Horizontal To Vertical Spectral Ratio Research Articles

Empirical site classification of seismological stations in Chile using horizontal-to-vertical spectral ratios determined from recordings of large subduction-zone earthquakes

Despite the significant upgrade and expansion of the seismic monitoring network in Chile over the past several years, precise site characterization of a large number of seismological stations is still lacking, thus hindering a robust development of tools that could improve prediction of regional seismic hazard. To enhance our understanding of site effects in Chilean seismological data, this study classifies 136 stations using the horizontal-to-vertical spectral ratio (HVSR) method based on a database of 283 triaxial ground-motion records from 22 subduction interface earthquakes with moment magnitudes ranging from 6.8 to 8.8 that occurred between 1985 and 2015. This classification, which is based on the SESAME guidelines, divides recording stations into four types according to the shape of the station-average HVSR curve (single-peak, double-peak, broad/multiple-peak, and flat). Furthermore, the variability of the mean HVSRs with different source, path and site parameters is investigated. The derived HVSR results are also compared with those presented in previous HVSR studies for Chile. Finally, representative shear-wave velocity profiles along with parametric uncertainties are estimated for stations with a single-peak HVSR curve using a Bayesian statistical inversion framework.

Site-Specific Relationships between Bedrock Depth and HVSR Fundamental Resonance Frequency Using KiK-NET Data from Japan

It is commonly accepted that the horizontal-to-vertical spectral ratio (HVSR) technique enables the detection of the fundamental resonance frequency ($$f_{\text{HVSR}}$$) of a given site. The utility of this $$f_{\text{HVSR}}$$ is analyzed using the nonlinear regression relationships between $$f_{\text{HVSR}}$$ and bedrock depth ($$h$$). The derived relationships are mostly site-specific, so that the present paper consists of two main parts. The first is a literature review for the available empirical relationships between $$f_{\text{HVSR}}$$ and $$h$$. The aim of this part is to highlight the practical limitations of these established relationships and to make fair comparisons. The second is to generate new relationships, taking advantage of the very wide range of available lithological, geophysical, and geotechnical borehole drilling data of the 697 KiK-NET seismic stations in Japan. For this purpose, HVSR are calculated using 10,000 weak earthquakes or linear events recorded at KiK-NET stations to determine the $$f_{\text{HVSR}}$$ and correlate it with the corresponding $$h$$. The overlying layers/bedrock interface falling within sedimentary, igneous, or metamorphic layers significantly affect the derived frequency–depth relationships. In addition, these relationships are strongly reproduced by the $$V_{\text{p}} /V_{\text{s}}$$ ratio of the bedrock in the range of 1.6–2.2. Interestingly, it is found that $$f_{\text{HVSR}}$$ less than 1 Hz corresponding to $$h$$ more than 100 m leads the trend of the overall frequency–depth relationship.

A study of site response and regional attenuation in the Longmen Shan region, eastern Tibetan Plateau, SW China, from seismic recordings using the generalized inversion method

In this study, more than 1600 seismic recordings from 88 small-to-moderate earthquakes during 2009 and 2013, which were recorded at 36 seismic stations, were used to calculate the high-frequency attenuation parameter (κ0). By comparing the κ0 of six seismic stations with neighboring strong motion stations, we observed that the surficial soil layers have aggravated the high-frequency attenuation phenomenon. Besides, we found that stations located in crustal low-velocity anomaly areas maintained higher κ0 and those located in high-velocity anomaly areas tended to have lower κ0. The correlation between κ0 and S-wave velocity anomaly showed that, at the 0–10 km depth range, the κ0 values clearly decrease as the velocity anomaly increases. The generalized inversion technique (GIT) was adopted to estimate the Q(f) model of the Sichuan Basin (SB) and Songpan-Garzê Orogen (SGO), in accompaniment with the site responses of 28 seismic stations. The derived Q(f) model were similar to those obtained from previous studies. Analyses of site responses revealed that the amplification curves and levels of SB and SGO were significantly different. Then, Site responses estimated from the genetic algorithm and GIT were compared. The site response curves of most stations are similar. For stations having significantly different site responses, we investigated by comparing with the results obtained from accelerograms recorded at nearby strong motion stations by applying the horizontal-to-vertical spectral ratio (HVSR) method. The results showed that site responses obtained from the GIT were closer to those of HVSR than those of the genetic algorithm.

