A Robust Method for Assessing 3-D Topographic Site Effects: A Case Study at the LSBB Underground Laboratory, France

2012 ◽  
Vol 28 (3) ◽  
pp. 1097-1115 ◽  
Author(s):  
Emeline Maufroy ◽  
Víctor M. Cruz-Atienza ◽  
Stéphane Gaffet
Keyword(s):  
Site Effects ◽  
Amplification Factor ◽  
Three Dimensional ◽  
Reference Method ◽  
Spectral Ratio ◽  
Site Effect ◽  
Point Sources ◽  
Ratio Method ◽  
Double Couple

By means of three-dimensional (3-D) numerical simulations, including the Laboratoire Souterrain à Bas-Bruit (LSBB) topography, we carefully analyze site effects assessments yielded by two approaches: the classical site to reference spectral-ratio method (SRM) and the statistical median reference method (MRM). We show for both isotropic and double-couple point sources that a 94% reduction in the number of stations of a regularly spaced array yields MRM site-effect estimates within 5% of those obtained from the absolute regional median, and within 20% using a 98% station reduction with irregularly located sites. In contrast, the SRM yielded site-effect overestimates greater than 50% in some areas and up to 100% in specific sites, which makes the MRM much more robust than the SRM. We determined a 33% probability to exceed an amplification factor of 2, and an 8% probability to exceed a factor of 3 due to topography in the surroundings of the sharpest summit of the LSBB area.

Use of reciprocity theorem for obtaining Rayleigh wave radiation patterns

1966 ◽  
Vol 56 (4) ◽  
pp. 925-936 ◽  
Author(s):  
I. N. Gupta
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Three Dimensional ◽  
Reciprocity Theorem ◽  
Point Sources ◽  
Dimensional Case ◽  
Wave Radiation ◽  
Radiation Patterns ◽  
Homogeneous Half Space ◽  
Double Couple

abstract The reciprocity theorem is used to obtain Rayleigh wave radiation patterns from sources on the surface of or within an elastic semi-infinite medium. Nine elementary line sources first considered are: horizontal and vertical forces, horizontal and vertical double forces without moment, horizontal and vertical single couples, center of dilatation (two dimensional case), center of rotation, and double couple without moment. The results are extended to the three dimensional case of similar point sources in a homogeneous half space. Haskell's results for the radiation patterns of Rayleigh waves from a fault of arbitrary dip and direction of motion are reproduced in a much simpler manner. Numerical results on the effect of the depth of these sources on the Rayleigh wave amplitudes are shown for a solid having Poisson's ratio of 0.25.

scholarly journals Microseismic Wave Measurements to Detect Landslides in Bengkulu Shore with Attenuation Coefficient and Shear Strain Indicator

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Muhammad Farid
Keyword(s):  
Shear Strain ◽  
Attenuation Coefficient ◽  
Peak Ground Acceleration ◽  
Amplification Factor ◽  
Spectral Ratio ◽  
Coastal Areas ◽  
Ratio Method ◽  
Ground Acceleration ◽  
Wave Measurements ◽  
Microseismic Data

<p>It has been detected that the condition of landslides that occurred in Bengkulu Shore can change the position of the shoreline. This research aimed to: (1) calculate of shear strain (γ) and attenuation coefficient (ά) value  based on microseismic data in coastal areas that experienced landslides; (2) determine the correlation between levels of landslides with  shear strain  and attenuation coefficient value (3) determine the correlation between the shear strain and attenuation coefficient value. Microseismic data were processed and analyzed quantitatively using the Horizontal to Vertical Spectral Ratio method (HVSR) to obtain the ground vibrations resonance frequency (<em>f<sub>o</sub></em>) and amplification factor (<em>A</em>). Shear strain value was calculated from the of <em>f<sub>o</sub></em>, <em>A</em> and Peak Ground Acceleration (<em>α<sub>max</sub></em>) value. Peak Ground Acceleration value was calculated based on 100-year period of recorded earthquake data.  Attenuation coefficient was calculated based on the equation (2). The results of study showed that the value of shear strain in the coastal areas varied from 1.0 × 10<sup>-4</sup> to 3.6 × 10<sup>-3</sup>,  in accordance with the conditions of landslides. The attenuation coefficient value varied from 0.005 to 0.020.  Level of landslides that occurred varied from moderate, to very severe. There was a tendency that the more severe the landslide level,  the greater the shear strain and attenuation coefficient value were.</p>

