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The time-averaged shear-wave velocity in the top 30 m, VS30, is used to represent the site condition in many ground-motion models (GMMs). Regionalized GMMs account for regional differences in the in(VS30) scaling by including region-specific coefficients for the site term. For example, recent GMMs developed for subduction zone earthquakes as part of the Next Generation Attenuation-Subduction (NGA-Sub) project include region-specific VS30 scaling for seven regions: South America, Central America, Japan, New Zealand, Taiwan, Cascadia (Pacific Northwest America), and Alaska. Of these seven regions, South America has the largest within-event standard deviation. One cause for the larger within-event standard deviation is a weaker relation between VS30 and the site term in South America compared to other regions. A cause for this weak correlation is that most of the VS30 values for the South American region in the NGA-Sub data set are based on proxies. The relation between VS30 and the site term improves significantly for periods less than 1 s if only stations with measured VS30 are considered, but the correlation is weak for periods greater than 1 s even for stations with measured VS30, indicating that, for the South America region, VS30 is not well correlated with the deeper shear-wave velocity profile that controls the long-period amplification. To improve the site terms for South America, we develop a model based on the horizontal-to-vertical spectral ratio (HVSR) from microtremors, similar to the approach used by Pinilla-Ramos et al. (2022) for California. The data set includes 660 recordings from 51 earthquakes recorded at 274 sites. The site-term model includes the period-dependent HVSR amplitude and the geometric mean of the average HVSR amplitude over the frequency band of 0.25 to 15 Hz. Including these two parameters reduces the standard deviation of site-specific site terms over the period range 0.3-3 s, with the largest reduction in the period range 1-2 s. This site-term model can be incorporated into subduction GMMs and implemented in probabilistic seismic hazard analyses for South America. [ABSTRACT FROM AUTHOR]

The horizontal-to-vertical spectral ratio (HVSR) method has been used to characterize site-effect parameters that are indispensable in seismic hazard and risk-reduction studies in urban areas and rapid land-use planning. This method is widely used because it is the cheapest and simplest geophysical method for the acquisition and processing stages. In subsequent developments, the HVSR method has been widely used to determine elastic rock parameters, particularly shear wave velocity (vS), through the HVSR curve inversion process. Furthermore, the vS structural model can be used to delineate the presence of complex geological structures, particularly faults and sedimentary basins. Bandar Lampung is a city in Lampung Province with many fault structures and groundwater basins to the south. There are 83 HVSR measurement points around Bandar Lampung for delineating the presence of fault structures and groundwater basins. We produced the HVSR curve from the measurement results and then performed an inversion process using the particle swarm optimization algorithm to obtain vS for the depth profile. Subsequently, from this profile, we produced a two-dimensional (2D) lateral and vertical model. The mean vS value was calculated from all the measurement points, and we found stiff soil layers reaching depths of approximately 5 m, with a value of vS < 330 m/s. A bedrock layer with a velocity exceeding 1250 m/s was visible at a depth of 100 m. Based on the 2D model, the vS structure shows that the city of Bandar Lampung is divided into two zones, with a NW-SE boundary. The north-middle-eastern part of the city consists of harder rocks. This harder rock is characterized by extremely high vS values, starting from a depth of 50 m. In contrast, the south-middle-west exhibits a low-moderate vS anomaly associated with groundwater basins SW of the city. From the 2D vS structural model, fault structures can be found along the city, characterized by a contrast of vS values from low to medium and from medium to high.

The horizontal-to-vertical spectral ratio (HVSR) method has been used to characterize site-effect parameters that are indispensable in seismic hazard and risk-reduction studies in urban areas and rapid land-use planning. This method is widely used because it is the cheapest and simplest geophysical method for the acquisition and processing stages. In subsequent developments, the HVSR method has been widely used to determine elastic rock parameters, particularly shear wave velocity (vS), through the HVSR curve inversion process. Furthermore, the vS structural model can be used to delineate the presence of complex geological structures, particularly faults and sedimentary basins. Bandar Lampung is a city in Lampung Province with many fault structures and groundwater basins to the south. There are 83 HVSR measurement points around Bandar Lampung for delineating the presence of fault structures and groundwater basins. We produced the HVSR curve from the measurement results and then performed an inversion process using the particle swarm optimization algorithm to obtain vS for the depth profile. Subsequently, from this profile, we produced a two-dimensional (2D) lateral and vertical model. The mean vS value was calculated from all the measurement points, and we found stiff soil layers reaching depths of approximately 5 m, with a value of vS < 330 m/s. A bedrock layer with a velocity exceeding 1 250 m/s was visible at a depth of 100 m. Based on the 2D model, the vS structure shows that the city of Bandar Lampung is divided into two zones, with a NW-SE boundary. The north-middle-eastern part of the city consists of harder rocks. This harder rock is characterized by extremely high vS values, starting from a depth of 50 m. In contrast, the south-middle-west exhibits a low-moderate vS anomaly associated with groundwater basins SW of the city. From the 2D vS structural model, fault structures can be found along the city, characterized by a contrast of vS values from low to medium and from medium to high. [ABSTRACT FROM AUTHOR]