SVIM: A Program for Seismic Vulnerability Index Determination and HVSR Data Processing

The seismic vulnerability of an area is important to be determined in order to reduce the risk of earthquake disaster. Ones need to calculate the values of dominant frequency and amplification from the Horizontal to Vertical Spectral Ratio (HVSR). Currently existing software for HVSR data processing, Geopsy, does not include seismic vulnerability index calculation. Using Geopsy, ones also need additional software for mapping purposes. From that problem, we introduce a Graphical User Interface (GUI) program for seismic vulnerability index determination and Horizontal to Vertical Spectral Ratio (HVSR) data processing and plotting the results into a map of the study area. The program is called SVIM (Seismic Vulnerability Index of Microtremor). The program has been built using Matlab and successfully tested to 21 microtremor data points acquired in Lamteuba, Aceh Besar, Aceh, Indonesia. We compared our results with those resulted from the calculation by using Geopsy and validated using coefficient correlation. The validation shown that the correlation coefficient of seismic vulnerability index was 96,40%, the correlation coefficient of frequency was 84,19%, and the correlation coefficient of amplification was 95,80%. We conclude the SVIM program can be used for seismic vulnerability index determination and HVSR data processing. The mapping part will be included in the SVIM software so that the users can easily obtain the necessary map.

Preliminary Results of Horizontal to Vertical Spectral Ratio (HVSR) Across Lembang Fault, Bandung, Indonesia

Lembang Fault is located in the Bandung basin with is a thick sedimentary of volcanic rocks and the depositional remnants of an ancient lake. Bandung region has a dense population and infrastructure that possible to be vulnerable of seismic hazard. Based on geological studies, Lembang fault is an active fault that possibility to produce a magnitude more than 6.0. Seismic hazard estimation is one of some method to identification of hazard potential due to the Lembang Fault activity. Horizontal to Vertical Spectral Ratio (HVSR) method is one of way to seismic microzonation that identified the dominant frequency (F0). We deployed 6 seismometers across Lembang Fault area for about 3 months observation. Then we computed the seismic response that corelated with physical properties inside the basin. The variation of seismic susceptibility index around Lembang area indicates the vulnerability of seismic hazard. LEM01 and LEM06 have relatively lower of natural frequency, its about 1.22 (LEM01) and 1.49 (LEM06). The number of natural frequency indicate thick of sediment and vulnerable of seismic hazard.

Estimativa de Velocidade de Onda de Cisalhamento pela Inversão Conjunta de Curvas HVSR e f-k sob a Hipótese do Campo Difuso: um Estudo de Caso do Deslizamento de Sobradinho

Brazilian landslides are characterized as shallow, clay rich and are commonly triggered by the summer rainfalls. Therefore, the landslide geological information, such as shear surface location, has a paramount importance in their mechanism comprehension. The most adapted methods for the estimation of shear wave velocity profile are borehole stratigraphic logs or Standard Penetration Test (SPT) and Cone Penetration Test (CPT). However, the present study applied shear wave velocity estimation of Sobradinho landslide (SLS) by a joint inversion of horizontal to vertical spectral ratio (HVSR) curve and dispersion curve (DC) extracted from frequency-wavenumber (f-k) analysis of ambient noise records. HVSR curves at all the stations in the area exhibit the ubiquitous resonance frequency peak at 2 Hz indicates that at these stations the substratum is common. The f-k results for E-W component let us obtain an acceptable DC between 5 and 7 Hz range. Finally, joint inversion was interpreted based on the diffuse field assumption. The initial model was proposed to be a three-layered over a half-space. Results of joint inversion indicate that the substratum is at 24 m depth, with Vs values close to 1500 m/s. DC defines two layers overlaying the substratum: superficial layer with velocities near to 200 m/s (7m thick), and the second layer with Vs value of 1000 m/s. We think that abrupt rheology (stiffness) change between the first and the second layer could provide an evidence of the landslide re-activation during moderate to strong rainfall events. The proposed methodology will prove a reconnaissance survey for the detailed geotechnical investigations that will confirm the obtained results.

IDENTIFIKASI KELAYAKAN JEMBATAN BATANGHARI II KOTA JAMBI MENGGUNAKAN MIKROTREMOR DENGAN METODE HORIZONTAL TO VERTICAL SPECTRAL RATIO (HVSR)

The feasibility study of Batanghari II Bridge with the value of natural frequency of Bridge using microtremor has been done. The purpose of this research is to know the bridge's natural frequency value using Horizontal to Vertical Spectral Ratio (HVSR) method and to know the relative damage to Bridge. In this study Bridge as an object because, Bridge is an alternative way that connects one place with another place separated by a river or ditch which is often used by society for activity. To get the bridge's natural frequency value using Microtremor sensor which is directly placed bridged with geopsy software to process its data and using HVSR method. The result of this research is the natural bridge frequency value of 7.40441 Hz. To determine the feasibility of the bridge compared with the standard value of the bridge frequency of 7,675 Hz and stated the state of the Batanghari II bridge is still intact from the structural and the natural frequency value of the soil on the bridge buffer of 12.7489 Hz and 13.6343 Hz that the soil type is older soil. Can be said the foundation of the bridge last long.

