Journal articles: 'HVSR inversion'

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Neukirch, Maik, Antonio García-Jerez, Antonio Villaseñor, Francisco Luzón, Jacques Brives, and Laurent Stehly. "On the Utility of Horizontal-to-Vertical Spectral Ratios of Ambient Noise in Joint Inversion with Rayleigh Wave Dispersion Curves for the Large-N Maupasacq Experiment." Sensors 21, no. 17 (September 4, 2021): 5946. http://dx.doi.org/10.3390/s21175946.

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Horizontal-to-Vertical Spectral Ratios (HVSR) and Rayleigh group velocity dispersion curves (DC) can be used to estimate the shallow S-wave velocity (VS) structure. Knowing the VS structure is important for geophysical data interpretation either in order to better constrain data inversions for P-wave velocity (VP) structures such as travel time tomography or full waveform inversions or to directly study the VS structure for geo-engineering purposes (e.g., ground motion prediction). The joint inversion of HVSR and dispersion data for 1D VS structure allows characterising the uppermost crust and near surface, where the HVSR data (0.03 to 10s) are most sensitive while the dispersion data (1 to 30s) constrain the deeper model which would, otherwise, add complexity to the HVSR data inversion and adversely affect its convergence. During a large-scale experiment, 197 three-component short-period stations, 41 broad band instruments and 190 geophones were continuously operated for 6 months (April to October 2017) covering an area of approximately 1500km2 with a site spacing of approximately 1 to 3km. Joint inversion of HVSR and DC allowed estimating VS and, to some extent density, down to depths of around 1000m. Broadband and short period instruments performed statistically better than geophone nodes due to the latter’s gap in sensitivity between HVSR and DC. It may be possible to use HVSR data in a joint inversion with DC, increasing resolution for the shallower layers and/or alleviating the absence of short period DC data, which may be harder to obtain. By including HVSR to DC inversions, confidence improvements of two to three times for layers above 300m were achieved. Furthermore, HVSR/DC joint inversion may be useful to generate initial models for 3D tomographic inversions in large scale deployments. Lastly, the joint inversion of HVSR and DC data can be sensitive to density but this sensitivity is situational and depends strongly on the other inversion parameters, namely VS and VP. Density estimates from a HVSR/DC joint inversion should be treated with care, while some subsurface structures may be sensitive, others are clearly not. Inclusion of gravity inversion to HVSR/DC joint inversion may be possible and prove useful.

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Rong, Mianshui, Xiaojun Li, and Lei Fu. "Improvement of the objective function in the velocity structure inversion based on horizontal-to-vertical spectral ratio of earthquake ground motions." Geophysical Journal International 224, no. 1 (July 21, 2020): 1–16. http://dx.doi.org/10.1093/gji/ggaa347.

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SUMMARY Given the improvements that have been made in the forward calculations of seismic noise horizontal-to-vertical spectral ratios (NHVSRs) or earthquake ground motion HVSRs (EHVSRs), a number of HVSR inversion methods have been proposed to identify underground velocity structures. Compared with the studies on NHVSR inversion, the research on the EHVSR-based inversion methods is relatively rare. In this paper, to make full use of the widely available and constantly accumulating strong-motion observation data, we propose an S-wave HVSR inversion method based on diffuse-field approximation. Herein, the S-wave components of earthquake ground motion recordings are considered as data source. Improvements to the objective function has been achieved in this work. An objective function with the slope term is introduced. The new objective function can mitigate the multisolution phenomenon encountered when working with HVSR curves with multipeaks. Then, a synthetic case is used to show the verification of the proposed method and this method has been applied to invert underground velocity structures for six KiK-net stations based on earthquake observations. The results show that the proposed S-wave EHVSR inversion method is effective for identifying underground velocity structures.

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Neukirch, Maik, Antonio García-Jerez, Antonio Villaseñor, Francisco Luzón, Mario Ruiz, and Luis Molina. "Horizontal-to-Vertical Spectral Ratio of Ambient Vibration Obtained with Hilbert–Huang Transform." Sensors 21, no. 9 (May 10, 2021): 3292. http://dx.doi.org/10.3390/s21093292.

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The Horizontal-to-Vertical Spectral Ratio (HVSR) of ambient vibration measurements is a common tool to explore near surface shear wave velocity (Vs) structure. HVSR is often applied for earthquake risk assessments and civil engineering projects. Ambient vibration signal originates from the combination of a multitude of natural and man-made sources. Ambient vibration sources can be any ground motion inducing phenomena, e.g., ocean waves, wind, industrial activity or road traffic, where each source does not need to be strictly stationary even during short times. Typically, the Fast Fourier Transform (FFT) is applied to obtain spectral information from the measured time series in order to estimate the HVSR, even though possible non-stationarity may bias the spectra and HVSR estimates. This problem can be alleviated by employing the Hilbert–Huang Transform (HHT) instead of FFT. Comparing 1D inversion results for FFT and HHT-based HVSR estimates from data measured at a well studied, urban, permanent station, we find that HHT-based inversion models may yield a lower data misfit χ2 by up to a factor of 25, a more appropriate Vs model according to available well-log lithology, and higher confidence in the achieved model.

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Chávez-García, Francisco J., Miguel Rodríguez, Edward H. Field, and Denis Hatzfeld. "Topographic site effects. A comparison of two nonreference methods." Bulletin of the Seismological Society of America 87, no. 6 (December 1, 1997): 1667–73. http://dx.doi.org/10.1785/bssa0870061667.

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Abstract We present an experimental study of topographic site effects. The data we use come from an experiment carried out during the summer of 1989, in Epire (northern Greece). Ten digital stations recorded a total of 68 small earthquakes. A recent article (Chávez-García et al., 1996) presented a comparison between site effects determined using horizontal-to-vertical spectral ratios (HVSR) for this data set and theoretical modeling. In this note, we compare the topographic site effects determined using HVSR with another, independent, experimental estimate: a generalized inversion scheme (GIS). Neither HVSR nor GIS depend on the availability of a reference site. We obtain a very good agreement between both estimates of topographic site effects for both horizontal components. Our results support the use of HVSR to determine topographic site effects.

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Zuhaera, Andina, Suharno Suharno, and Bagus Sapto Mulyatno. "INVERSI MIKROTREMOR UNTUK PROFILING KECEPATAN GELOMBANG GESER (Vs) DAN MIKOROZONASI KABUPATEN BANDUNG." Jurnal Geofisika Eksplorasi 5, no. 2 (January 17, 2020): 3–14. http://dx.doi.org/10.23960/jge.v5i2.25.

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Bandung Regency is a highland area with a slope between 0 - 8%, 8-15% to above 45%. The district is located at an altitude of 768 m above sea level with the northern region higher than the south. The purpose of this study was to determine the distribution of Vs30 waves and determine the impact of damage due to wave amplification (amplification). To minimize the impact of this earthquake identification can be done including a survey to map soil characteristics in response to earthquake shocks using the seismic Horizontal to Vertical Spectral Ratio (HVSR) method. Based on the results of the study, the distribution of the dominant frequency values, Bandung Regency was identified as having hard and soft rock soil and having solid clay with a thickness of tens of meters. The amplification value in Bandung Regency has a value (0 Ao 6) which can be categorized that Bandung Regency has a small impact on the earthquake. The difference between the results of inversion processing and HVSR is due to the assumption that the layer inversion is heterogeneous and the HVSR layer is homogeneous.

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Perdhana, Radhitya, and Budi Eka Nurcahya. "Seismic microzonation based on microseismic data and damage distribution of 2006 Yogyakarta Earthquake." E3S Web of Conferences 76 (2019): 03008. http://dx.doi.org/10.1051/e3sconf/20197603008.

