scholarly journals The horizontal-to-vertical spectral ratio and its applications

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Rong Xu ◽  
Lanmin Wang
Keyword(s):  
Shear Wave ◽  
Velocity Structure ◽  
Site Response ◽  
Mineral Exploration ◽  
Spectral Ratio ◽  
Site Effect ◽  
Research Area ◽  
Site Classification ◽  
S Wave ◽  
Borehole Data

AbstractThe horizontal-to-vertical spectral ratio (HVSR) has been extensively used in site characterization utilizing recordings from microtremor and earthquake in recent years. This method is proposed based on ground pulsation, and then it has been applied to both S-wave and ambient noise, accordingly, in practical application also different. The main applications of HVSR are site classification, site effect study, mineral exploration, and acquisition of underground average shear-wave velocity structure. In site response estimates, the use of microtremors has been introduced long ago in Japan, while it has long been very controversial in this research area, as there are several studies reporting difficulties in recognizing the source effects from the pure site effects in noise recordings, as well as discrepancies between noise and earthquake recordings. In practice, the most reliable way is the borehole data, and the theoretical site response results were compared with the HVSR using shear wave to describe site response. This paper summarizes the applications of the HVSR method and draws conclusions that HVSR has been well applied in many fields at present, and it is expected to have a wider application in more fields according to its advantages.

scholarly journals A Quantitative Site-Specific Classification Approach Based on Affinity Propagation Clustering

2020 ◽  
Author(s):  
Sayed Moustafa ◽  
Farhan Khan ◽  
Mohamed Metwaly ◽  
Eslam A.Elawadi ◽  
Nassir Al-Arifi
Keyword(s):  
Urban Areas ◽  
Clustering Algorithm ◽  
Site Response ◽  
Seismic Hazard Assessment ◽  
Spectral Ratio ◽  
Site Effect ◽  
Affinity Propagation ◽  
Site Classification ◽  
Site Specific ◽  
Affinity Propagation Clustering

Abstract Investigations made to evaluate the site effect characteristics and develop a reliable site classification scheme have received the paramount importance for the planning of urban areas and for a reliable site-specific seismic hazard assessment. This paper presents a new approach for site classification based on affinity propagation (AP) along with a selected set of representative horizontal to vertical spectral ratio (HVSR) curves inside King Saud University (KSU) campus. Measurements of the ambient vibrations were performed to cover the entire campus area by about 307 stations with 20 minutes recording length and sample rate of 128 Hz for each station to satisfy the criteria for reliable and unambiguous HVSR results. Predominant period values were used for identifying of site response and subsequent site classification. Empirical equations from the literature relating frequency of HVSR peak to average shear wave velocity in the upper 30m, commonly used as a proxy for site classification, were found to be unreliable, making site classification difficult. To overcome this problem, Affinity propagation clustering algorithm is used. The obtained results illustrated that microtremors spectral ratios can be remarkably robust tool in determining site effects. The survey results concluded to the preliminary seismic site classification map for the mapped area, which would be useful for future safe design of structures. Finally, the results presented in this study are encouraging prolongation of this type of study in other parts of Saudi Arabia using the microtremors data and site response functions.

scholarly journals Rapid assessment of S-wave profiles from the inversion of multichannel

1998 ◽  
Vol 41 (1) ◽  
Author(s):  
G. A. Tselentis ◽  
G. Delis
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Structure ◽  
Rapid Assessment ◽  
Detailed Knowledge ◽  
S Wave ◽  
Surface Wave Dispersion ◽  
Wave Profiles ◽  
Shear Wave Velocity Structure

The importance of detailed knowledge of the shear-wave velocity structure of the upper geological layers was recently stressed in strong motion studies. In this work we describe an algorithm which we have developed to infer the 1D shear wave velocity structure from the inversion of multichannel surface wave dispersion data (ground-roll). Phase velocities are derived from wavenumber-frequency stacks while the inversion process is speeded up by the use of Householder transformations. Using synthetic and experimental data, we examined the applicability of the technique in deducing S-wave profiles. The comparison of the obtained results with those derived from cross-hole measurements and synthesized wave fields proved the reliability of the technique for the rapid assessment of shear wave profiles during microzonation investigations.