Seismic response across the Tronto Valley (at Acquasanta Terme, AP, Marche) based on the geophysical monitoring of the 2016 Central Italy seismic sequence

Since August 2016, Central Italy has been struck by three strong earthquakes (Mw 6.0 Amatrice, Mw 5.9 Visso and Mw 6.5 Norcia). This seismic sequence resulted in ground failure, infrastructural damages and destruction of several villages. This work aims to analyze the site effects on the ground shaking along the valley of the Tronto River across the Acquasanta Terme municipality, where some historical sites were located. These suffered heavy and differentiated damage during the seismic sequence. Following the Amatrice earthquake of August 24, authors managed the deployment and acquisition of seismic stations located in an array along the valley of the Tronto River approximately 25 km from the epicenter. By recording the two stronger earthquakes (i.e., Mw 5.9 Visso and Mw 6.5 Norcia) and 30 aftershocks with varying magnitudes and also ambient vibration, the site effects were preliminarily studied using the horizontal-to-vertical spectral ratio (HVSR). Furthermore, the amplification effects on the ground motion were also evaluated with reference to the earthquakes in terms of the standard spectral ratio (SSR) and the normalized energy content, in both cases using the bottom of the valley where the seismic bedrock outcrops as a reference. The comparison between the spectral accelerations due to the two strong earthquakes and those provided by ground motion prediction equations displayed values that were usually inadequately precautionary for periods lower than 0.35 s. High spectral accelerations were detected in period ranges corresponding to those predominant for masonry structures that are available in the literature. According to the current knowledge about surface geology, the local site effects seem to have significantly influenced ground shaking along the slopes of the valley, thus producing a larger seismic effect on ancient structures with more than two floors. The results can provide useful information for undertaking a possible future microzonation study that would be able to support urban planning and seismic designs in the rebuilding phase.

Ice Thickness Estimation from Geophysical Investigations on the Terminal Lobes of Belvedere Glacier (NW Italian Alps)

: Alpine glaciers are key components of local and regional hydrogeological cycles and real-time indicators of climate change. Volume variations are primary targets of investigation for the understanding of ongoing modifications and the forecast of possible future scenarios. These fluctuations can be traced from time-lapse monitoring of the glacier topography. A detailed reconstruction of the ice bottom morphology is however needed to provide total volume and reliable mass balance estimations. Non-destructive geophysical techniques can support these investigations. With the aim of characterizing ice bottom depth, ground-penetrating radar (GPR) profiles and single-station passive seismic measurements were acquired on the terminal lobes of Belvedere Glacier (NW Italian Alps). The glacier is covered by blocks and debris and its rough topography is rapidly evolving in last years, with opening and relocation of crevasses and diffuse instabilities in the frontal sectors. Despite the challenging working environment, ground-based GPR surveys were performed in the period 2016–2018, using 70-MHz and 40-MHz antennas. The 3D ice bottom morphology was reconstructed for both frontal lobes and a detailed ice thickness map was obtained. GPR results also suggested some information on ice bottom properties. The glacier was found to probably lay on a thick sequence (more than 40 m) of subglacial deposits, rather than on stiff bedrock. Week deeper reflectors were identified only in the frontal portion of the northern lobe. These interfaces may indicate the bedrock presence at a depth of around 80 m from the topographic surface, rapidly deepening upstream. Single-station passive seismic measurements, processed with the horizontal-to-vertical spectral ratio (HVSR) method, pointed out the absence of sharp vertical contrast in acoustic impedance between ice and bottom materials, globally confirming the hypotheses made on GPR results. The obtained results have been compared with previous independent geophysical investigations, performed in 1961 and 1985, with the same aim of ice thickness estimation. The comparison allowed us to validate the results obtained in the different surveys, supply a reference base map for the glacier bottom morphology and potentially study ice thickness variations over time.