Estimating the site effects in Luoyang basin using horizontal-to-vertical spectral ratio method from a short-period dense array

2018 ◽  
Vol 31 (5-6) ◽  
pp. 272-280
Author(s):  
Yujuan Tan ◽  
◽  
Yunhao Wei ◽  
Yonghong Duan ◽  
Fuyun Wang ◽  
...  
Keyword(s):  
Site Effects ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Dense Array ◽  
Short Period ◽  
Spectral Ratio Method

Site effect evaluation using spectral ratios with only one station

1993 ◽  
Vol 83 (5) ◽  
pp. 1574-1594
Author(s):  
Javier Lermo ◽  
Francisco J. Chávez-García
Keyword(s):  
Transfer Function ◽  
Rayleigh Waves ◽  
Site Effects ◽  
Spectral Ratio ◽  
Site Effect ◽  
Reference Station ◽  
Effect Evaluation ◽  
Spectral Ratios ◽  
S Wave ◽  
Dominant Period

Abstract The spectral ratio technique is a common useful way to estimate empirical transfer function to evaluates site effects in regions of moderate to high seismicity. The purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station. The technique, originally proposed by Nakamura to analyze Rayleigh waves in the microtremor records, is presented briefly and it is discussed why it may be applicable to study the intense S-wave part in earthquake records. Results are presented for three different cities in Mexico: Oaxaca, Oax., Acapulco, Gro., and Mexico City. These cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city. Each time we compare the results of Nakamura's technique with standard spectral ratios. In all three cases the results are very encouraging. We conclude that, if site effects are caused by simple geology, a first estimate of dominant period and local amplification level can be obtained using records of only one station.

scholarly journals Site Effect Potential in Fond Parisien, in the East of Port-au-Prince, Haiti

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 175
Author(s):  
Sophia Ulysse ◽  
Dominique Boisson ◽  
Valmy Dorival ◽  
Kelly Guerrier ◽  
Claude Préptit ◽  
...  
Keyword(s):  
Site Effects ◽  
Geophysical Methods ◽  
Spectral Ratio ◽  
Site Effect ◽  
Seismic Properties ◽  
Fine Sediments ◽  
The North ◽  
Seismic Motion ◽  
Sediment Deposits ◽  
Hvsr Technique

In the frame of a Belgo-Haitian cooperation project (PIC 2012–2016), a study of the local seismic hazard was performed in Fond Parisien, an area located on the foothills of the “Massif de la Selle”, along the easternmost portion of the Enriquillo Plantain Garden Fault (EPGF). The H/V Spectral Ratio (HVSR) technique was applied to study the resonance frequency of the target areas and the azimuth of the wave field. The amplification factors were estimated using Standard Spectral Ratios obtained from earthquakes recorded by a temporary seismic network. Using the Multichannel Analysis of Surface Waves method, the seismic properties of the shallow layers were investigated. Then, the results were compared to local Electrical Resistivity Tomography data. These results highlight, in the central part of Fond Parisien, an E-W zone of low velocities ranging from 200 m/s to 450 m/s and low resistivities between 1 Ωm and 150 Ωm, due both to tectonic folding of the rocks and to the presence of sediment filling in the eastern part. The latter is marked, in most of its sites, by resonances at one or more frequencies ranging from 0.7 Hz to 20 Hz. Infiltration and storage of brackish water in the underground layers also contribute to the low resistivity values. With the noise HVSR data, we also evidenced a significant influence of the EPGF on the main orientation of the seismic wavefield as in the vicinity of this fault, the azimuths are parallel to the orientation of the fault. Overall, the results also show greater potential for site effects in the block formed by the sedimentary basin and strong amplification of the seismic ground motion for the sites bordering the basin to the north and west. We interpret the amplification in the north and south-west as probably originating from topographic irregularities locally coupled with sediment deposits, while in the center of the western part, the site effects could be explained by the presence of folds and related weakened and softened rocks. By the integration of several geophysical methods, we could distinguish areas where it is possible to build more safely. These zones are located in the northern part and encompass Quisqueya Park and neighboring areas as well as the village “La Source” in the southern part. In the rest of Fond Parisien, i.e., in the more central and eastern parts, buildings should be erected with caution, taking into account the nearby presence of the EPGF and the influence of fine sediments on the amplification of the seismic motion.