A Method to Directly Estimate S-Wave Site Amplification Factor from Horizontal-to-Vertical Spectral Ratio of Earthquakes (eHVSRs)

2020 ◽  
Vol 110 (6) ◽  
pp. 2892-2911
Author(s):  
Eri Ito ◽  
Kenichi Nakano ◽  
Fumiaki Nagashima ◽  
Hiroshi Kawase
Keyword(s):  
Amplification Factor ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Site Amplification ◽  
Body Waves ◽  
Correction Function ◽  
Site Classification ◽  
Frequency Range ◽  
S Wave ◽  
Site Amplification Factor

ABSTRACT The main purpose of the site classification or velocity determination at a target site is to obtain or estimate the horizontal site amplification factor (HSAF) at that site during future earthquakes because HSAF would have significant effects on the strong-motion characteristics. We have been investigating various kinds of methods to delineate the S-wave velocity structures and the subsequent HSAF, as precisely as possible. After the advent of the diffuse field concept, we have derived a simple formula based on the equipartitioned energy density observed in the layered half-space for incident body waves. In this study, based on the diffuse field concept, together with the generalized spectral inversion technique (GIT), we propose a method to directly estimate the HSAF of the S-wave portion from the horizontal-to-vertical spectral ratio of earthquakes (eHVSRs). Because the vertical amplification is included in the denominator of eHVSR, it cannot be viewed as HSAF without correction. We used GIT to determine both the HSAF and the vertical site amplification factor (VSAF) simultaneously from strong-motion data observed by the networks in Japan and then deduced the log-averaged vertical amplification correction function (VACF) from VSAFs at a total of 1678 sites in which 10 or more earthquakes have been observed. The VACF without a category has a constant amplitude of about 2 in the frequency range from 1 to 15 Hz. By multiplying eHVSR by VACF, we obtained the simulated HSAF. We verified the effectiveness of this correction method using data from observation sites not used in the aforementioned averaging in the frequency range from 0.12 to 15 Hz.

Estimation Study on Shear Wave Velocity of Seabed Using GRNN

2014 ◽  
Vol 580-583 ◽  
pp. 264-267
Author(s):  
Sheng Jie Di ◽  
Zhi Gang Shan ◽  
Xue Yong Xu
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Analysis ◽  
Site Response ◽  
Estimation Method ◽  
Response Analysis ◽  
Generalized Regression Neural Network ◽  
Engineering Practice ◽  
Site Classification

Characterization of the shear wave velocity of soils is an integral component of various seismic analysis, including site classification, hazard analysis, site response analysis, and soil-structure interaction. Shear wave velocity at offshore sites of the coastal regions can be measured by the suspension logging method according to the economic applicability. The study presents some methods for estimating the shear wave velocity profiles in the absence of site-specific shear wave velocity data. By applying generalized regression neural network (GRNN) for the estimation of in-situ shear wave velocity, it shows good performances. Therefore, this estimation method is worthy of being recommended in the later engineering practice.

An Empirical Geotechnical Seismic Site Response Procedure

2001 ◽  
Vol 17 (1) ◽  
pp. 65-87 ◽  
Author(s):  
Adrián Rodríguez-Marek ◽  
Jonathan D. Bray ◽  
Norman A. Abrahamson
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Classification System ◽  
Soil Depth ◽  
Site Response ◽  
Dynamic Stiffness ◽  
Evaluation Procedure ◽  
Site Classification ◽  
Seismic Site Response

A simplified empirically based seismic site response evaluation procedure that includes measures of the dynamic stiffness of the surficial materials and the depth to bedrock as primary parameters is introduced. This geotechnical site classification scheme provides an alternative to geologic-based and shear wave velocity-based site classification schemes. The proposed scheme is used to analyze the ground motion data from the 1989 Loma Prieta and 1994 Northridge earthquakes. Period-dependent and intensity-dependent spectral acceleration amplification factors for different site conditions are presented. The proposed scheme results in a significant reduction in standard error when compared with a simpler “rock vs. soil” classification system. Moreover, results show that sites previously grouped as “rock” should be subdivided as competent rock sites and weathered soft rock/shallow stiff soil sites to reduce uncertainty in defining site-dependent ground motions. Results also show that soil depth is an important parameter in estimating seismic site response. The standard errors resulting from the proposed site classification system are comparable with those obtained using the more elaborate code-based average shear-wave velocity classification system.

scholarly journals A Comparative Study on the VS30 and N30 Based Seismic Site Classification in Kahramanmaras, Turkey