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The 2006 Yogyakarta earthquake caused an extensive damage to various areas of Yogyakarta regions. The damage distribution indicates the role of local site effects during the earthquake as the damage extended from Bantul Regency in Yogyakarta Province to Klaten Regency in Central Java. Microzonation based on the damage distribution is then carried out using Horizontal-to-Vertical Spectral Ratio (HVSR) technique. From this technique, amplification factor and predominant frequency can be obtained and then spatially mapped. Inversion can also be conducted to the HVSR curves to infer the geological condition of the study area.

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Thomas, Amanda M., Zack Spica, Miles Bodmer, William H. Schulz, and Joshua J. Roering. "Using a Dense Seismic Array to Determine Structure and Site Effects of the Two Towers Earthflow in Northern California." Seismological Research Letters 91, no. 2A (January 8, 2020): 913–20. http://dx.doi.org/10.1785/0220190206.

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Abstract We deployed a network of 68 three-component geophones on the slow-moving Two Towers earthflow in northern California. We compute horizontal-to-vertical spectral ratios (HVSRs) from the ambient seismic field. The HVSRs have two prominent peaks, one near 1.23 Hz and another between 4 and 8 Hz at most stations. The 1.23 Hz resonance is a property of the background noise field and may be due to a velocity contrast at a few hundred meters depth. We interpret the higher frequency peaks as being related to slide deposits and invert the spectral ratios for shallow velocity structure using in situ thickness measurements as a priori constraints on the inversion. The thickness of the shallowest, low-velocity layer is systematically larger than landslide thicknesses inferred from inclinometer data acquired since 2013. Given constraints from field observations and boreholes, the inversion may reflect the thickness of deposits of an older slide that is larger in spatial extent and depth than the currently active slide. Because the HVSR peaks measured at Two Towers are caused by shallow slide deposits and represent frequencies that will experience amplification during earthquakes, the depth of the actively sliding mass may be less relevant for assessing potential slide volume and associated hazard than the thicknesses determined by our inversions. More generally, our results underscore the utility of combining both geotechnical measurements and subsurface imaging for landslide characterization and hazard assessment.

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Sudjono, Dwi Sudarmawan, Udi Harmoko, and Gatot Yuliyanto. "Delineation of Geothermal Manifestation in Sangubanyu Area Based on Microtremor HVSR Method." E3S Web of Conferences 125 (2019): 14012. http://dx.doi.org/10.1051/e3sconf/201912514012.

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The aims of this study is to describe the distribution of P wave velocity and S wave velocity value and Vp/Vs ratio based on microtremor HVSR method and its relationship with the appearance of hot spring at Sangubanyu Village. Geothermal manifestations in the Sangubanyu area are located in Bawang sub-district, Batang regency, and Plantungan sub-district, Kendal regency, Central Java province. HVSR method is used to process microtremor data which produces the dominant frequency value and amplification factor then do inversion on the H/V curve to get the value of the Vp and Vs. The results of the microtremor HVSR processing obtained the distribution of the dominant frequency values in the study area between 0.62 to 0.73 Hz and amplification factor values 1.09 to 1.39, the inversion results on the H/V curve obtained the distribution of Vp values between 131.76 m/s to 2181.19 m/s, Vs values between 76.61 to 1129.42 m/s, Vp/Vs ratio 1.64 – 3.35. Based on the results of the analysis and wave velocity interpretation, the subsurface structure of manifestation area of Sangubanyu is composed of tuffaceous sandstone and volcanic breccia, the normal faults with southern blocks relatively downthrown, that cause the appearance of hot springs.

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Zega, B. N., Z. Zulfakriza, S. Rosalia, and N. T. Puspito. "Seismic Hazard Potential in Yogyakarta Based on HVSR Curve Estimation." IOP Conference Series: Earth and Environmental Science 1047, no. 1 (July 1, 2022): 012028. http://dx.doi.org/10.1088/1755-1315/1047/1/012028.

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Abstract In 2006, the Special Region of Yogyakarta was shaken by a destructive earthquake. The United States Geological Survey (USGS) recorded that the earthquake had a magnitude of 6.3 Mw at a depth of 12.5 km below the surface that was triggered by strike slip fault activity. The severe damage occurred in Bantul district and Klaten district, where the Klaten area location were far from the earthquake epicenter. This proves that the magnitude and the earthquake source distance are not the only parameters for seismic hazard potential, but rather the presence of local site effects and building conditions. The present study aims to determine the characteristics of the soil and estimate the seismic hazard potential by using HVSR method. Horizontal to Vertical Spectral Ratio (HVSR) is one method that can be used to obtain the subsurface information from single station measurements. Furthermore, the inversion of Rayleigh wave ellipticity curve is used to obtain 1-D of shear wave velocity (Vs). The parameters from HVSR calculation and Rayleigh wave inversion were mapped to understand the subsurface structure beneath the Yogyakarta area. Based on the soil classification to Vs, Yogyakarta area is categorized to SD (Stiff soil/soft soil) and SC (Very dense soil and soft rock). The results of the mapping analysis indicated that Bantul district is an area with the highest potential of seismic hazard.

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Krylov, Artem A., Mikhail E. Kulikov, Sergey A. Kovachev, Igor P. Medvedev, Leopold I. Lobkovsky, and Igor P. Semiletov. "Peculiarities of the HVSR Method Application to Seismic Records Obtained by Ocean-Bottom Seismographs in the Arctic." Applied Sciences 12, no. 19 (September 23, 2022): 9576. http://dx.doi.org/10.3390/app12199576.

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The application of the horizontal-to-vertical spectral ratio (HVSR) modeling and inversion techniques is becoming more and more widespread for assessing the seismic response and velocity model of soil deposits due to their effectiveness, environmental friendliness, relative simplicity and low cost. Nevertheless, a number of issues related to the use of these techniques in difficult natural conditions, such as in the shelf areas of the Arctic seas, where the critical structures are also designed, remain poorly understood. In this paper, we describe the features of applying the HVSR modeling and inversion techniques to seismic records obtained by ocean-bottom seismographs (OBS) on the outer shelf of the Laptev Sea. This region is characterized by high seismotectonic activity, as well as sparse submarine permafrost distribution and the massive release of bubble methane from bottom sediments. The seismic stations were installed for one year and their period of operation included periods of time when the sea was covered with ice and when the sea was ice-free. The results of processing of the recorded ambient seismic noise, as well as the wave recorder data and ERA5 and EUMETSAT reanalysis data, showed a strong dependence of seafloor seismic noise on the presence of sea ice cover, as well as weather conditions, wind speed in particular. Wind-generated gravity waves, as well as infragravity waves, are responsible for the increase in the level of ambient seismic noise. The high-frequency range of 5 Hz and above is strongly affected by the coupling effect, which in turn also depends on wind-generated gravity waves and infragravity waves. The described seafloor seismic noise features must be taken into account during HVSR modeling and interpretation. The obtained HVSR curves plotted from the records of one of the OBSs revealed a resonant peak corresponding to 3 Hz, while the curves plotted from the records of another OBS did not show clear resonance peaks in the representative frequency range. Since both OBSs were located in the area of sparse distribution of submarine permafrost, the presence of a resonance peak may be an indicator of the presence of a contrasting boundary of the upper permafrost surface under the location of the OBS. The absence of a clear resonant peak in the HVSR curve may indicate that the permafrost boundary is either absent at this site or its depth is beyond the values corresponding to representative seismic sensor frequency band. Thus, HVSR modeling and inversion techniques can be effective for studying the position of submarine permafrost.

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Sedaghati, Farhad, Sahar Rahpeyma, Anooshiravan Ansari, Shahram Pezeshk, Mehdi Zare, and Siamak Daneshvaran. "A study of horizontal-to-vertical component spectral ratio as a proxy for site classification in central Asia." Geophysical Journal International 223, no. 2 (August 12, 2020): 1355–77. http://dx.doi.org/10.1093/gji/ggaa370.