scholarly journals Microseismic Wave Measurements to Detect Landslides in Bengkulu Shore with Attenuation Coefficient and Shear Strain Indicator

2016 ◽  
Vol 1 ◽  
Author(s):  
Muhammad Farid
Keyword(s):  
Shear Strain ◽  
Attenuation Coefficient ◽  
Peak Ground Acceleration ◽  
Amplification Factor ◽  
Spectral Ratio ◽  
Coastal Areas ◽  
Ratio Method ◽  
Ground Acceleration ◽  
Wave Measurements ◽  
Microseismic Data

<p>It has been detected that the condition of landslides that occurred in Bengkulu Shore can change the position of the shoreline. This research aimed to: (1) calculate of shear strain (γ) and attenuation coefficient (ά) value  based on microseismic data in coastal areas that experienced landslides; (2) determine the correlation between levels of landslides with  shear strain  and attenuation coefficient value (3) determine the correlation between the shear strain and attenuation coefficient value. Microseismic data were processed and analyzed quantitatively using the Horizontal to Vertical Spectral Ratio method (HVSR) to obtain the ground vibrations resonance frequency (<em>f<sub>o</sub></em>) and amplification factor (<em>A</em>). Shear strain value was calculated from the of <em>f<sub>o</sub></em>, <em>A</em> and Peak Ground Acceleration (<em>α<sub>max</sub></em>) value. Peak Ground Acceleration value was calculated based on 100-year period of recorded earthquake data.  Attenuation coefficient was calculated based on the equation (2). The results of study showed that the value of shear strain in the coastal areas varied from 1.0 × 10<sup>-4</sup> to 3.6 × 10<sup>-3</sup>,  in accordance with the conditions of landslides. The attenuation coefficient value varied from 0.005 to 0.020.  Level of landslides that occurred varied from moderate, to very severe. There was a tendency that the more severe the landslide level,  the greater the shear strain and attenuation coefficient value were.</p>

Site Effect Investigation using Spectral Ratio Method in Muara Labuh Geothermal Field, Indonesia

2013 ◽  
Author(s):  
Prima Wira K. Wardhani ◽  
Bambang T. Sumbodo ◽  
Wiwit Suryanto ◽  
Novianto
Keyword(s):  
Spectral Ratio ◽  
Site Effect ◽  
Geothermal Field ◽  
Ratio Method ◽  
Spectral Ratio Method

scholarly journals Ground motion prediction model for southeastern México removing site effects using the Earthquake horizontal-to-vertical ratio (EHVSR)

2020 ◽  
Vol 59 (4) ◽  
pp. 257-272
Author(s):  
Javier Lermo-Samaniego
Keyword(s):  
Ground Motion ◽  
Site Effects ◽  
Spectral Ratio ◽  
Site Effect ◽  
Prediction Equation ◽  
Reliable Estimate ◽  
Motion Prediction ◽  
Ground Motion Prediction ◽  
Attenuation Model ◽  
Hypocentral Distance

We propose a ground motion attenuation model (ground motion prediction equation, GMPE) for Southeast Mexico. We suppress site effects obtained from Earthquake Horizontal to Vertical Spectral Ratio (EHVSR) as a reliable estimate of site effects. (The attenuation model was built as a function of magnitude and hypocentral distance)). We used 86 seismic events with 5.0 ? Mw ? 8.2 (earthquake recordings for the 9/7/2017, Mw8.2 Tehuantepec earthquake are included), and distances between 52 ? R ? 618 km. They were recorded in nine stations of the Engineering Institute of the National Autonomous University of Mexico (II-UNAM) accelerometric network installed in the states of Chiapas, Oaxaca, Tabasco and Veracruz. Site effects at each of these stations were estimated by using the average EHVSR. Then, by means of this spectral ratio the site effects were suppressed at each station and for every record. This work points out the need to remove the site effect in the GMPE. The current models overestimate this effect. 

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

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