Determining Soft Layer Thickness Using Ambient Seismic Noise Record Analysis in Kota Baru, South Lampung

The local site effect of an earthquake can be calculated through an analysis of short period ambient noise, known as microtremors. The fundamental frequency and amplification factors can be identified by analyzing microtremors using the Horizontal to Vertical Spectral Ratio ( HVSR) method. This information can then be used to determine the thickness of the soft layers of sediment. This study analyzed microtremor recordings made in Kota Baru, South Lampung. The amplification factor range according to the HVSR method was 2.3 to 6.17, and the fundamental frequency range was 0.56 Hz to 1.46 Hz. Some spectrums exhibit two peaks with f 0 > f 1 . We suggest that these locations have two layers with significant impedance contrast, which aligns with the geological conditions. The center of the Kota Baru area, especially the region around T11 and T15, has a thicker soft layer than the outskirts; in the central area, the soft layer is approximately 85 to 102 meters thick. The western part of the analyzed area has a shallower soft layer of about 32 to 46 meters. The analysis indicates that the western part has less amplification because it is shallower than the other parts of the analyzed region.

Application of HVSR technique in the site effects estimation at the south of Marsa Alam city, Egypt

The Egyptian government intends to develop the current urban cities especially those located on the Egyptian shorelines, to exploit the ports of these cities to increase the rate of importing and exporting, besides establishing new communities away from the narrow River Nile valley. The southern extension of Marsa Alam city, which is situated on the Red Sea coast will take the chance of development, this city lies south of Hurgada urban city with distance of 310 Km. The area subjects to many earthquakes, particularly from Abu Dabbab active seismic zone.The aim of this paper is using the fundamental frequency term derived from Horizontal to Vertical Spectral Ratio (HVSR) method to evaluate the impact of the surface and subsurface soil sediments on seismic ground motion. Forty-four sites have been chosen for measuring the ambient noise. The obtained zonation map shows that; the lowest value of fundamental frequencies (f0 < 1 Hz) are observed mainly in the regions parallel to the sea coast, these results are compatible with the thickness of sediments in these directions. While the areas aligned at the center of the map are distinguished by a high value of fundamental frequency (f0 = 1–3.7 Hz). On the other hand, the zones extend from the northwest to southeast, west, and south of the study area, characterized by flat HVSR curves. The velocity models derived from seismic refraction and Multi-Channel Analysis of Surface Waves (MASW) approaches show occurrence of shallow bedrock at these zones. The obtained HVSR amplitude (A0) zonation map is compatible with the fundamental frequency (f0) values. Moreover, the fundamental frequency zonation map was simply interpreted taking into account the height of the buildings may be construct in the area. The outcomes will help in understanding the soil-structure resonance phenomena could be happen in the area. The risk of building-soil resonance should be taken in consideration with integration of the provisions of the Egyptian Seismic Code to overcome the probability of buildings collapsing due to the seismic activity in vicinity of the study area.

Identification ground layer structure of land subsidence sensitive area in semarang city with horizontal to vertical spectral ratio method

Semarang City is located in the northern coastal plain of Java which is geologically composed of alluvial deposits and the land subsidence sensitive area. The drilling data and various research indicates that not all layers of lithology are soft layers supporting the land subsidence. However, vertical distribution of the soft layer is still unclear. One the other side, an analysis regarding this kind of research can be done based on microtremor by using Horizontal to Vertical Spectral Ratio (HVSR). The goals of this research are to determine the layer which contribute to land subsidence based on Vs and Vp/Vs profile in Semarang City. Based Vs and Vp/Vs profile can be obtained some conclusion that the lithology layer with Vs less than 1000 meter/second and Vp/Vs less than 1.7 is the dominant lithology in high rate of land subsidence. Compare to drilling data, this lithology is composed by clay, silt and sandy clay that has the low bearing capacity.

Site characterization through combined analysis of seismic and electrical resistivity data at a site of Dhanbad, Jharkhand, India