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SUMMARY Tien Shan of central Asia is known as one of the world's largest, youngest and most active intracontinental orogens. In this study, we implemented the horizontal-to-vertical spectral ratio (HVSR) technique as a widely used first-order approximation of the site effect parameters (i.e. fundamental frequency and site amplification). A set of data including 2119 strong-motion recordings from 468 earthquakes with hypocentral distances up to 500 km and small to moderate moment magnitudes ($ {M_{\rm{w}}}\sim $3.0–5.5) recorded by 24 broad-band stations from five different networks, located in Afghanistan, Tajikistan and Kyrgyzstan was deployed to investigate site-specific characteristics. We fitted a Gaussian-shape pulse function to evaluate fundamental frequencies and site amplifications. The HVSRs analysis revealed that although the majority of the stations (16 out of 24) show flat amplification functions, there are few stations with single sharp amplification functions. Then, we classified the stations based on the predominant frequency. Furthermore, we approximated the time-averaged shear wave velocity in the uppermost 30 m (${V_{{\rm{S}}30}}$) using the fundamental frequency and its corresponding amplitude. Moreover, we compared the HVSRs obtained from P waves, S waves, coda and pre-event noise. All peak frequencies including the fundamental frequency estimated from different seismic phases are in good agreement; whereas generally, the amplitude of the P-wave window is the lowest, the amplitudes of the S wave and noise windows are similar to the whole record and the amplitudes of early and late coda windows are the highest. We also observed that the HVSRs of noise using a 5 s window may have anomalous high amplitudes and peaks. These anomalous high amplitudes and peaks in the noise HVSRs indicate the existence of some unnatural sources or artefacts such as traffic and wind with specific resonance frequencies, suggesting 5 s ambient noise window is insufficient to capture site characteristics. Finally, to assess the reliability of the determined geotechnical results, we implemented a blind theoretical HVSR inversion to obtain representative shear wave velocity profiles as well as ${V_{{\rm{S}}30}}$ along with associated uncertainties for stations characterized by a single-peak HVSR curve using a Bayesian statistical framework.

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El-Hady, Sherif, Elsayed Abdel-Azeem Fergany, Adel Othman, and Gad ElKareem Abdrabou Mohamed. "Seismic microzonation of Marsa Alam, Egypt using inversion HVSR of microtremor observations." Journal of Seismology 16, no. 1 (October 7, 2011): 55–66. http://dx.doi.org/10.1007/s10950-011-9249-4.

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Tian, Ruyun, Liwei Ma, Xiaohua Zhou, Junqiu Wang, Jun Lin, and Dongsheng Li. "Site Characterization of Soil-rock Mixture Sedimentary Stratum Based on HVSR Analysis in the Chinese Loess Plateau." Journal of Environmental and Engineering Geophysics 25, no. 1 (March 2020): 101–9. http://dx.doi.org/10.2113/jeeg19-060.

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The soil-rock mixture sedimentary stratum is a compound with complex and loose topography, of which the structure is difficult to detect by the ordinary geophysical method. There is a need for a convenient, efficient and effective geophysical method to detect site effects in this area. This paper is an application of the S wave velocity profile inversion for the soil-rock mixture sedimentary stratum, using HVSR (Horizontal to Vertical Spectral Ratio) analysis of ambient noise by some three-component observations in the Chinese Loess Plateau. We carried out the measurement using three nested circular arrays and data recording systems with a spectrum expansion circuit. Inversion of the HVSR curves was performed by a three-layer model. Results of geological observation reveal that the upper part of the sedimentary stratum is Quaternary strata containing a large amount of humus and loess, the middle layer part is the stratum of the loose gravel and the under part is completely weathered granite with homogeneous lithology and fewer rocks. Interpretation results are consistent with previous drilling data, providing a valid geophysical basis for evaluating the stability of the soil erosion and designing a reasonable water and soil erosion control scheme.

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Rohaendi, Nendi, Rahayu Robiana, Emi Sukiyah, Dicky Muslim, and Athanasius Cipta. "Seismic Hazard Zonation in Gedebage Future Development in Bandung City Using HVSR Inversion." International Journal on Advanced Science, Engineering and Information Technology 11, no. 3 (June 14, 2021): 947. http://dx.doi.org/10.18517/ijaseit.11.3.14996.

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Ikeda, Tatsunori, Michael Asten, and Toshifumi Matsuoka. "Joint inversion of spatial autocorrelation curves with HVSR for site characterization in Newcastle, Australia." ASEG Extended Abstracts 2013, no. 1 (December 2013): 1–4. http://dx.doi.org/10.1071/aseg2013ab315.

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Bignardi, S., A. Mantovani, and N. Abu Zeid. "OpenHVSR: imaging the subsurface 2D/3D elastic properties through multiple HVSR modeling and inversion." Computers & Geosciences 93 (August 2016): 103–13. http://dx.doi.org/10.1016/j.cageo.2016.05.009.

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Molnar, Sheri, John Onwuemeka, and Sujan Raj Adhikari. "Rapid Post-Earthquake Microtremor Measurements for Site Amplification and Shear Wave Velocity Profiling in Kathmandu, Nepal." Earthquake Spectra 33, no. 1_suppl (December 2017): 55–72. http://dx.doi.org/10.1193/121916eqs245m.

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This paper presents application of microtremor (ambient vibration) and surface wave field techniques for post-earthquake geotechnical reconnaissance purposes in Kathmandu, Nepal. Horizontal-to-vertical spectral ratios (HVSR) are computed from microtremor recordings at 16 individual measurement locations to obtain an estimate of fundamental frequency (site period) of the subsurface soils. A combination of active- and passive-source surface wave array testing was accomplished at five key sites including Kathmandu's Durbar Square and Airport. Joint inversion of each site's higher frequency dispersion and lower frequency HVSR data sets provides an estimate of subsurface material stiffness [i.e., shear wave velocity ( V S) depth profiles]. Direct comparison of our V S profiling at Kathmandu Durbar Square and that accomplished by downhole V S and/or standard penetration testing (SPT) profiling yield similar results. Classification of the five sites based on average V S, site period, and/or basin depth is presented. There is little differentiation in these site classification designations amongst the five sites, which does not capture significant differences in observed earthquake damage.

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Di Stefano, P., D. Luzio, P. Renda, R. Martorana, P. Capizzi, A. D'Alessandro, N. Messina, G. Napoli, S. Todaro, and G. Zarcone. "Integration of HVSR measures and stratigraphic constraints for seismic microzonation studies: the case of Oliveri (ME)." Natural Hazards and Earth System Sciences Discussions 2, no. 4 (April 10, 2014): 2597–637. http://dx.doi.org/10.5194/nhessd-2-2597-2014.

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Abstract. Because of its high seismic hazard the urban area of Oliveri has been subject of first level seismic microzonation. The town develops on a large coastal plain made of mixed fluvial/marine sediments, overlapping a complexly deformed substrate. In order to identify points on the area probably suffering relevant site effects and define a preliminary Vs subsurface model for the first level of microzonation, we performed 23 HVSR measurements. A clustering technique of continuous signals has been used to optimize the calculation of the HVSR curves. 42 reliable peaks of the H/V spectra in the frequency range 0.6–10 Hz have been identified. A second clustering technique has been applied to the set of 42 vectors, containing Cartesian coordinates, central frequency and amplitude of each peak to identify subsets which can be attributed to continuous spatial phenomena. The algorithm has identified three main clusters that cover significant parts of the territory of Oliveri. The HVSR data inversion has been constrained by stratigraphic data of a borehole. To map the trend of the roof of the seismic bedrock, from the complete set of model parameters only the depth of the seismic interface that generates peaks fitting those belonging to two clusters characterized by lower frequency has been extracted. The reconstructed trend of the top of the seismic bedrock highlight its deepening below the mouth of the Elicona Torrent, thus suggesting the possible presence of a buried paleo-valley.

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Arimuko, A., E. Santoso, and B. Sunardi. "Investigation of Site Condition Using Elliptical Curve Inversion from Horizontal-to-Vertical Spectral Ratio (HVSR)." Journal of Physics: Conference Series 1491 (March 2020): 012031. http://dx.doi.org/10.1088/1742-6596/1491/1/012031.

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Lianza Bakri, Najla Insyirah, Tedi Yudistira, and Yayan Sopyan. "Vulnerability Analysis of Earthquake Hazards in Tasikmalaya City Using Horizontal to Vertical Spectral Ratio (HVSR) Method." IOP Conference Series: Earth and Environmental Science 873, no. 1 (October 1, 2021): 012085. http://dx.doi.org/10.1088/1755-1315/873/1/012085.

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Abstract Tasikmalaya City is one of the regions in West Java Province that is often hit by earthquakes due to its location near the Indo-Australian Plate subduction zone towards the Eurasian Plate. The surface deposits in this city are alluvium and weakly consolidated step deposits which can cause wave amplification during an earthquake. As a mitigation effort, seismic zoning needs to be carried out to map the areas that will experience heavy damage when an earthquake occurs. This study uses the Horizontal to Vertical Spectral Ratio (HVSR) method which is applied to the microtremor recording data to obtain spatial variations in the predominant frequency and amplification values that can explain the characteristics of the geological layer beneath the surface. Based on the obtained results, the predominant frequency ranging from 0.7 to 9.5 Hz with the lowest frequency distribution in the eastern and northwestern parts, which indicates a thicker sediment layer. Amplification ranging from 1.2 to 12.6 with the distribution of higher values in the eastern, southeastern, and northwestern parts. The inversion of the HVSR curves was carried out to determine the value of shear wave velocity (V s ) in order to obtain a more detailed subsurface geological structure that can be used to determine the level of vulnerability of earthquake hazards. The Neighborhood Algorithm is used to find an optimum model. Based on the results of the inversion process, the V s ranging from 150 - 3054 m/s with lower V s values in the eastern, southeastern, and northwestern parts at depth of about 25 meters. The average value of shear wave velocity at a depth of 30 meters (V s 30) can also be used to determine the type of soil for geotechnical study. From the obtained V s 30data, the types of soil in the research area are classified into moderate soil, hard soil, and rocks.

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Di Giacomo, D. "Analysis and Modeling of HVSR in the Presence of a Velocity Inversion: The Case of Venosa, Italy." Bulletin of the Seismological Society of America 95, no. 6 (December 1, 2005): 2364–72. http://dx.doi.org/10.1785/0120040242.

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Yusran, Y., Aulia Khalqillah, Umar Muksin, Muhammad Syukri, Syamsul Rizal, and Nazli Ismail. "Estimation of Shear Wave Velocity of Darul Imarah District, Aceh Besar, Indonesia by Using 1D HVSR Inversion." IOP Conference Series: Materials Science and Engineering 846 (May 28, 2020): 012068. http://dx.doi.org/10.1088/1757-899x/846/1/012068.

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Haryono, A., Sungkono, M. A. Caesardi, B. J. Santosa, F. Syaifuddin, and A. Widodo. "Estimation of Shear Wave Velocity Using Horizontal to Vertical Spectrum Ratio (HVSR) Inversion to Identify Faults in Pacitan." IOP Conference Series: Earth and Environmental Science 506 (June 11, 2020): 012051. http://dx.doi.org/10.1088/1755-1315/506/1/012051.

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Borges, J. F., H. G. Silva, R. J. G. Torres, B. Caldeira, M. Bezzeghoud, J. A. Furtado, and J. Carvalho. "Inversion of ambient seismic noise HVSR to evaluate velocity and structural models of the Lower Tagus Basin, Portugal." Journal of Seismology 20, no. 3 (March 4, 2016): 875–87. http://dx.doi.org/10.1007/s10950-016-9564-x.

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Issaadi, Abdelouahab, Ahmed Saadi, Fethi Semmane, Abdelkrim Yelles-Chaouche, and Juan José Galiana-Merino. "Liquefaction Potential and Vs30 Structure in the Middle-Chelif Basin, Northwestern Algeria, by Ambient Vibration Data Inversion." Applied Sciences 12, no. 16 (August 12, 2022): 8069. http://dx.doi.org/10.3390/app12168069.

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The Middle-Chelif basin, in northwestern Algeria, is located in a seismically active region. In its western part lies the El-Asnam fault, a thrust fault responsible for several strong earthquakes. The most important being the El-Asnam earthquake (Ms = 7.3) of 1980. In the present study, ambient vibration data with single-station and array techniques were used to investigate the dynamic properties of the ground and to estimate the Vs30 structure in the main cities of the basin. Soil resonance frequencies vary from 1.2 to 8.3 Hz with a maximum amplitude of 8.7 in. Collapsing behavior has also been demonstrated west of the city of El-Attaf, reflecting a strong potential for liquefaction. A Vs30 variation map and a soil classification for each city were obtained mainly by inversion of the HVSR and Rayleigh wave dispersion curves. Finally, an empirical prediction law of Vs30 for the Middle-Chelif basin was proposed.

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Maghami, Shahram, Abdollah Sohrabi-Bidar, Samuel Bignardi, Ahmad Zarean, and Mohsen Kamalian. "Extracting the shear wave velocity structure of deep alluviums of “Qom” Basin (Iran) employing HVSR inversion of microtremor recordings." Journal of Applied Geophysics 185 (February 2021): 104246. http://dx.doi.org/10.1016/j.jappgeo.2020.104246.

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Sivaram, K., Sandeep Gupta, Sudesh Kumar, and B. N. V. Prasad. "Shear velocity structural characterization around the Lonar crater using joint inversion of ambient noise HVSR and Rayleigh wave dispersion." Journal of Applied Geophysics 159 (December 2018): 773–84. http://dx.doi.org/10.1016/j.jappgeo.2018.10.022.

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Wahyu, Anna, Ade Filla Intan, Arddhiles Adhitama, Febrian Nur Fadhli, Ferda Elita Putri, Gunarta Sutantio, Henest Paskah, et al. "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." Jurnal Fisika Indonesia 22, no. 3 (April 27, 2020): 23. http://dx.doi.org/10.22146/jfi.v22i3.55648.

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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.

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Luthfiyani, N., T. Yudistira, and V. Ry Rexha. "Shear Velocity (VS) Estimation with HVSR (Horizontal to Vertical Spectrum Ratio) Curve Inversion Method of Microtremor Measurement in Bandung Basin." IOP Conference Series: Earth and Environmental Science 318 (August 14, 2019): 012034. http://dx.doi.org/10.1088/1755-1315/318/1/012034.

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Martorana, Raffaele, Mauro Agate, Patrizia Capizzi, Francesca Cavera, and Antonino D'Alessandro. "Seismo-stratigraphic model of "La Bandita" area in the Palermo Plain (Sicily, Italy) through HVSR inversion constrained by stratigraphic data." Italian Journal of Geosciences 137, no. 1 (February 2018): 73–86. http://dx.doi.org/10.3301/ijg.2017.18.

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Tawakal, M. I., A. Haris, and A. A. Martha. "Estimating shear wave velocity (Vs30) of East Java, Indonesia, using ambient noise inversion of horizontal to vertical spectral ratio (HVSR)." IOP Conference Series: Earth and Environmental Science 538 (July 29, 2020): 012012. http://dx.doi.org/10.1088/1755-1315/538/1/012012.

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Alfaro-Diaz, Richard, and Ting Chen. "Imaging the Shallow Structure of the Yucca Flat at the Source Physics Experiment Phase II Site with Horizontal-to-Vertical Spectral Ratio Inversion and a Large-N Seismic Array." Seismological Research Letters 92, no. 5 (April 28, 2021): 2952–60. http://dx.doi.org/10.1785/0220200381.

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Abstract The Source Physics Experiment (SPE) is a series of chemical explosions at the Nevada National Security Site (NNSS) with the goal of understanding seismic-wave generation and propagation of underground explosions. To understand explosion source physics, accurate geophysical models of the SPE site are needed. Here, we utilize a large-N seismic array deployed at the SPE phase II site to generate a shallow subsurface model of shear-wave velocity. The deployment consists of 500 geophones and covers an area of, approximately, 2.5×2 km. The array is located in the Yucca Flat in the northeast corner of the NNSS, Nye County, Nevada. Using ambient-noise recordings throughout the large-N seismic array, we calculate horizontal-to-vertical spectral ratios (HVSRs) across the array. We obtain 2D seismic images of shear-wave velocities across the SPE phase II site for the shallow structure of the basin. The results clearly image two significant seismic impedance interfaces at ∼150–500 and ∼350–600 m depth. The shallower interface relates to the contrast between Quaternary alluvium and Tertiary volcanic rocks. The deeper interface relates to the contrast between Tertiary volcanic rocks and the Paleozoic bedrock. The 2D subsurface models support and extend previous understanding of the structure of the SPE phase II site. This study shows that the HVSR method in conjunction with a large-N seismic array is a quick and effective method for investigating shallow structures.

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Giallini, Silvia, Enrico Paolucci, Pietro Sirianni, Dario Albarello, Iolanda Gaudiosi, Federica Polpetta, Maurizio Simionato, et al. "Reconstruction of a Reference Subsoil Model for the Seismic Microzonation of Gori (Georgia): A Procedure Based on Principal Component Analysis (PCA)." Bulletin of the Seismological Society of America 111, no. 4 (July 6, 2021): 1921–39. http://dx.doi.org/10.1785/0120200341.

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ABSTRACT This article focuses on the full exploitation of geological and economically viable geophysical surveys for the seismic characterization of the shallow subsoil in the frame of microzonation studies in urban areas where economic resources for detailed seismic response analyses are scarce. In these conditions, the outcomes of inexpensive geophysical surveys (e.g., based on ambient vibration monitoring or surface-wave prospecting) must be fully exploited. To reduce the uncertainties related to these kinds of procedures, their joint interpretation in the light of geological evidence is mandatory. To this purpose, we propose the application of principal component analysis to combine the results of distributed single-station ambient vibration measurements (horizontal-to-vertical spectral ratio [HVSR] technique) to provide a preliminary zonation of the study area. The zones identified in this way are then characterized by considering the available geognostic boreholes, VS profiles deduced by the joint inversion of HVSR curves, and available Rayleigh-wave dispersion curves deduced from active seismic prospecting (multichannel analysis of surface-waves technique). The final outcome allows the definition of a preliminary seismic model of the study area, which is also constrained by the available geological data deduced from on-purpose surveys. The proposed approach has been applied to the city of Gori (Georgia). The proposed approach allowed a reliable assessment of buried geometries, geological domains, and the distribution of lithofacies, which can control the local seismic response. In detail, the major role of paleovalley infills and interfluve domains has been enlightened by adding in evidence concerning the peculiar stratigraphic relationships and buried morphologies, which may determine 1D and 2D resonance effects.

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Issaadi, Abdelouahab, Fethi Semmane, Abdelkrim Yelles-Chaouche, Juan José Galiana-Merino, and Khalissa Layadi. "A Shear-Wave Velocity Model in the City of Oued-Fodda (Northern Algeria) from Rayleigh Wave Ellipticity Inversion." Applied Sciences 10, no. 5 (March 3, 2020): 1717. http://dx.doi.org/10.3390/app10051717.

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The city of Oued-Fodda is located in north-central Algeria on the margins of the Middle-Cheliff Basin. This region has suffered several destructive earthquakes. The strongest was the 1980 El-Asnam earthquake (Ms7.3), whose causative fault was located about 1 km north of the city of Oued-Fodda. Therefore, a good knowledge of the soil characteristics in this city may allow a better evaluation of the seismic risk and help to minimize damages in the future. With this objective, a detailed microzonation study of Oued-Fodda has been carried out in this study. For that, the horizontal-to-vertical spectral ratio (HVSR) method has been applied on 102 sites along the city, estimating the soil fundamental frequencies and their corresponding amplitudes. Besides, the Rayleigh wave ellipticity inversion has been accomplished in order to estimate the corresponding Vs profiles and provide two cross-sections of the geology under the city. In the central part of the city, high-frequency peaks are observed, between 12.5 and 15 Hz, which correspond to impedance contrasts at shallow depth (<20 m). In the surrounding plain, two clear peaks are identified in the ranges 1.8–3.5 Hz (fundamental frequencies) and 6.5–15 Hz (secondary peaks).

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HUSSAIN, Y., M. CARDENAS-SOTO, R. UAGODA, S. MARTINO, N. P. SANCHEZ, C. A. MOREIRA, and H. MARTINEZ-CARVAJAL. "Shear Wave Velocity Estimation by a Joint Inversion of HVSR and f-k Curves under Diffuse Field Assumption: A Case Study of Sobradinho Landslide." Anuário do Instituto de Geociências - UFRJ 42, no. 1 (May 13, 2019): 742–50. http://dx.doi.org/10.11137/2019_1_742_750.

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Permanasari, Ikah Ning P., Vico Luthfi Ipmawan, Rifki Prayoga, and Alamta Singarimbun. "Landslide Potential Analysis Using Microtremor Data on The Main Route to Beach Tourism in Tanjung Pandan, Pesawaran, Lampung." IOP Conference Series: Earth and Environmental Science 830, no. 1 (September 1, 2021): 012027. http://dx.doi.org/10.1088/1755-1315/830/1/012027.

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Abstract Tanjung Pandan has much beach tourism which attracts many tourists. However, the only road access to these tourist destinations is bordered by hills and cliffs on either side. Its condition has a potential to landslides. This study aims to determine the landslides potential caused by earthquakes considered as external force by obtaining the ground shear strain (GSS) value and obtaining the depth of the slip surface at the measurement location. There are 10 measurement points in two different locations. The method used is the horizontal to vertical spectral ratio (HVSR) method to obtain the value of the dominant frequency and the amplification factor. These two parameters are then used to obtain the value of peak ground acceleration (PGA) and GSS. The depth of the slip surface is obtained by the ellipticity curve inversion method. The frequency natural values vary from 1.4 to 8.2 Hz and the amplification factor values vary from 2.4 to 5.2. The PGA values obtained from Fukushima-Tanaka equation have range from 3.02 to 3.04 gal using the 6.6 Mw Liwa earthquakes considered as the reference earthquake. The GSS values vary from 3.5x10−6 to 3.2x10−5. Based on the value, the caused-earthquake landslides potential is very small. This result does not rule out landslides caused by other factors, such as rainfall. Meanwhile, from the inversion method, it is found that the depth of the slip plane at the second location is about 11 to16 meters with a slope ranging from 23° to 33°.

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Permanasari, Ikah Ning P., Vico Luthfi Ipmawan, Rifki Prayoga, and Alamta Singarimbun. "Landslide Potential Analysis Using Microtremor Data on The Main Route to Beach Tourism in Tanjung Pandan, Pesawaran, Lampung." IOP Conference Series: Earth and Environmental Science 830, no. 1 (September 1, 2021): 012027. http://dx.doi.org/10.1088/1755-1315/830/1/012027.