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Dalia Munaff Naji ◽  
Muge K. Akin ◽  
Ali Firat Cabalar
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Soil Structure ◽  
Site Response ◽  
Dead Sea ◽  
Site Classification ◽  
Earthquake Hazards ◽  
Class D ◽  
Average Shear

Assessment of seismic site classification (SSC) using either the average shear wave velocity (VS30) or the average SPT-N values (N30) for upper 30 m in soils is the simplest method to carry out various studies including site response and soil-structure interactions. Either the VS30- or the N30-based SSC maps designed according to the National Earthquake Hazards Reduction Program (NEHRP) classification system are effectively used to predict possible locations for future seismic events. The main goal of this study is to generate maps using the Geographic Information System (GIS) for the SSC in Kahramanmaras city, influenced by both East Anatolian Fault and Dead Sea Fault Zones, using both VS30 and N30 values. The study also presents a series of GIS maps produced using the shear wave velocity (VS) and SPT-N values at the depths of 5 m, 10 m, 15 m, 20 m, and 25 m. Furthermore, the study estimates the bed rock level and generates the SSC maps for the average VS values through overburden soils by using the NEHRP system. The VS30 maps categorize the study area mainly under class C and limited number of areas under classes B and D, whereas the N30 maps classify the study area mainly under class D. Both maps indicate that the soil classes in the study area are different to a high extent. Eventually, the GIS maps complied for the purpose of urban development may be utilized effectively by engineers in the field.

scholarly journals Estimation of S-Wave Velocity Profiles at Lima City, Peru Using Microtremor Arrays

2014 ◽  
Vol 9 (6) ◽  
pp. 931-938 ◽  
Author(s):  
Selene Quispe ◽  
◽  
Kosuke Chimoto ◽  
Hiroaki Yamanaka ◽  
Hernando Tavera ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Velocity Structure ◽  
Site Effect ◽  
Site Amplification ◽  
Velocity Profiles ◽  
S Wave ◽  
Phase Velocity Dispersion ◽  
Seismic Recording ◽  
Phase Velocity Dispersion Curve ◽  
Alluvial Material

Microtremor exploration was performed around seismic recording stations at five sites in Lima city, Peru in order to know the site amplification at these sites. The Spatial Autocorrelation (SPAC) method was applied to determine the observed phase velocity dispersion curve, which was subsequently inverted in order to estimate the 1-D S-wave velocity structure. From these results, the theoretical amplification factor was calculated to evaluate the site effect at each site. S-wave velocity profiles at alluvial gravel sites have S-wave velocities ranging from ∼500 to ∼1500 m/s which gradually increase with depth, while Vs profiles at sites located on fine alluvial material such as sand and silt have Swave velocities that vary between ∼200 and ∼500 m/s. The site responses of all Vs profiles show relatively high amplification levels at frequencies larger than 3 Hz. The average transfer function was calculated to make a comparison with values within the existing amplification map of Lima city. These calculations agreed with the proposed site amplification ranges.

scholarly journals Shallow Subsurface Structure in the Hualien Basin and Relevance to the Damage Pattern and Fault Rupture during the 2018 Hualien Earthquake

2020 ◽  
Vol 110 (6) ◽  
pp. 2939-2952
Author(s):  
Masumi Yamada ◽  
Ikuo Cho ◽  
Chun-Hsiang Kuo ◽  
Che-Min Lin ◽  
Ken Miyakoshi ◽  
...  
Keyword(s):  
Soil Structure ◽  
Velocity Structure ◽  
Spectral Ratio ◽  
Peak Ground Velocity ◽  
Subsurface Structure ◽  
The South ◽  
S Wave ◽  
Shallow Subsurface ◽  
Subsurface Soil ◽  
Large Peak

ABSTRACT The 2018 Mw 6.4 Hualien earthquake generated a large peak-to-peak velocity of over 2  m/s, with a period of 3 s at the south end of the Milun fault, which resulted in the collapse of five buildings. To investigate the shallow subsurface soil structure and evaluate possible effects on the ground motion and building damage, we performed microtremor measurements in the Hualien basin. Based on the velocity structure jointly inverted from both Rayleigh-wave dispersion curves and microtremor horizontal-to-vertical spectral ratio data, we found that the shallow subsurface structure generally deepens from west to east. Close to the Milun fault, the structure becomes shallower, which is consistent with faulting during the 2018 earthquake and the long-term tectonic displacement. There is no significant variation for the site conditions in the north–south direction that can explain the large peak ground velocity in the south. As a result of the dense measurements in the heavily damaged area, where three high-rise buildings totally collapsed, these locations have the average S-wave velocity of the upper 30 m (AVS30) values and are relatively high compared to the more distant area from the Meilun River. This is somewhat unusual, because lower AVS30 values indicating softer ground conditions are expected close to the river. We did not find any characteristic subsurface soil structure that may contribute to the building collapses. The large 3 s pulse was probably generated by source effects, rather than subsurface soil amplification.