We present the seismic site characterization study using joint modelling of Horizontal-to-Vertical Spectral-Ratio (HVSR) and Rayleigh wave-phase velocity-dispersion curves obtained from Multi-channel Simulation with One Receiver (MSOR) in a part of Dhanbad, Jharkhand, India. The joint analysis of these two different but complementary datasets puts stronger constraints on the model parameter search space than one dataset and may help us in finding more unique shear-wave velocity model. The microtremor data from 12 observation points were utilized to iteratively search 1D shear-wave velocity profiles in a predefined model search space. These 1D shear-wave velocity models were interpolated to generate a 2D shear-wave velocity profile of the site using the cubic spline method. Our results show that the high peak amplitude value of HVSR is associated with low peak-period values of HVSR at a distance of ~ 60 m from the southern end of the profile; which may indicate the presence of the Basin Edge Effect. We identified four layers based on significant changes in the shear wave velocities to a depth of ~ 60 m. The major impedance contrasts are located at average depths of ~ 13 m, ~ 40 m and ~ 55 m, respectively. These layers from the surface may indicate the presence of soil, highly weathered rock mass, moderately weathered rock and bedrock, respectively. The depth of engineering solid bedrock (Vs > 600 m/s) is found at the depth of 55 m in the south which gradually decreases to a depth of 40 m in the northern end of the profile. The shear-wave velocity (Vs 30) for this area varies between 293 and 357 m/s; which can be classified as “D-type site”. For validation and comparison of our results, the Electrical Resistivity Tomography (ERT) data were also recorded along the same traverse using Wenner and Schlumberger configurations. Our results show a significant amount of correlation between the 2D shear-wave velocity and resistivity profiles obtained from joint analysis of tremor and ERT data.

Ambient seismic noise

Rainfall-induced variations in pore water pressures are the most common sources of significant disasters like landslides, dams’ failure, and other structural collapses. This study aimed at communicating preliminary results of seasonal monitoring of the Sobradinho landslide, Brasilia, Brazil, using ambient seismic noise. The noise was recorded before, during and after the rainy season with three L4-3A seismometers (2Hz) installed in a triangular array at the landslide mass. These records were processed using horizontal to vertical spectral ratio (HVSR) technique. As it resulted from the performed analyses, two frequency (ubiquitous (2Hz) and iniquitous (&gt;2Hz)) peaks were observed over HVSR curves. The fluctuations in the secondary peak of HVSR curves are possibly related to the saturated soil properties of landslide mass in response to seasonal meteorological conditions. Experiments with a denser observation system are required to validate such a further behavior. The proposed method can be used for the monitoring of landslides as well as civil engineering structures like dams, bridges,and building.

Seismic Site Effect along Bukit Tinggi Fault Line from Microtremor Analysis

In the shallow subsurface analysis, the potential hazard is identified and evaluated through the site investigation studies which can be determined either by conducting standard penetration test, cone penetration test, and multichannel analysis of surface wave (MASW). While the three methods stated are widely established and highly reliable, the result produced is sometimes unconvincing and lack of details. In this study, the horizontal to vertical spectral ratio (HVSR) analysis method is proposed instead of the more established methods. HVSR is a technique that based on the spectral analyses of recorded ambient noise in order to estimate the site effect parameters such as fundamental frequency and the amplification factor of local soil. The HVSR method was implemented in Bukit Tinggi, Pahang, Malaysia, which known to experience several small earthquakes between 2007 to 2009. Since the earthquake in central Peninsular Malaysia is uncommon, the tremor has caused panic and requires a thorough investigation of the soil effect in the region. The work conducted is motivated by this after effects with focus on the potential fault line investigation using the spectral ratio method (HVSR). The ambient noise signal measurements were performed at 20 sites along the probable fault line in order to calculate the HVSR. Receiver array arrangement and dimensions are chosen based on the prior information about the earthquake location as experienced by the local resident. At the end of the work, the amplification spectra for the soil column is evaluated at each site location, and the nominal frequency obtained, and maximum amplitudes are contoured showing the corresponding value trends in the region.

Inversion of shallow subsurface structure from Rayleigh ellipticity beneath a station in Tangerang, Indonesia

Horizontal to vertical spectral ratio (HVSR) method has been widely used for estimating site effects and soil properties beneath a station. Recent studies have shown that it is possible to extract Rayleigh wave ellipticity from the record of seismic noise or vibration. In this study, we applied HVSR method to obtain frequency resonance and site amplification beneath a seismic station in Tangerang, Indonesia. We applied time frequency analysis (HVTFA) using a continuous wavelet transform to extract Rayleigh ellipticity. We carried out inversion from the computed Rayleigh ellipticity to estimate shallow subsurface structure. We applied non linear inversion using two layers as initial model to obtain the best fit subsurface structure. We obtained that the layer boundary between two layer model is found at depth of about 100 m.

