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 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 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 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 Variation of Shear Wave Velocity with SPT N Values in the City of Sharjah written by Niamatullah Haji Bismillah and published by . This book was released on 2014 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Modern building codes require the evaluation of a shear wave velocity profile of the foundation soils for a dynamic analysis of structures and sites to occur. Wave velocities are typically evaluated by conducting laboratory and field tests. Due to the rapid pace of development in the UAE,consultants often rely on shear wave velocity (VS) obtained from correlations of shear wave velocity (VS) with N values from Standard Penetration Tests (SPT). Significant variations in previous studies that predict wave velocities justifythis new study in order to develop correlations specific to the region and applicable to areas of similar geology. These variations can be attributed to factors such as biases in conducting field tests and shortcomings in seismic techniques. This study presents the correlations developed between wave velocity and N values for the city of Sharjah by performing seismic tests in various locations. The velocity profiles are evaluated by using vertical geophones that are traditionally used, as well as, horizontal geophones to evaluate their ability in calculating similar profiles. The analysis of surface waves for velocity evaluation is preferred due to its ability in delineating hidden layers of weaker velocities and for the better characterization of shallow depths from the generation of higher frequency phases. The benefits of using a seismic technique based on surface waves are presented and the results of the regression of VS-N pairs are compared with the findings of previous studies discussed here. The effect of using horizontal and vertical geophones on the results is evaluated in order to validate the theoretical basis of particle motion during the propagation of surface waves. The results indicate many previous models underestimate the wave velocity as function of N valuesas compared to the proposed model, especially at N values larger than 15. Most recent studies, however, tend to agree with the prediction model of this study;only one model significantly overestimates the shear wave velocity. The velocity profiles computed from horizontal and vertical geophones agree, indicating that the theoretical basis of elliptical particle motion with both horizontal and vertical components in the propagation of surface waves is valid. "--Abstract.

Download or read book Shear wave Exploration written by S. H. Danbom and published by . This book was released on 1987 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: The application of shear (S) waves in seismic petroleum exploration is in a critical stage of development. This book outles the past technologies, the current ones and the possible future ones.The current efforts in S- wave exploration described in this paper consist of investigation of problems in S- wave recording for example surface wave interference, processing for example, reflectiion static time corrections and interpretation for example correlation of reflections on P- and S- wave seismic sections. It also looks at a recent development that will advance S- wave exploration considerably.

