Maps Relating to the South Eastern and Chatham Railway Its Constituents and Successors written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Empirical Relationships to Estimate Shear wave Velocity Profiles from SPT Information in the New Madrid Seismic Zone written by Andrew C. Kizze and published by . This book was released on 2009 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Comparison of Phase Velocities from Array Measurements of Rayleigh Waves Associated with Microtremor and Results Calculated from Borehole Shear wave Velocity Profiles written by Hsi-Ping Liu and published by . This book was released on 2000 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterizing the Shear Wave Velocity Profile at the Seismic Network Stations in Israel written by Yuval Peleg and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "... In this study, we develop an indispensable database of Vs profiles in the location of 32 network stations in Israel, using the ReMi (Refraction Microtremor) method (Louie, 2001). ... " -- from the abstract.
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 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 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 Reducing Uncertainties in the Velocities Determined by Inversion of Phase Velocity Dispersion Curves Using Synthetic Seismograms written by Seyed Mehrdad Hosseini and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Characterizing the near-surface shear-wave velocity structure using Rayleigh-wave phase velocity dispersion curves is widespread in the context of reservoir characterization, exploration seismology, earthquake engineering, and geotechnical engineering. This surface seismic approach provides a feasible and low-cost alternative to the borehole measurements. Phase velocity dispersion curves from Rayleigh surface waves are inverted to yield the vertical shear-wave velocity profile. A significant problem with the surface wave inversion is its intrinsic non-uniqueness, and although this problem is widely recognized, there have not been systematic efforts to develop approaches to reduce the pervasive uncertainty that affects the velocity profiles determined by the inversion. Non-uniqueness cannot be easily studied in a nonlinear inverse problem such as Rayleigh-wave inversion and the only way to understand its nature is by numerical investigation which can get computationally expensive and inevitably time consuming. Regarding the variety of the parameters affecting the surface wave inversion and possible non-uniqueness induced by them, a technique should be established which is not controlled by the non-uniqueness that is already affecting the surface wave inversion. An efficient and repeatable technique is proposed and tested to overcome the non-uniqueness problem; multiple inverted shear-wave velocity profiles are used in a wavenumber integration technique to generate synthetic time series resembling the geophone recordings. The similarity between synthetic and observed time series is used as an additional tool along with the similarity between the theoretical and experimental dispersion curves. The proposed method is proven to be effective through synthetic and real world examples. In these examples, the nature of the non-uniqueness is discussed and its existence is shown. Using the proposed technique, inverted velocity profiles are estimated and effectiveness of this technique is evaluated; in the synthetic example, final inverted velocity profile is compared with the initial target velocity model, and in the real world example, final inverted shear-wave velocity profile is compared with the velocity model from independent measurements in a nearby borehole. Real world example shows that it is possible to overcome the non-uniqueness and distinguish the representative velocity profile for the site that also matches well with the borehole measurements.
Download or read book Estimation of Shear Wave Velocities from P P and P S Seismic Data Using Equivalent Offset Migration written by Thais Guirigay and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Automatic Shear Wave Velocity Estimation in Bender Element Testing written by M. Finas and published by . This book was released on 2016 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamic properties of soils, such as shear wave velocity and damping, are some of critical parameters in the design of civil infrastructures subjected to vibrations from earthquakes and machine foundations. Bender element (BE) testing is used in the laboratory to determine shear wave velocity; however, there is no standard procedure for the interpretation of the results. The main limitation in BE testing is the correct estimation of the shear wave arrival time leading to uncertainty in the values of shear wave velocity. In this paper, three different automatic methods for the shear wave arrival time detection were tested. From these methods, a new procedure was proposed for the automatic determination of the shear wave arrival time using the Akaike information criterion. The method is tested on a series of bender element measurements giving less than 5 % error when the results were compared with the standard method for a signal-to-noise ratio higher than four.
