scholarly journals Estimation of glacier thicknesses and basal properties using the horizontal-to-vertical component spectral ratio (HVSR) technique from passive seismic data

2017 ◽  
Vol 63 (238) ◽  
pp. 229-248 ◽  
Author(s):  
STEFANO PICOTTI ◽  
ROBERTO FRANCESE ◽  
MASSIMO GIORGI ◽  
FRANCO PETTENATI ◽  
JOSÉ M. CARCIONE
Keyword(s):  
Seismic Data ◽  
Vertical Component ◽  
Cost Effective ◽  
Spectral Ratio ◽  
Site Effect ◽  
Glacier Surface ◽  
Wide Range ◽  
Passive Seismic ◽  
Geophysical Imaging ◽  
Hvsr Technique

ABSTRACTMicrotremor measurements and the horizontal-to-vertical spectral ratio (HVSR) technique, generally used for site effect studies as well as to determine the thickness of soft sedimentary layers, can effectively be applied to map the thickness of glaciers. In this work the radio-echo sounding, geoelectric and active seismic methods, widely employed to image the earth interior, are applied to verify the reliability of the HVSR technique in Alpine and Antarctic glacial environments. The technique has been used to analyze passive seismic data from glaciers of the Adamello and Ortles-Cevedale massifs (Italy), the Bernese Oberland Alps (Switzerland) and from the Whillans Ice Stream (West Antarctica). Comparing with the results obtained from the different geophysical imaging methods, we show that the resonance frequency in the HVSR spectra correlates well with the ice thickness at the site, in a wide range from a few tens of meters to more than 800 m. The reliability of the method mainly depends on the coupling of sensors at the glacier surface and on the basal impedance contrast. This passive seismic technique offers a logistically efficient and cost effective method to map glacier and ice-sheet thicknesses. Moreover, under certain conditions, it allows reliable estimations of the basal seismic properties.

Integrated Analysis of Microtremor Horizontal to Vertical Spectral Ratio, Surface Waves Dispersion Curve, and Seismic Refraction Tomography to Estimate Weathered Layer Thickness and Seismic Vulnerability: Case Study Kalirejo Village, Kokap Sub-District, Kulon Progo Regency

2020 ◽  
Vol 22 (3) ◽  
pp. 23
Author(s):  
Anna Wahyu ◽  
Ade Filla Intan ◽  
Arddhiles Adhitama ◽  
Febrian Nur Fadhli ◽  
Ferda Elita Putri ◽  
...  
Keyword(s):  
Surface Waves ◽  
Dispersion Curve ◽  
Layer Thickness ◽  
Seismic Data ◽  
Seismic Vulnerability ◽  
Seismic Refraction ◽  
Spectral Ratio ◽  
Refraction Tomography ◽  
Passive Seismic ◽  
Weathered Layer

Subduction of Indo-Australia plate to Eurasia plate and locally active fault nearby Kulon Progo play as major source for earthquake events. After effect due to earthquake has different level of damage which depend on the magnitude and site characteristics. The horizontal-to-vertical spectral ratio (HVSR) passive seismic method is being used drastically to help in mapping the level of site vulnerability to earthquake event. HVSR analysis results help us acquire some physical values including weathered layer thickness where Vs 30 reference came from surface waves dispersion curve analysis of the MASW method as it is used as a parameter in calculating thickness value. Seismic refraction tomography is used to create subsurface model thus we may see the extent of underlying layer and its implication to earthquake event.Data measurements distribution are scattered in Kalirejo Village with the total of 63 passive seismic data, 33 MASW data, and 7 lines of seismic refraction acquisition. Some data show inadequate quality to be taken into further processing step, so data sorting activity should be carefully done. As a result, 21 of 63 passive seismic data are considered adequate to represent site physical values. Dominant frequency values ranging from 2 to 20 Hz, amplification factor varies between 1.5-12.5, and seismic vulnerability indices varies between 0.3-20. Surface waves dispersion curve inversion results are Vs 30 values ranging from 350 m/s to 980 m/s and seismic refraction tomography model shows Vp model with velocity values ranging from 0.2 to 3.2 km/s.

scholarly journals HVSR Analysis of Rockslide Seismic Signals to Assess the Subsoil Conditions and the Site Seismic Response

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Alessia Lotti ◽  
Veronica Pazzi ◽  
Gilberto Saccorotti ◽  
Andrea Fiaschi ◽  
Luca Matassoni ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Noise ◽  
Spectral Ratio ◽  
Effect Of Temperature ◽  
Precipitation Trend ◽  
Seismic Signals ◽  
Rock Falls ◽  
Time Frequency ◽  
Passive Seismic ◽  
On Line

Many Italian rock slopes are characterized by unstable rock masses that cause constant rock falls and rockslides. To effectively mitigate their catastrophic consequence thorough studies are required. Four velocimeters have been placed in the Torgiovannetto quarry area for an extensive seismic noise investigation. The study area (with an approximate surface of 200×100 m) is located near the town of Assisi (Italy) and is threatened by a rockslide. In this work, we present the results of the preliminary horizontal to vertical spectral ratio analysis of the acquired passive seismic data aimed at understanding the pattern of the seismic noise variation in case of stress state and/or weathering conditions (fluid content and microfracturing). The Torgiovannetto unstable slope has been monitored since 2003 by Alta Scuola of Perugia and the Department of Earth Sciences of the University of Firenze, after the observation of a first movement by the State Forestry Corps. The available data allowed an extensive comparison between seismic signals, displacement, and meteorological information. The measured displacements are well correlated with the precipitation trend, but unfortunately no resemblance with the seismic data was observed. However, a significant correlation between temperature data and the horizontal to vertical spectral ratio trend of the seismic noise could be identified. This can be related to the indirect effect of temperature on rock mass conditions and further extensive studies (also in the time frequency domain) are required to better comprehend this dependency. Finally, the continuous on-line data reveal interesting applications to provide near-real time warning systems for emerging potentially disastrous rockslides.

Role of the inhomogeneity angle in anisotropic attenuation analysis

Geophysics ◽  
2009 ◽  
Vol 74 (5) ◽  
pp. WB177-WB191 ◽  
Author(s):  
Jyoti Behura ◽  
Ilya Tsvankin
Keyword(s):  
Attenuation Coefficient ◽  
Seismic Data ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Attenuation Coefficients ◽  
Anisotropic Models ◽  
High Attenuation ◽  
Wide Range ◽  
Anisotropy Parameters ◽  
Attenuation Anisotropy

The inhomogeneity angle (the angle between the real and imaginary parts of the wave vector) is seldom taken into account in estimating attenuation coefficients from seismic data. Wave propagation through the subsurface, however, can result in relatively large inhomogeneity angles [Formula: see text], especially for models with significant attenuation contrasts across layer boundaries. Here we study the influence of the angle [Formula: see text] on phase and group attenuation in arbitrarily anisotropic media using the first-order perturbation theory verified by exact numerical modeling. Application of the spectral-ratio method to transmitted or reflected waves yields the normalized group attenuation coefficient [Formula: see text], which is responsible for amplitude decay along seismic rays. Our analytic solutions show that for a wide range of inhomogeneity angles, the coefficient [Formula: see text] is close to the normalized phase attenuation coefficient [Formula: see text] computed for [Formula: see text] [Formula: see text]. The coefficient[Formula: see text] can be inverted directly for the attenuation-anisotropy parameters, so no knowledge of the inhomogeneity angle is required for attenuation analysis of seismic data. This conclusion remains valid even for uncommonly high attenuation with the quality factor [Formula: see text] less than 10 and strong velocity and attenuation anisotropy. However, the relationship between group and phase attenuation coefficients becomes more complicated for relatively large inhomogeneity angles approaching so-called ‘‘forbidden directions.’’ We also demonstrate that the velocity function remains practically independent of attenuation for a wide range of small and moderate angles [Formula: see text]. In principle, estimation of the attenuation-anisotropy parameters from the coefficient [Formula: see text] requires computation of the phase angle, which depends on the anisotropic velocity field. For moderately anisotropic models, however, the difference between the phase and group directions should not significantly distort the results of attenuation analysis.

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 Comparison of site effect values obtained by HVSR and HVSRN methods for single-station measurements in Tarnówek, South-Western Poland.