Download or read book Measurement and Use of Shear Wave Velocity for Evaluating Dynamic Soil Properties written by Richard D. Woods and published by . This book was released on 1985 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shear wave Velocity Compilation for Northridge Strong motion Recording Sites written by Roger D. Borcherdt and published by . This book was released on 2002 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Development of Uncertainty consistent One dimensional Shear Wave Velocity Profiles from Inversion of Surface Wave Dispersion Data written by Joseph Philip Vantassel and published by . This book was released on 2021 with total page 318 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 An Improved Framework for the Analysis and Dissemination of Seismic Site Characterization Data at Varying Resolutions written by Sean Kamran Ahdi and published by . This book was released on 2018 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most commonly used parameter for representing site conditions for ground motion studies is the time-averaged shear-wave velocity in the upper 30 m, or VS30. While it is preferred to compute VS30 from a directly measured shear-wave velocity (VS) profile using in situ geophysical methods, this information is not always available. One major application of VS30 is the development of ergodic site amplification models, for example as part of ground motion model (GMM) development projects, which require VS30 values for all sites. The first part of this dissertation (Chapters 2-4) addresses the development of proxy-based models for estimation of VS30 for application in subduction zone regions. These procedures are applied at 6433 strong motion recording stations (SMSs) for the NGA-Subduction project, which has the goal of developing GMMs for global subduction zone (SZ) earthquakes. Relatively detailed VS30 prediction models are developed in this thesis for application to the Cascadia SZ in the Pacific Northwest (PNW) region and the Alaska/Aleutian SZs. These are the portions of the United States at greatest risk to seismic hazards from subduction zone earthquakes. In these regions, only 8% of SMSs have measured VS30 values. Proxy-based VS30 statistical models based on in situ measurements were developed from information including surficial geology, topographic gradient (i.e. "slope"), and geomorphic terrain categories. The PNW and Alaska studies result in proxy-based VS30 models based on (1) a hybrid of generalized surficial geologic groups conditioned on topographic slope, and (2) geomorphic terrain categories. With 928 measured VS30 values available in the PNW, statistically robust proxy models were developed, with 18 generally well-populated geology groups assigned logarithmic mean and standard deviation VS30 values, six of which are conditioned on topographic slope, and certain groups reflecting glacial and volcanic geology. Additionally, 13 of a possible 16 terrain classes were well-populated, and these were also assigned VS30 statistical moments. Ultimately, due to strong correlation between the two proxies but an overall lower dispersion of model residuals for the hybrid geology-slope proxy compared to the terrain proxy, use of the hybrid slope-geology proxy model was recommended. For Alaska, a different approach was required, as most geology groups were not well populated. In these cases, VS30 data from the PNW were borrowed for similar geologic groups, residuals analysis for Alaska-only and combined Alaska-PNW group moments were computed, and bias was considered in model prediction. The standard deviations of such groups' model predictions were increased by adding an epistemic uncertainty in the mean to reflect the uncertainty in adopting a proxy for use outside of its original intended region of application. Other SZ regions included in NGA-Subduction project rely on regional VS30 prediction models developed previously or concurrent with this project by others (i.e., Japan, Taiwan, New Zealand, and Chile), or required development of procedures as part of the present work to assign VS30 where regional models are unavailable (i.e., Central America/Mexico and South America outside of Chile). The VS data collection effort for the latter two regions resulted in a general lack of measured VS30 data and proxy information, precluding robust proxy model development. As such, an existing geomorphic terrain class proxy model was borrowed from California, with an additional assigned epistemic uncertainty in the mean to account for increased uncertainty in implementing proxy-based models outside of their original intended region of use. Basin depth terms are also provided for VS profiles that exceed velocity thresholds (e.g., 1.0 or 2.5 km/s) or estimated for regions where 3D seismic velocity models exist (e.g., Cascadia, Japan, New Zealand, and Taiwan). A similar study was undertaken in Iran to populate a site database with VS30 values for a ground motion modeling. Analysis of measured Iranian VS data and comparison of within-group moments for geology and terrain proxies in other regions around the world showed that the Iranian VS30 values did not vary much across different geology groups, a possible sign that the seismic refraction velocity data lacked adequate resolution in the upper 30 m to provide accurate VS30. To mitigate this, a third approach for proxy development was formally developed, in which moments for similar geologic groups were borrowed from the PNW and California, averaged, and used for assignment to Iranian strong motion stations, again with care to factor in inter-regional epistemic uncertainty. This work defined the framework for the assignments of VS30 to the aforementioned data-poor regions of Central America, Mexico, and South America. The second part of this dissertation (Chapter 6) concerns the development of the United States Community VS Profile Database (PDB), a major multi-institutional effort to develop an open-access VS profile database for sites in the United States. The data described herein was collected from diverse sources that include consulting engineering reports from private industry, university research reports and other documents, federal open-file and similar reports, California state agency documents, and reports provided by electric utilities for selected sites. All data are strictly within the public domain, but much of it was for practical purposes inaccessible to most potential users. The VS data sources encompass a wide array of geophysical techniques, are presented in many different formats, and are accompanied by widely divergent supplementary data, including P-wave velocities, geotechnical logs and other data, and penetration test data. A relational database schema of sufficient breadth and flexibility was developed to accommodate this diverse data set. The data are digitized and otherwise prepared in the standardized format specified by the database schema. A web interface (www.uclageo.com/VPDB) was developed for data query, visualization, and download. This resource is anticipated to be useful to geotechnical engineers and engineering seismologists for diverse applications in research and industry practice.