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Abstract Tanjung Pandan has much beach tourism which attracts many tourists. However, the only road access to these tourist destinations is bordered by hills and cliffs on either side. Its condition has a potential to landslides. This study aims to determine the landslides potential caused by earthquakes considered as external force by obtaining the ground shear strain (GSS) value and obtaining the depth of the slip surface at the measurement location. There are 10 measurement points in two different locations. The method used is the horizontal to vertical spectral ratio (HVSR) method to obtain the value of the dominant frequency and the amplification factor. These two parameters are then used to obtain the value of peak ground acceleration (PGA) and GSS. The depth of the slip surface is obtained by the ellipticity curve inversion method. The frequency natural values vary from 1.4 to 8.2 Hz and the amplification factor values vary from 2.4 to 5.2. The PGA values obtained from Fukushima-Tanaka equation have range from 3.02 to 3.04 gal using the 6.6 Mw Liwa earthquakes considered as the reference earthquake. The GSS values vary from 3.5x10−6 to 3.2x10−5. Based on the value, the caused-earthquake landslides potential is very small. This result does not rule out landslides caused by other factors, such as rainfall. Meanwhile, from the inversion method, it is found that the depth of the slip plane at the second location is about 11 to16 meters with a slope ranging from 23° to 33°.

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Li, Jiangyi, Bengang Zhou, Mianshui Rong, Su Chen, and Yue Zhou. "Estimation of Source Spectra, Attenuation, and Site Responses from Strong-Motion Data Recorded in the 2019 Changning Earthquake Sequence." Bulletin of the Seismological Society of America 110, no. 2 (February 25, 2020): 410–26. http://dx.doi.org/10.1785/0120190207.

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ABSTRACT This study used 306 accelerograms recorded at 22 strong-motion stations to investigate the source parameters, quality factor (Q), and site effects of S-wave Fourier acceleration amplitude spectrum (FAS) of the 2019 MS 6.0 Changning earthquake sequence in China with surface-wave magnitudes (MS) of 4.1–6.0. The generalized inversion technique (GIT) was adopted. The inverted stress drop of the mainshock was 1.15 MPa, and those of the aftershocks varied from 0.11 to 1.04 MPa with an average value of 0.43 MPa. The MS of these earthquakes were larger than Mw with an average magnitude difference of 0.22. The inverted Q values increase rapidly with frequencies at 0.5–4.0 Hz from 62 to 2920 and become less dependent at 4.0–25.0 Hz. Such a phenomenon indicates that the propagation path attenuation mechanism transited to intrinsic at high frequencies. A bilinear Q(f) model for which Q(f)=237.6f1.27 (Q<1280) and Q=1280 at higher frequencies was obtained. The high-frequency attenuation model of the study area was κ=0.0420+0.0001262R. The inverted site responses of the 22 stations were compared with those calculated using the horizontal-to-vertical spectral ratio (HVSR) method. In general, the amplification curves of most stations obtained with the GIT were similar to those of HVSR, and the amplification levels were relatively higher. Contrarily, obvious discrepancies were observed between the results estimated from the two methods at several stations. Such effects were attributed to the limitation that the majority of the stations were distributed along the boundary of the basin and mountainous areas, and the inverted Q values were representative of the specific area rather than the pure basin and mountainous areas. Finally, a nonlinear soil site effect was observed at 51GXT in earthquakes with peak ground acceleration greater than 300 cm/s2. The nonlinearity obviously aggravated the site amplification at 1.0–5.0 Hz.

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Mi, Binbin, and Jianghai Xia. "Estimation of near-surface shear-wave velocity by joint inversion of dispersion and HVSR curves of Rayleigh waves from multicomponent active-seismic records." IOP Conference Series: Earth and Environmental Science 660, no. 1 (February 1, 2021): 012056. http://dx.doi.org/10.1088/1755-1315/660/1/012056.

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Widyadarsana, Skolastika Novita, and Eddy Hartantyo. "Lithological modelling based on shear wave velocity using horizontal to vertical spectral ratio (HVSR) inversion of ellipticity curve method to mitigate landslide hazards at the main road Of Samigaluh District, Kulon Progo Regency, Yogyakarta." E3S Web of Conferences 325 (2021): 01009. http://dx.doi.org/10.1051/e3sconf/202132501009.

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Many landslides occur in Samigaluh District, Kulon Progo Regency, Yogyakarta, Indonesia. However, no research discusses landslides that often occur on the main road connecting the city of Yogyakarta and various tourist resorts in Samigaluh. This study aims at determining the soil vulnerability and lithology model at that main road as a contribution to landslide mitigation planning. This lithology model is based on shear wave velocity (Vs) and layer thickness derived by microtremor datasets. The data were processed by the inversion of the Horizontal to Vertical Spectral Ratio (HVSR) technique of the ellipticity curve method. The result of the study shows that the first layer is associated with topsoil which has Vs of 263 m/s, the second layer is clay which has Vs of 607 m/s, the third layer consists of clay, breccia, and pumice which has Vs of 1119 m/s, and the fourth layer is andesite bedrock which has Vs of 1721 m/s. Andesite is impermeable to water and can become a slip field for landslides. Clay, breccias, and pumice can absorb water so that their weight increases when it rains. When they are on an impermeable rock on a certain slope, a landslide occurs.

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Davatgari Fami Tafreshi, Mehran, Sanjay Singh Bora, Noorbakhsh Mirzaei, Hadi Ghofrani, and Javad Kazemian. "Spectral models for seismological source parameters, path attenuation and site-effects in Alborz region of northern Iran." Geophysical Journal International 227, no. 1 (June 9, 2021): 350–67. http://dx.doi.org/10.1093/gji/ggab227.

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SUMMARY We analysed 478 three-component strong ground motion time-series from 65 events in the moment magnitude (Mw) 3–6.5 range recorded at 111 stations at distances up to 150 km from 1997 to 2019 in the Alborz region. Non-parametric spectral functions for seismological source, path and site-effects were derived from Fourier amplitude spectra of observed acceleration time-histories using the generalized inversion technique (GIT) for the Alborz region of Iran. To characterize the spectral models in terms of the anelastic attenuation (Q), geometrical spreading, magnitude and stress parameter (Δσ), we fitted non-parametric attenuation and source functions (resulted from inversion) with the standard parametric models. The frequency-dependent non-parametric attenuation function shows a rapid decay at close distances (<60 km) and decreases monotonically at larger distances. The frequency-independent geometrical spreading follows a bilinear hinged model with a crossover distance at 70 km. For hypocentral distances Rhypo < 70 km, the geometrical spreading is ${R^{ - 1.01}}$, and for Rhypo > 70 km it is ${R^{ - 1.37}}$. The corresponding quality factor is $Q\ ( f ) = \ 146{f^{0.91}}$. The non-parametric source spectra were found in a good agreement with Brune's ω-squared model. The stress-parameter (Δσ) values were found to exhibit large variability from 0.36 to 86.7 MPa with no significant magnitude-dependence. The average Δσ was found to be 8.6 MPa. The mean value of the estimated near-surface attenuation (κ0) from high-frequency part of non-parametric source function is 0.032 s (±0.01 s). In general, there is a good agreement between subsoil resonance frequencies and amplification levels estimated from GIT and HVSR (horizontal to vertical spectral ratio). The results of this study provide updated values of seismological source, attenuation and site properties in the Alborz region of northern Iran, which are expected to improve regional seismic hazard analysis studies in the region.

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Angelis, L. G., P. Stephanopoulos, and P. St Papamarinopoulos. "Geoelectric prospecting in University Campus region for detection of possible geological discontinuities, Rio, Patra, Greece." Bulletin of the Geological Society of Greece 47, no. 3 (December 21, 2016): 1042. http://dx.doi.org/10.12681/bgsg.10941.

