Noninvasive Techniques for Site Characterization of Alberta Seismic Stations Based on Shear‐Wave Velocity

2017 ◽  
Vol 107 (6) ◽  
pp. 2885-2902 ◽  
Author(s):  
Joseph J. Farrugia ◽  
Sheri Molnar ◽  
Gail M. Atkinson
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Characterization ◽  
Noninvasive Techniques ◽  
Seismic Stations

Dynamic Characterization of Settled Pond Ash Using Measured Shear Wave Velocity (Vs) and SPT-N Values

2011 ◽  
Vol 2 (1) ◽  
pp. 83-97 ◽  
Author(s):  
Ravi Sankar Jakka ◽  
B. Janaki Ramaiah ◽  
G. V. Ramana
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Power Plants ◽  
Site Characterization ◽  
Response Analysis ◽  
Specific Response ◽  
Dynamic Characterization ◽  
Ash Ponds

Reclamation of abandoned ash ponds for the construction of engineered facilities like gas based power plants, light weight structures, or parking lots often requires site specific response analysis to assess associated seismic hazards in seismically active areas. This requires dynamic site characterization of the ash ponds. In the present study, shear wave velocity measurements (Vs) from SASW technique are used for in-situ dynamic site characterization of the ash ponds. Measuring Vs on the ash ponds is difficult compared to the soils, as the ash deposited in the ponds is often in a very loose state and in swampy conditions. Shear wave velocities measured at three hydraulically deposited ash ponds in Delhi are presented. An empirical correlation between SPT (N) value and measured Vs is also developed. The authors observe that the developed correlation between N and Vs is significantly different than those reported for the soils, which signifies the importance of dynamic characterization of ash ponds using shear wave measurements rather than using empirical relations developed for soils.

scholarly journals Multi-method site characterization to verify the hard rock (Site Class A) assumption at 25 seismograph stations across Eastern Canada

2021 ◽  
pp. 875529302110010
Author(s):  
Sameer Ladak ◽  
Sheri Molnar ◽  
Samantha Palmer
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hard Rock ◽  
Site Characterization ◽  
Eastern Canada ◽  
Site Class ◽  
Paleozoic Rock ◽  
Rock Types ◽  
Site Period

Site characterization is a crucial component in assessing seismic hazard, typically involving in situ shear-wave velocity ( VS) depth profiling, and measurement of site amplification including site period. Noninvasive methods are ideal for soil sites and become challenging in terms of field logistics and interpretation in more complex geologic settings including rock sites. Multiple noninvasive active- and passive-seismic techniques are applied at 25 seismograph stations across Eastern Canada. It is typically assumed that these stations are installed on hard rock. We investigate which site characterization methods are suitable at rock sites as well as confirm the hard rock assumption by providing VS profiles. Active-source compression-wave refraction and surface wave array techniques consistently provide velocity measurements at rock sites; passive-source array testing is less consistent but it is our most suitable method in constraining the rock VS. Bayesian inversion of Rayleigh wave dispersion curves provides quantitative uncertainty in the rock VS. We succeed in estimating rock VS at 16 stations, with constrained rock VS estimates at 7 stations that are consistent with previous estimates for Precambrian and Paleozoic rock types. The National Building Code of Canada uses solely the time-averaged shear-wave velocity of the upper 30 m ( VS30) to classify rock sites. We determine a mean VS30 of ∼ 1600 m/s for 16 Eastern Canada stations; the hard rock assumption is correct (>1500 m/s) but not as hard as often assumed (∼2000 m/s). Mean variability in VS30 is ∼400 m/s and can lead to softer rock classifications, in particular, for Paleozoic rock types with lower average rock VS near the hard/soft rock boundary. Microtremor and earthquake horizontal-to-vertical spectral ratios are obtained and provide site period classifications as an alternative to VS30.