Application of Refraction Microtremor (ReMi) to identify earthquake hazard in Kartasura, Central Java

A research of the potential hazard of earthquakes has been conducted in Kartasura, Sukoharjo regency, Central Java province, Indonesia. The research aims to know the local land response as an attempt of earthquake disaster mitigation. The method used in this research is the microtremor method through analyzing HVSR (Horizontal to Vertical Spectral Ratio) curves. PASI Seismograph 16S24-P and 3D Borehole Geophone Model GFA 60/100 are used for data acquisition at 14 locations with interval spacing between locations of 1-3 km. Based on HVSR curves, parameters have been obtained in the forms of (A0) amplitude value and dominant period (T0). The largest amplitude (A0) in location Gumpang with the value of 2,14 and the largest period (T0) in location Ngadirejo with the value of 0,43 second.

Fault detection using microtremor data (HVSR-based approach) and electrical resistivity survey

The faults and fractures are known as two of the most important parameters in earthquake occurrence. During the construction in urban areas, faults and fractures may be covered in depth and thus are not visible at the ground surface. In this context, non-invasive geophysical prospecting methods (microtremor and geoelectrical methods) and borehole data were used to detect subsurface geological structures (hidden faults) in a suburb of Shiraz in Iran. The horizontal to vertical spectral ratio (HVSR) method was used to obtain the dynamic parameters (predominant frequency and resonance amplitude) of the soil, to detect hidden faults. The results show that the abrupt changes in the sediment thickness and predominant frequencies at a specific direction (NW-SE) can be related to the displacement of a nearly vertical fault with NW-SE trend. In addition, the electrical resistivity method using continuous resistivity profiling (CRP) and Schlumberger arrays was employed to detect a hidden fault and the results were compared with previous data. The obtained results of both arrays illustrate the presence of a nearly vertical fault with NW-SE trend in the region. Comparison of all results shows that the detected faults by both methods are consistent with each other. Therefore, it can be conclusive that combination of the two methods is a useful and reliable approach to study and detect hidden faults.

Underground survey to locate weathered bedrock depth using noninvasive microtremor measurements in Jurong sedimentary formation, Singapore

Determination of bedrock depth is an essential part of design/alignment/initial planning of any infrastructure projects such as tunneling, foundations and underground utilities. Drilling a borehole to identify the depth of bedrock is often time consuming, costly and cumbersome process. In the present study, microtremor methods are used to identify the depth of weathered bedrock. Series of ambient microtremor array measurements (MAM) and 3-component microtremor methods are conducted in the weathered rock of Jurong formation in Singapore. Based on these surface wave measurements and available reference borelog information, three different approaches – (1) shear wave velocity (Vs) based approach; (2) wavelength based approach and (3) Horizontal to Vertical Spectral Ratio (HVSR) approach – are proposed to identify the depth of bedrock in the Jurong formation. For the Vs based approach, a specific reference value of Vs is suggested to estimate the depth of bedrock in the Jurong formation, which is readily determined by the Vs profile. In the wavelength based approach, an experimental dispersion curve in the form of wavelength and phase velocity is found able to identify a deviation point that can be used for predicting the corresponding bedrock depth. A relationship between the deviation point in wavelength and bedrock depth has been established. In the HVSR based approach, an empirical correlation model is formed between the natural frequency obtained from the HVSR profile and the bedrock depth information. To conclude, all three approaches can provide overall reasonable estimates in the depth of bedrock although the Vs based approach is slightly better in statistics, followed by HVSR based approach. In practice, the HVSR approach would be easy to implement in terms of field testing and analysis.

Efficiency of ambient vibration HVSR investigations in soil engineering studies: backfill study in the Algiers (Algeria) harbor container terminal

This paper deals with the contribution of the ambient vibration horizontal-to-vertical spectral ratio (HVSR) method in soil engineering studies, particularly in backfill compactness assessment. The study is based on 60 ambient vibration recordings performed in 2015 at the container terminal of Algiers harbor, subjected a year before to a geotechnical study based on 23 boreholes and 13 cone penetration tests (CPT) for backfill improvement. To highlight the contribution of the HVSR method, the results of the geotechnical and HVSR studies are first analyzed separately and then in combination. The HVSR method provides a compactness zonation map based on peak amplitude variation. Both methods define the same pattern: a southern section where the backfill is more compact, and a northern section where the backfill is less compact. This shows that the HVSR peak amplitudes are sensitive to compactness variations, which may be sufficient for qualitative zonation. In addition, with the combination of the two methods, rough estimations of shear-wave velocity and thickness of the backfill can be retrieved. This study shows that the HVSR method can be a very useful investigative tool in soil engineering studies. When the HVSR method is deployed before any conventional technique, a geotechnical investigation campaign can be significantly optimized. Moreover the combined interpretation brings complementary quantitative soil information.