A site effect study in Acapulco, Guerrero, Mexico: Comparison of results from strong-motion and microtremor data

1992 ◽  
Vol 82 (2) ◽  
pp. 642-659 ◽  
Author(s):  
Carlos Gutierrez ◽  
Shri Krishna Singh
Keyword(s):  
Seismic Waves ◽  
Site Response ◽  
Nonlinear Behavior ◽  
Strong Motion ◽  
Site Effect ◽  
Seismic Gap ◽  
S Wave ◽  
Data Set ◽  
S Waves ◽  
The City

Abstract The city of Acapulco is located near or above the mature seismic gap of Guerrero along the Mexican subduction zone. With the purpose of studying the character of strong ground motion on soft sites, four digital accelerographs have been installed in the city on such sites. These instruments have been in operation since 1988. Two additional instruments, part of the Guerrero Accelerograph Array, are located on hard sites in the area. One of these, VNTA, has been in operation since 1985 and the other, ACAN, since 1989. These stations have recorded several earthquakes. We use data from eight events (4.2 ≤ M ≤ 6.9) to study spectral amplification of seismic waves at the soft sites with respect to VNTA. The S waves are amplified by a factor of 6 to 25 at the soft sites in a fairly broad range of frequencies; both the amplification and the frequency band over which it occurs depend upon the site. Although the largest earthquake in our data set (M = 6.9) gave rise to a peak horizontal acceleration exceeding 0.3 g at one of the soft sites, no clear evidence of nonlinear behavior of the subsoil is found. Spectral amplifications of S-wave coda are very similar to those of S waves. We also measured microtremors at the strong-motion sites. The microtremor spectra were interpreted, using reasonable assumptions, to test the feasibility of this technique in reproducing the spectral amplifications observed during earthquakes. Our results show that only a rough estimate of site response can be obtained from this technique, at least in Acapulco; caution is warranted in its use elsewhere.

Upper mantle shear-wave velocity structure in the Japan region

1974 ◽  
Vol 64 (2) ◽  
pp. 355-374
Author(s):  
K. L. Kaila ◽  
V. G. Krishna ◽  
Hari Narain
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Upper Mantle ◽  
Inflection Point ◽  
Velocity Structure ◽  
Epicentral Distance ◽  
S Wave ◽  
Transition Depth ◽  
Shear Wave Velocity Structure

abstract The upper mantle shear-wave velocity structure in the Japan region has been determined from S travel times of 101 earthquakes with focal depths varying from 40 to 600 km, using a new analytical method given by Kaila (1969). In southwestern Japan, the S velocity obtained as 4.35 km/sec at a 40-km depth remains almost constant to a depth of about 170 km. The shear velocity in northeastern Japan increases linearly from 4.42 km/sec at a depth of 45 km to 4.62 km/sec at a depth of 145-km. For central Japan, the S velocity determined as 4.41 km/sec at a 40-km depth increases linearly to 4.55 km/sec at a 170-km depth, followed by a slight decrease in the velocity gradient, with velocity still increasing linearly to 4.68 km/sec at a depth of 345 km. At this transition depth, there is a first-order velocity discontinuity, the velocity increasing from 4.68 to 4.92 km/sec. Below this depth, velocity again increases linearly from 4.92 to 5.04 km/sec at a depth of 600 km. The shear velocities at depths between 440 to 640 km in Japan are found to be extremely low in comparison to those of Jeffreys (1939), Gutenberg (1959), and Arnold (1967). These low S velocities can explain satisfactorily the late S arrivals from shallow earthquakes between Δ = 20° to 30° as observed in the Japanese region. Graphs have been drawn to show the variation with depth of Δ*, the epicentral distance to the inflection point, Δ1, Δ2, (Δ2 − Δ1), ptrue =∂T/∂Δ, and αS = (T − pΔ) at the inflection point as obtained from the S-wave travel-time analysis.

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