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Geophysical prospecting is a non catastrophic technique, applicable on a wide range of problems, including archaeological, environmental and geological problems. At Campus University of Patras, a detailed geophysical investigation applied for detection of possible existing geological discontinuities, which produced serious problems at buildings and main roads of Campus. As main technique used the electric mapping and electric imaging. These were applied on already prepared geophysical grids by measuring parallel profiles along and perpendicular to the geomagnetic north. The two geophysical grids were separated 100 meters away each other. Firstly, an electric mapping procedure took place by using twin-probe array with four electrodes in distance between 0.5-3 meters. As result was the recording of soil resistance on horizontal layer with constant depth. By processing the data through Geosoft Oasis Montaj software, the distribution of this physical property was illustrated on color scale maps. Secondly, electric imaging technique applied with twenty-five equal space electrodes along straight lines, with one meter space byusing the hybrid arrangement Wenner-Schlumberger (Stephanopoulos, 2002). As result was the recording of distribution of soil apparent resistivity on a vertical layer in eight separated depths. Resistivity calculated by processing imaging data through 2D mathematical algorithm based on least squares inversion (Res2Dinv). Furtherprocessing by Oasis Montaj, had as a result the production of horizontal slices (Stephanopoulos 2002) and 3D maps, where the resistivity distribution was illustrated on separated depths, in color and grey schedule format. The combined geophysical investigation with the contribution of the HVSR (Horizontal to Vertical Spectral Ratio) technique confirmed the existence of geological discontinuity.

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Meneisy, Ahmed M., Mostafa Toni, and Awad A. Omran. "Soft Sediment Characterization using Seismic Techniques at Beni Suef City, Egypt." Journal of Environmental and Engineering Geophysics 25, no. 3 (September 2020): 391–401. http://dx.doi.org/10.32389/jeeg19-069.

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It is well known that the local geological characteristics in terms of topographic setting and the existence of soft sediments over bedrock may affect earthquake waves and cause seismic amplification. These effects are called “site effects”. Microtremors which provide an efficient practical tool for site effects estimation were recorded at 43 sites in Beni Suef City, Egypt. The recorded seismic signals were analyzed using the Horizontal-to-Vertical Spectral Ratio (HVSR) method. The targeted site parameters are the fundamental frequency ( f0) and the corresponding amplitude of seismic waves ( A0). Selected H/V curves with clear peak frequency have been inverted to infer the S-wave velocity profile of the underlying sediments. Information about subsurface sediments needed for the inversion process was extracted from available boreholes data. Moreover, the estimated values of f0 and A0 have been used for a preliminary calculation of the seismic vulnerability index ( Kg) which represents an indicator of soil liquefaction potentiality in the event of future earthquakes at the study area. The estimated H/V curves reveals significant variations in f0 and A0 parameters, reflecting variations in the soil characteristics (thickness and type) at the study area. The estimated values of f0 are (0.4–3.7 Hz), and commonly decrease from east to west. The A0 values vary from flat H/V curves (without any clear peak) at rock sites to 7.8 near to the Nile River and in the cultivated areas. The obtained velocity profiles could investigate S-wave structure down to 200 m depth. The estimated Kg varies from 10 to more than 50 μstrain/gal. The highest Kg values are noticed in the west and northwest in the study area were the soft sediments exist with considerable thickness, while the smallest Kg values are noticed in the south east where limestone and stiff soil occur near the ground surface.

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Sugianto, Nanang, and Refrizon Refrizon. "Struktur Kecepatan Gelombang Geser (Vs) di Daerah Rawan Gerakan Tanah (Longsor) Jalan Lintas Kabupaten Bengkulu Tengah-Kepahiang." INDONESIAN JOURNAL OF APPLIED PHYSICS 11, no. 2 (October 17, 2021): 134. http://dx.doi.org/10.13057/ijap.v11i2.41699.

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Shear wave velocity (Vs) structure at along of Central Bengkulu-Kepahiang crossline has been mapped. This research aims to identify the subsurface structure and to estimate the constituent material type of rock in landslide-prone areas (Central Bengkulu-Kepahiang crossline). Shear wave velocity structure on each site is obtained by the HVSR-inversion of 146 microtremor data (ambient noise recording of seismometer). Vs structure at the line mapped from the surface until to 30 meters of the depth. Groups of Vs are identified in class E (Vs <180), Class D (180≤ Vs <360), Class C (360≤ Vs <760), and Class B (760≤ Vs <1500). The subsurface structure at the depth of 0 to 10 meters are dominated by stiff soil, very dense soil, and soft rock which has highly fractured and weathered rock properties. At the depth of 15 meters to 30 meters, the subsurface structure is dominated by hard rock but it is high potential or easy to fracturing and weathering like the properties of the rocks in areas that have landslides in the past. Based on Vs value, rock constituent materials are deposition of sand, clay, gravel and alluvium ranging from soft to relatively hard structures at the depth.

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Kang, Su Young, Kwang-Hee Kim, Jer-Ming Chiu, and Lanbo Liu. "Microtremor HVSR analysis of heterogeneous shallow sedimentary structures at Pohang, South Korea." Journal of Geophysics and Engineering 17, no. 5 (July 25, 2020): 861–69. http://dx.doi.org/10.1093/jge/gxaa035.

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Abstract We apply the single-station microtremor horizontal-to-vertical spectral ratio (HVSR) method to image the geometry of Pohang Basin, South Korea, which experienced the greatest earthquake damage in Korea during a series of anthropogenic earthquakes between November 2017 and February 2018. We collected and analysed the ambient seismic noise at 124 temporary stations. The resonance frequencies, which vary significantly across the area (0.35–19.86 Hz), were inverted to constrain the depth of the major impedance contrast, which is interpreted to be the sediment–bedrock interface beneath each station. The sedimentary layer thickness is generally thin in the north and thickens to the southern and central parts of the basin, where the depth to bedrock is up to 340 m. We compare the HVSR results with six borehole observations in the area, whose depth to bedrock ranges from 189 to 359 m. The sediment thicknesses obtained via the direct borehole measurements and HVSR method are comparable with each other. The resultant three-dimensional shape of the sedimentary basin provides crucial information for the microzonation of the Pohang area for seismic risk mitigation. It also provides a realistic initial velocity model for three-dimensional tomographic inversions to elucidate the detailed subsurface structure of the region.

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Kameda, Tomoaki, Michito Namekawa, Haruo Shimazaki, Daisuke Minakata, Tohru Matsuura, and Imaharu Nakano. "Unique combination of hyperintense vessel sign on initial FLAIR and delayed vasoconstriction on MRA in reversible cerebral vasoconstriction syndrome: A case report." Cephalalgia 34, no. 13 (April 7, 2014): 1093–96. http://dx.doi.org/10.1177/0333102414529197.

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Background Reversible cerebral vasoconstriction syndrome is characterized by thunderclap headache and reversible cerebral vasoconstriction on angiographic findings. It can be difficult to diagnose when initial angiography is normal. Case results A 30-year-old woman was admitted because of sudden-onset thunderclap headache and seizure on postpartum day 7. Brain MRI on fluid-attenuated inversion recovery (FLAIR) showed hyperintense vessel sign (HVS), which usually means slow flow due to severe proximal arterial stenosis. However, magnetic resonance angiography (MRA) indicated that proximal arteries was normal. After nicardipine treatment, her symptoms improved dramatically. Follow-up FLAIR on day 7 showed complete resolution of HVS, while a series of MRAs revealed reversible multifocal segmental vasoconstriction. Conclusions HVS on initial FLAIR is useful for an early diagnosis of reversible cerebral vasoconstriction syndrome. As the delayed vasoconstriction on MRA can be observed, reversible cerebral vasoconstriction syndrome may progress from distal small to proximal larger arteries.

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Imai, Masaaki, Masami Shimoda, Shinri Oda, Kaori Hoshikawa, Takahiro Osada, Rie Aoki, and Azusa Sunaga. "Hyperintense posterior cerebral artery sign in patients with reversible cerebral vasoconstriction syndrome." Surgical Neurology International 12 (November 16, 2021): 558. http://dx.doi.org/10.25259/sni_1023_2021.