2016 ◽  
Vol 5 (1) ◽  
pp. 18-27 ◽  
Author(s):  
Maciej J. Mendecki ◽  
Barbara Bieta ◽  
Mateusz Mateuszów ◽  
Paweł Suszka
Keyword(s):  
Love Wave ◽  
Seismic Waves ◽  
Seismic Station ◽  
Spectral Ratio ◽  
Site Effect ◽  
Single Station ◽  
Subsurface Layers ◽  
Loose Sediments ◽  
Hvsr Technique ◽  
The Village

Abstract This study compares the HVSR technique (Horizontal to Vertical Spectral Ratio), based on seismic event records, and the HVSRN technique (Horizontal to Vertical Spectral Ratio of Noise) using seismic noise registrations. Both methods allow us to study the amplification phenomenon of a horizontal component of seismic waves when the waves reach loose sediments in subsurface layers. The seismic data were measured at a three-component single seismic station located in the village of Tarnówek, in the Legnica-Głogów Copper District. The results of the study demonstrate that average HVSRN and HVSR maxima can be distinguished: for periods approximately 3.78 s (H/V = 6.2) and 3.969 s (H/V = 8.98) respectively. The evaluated share of the Rayleigh wave component in the recorded values was β = 0.58 and it can be suggested that the Love wave share in surface motion was insignificant. The Love wave share remains unknown.

2D Color-Intensity Representation of Ultrasonic Thickness Gauge Measurements

2020 ◽  
pp. 1192-1198
Author(s):  
M.S. Mohammad ◽  
Tibebe Tesfaye ◽  
Kim Ki-Seong
Keyword(s):  
Cost Effective ◽  
The Other ◽  
Thickness Gauge ◽  
Color Intensity ◽  
Digital Readout ◽  
Flat Surfaces ◽  
Video Cameras ◽  
Wide Range ◽  
Cost Effective Alternative ◽  
Ultrasonic Thickness

Ultrasonic thickness gauges are easy to operate and reliable, and can be used to measure a wide range of thicknesses and inspect all engineering materials. Supplementing the simple ultrasonic thickness gauges that present results in either a digital readout or as an A-scan with systems that enable correlating the measured values to their positions on the inspected surface to produce a two-dimensional (2D) thickness representation can extend their benefits and provide a cost-effective alternative to expensive advanced C-scan machines. In previous work, the authors introduced a system for the positioning and mapping of the values measured by the ultrasonic thickness gauges and flaw detectors (Tesfaye et al. 2019). The system is an alternative to the systems that use mechanical scanners, encoders, and sophisticated UT machines. It used a camera to record the probe’s movement and a projected laser grid obtained by a laser pattern generator to locate the probe on the inspected surface. In this paper, a novel system is proposed to be applied to flat surfaces, in addition to overcoming the other limitations posed due to the use of the laser projection. The proposed system uses two video cameras, one to monitor the probe’s movement on the inspected surface and the other to capture the corresponding digital readout of the thickness gauge. The acquired images of the probe’s position and thickness gauge readout are processed to plot the measured data in a 2D color-coded map. The system is meant to be simpler and more effective than the previous development.

The Future of Plasma-Based Surface Engineering Techniques in Tribology (Keynote)

2005 ◽  
Author(s):  
Allan Matthews ◽  
Adrian Leyland
Keyword(s):  
Surface Engineering ◽  
Performance Enhancement ◽  
Bulk Material ◽  
Cost Savings ◽  
Cost Effective ◽  
Ceramic Coatings ◽  
Performance Improvements ◽  
Treatment Techniques ◽  
Wide Range ◽  
Macro Scale

Over the past twenty years or so, there have been major steps forward both in the understanding of tribological mechanisms and in the development of new coating and treatment techniques to better “engineer” surfaces to achieve reductions in wear and friction. Particularly in the coatings tribology field, improved techniques and theories which enable us to study and understand the mechanisms occurring at the “nano”, “micro” and “macro” scale have allowed considerable progress to be made in (for example) understanding contact mechanisms and the influence of “third bodies” [1–5]. Over the same period, we have seen the emergence of the discipline which we now call “Surface Engineering”, by which, ideally, a bulk material (the ‘substrate’) and a coating are combined in a way that provides a cost-effective performance enhancement of which neither would be capable without the presence of the other. It is probably fair to say that the emergence and recognition of Surface Engineering as a field in its own right has been driven largely by the availability of “plasma”-based coating and treatment processes, which can provide surface properties which were previously unachievable. In particular, plasma-assisted (PA) physical vapour deposition (PVD) techniques, allowing wear-resistant ceramic thin films such as titanium nitride (TiN) to be deposited on a wide range of industrial tooling, gave a step-change in industrial productivity and manufactured product quality, and caught the attention of engineers due to the remarkable cost savings and performance improvements obtained. Subsequently, so-called 2nd- and 3rd-generation ceramic coatings (with multilayered or nanocomposite structures) have recently been developed [6–9], to further extend tool performance — the objective typically being to increase coating hardness further, or extend hardness capabilities to higher temperatures.

Sign in / Sign up

Export Citation Format

Share Document