Download or read book Geostatic Stress State Evaluation by Directional Shear Wave Velocities with Application Towards Geocharacterization at Aiken SC written by Taeseo Ku and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Evaluations of stress history and the geostatic state of stress of soils are ascertained on the basis of field geophysical measurements that provide paired complementary types of shear waves. It is well-established that multiple types of shear waves occur in the ground due to their directional and polarization properties. The shear wave velocity (Vs) provides the magnitude of small strain stiffness (G0) which depends on effective stress, void ratio, stress history, and other factors (cementation, age, saturation). Herein, this study examines a hierarchy of shear wave modes with different directions of propagation and particle motion from in-situ geophysical tests (HH, VH, and HV) and laboratory bender element data. A special compiled database from well-documented worldwide sites is assembled where full profiles of stress state, stress history, and several paired modes of Vs profiles have been obtained from crosshole tests (CHT), downhole tests (DHT), and rotary crosshole (RCHT). Reference profiles of the lateral stress coefficient (K0) are available from direct in-situ measurements (self-boring pressuremeter, hydrofracture, and push-in spade cells). Stress history is documented in terms of yield stress ratio (YSR) from consolidation testing and careful engineering geology studies. A methodology is developed that relates both the YSR and K0 to stiffness ratios obtained from directional shear wave velocities. In further efforts, means to extract reliable shear wave profiles from continuous downhole testing via a new GT autosource and seismic piezocone testing are outlined and applied to results from three test sites in Windsor/VA, Norfolk/VA, and Richmond/BC.\r : A driving impetus to this research involves the geologic conditions at the US Dept. of Energy's Savannah River Site (SRS) in South Carolina. Here, the overburden soils in the upper 60 m depths consist of very old Miocene and Eocene sediments, primarily layered deposits of sands, clayey sands, silty sands, and interbedded clays which exhibit an apparent and unusual stress history profile. Special geologic conditions include the dissolutioning of old calcareous sediments (Santee Formation) at depths of 40 to 50 m below grade, similar to karstic limestone deposits. As a consequence, caves, voids, and infilled soft soil zones occur within the soil matrix at these elevations, probably resulting in localized collapse of the overlying soil column. Based on conventional laboratory and in-situ test data conducted during geotechnical investigations at SRS, available interpretative relationships for assessing the soil stress history and geostatic stress states show scattered and inconsistent results. Complications abound in the systematic assessments of these geomaterials due to effects of very old ageing, cementation, desiccation, and diagenesis, as evidenced by unusual in-situ shear wave velocity profiles that decrease in magnitude with depth, as measured by CHT and DHT. Based on the findings of this study, it is recommended that a new set of shear wave velocity measurements be made at SRS to obtain HH waves (and complementary VH waves) needed for an independent assessment of YSR in the upper soil column.

Download or read book Determination of Shear wave Velocity Profiles from Surface Rayleigh Seismic Waves written by and published by . This book was released on 2003 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shear Wave Profile Database Augmentation with Information from California Bridge Sites and Database Utilization for VS Prediction Model Validation written by Ching-Yu Chuang and published by . This book was released on 2021 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Shear Wave Velocity Profile Database (VSPDB) was developed in prior work to archive and disseminate data from sites with shear wave velocity (VS) profiles, including seismic velocities, soil stratigraphic information, and penetration resistances. The VSPDB is organized as a structure query language (SQL) relational database and is populated to date mainly with data from California. The first major component of this project was to augment the database with information from 30 bridge sites in California with 251 borehole logs and 88 VS profiles. The information was obtained from the California Department of Transportation (Caltrans) and translated into unified machine-readable formats via a computed program (UNIFY). The second major component of this project was related to VS prediction models. A number of models were reviewed and conditioned on penetration resistance, depth, and soil type parameters. A major distinguishing characteristic of available models is whether they allow for different levels of VS and penetration resistance scaling with depth (or overburden stress). I selected a model by Brandenberg et al. (2010) for validation against VSPDB data, which includes differential scaling features. That SPT-based model was developed and recommended by Building Seismic Safety Council for VS prediction for California sites. Querying of the VSPDB led to 2453 data pairs (1415 for sand, 641 for clay, and 397 for silt) consisting of all predictor variables (penetration resistance, depth, soil type) and VS values. Plots of data trends relative to model predictions were examined, and residuals analyses were performed to investigate potential model biases and whether the data requires different levels of scaling with N60-values or overburden pressure. The results indicate that the model overpredicts VS for all three soil types (sand, clay, and silt) but mainly for clay. The scaling of VS with N60 is stronger from the data for sand but not the other soil types. No adjustments to overburden scaling were required. Adjusted model coefficients based on the data analyses are provided.

Download or read book Shear wave Velocities in Parkway Basin Wainuiomata from Refraction Microtremor Surface Wave Dispersion written by A. E. Kaiser and published by . This book was released on 2006 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High density Shallow Shear Wave Velocity Characterisation of the Urban Christchurch New Zealand Region written by Christopher McGann and published by . This book was released on 2015 with total page 59 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: