Site Response Characteristics of Simeulue Island, Indonesia as Inferred from H/V Spectral Ratio of Ambient Noise Records

Estimation of site effects is an essential part of local seismic hazard and risk assessment, especially in densely populated urban areas. The goal of this study is to assess the site response variability in the city of Lucerne (Central Switzerland), located in a basin filled with unconsolidated deposits. Even though it is a low-to-moderate seismicity area, the long-term seismic risk cannot be neglected, in particular, because the region was struck by strong earthquakes in the past (i.e. Mw 5.9 in 1601).To determine the spatial distribution of the soil response in the test area, we combined earthquake and ambient noise recordings using the Hybrid Standard Spectral Ratio method (SSRh) introduced by Perron et al. (2018). In the first step, we installed a temporary seismic network to record ground-motion from low-magnitude or distant earthquakes. At selected urban sites inside the sedimentary basin, the dataset was used to estimate the amplification factors with respect to a rock site using the Standard Spectral Ratio approach (SSR - Borcherdt, 1970). Then, a survey including several dozens of densely distributed single-station ambient noise measurements was performed which enabled us to estimate the basin response variability relative to the seismic stations of the temporary seismic network. Finally, we corrected the noise-based evaluation using the SSR amplification functions. To verify the useability of the presented technique in the Lucerne area, we applied the SSRh method also to the temporary stations, the resulting amplification functions largely coincide with the SSR curves. However, the daily variability of the noise wavefield due to human activities can slightly affect the results. We will also discuss the influence of the station distribution and density of the temporary network deployment.The amplification model for the Lucerne area estimated using the SSRh method shows consistency with geological data. The results indicate that seismic waves can be amplified up to 10 times in some parts of the basin compared to the rock site. The highest amplification factors are observed for frequencies between 0.8 and 2Hz. This means a local significant increase in seismic hazard.The presented work is a part of a detailed site response analysis study for the Lucerne area, considering 2D and 3D site effects and potential non-linear soil behaviour. This PhD project is performed in the framework of the Horizon 2020 ITN funded project URBASIS-EU, which focuses on seismic hazard and risk in urban areas.REFERENCESBorcherdt, R.D., 1970. Effects of local geology on ground motion near San Francisco Bay. Bull. Seismol. Soc. Am. 60, 29&#8211;61.Perron, V., G&#233;lis, C., Froment, B., Hollender, F., Bard, P.-Y., Cultrera, G., Cushing, E.M., 2018. Can broad-band earthquake site responses be predicted by the ambient noise spectral ratio? Insight from observations at two sedimentary basins. Geophys. J. Int. 215, 1442&#8211;1454.

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Preliminary results of the analysis of site response across the San Gabriel and San Bernardino Basins using ambient-noise spectral-ratio measurements

10.1190/segam2018-2998524.1 ◽

2018 ◽

Author(s):

Anisha Tyagi ◽

Margaret Grenier ◽

Rachel Kreuziger ◽

Jacob Kays ◽

Jascha Polet

Keyword(s):

Ambient Noise ◽

Site Response ◽

Spectral Ratio ◽

Preliminary Results ◽

San Bernardino

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The dynamic response of coseismic liquefaction-induced ruptures associated with the 2019 Mw 5.8 Mirpur, Pakistan, earthquake using HVSR measurements

The Leading Edge ◽

10.1190/tle40080590.1 ◽

2021 ◽

Vol 40 (8) ◽

pp. 590-600

Author(s):

Muhammad Younis Khan ◽

Syed Ali Turab ◽

Liaqat Ali ◽

Muhammad Tahir Shah ◽

S. M. Talha Qadri ◽

...

Keyword(s):

Site Response ◽

Hazard Analysis ◽

Active Regions ◽

Cost Effective ◽

Spectral Ratio ◽

Shallow Subsurface ◽

Response Characteristics ◽

Liquefaction Hazard ◽

Collapsed Buildings ◽

The Impact

The Mirpur area of Pakistan was severely damaged by extensive coseismic liquefaction following an earthquake of Mw 5.8 on 24 September 2019. Villages within 6 km of the epicenter were adversely affected due to extensive coseismic liquefaction-induced surface and shallow subsurface deformations. The earthquake affected all types of buildings and key infrastructure (e.g., the Upper Jhelum Canal and the main Jhelum–Jatlan road). Field observations and associated effects are presented, including horizontal-to-vertical spectral ratio (HVSR) data sets acquired from three sites to evaluate the site response characteristics of the liquefaction-affected soil profiles. As a result, rupture events strongly influenced spectral features (amplitude and frequency) and site-specific 1D shear-wave velocity profiles at sites S1 and S2. The dynamic behavior of HVSRs across ruptures at sites S1 and S2 corresponds to varied levels of seismic amplification, demonstrating the impact of liquefaction-induced ruptures of seismic origin on the site response that have not been reported previously in the literature. The consistent HVSR pattern of well-established high-frequency peaks at site S3 adjacent to partially damaged to completely collapsed buildings of different types further indicates the susceptibility of potential liquefaction hazard. These results agree with the surface liquefaction signatures in the field, revealed by inverted electrical resistivity tomography models in terms of liquified sand plugs, clay lenses and associated fractures, and increasing trends of radon concentration in the soil with decrease in the distance toward ruptures. Additionally, the successful application of HVSR as a cost-effective and speedy tool attests to the potential of the proposed approach in furnishing complementary information for better assessment of liquefaction hazards in the developing world, where financial constraints are a major issue. This can help with seismic hazard analysis and mitigation in the Mirpur area and may have applications in other seismically active regions of the world.

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Centrifuge Model Tests of the Effect of the Ground Motion Coherence Function on the Amplification of a Saturated Soil–Water Site

Geofluids ◽

10.1155/2021/5575433 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Xijun Song ◽

Juan Liu ◽

Jingyan Lan ◽

Ting Wang

Keyword(s):

Soil Water ◽

Site Response ◽

Coherence Function ◽

Spectral Ratio ◽

Saturated Soil ◽

Order Mode ◽

Overlying Water ◽

First Order ◽

Site Model ◽

Frequency Phase

Two sets of dynamic centrifugal model tests were designed and implemented in this study: the overlying waterless surface and the water-covered surface. Based on the use of the El Centro waves with different intensities as the base input, the seismic time history at the surface of two sets of free site models was obtained. According to the results of the site response at two sets of the free site surface obtained with a traditional spectral ratio, the coherence functions at the surface and the base were used to modify the traditional spectral ratio for analysis and to evaluate the effect of the ground motion coherence function for site amplification. The modal characteristics and the amplification effect of a typical saturated soil water free site were summarized at the same time. The results showed that the ground response results of the two groups of typical free site centrifugal models were greatly influenced by the coherence function. In the low frequency phase, the coherence function of the amplification spectrum of the site response decreased significantly, while in the high frequency phase, the decrease trend decreased. The coherence function had a significant effect on the first-order mode of the free site. The first-order mode frequency and the amplification factor of a typical free site could be identified effectively. Compared with the saturated land free site model, the saturated soil water free site model had higher-order modes due to the overlying water. It was shown that the overlying water, as part of a complex medium system, could be ignored in the site response and basic cycle estimation.

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Feasibility of the use of Microtremors in Estimating Site Response during Earthquakes: Some Test Cases in Italy

Earthquake Spectra ◽

10.1193/1.1585643 ◽

1991 ◽

Vol 7 (4) ◽

pp. 551-561 ◽

Cited By ~ 8

Author(s):

Antonio Rovelli ◽

Shri K. Singh ◽

Luca Malagnini ◽

Alessandro Amato ◽

Massimo Cocco

Keyword(s):

Ground Motion ◽

Seismic Waves ◽

Site Response ◽

Spectral Ratio ◽

Test Cases ◽

Spectral Ratios ◽

Cultural Noise ◽

Maximum Amplification

We explore the feasibility of the use of microtremors in estimating the amplification of seismic waves at soft sites in Italy. Microtremors were measured at three soft sites and nearby hard sites at night when the cultural noise was minimum. These soft sites were selected as those showing the largest amplifications of ground motion during earthquakes as compared to the records on the hard sites or with respect to the predicted spectra. We compare the soft-to-hard site microtremor spectral ratios with the corresponding acceleration spectral ratios. A rough estimate of the shape and level of spectral amplification is obtained from the microtremor data in all three cases. However, the details of the soft-to-hard site spectral ratio are not reproduced and some differences appear in (a) the frequency at which the maximum amplification occurs, and (b) the bandwidth of the significant amplification. More testing of the method is needed before its wider use for microzonation in Italy can be recommended.

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Hard as a rock? Looking for typical and atypical reference sites in the Greek network

10.5194/egusphere-egu21-13659 ◽

2021 ◽

Author(s):

Olga-Joan Ktenidou ◽

Faidra Gkika ◽

Erion-Vasilis Pikoulis ◽

Christos Evangelidis

Keyword(s):

Ground Motion ◽

Site Response ◽

Time Budget ◽

Strong Motion ◽

General Rule ◽

Spectral Ratio ◽

Reference Sites ◽

Motion Models ◽

Ground Motion Variability

Although it is nowadays desirable and even typical to characterise site conditions in detail at modern recording stations, this is not yet a general rule in Greece, due to the large number and geographical dispersion of stations. Indeed, most of them are still characterised merely through geological descriptions or proxy-based parameters, rather than through in-situ measurements. Considering: 1. the progress made in recent years with sophisticated ground motion models and the need to define region-specific rock conditions based on data, 2. the move towards large open-access strong-motion databases that require detailed site metadata, and 3. that Greek-provenance recordings represent a significant portion of European seismic data, there are many reasons to improve our understanding of site response at these stations. Moreover, it has been shown recently in several regions that even sites considered as rock can exhibit amplification and ground motion variability, which has given rise to more scientific research into the definition of reference sites. For Greece, in-situ-characterisation campaigns for the entire network would impose unattainable time/budget constraints; so, instead, we implement alternative empirical approaches using the recordings themselves, such as the horizontal-to-vertical spectral ratio technique and its variability. We present examples of 'well-behaved', typical rock sites, and others whose response diverges from what is assumed for their class.&#160;

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Earthquake site response estimation: A weak-motion case study

Bulletin of the Seismological Society of America ◽

10.1785/bssa0820062283 ◽

1992 ◽

Vol 82 (6) ◽

pp. 2283-2307

Author(s):

E. H. Field ◽

K. H. Jacob ◽

S. E. Hough

Keyword(s):

Site Response ◽

Spectral Ratio ◽

Large Degree ◽

One Dimensional ◽

Loma Prieta Earthquake ◽

Cross Spectrum ◽

Downward Bias ◽

Dimensional Models ◽

The Cross ◽

Input Motion

Abstract Using weak-motion recordings of aftershocks of the 1989 Loma Prieta earthquake recorded in Oakland, California, near the failed Nimitz Freeway, two methods have been applied to estimate the site response of an alluvium site and three mud-over-alluvium sites. The first estimate is the traditional spectral ratio, and the second utilizes the cross spectrum. Recordings obtained at a nearby bedrock site are used as estimates of the sediment site input motions. While the two site response estimates produce similar peaks and troughs, there is an approximate factor of 2 difference in amplitudes. This discrepancy is evidence that there is a much greater level of noise than would be expected from the pre-event ambient noise. We interpret this as signal-generated noise produced by scattering from heterogeneities, which causes the true sediment site input to differ significantly from the bedrock site recording. Given this level of noise, the cross-spectrum estimate suffers a severe downward bias (by a factor of 2 in this study) and should probably not be used when the input motion is estimated from a bedrock site recording. The spectral-ratio estimates are relatively unbiased, but the level of noise introduces a large degree of uncertainty. Therefore, inferences about site response from individual spectral ratios should probably be avoided. On the other hand, ensemble averages of the estimates significantly reduce the scatter to reveal resonances that agree quite well in frequency and overall shape with those of one-dimensional models whose parameters were determined independently. A discrepancy of higher observed amplitudes than predicted by theory remains unexplained but most likely results from the effects of boundary layer topography, which are not accounted for by the simple one-dimensional models.

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Directional variations of site response in a landslide area using ambient noise analysis via Nakamura’s and polarization-based method

Soil Dynamics and Earthquake Engineering ◽

10.1016/j.soildyn.2020.106492 ◽

2021 ◽

Vol 141 ◽

pp. 106492

Author(s):

Mohsen Kazemnia Kakhki ◽

Vincenzo Del Gaudio ◽

Sadegh Rezaei ◽

Webe João Mansur

Keyword(s):

Ambient Noise ◽

Site Response ◽

Noise Analysis ◽

Landslide Area

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Multiple Geophysical Techniques for Investigation and Monitoring of Sobradinho Landslide, Brazil

Sustainability ◽

10.3390/su11236672 ◽

2019 ◽

Vol 11 (23) ◽

pp. 6672 ◽

Cited By ~ 2

Author(s):

Yawar Hussain ◽

Martin Cardenas-Soto ◽

Salvatore Martino ◽

Cesar Moreira ◽

Welitom Borges ◽

...

Keyword(s):

Ambient Noise ◽

Geophysical Methods ◽

Spectral Ratio ◽

Dynamic Monitoring ◽

Physical Parameters ◽

Sliding Surface ◽

Time Duration ◽

Geophysical Techniques ◽

Short Time

Geophysical methods have a varying degree of potential for detailed characterization of landslides and their dynamics. In this study, the application of four well-established seismic-based geophysical techniques, namely Ambient Noise Interferometry (ANI), Horizontal to Vertical Spectral Ratio (HVSR), Multi-Channel Analysis of Surface Waves (MASW) and Nanoseismic Monitoring (NM), were considered to examine their suitability for landslide characterization and monitoring the effect of seasonal variation on slope mass. Furthermore, other methods such as Ground Penetrating Radar (GPR) and DC Resistivity through Electrical Resistivity Tomography (ERT) were also used for comparison purpose. The advantages and limitations of these multiple techniques were exemplified by a case study conducted on Sobradinho landslide in Brazil. The study revealed that the geophysical characterization of the landslide using traditional techniques (i.e., GPR, ERT and MASW) were successful in (i) the differentiation between landslide debris and other Quaternary deposits, and (ii) the delineation of the landslide sliding surface. However, the innovative seismic based techniques, particularly ambient noise based (HVSR and ANI) and emitted seismic based (NM), were not very effective for the dynamic monitoring of landslide, which might be attributed to the short-time duration of the data acquisition campaigns. The HVSR was also unsuccessful in landslide site characterization i.e., identification of geometry and sliding surface. In particular, there was no clear evidence of the light seasonal variations, which could have been potentially detected from the physical parameters during the (short-time) ambient noise and microseismic acquisition campaigns. Nevertheless, the experienced integration of these geophysical techniques may provide a promising tool for future applications.

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