Critical Insights in Laboratory Shear Wave Velocity Correlations of Clays

2021 ◽  
Author(s):  
Dania Elbeggo ◽  
Yannic Ethier ◽  
Jean-Sébastien Dubé ◽  
Mourad Karray
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Earth Pressure ◽  
Dynamic Parameter ◽  
Clay Deposits ◽  
Sample Disturbance ◽  
P Rat

Shear wave velocity is an important mechanical/dynamic parameter allowing the characterization of a soil in the elastic range (γ < 0.001 %). Thirty five existing laboratory correlations of small strains shear modulus or shear wave velocity were examined in this study and are grouped into different general forms based on their geotechnical properties. A database of 11 eastern Canadian clay deposits was selected and used for the critical insights. The effect of the coefficient of earth pressure at rest was also examined. A range of variation for each general form of correlation was determined to take the plasticity index and void ratio values of investigated sites into account. The analysis shows a significant scatter in normalized shear wave velocity values predicted by existing correlations and raises questions on the applicability of these correlations, especially for eastern Canadian clays. New correlations are proposed for Champlain clays based on laboratory measurement of shear wave velocity using the piezoelectric ring actuator technique, P-RAT, incorporated in consolidation cells. An analysis of P-RAT results reveals the sample disturbance effect and suggests an approach to correct the effect of disturbance on laboratory shear wave velocity measurements. The applicability of the proposed correlations, including the disturbance correction, is validated by comparison with in situ measurements using multi-modal analysis of surface waves (MMASW).

Characterization of the engineering geological units with the shear wave velocity parameter: statistical analysis of data from the Italian seismic microzonation studies

2021 ◽  
Author(s):  
Gino Romagnoli ◽  
Gianluca Carbone ◽  
Stefano Catalano ◽  
Massimo Cesarano ◽  
Stefania Fabozzi ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Working Group ◽  
Seismic Microzonation ◽  
Geophysical Data ◽  
Borehole Logs ◽  
Geological Units

&lt;p&gt;The availability of a unique database, where all data of the seismic microzonation studies carried out in about 1900 municipalities of Italy (https://www.webms.it/) are achieved with a standardized format, allowed statistical elaborations in terms of subsoil parameters. In particular, we analysed borehole logs and geophysical data in order to characterize them with the shear wave velocity (Vs) vertical profile, and the code of standardized engineering geological units, according to the Italian Guidelines for Seismic Microzonation (Seismic Microzonation Working Group, 2015; 2018). The Vs parameter, extracted from about 3700 geophysical surveys, was correlated to the engineering geological units from the borehole logs, with 1meter step. The correlation was performed for about 1700 available Down-Hole (DH) surveys and for about 2000 Multichannel Analyses of Surface Waves (MASW). For these latter, we selected only MASW surveys located near boreholes, no more than 100 m away. The statistical analysis on the distribution and dispersion of Vs parameter allowed to calculate the Vs values related to the mode, mean, median, standard deviation, first quartile, third quartile, minimum and maximum, and the trend with depth of Vs for each engineering geological unit. Validation with external datasets (e.g. Italian Vs30 map, Mori et al., 2020) demonstrates that the characterization of engineering geological units in term of Vs, based on velocity profiles extracted by the Italian seismic microzonation dataset, allow to reliably characterize the engineering geological model, where no geophysical data are available. Statistics of subsoil parameters will represent a fundamental tool for computing local seismic ground motion parameters (e.g. PGA, H&lt;sub&gt;SM&lt;/sub&gt;) in the areas not covered by seismic microzonation studies.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;- Mori, F., Mendicelli, A., Moscatelli, M., Romagnoli, 796 G., Peronace, E., Naso, G., 2020. A new Vs30 map for Italy based on the seismic microzonation dataset. Engineering Geology 275, 105745. https://doi.org/10.1016/j.enggeo.2020.105745.&lt;/p&gt;&lt;p&gt;- Seismic Microzonation Working Group, 2015. Guidelines for Seismic Microzonation http://www.protezionecivile.gov.it/httpdocs/cms/attach_extra/GuidelinesForSeismicMicrozonation.pdf&lt;/p&gt;&lt;p&gt;- Seismic Microzonation Working Group, 2018. Standard di rappresentazione e archiviazione informatica Versione 4.1. http://www.protezionecivile.gov.it/attivita-rischi/rischio-sismico/attivita/commissione-supporto-monitoraggio-studi-microzonazione/standard-rappresentazione-archiviazione-informatica&lt;/p&gt;

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