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Background: This study investigated hyperintense vessel signs (HVS) on fluid-attenuated inversion recovery imaging in the P1–2 portions of posterior cerebral arteries (PCAs) as a “hyperintense PCA sign” and HVS of cortical arteries. We retrospectively examined whether these signs would be useful in diagnosing reversible cerebral vasoconstriction syndrome (RCVS) in the acute phase. Methods: Eighty patients with RCVS who underwent initial magnetic resonance imaging (MRI) within 7 days of onset were included in this study. HVS and related clinical factors were examined. Results: On initial MRI of RCVS patients, hyperintense PCA sign and HVS of cortical arteries were seen in 21 cases (26%) and 38 cases (48%), respectively. In patients showing hyperintense PCA sign, vasoconstriction of the A2–3 portion was a significant clinical factor. Conversely, vasoconstriction of the M1 and P1 portions and the presence of white matter hyperintensity on initial and chronic-stage MRI were significantly associated with the presence of HVS in cortical arteries. Conclusion: Because rich collateral flow exists around PCAs, the frequency of hyperintense PCA sign is not high. However, hyperintense PCA sign findings in patients with suspected RCVS offer credible evidence of extreme flow decreases due to vasoconstriction in peripheral PCAs and other arteries associated with the collateral circulation of PCAs. Conversely, HVS in cortical arteries tend to reflect slow antegrade circulation due to vasoconstriction of peripheral vessel and major trunks. Both signs appear useful for auxiliary diagnosis of acute-phase RCVS.

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Chen, Shih-Pin, Jong-Ling Fuh, Jiing-Feng Lirng, and Shuu-Jiun Wang. "Hyperintense vessels on flair imaging in reversible cerebral vasoconstriction syndrome." Cephalalgia 32, no. 4 (January 30, 2012): 271–78. http://dx.doi.org/10.1177/0333102412437387.

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Objectives: To study the frequency and significance of distal hyperintense vessels (HVs) on fluid-attenuated inversion recovery (FLAIR) imaging in patients with reversible cerebral vasoconstriction syndrome (RCVS). Methods: Patients with RCVS were recruited during 2002 through 2009. Prominence and location of HVs on FLAIR images during the acute and recovery stages were documented. Clinical profiles, vasoconstriction scores, mean flow velocities of the middle cerebral artery (VMCA) and posterior cerebral artery (VPCA), and the Lindegaard index (LI) were collected for analysis. Results: Ninety-five patients with RCVS (11M/84F, mean age 47.8 ± 10.9 years) were recruited. Twenty-one (22.1%) had FLAIR HVs, which were noted at a mean of 14.3 ± 12.7 days and resolved by 44.9 ± 18.8 days. Compared with patients without HVs, patients with this finding had higher vasoconstriction scores for all arterial segments; higher VMCA (121.0 ± 39.5 cm/s vs. 93.3 ± 27.8, p = 0.002), VPCA (73.3 ± 35.0 vs. 50.5 ± 17.8 cm/s, p = 0.010), and LI (2.8 ± 1.2 vs. 1.9 ± 0.5, p = 0.018), and complications such as posterior reversible encephalopathy syndrome (PRES) [8/21 (38%) vs. 0/74 (0%), p < 0.001] or ischemic stroke [5/21 (24%) vs. 1/74 (1%), p = 0.002]. Conclusions: HVs in patients with RCVS might be attributed to the failure of cerebrospinal fluid (CSF) signal nulling on FLAIR imaging due to severe cerebral hemodynamic derangements and were associated with more frequent ischemic complications.

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Schindler, M., S. Meiners, and D. A. Cheresh. "RGD-dependent linkage between plant cell wall and plasma membrane: consequences for growth." Journal of Cell Biology 108, no. 5 (May 1, 1989): 1955–65. http://dx.doi.org/10.1083/jcb.108.5.1955.

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Soybean (Glycine max [L.] Merr. cv. Mandarin) root cells (SB-1 cell line) grown in suspension culture containing Glycyl-Arginyl-Glycyl-Aspartyl-Seryl-Proline (GRGDSP) (0.25 mg/ml), a synthetic peptide containing the RGD sequence found in many extracellular matrix adhesive proteins, demonstrated (a) significantly enhanced growth rate, and (b) aberrant cell wall/plasma membrane interactions and organization. Substitution of the Asp (D) by a Glu (E) amino acid in the hexapeptide, or inversion of the RGD sequence to GDR, abolished the morphological and growth effects observed for GRGDSP in plant cells. Immunoblots, which were prepared from beta-octylglucoside extracts of whole soybean cells and protoplasts, probed with polyclonal antibodies raised against human vitronectin receptor (hVNR) complex, demonstrated a single band with an apparent molecular mass of 70-72 kD. Chromatography of beta-octylglucoside extracts of SB-1 cells on a Gly-Arg-Gly-Asp-Ser-Pro-Lys-Sepharose affinity column demonstrated the retention of a single 70-72 kD polypeptide that reacted specifically with anti-hVNR antiserum. In contradistinction, no cross-reactivity was observed with antifibronectin receptor antiserum. Epifluorescence microscopy of whole soybean cells, after moderate treatment with pectinase, demonstrated punctate fluorescent patches at the cell membrane/wall boundary when probed with anti-hVNR and rhodamine-derivatized secondary antibodies. We propose that coordination and control of plant cell division and proper cell wall biosynthesis may be mediated by an RGD-dependent recognition system in which RGD binding protein(s) promote cell membrane-cell wall attachment.

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Sushentsev, Nikita, Joshua D. Kaggie, Rhys A. Slough, Bruno Carmo, and Tristan Barrett. "Reproducibility of magnetic resonance fingerprinting-based T1 mapping of the healthy prostate at 1.5 and 3.0 T: A proof-of-concept study." PLOS ONE 16, no. 1 (January 29, 2021): e0245970. http://dx.doi.org/10.1371/journal.pone.0245970.

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Facilitating clinical translation of quantitative imaging techniques has been suggested as means of improving interobserver agreement and diagnostic accuracy of multiparametric magnetic resonance imaging (mpMRI) of the prostate. One such technique, magnetic resonance fingerprinting (MRF), has significant competitive advantages over conventional mapping techniques in terms of its multi-site reproducibility, short scanning time and inherent robustness to motion. It has also been shown to improve the detection of clinically significant prostate cancer when added to standard mpMRI sequences, however, the existing studies have all been conducted on 3.0 T MRI systems, limiting the technique’s use on 1.5 T MRI scanners that are still more widely used for prostate imaging across the globe. The aim of this proof-of-concept study was, therefore, to evaluate the cross-system reproducibility of prostate MRF T1 in healthy volunteers (HVs) using 1.5 and 3.0 T MRI systems. The initial validation of MRF T1 against gold standard inversion recovery fast spin echo (IR-FSE) T1 in the ISMRM/NIST MRI system revealed a strong linear correlation between phantom-derived MRF and IR-FSE T1 values was observed at both field strengths (R2 = 0.998 at 1.5T and R2 = 0.993 at 3T; p = < 0.0001 for both). In young HVs, inter-scanner CVs demonstrated marginal differences across all tissues with the highest difference of 3% observed in fat (2% at 1.5T vs 5% at 3T). At both field strengths, MRF T1 could confidently differentiate prostate peripheral zone from transition zone, which highlights the high quantitative potential of the technique given the known difficulty of tissue differentiation in this age group. The high cross-system reproducibility of MRF T1 relaxometry of the healthy prostate observed in this preliminary study, therefore, supports the technique’s prospective clinical validation as part of larger trials employing 1.5 T MRI systems, which are still widely used clinically for routine mpMRI of the prostate.

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Journal articles on the topic 'HVSR inversion'

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