Bedrock mapping is essential for understanding seismic amplification, particularly in sediment-filled valleys or basins. However, this can be hard in urban environments. We conducted a geophysical investigation of the sediment-filled Bolzano basin in Northern Italy, where three valleys converge. This study uses low-impact, single-station geophysical methods suitable for urban areas to address the challenges of mapping in such environments. A dataset of 574 microtremor and gravity measurements, along with three seismic reflection lines, allows for the inference of the basin's deep bedrock morphology, even without direct stratigraphic data. The dataset facilitates a detailed analysis of the spatial patterns of resonance frequencies and amplitudes, revealing 1D and 2D characteristics of the resonances. Notably, 2D resonances predominate along the Adige valley, i.e., the deepest part of the basin with depths up to 900 m. These 2D resonances, which cannot be interpreted through simple 1D frequency-depth relationships, are better understood by integrating gravity data to develop a depth model. The study identifies resonance frequencies ranging from 0.27 to over 3 Hz in Bolzano, affecting different building types during earthquakes. Maximum resonance amplitudes occur at lower frequencies, specifically at 2D resonance sites, therefore primarily impacting high structures. The 2D resonances are directional, with the most significant amplification occurring longitudinally along the valley axes. The resulting 3D bedrock model aids in seismic site response modeling, hydrogeological studies, and geothermal exploration and provides insights into the geological history of the basin, highlighting the role of the Adige Valley as a major drainage pathway. [ABSTRACT FROM AUTHOR]

On September 28, 2018, a 7.5 Richter magnitude earthquake struck the Palu City neighborhood of Petobo. The tectonic activity along the Palu-Koro fault generated this earthquake, which resulted in soil liquefaction. The purpose of this study is to use microtremor measurements at 33 distinct places to investigate the properties of the soil layer after liquefaction. The obtained data was then evaluated utilizing Horizontal to Vertical Spectral Ratio (HVSR) methodologies such as Ground Shear Strength (GSS), amplification factor, and vulnerability index to determine the soil layer's properties and susceptibility. The dominant frequency ranges from 0.19 to 4.75 Hz, while the dominant period ranges from 0.21 to 5.17 seconds, according to the measurement results. According to these measurements, the silt layer varies between 5 and 30 m. GSS values in the 10-4 to 10-2 range indicate that soil cracking, subsidence, liquefaction, landslides, and compaction are likely. The soil vulnerability and amplification index values range from 2.36 to 4.37, respectively. These values show the potential level of danger, which might be low, medium, high, or extremely high. Peak ground acceleration varied from 299.52 to 301.52 gals, suggesting high to extremely high danger levels. The microzonation map created for this study is considered to be a useful resource for training disaster mitigation approaches and facilitating infrastructure development planning in the region.

In this study, an analysis was conducted on the seismic response of three archaeological structures located in the Chichén Itzá area. The objective of this analysis was to gather relevant information that may be utilized to monitor and ensure the preservation of these monuments. Ambient seismic noise measurements were conducted over three days using broad-band seismographs. The objective was to assess the vibration frequencies of three buildings, namely Las Monjas, El Caracol and El Castillo or Kukulkan Pyramid, using HVSR method. The findings indicate that the dominant frequency of the El Caracol building is 1.3 Hz. Nevertheless, it is noteworthy that within the Las Monjas and El Castillo structures, an observable fundamental frequency of 5.1 Hz is present, accompanied by a relative amplification of around 6. The findings of this study indicate the behavior of the two pyramids can be likened to that of a soil layer overlaying a stiff stratum. The noise recorded by a seismograph at the base of El Castillo enables the observation of a kinematic interaction phenomenon resulting from the disparate stiffness properties of the soil and the structure. No directional effect was observed on the HVSR ratios due to internal irregularities in the pyramids. Considering the half-width of the base of each pyramid and that the site response is of topographic origin, the calculus of shear velocity is 255 m/s. This velocity relates to non-compact materials resting on competent rocks with velocities more than 1000 m/s, materials subject to stress changes that may eventually lead to structural degradation. The findings of this study indicate the need for continuous monitoring and instrumentation of lower levels to assess the influence of substructures during preconstruction stages and determine whether there are any other effects due to the karstic nature of the subsurface. [ABSTRACT FROM AUTHOR]

Although Gümüşhane province is a quiet region in terms of seismicity, it is under earthquake danger due to its proximity to the NAFZ. Therefore, it is of great importance to reveal the local site effects in the central district of Gümüşhane province, which is in a rapid and intense construction process. For this purpose, the predominant frequency (or period), horizontal to vertical spectral ratio (HVSR) defining the amplification potential and S-wave velocity (VS30) values, which are important parameters in the detection of site effects, were calculated by applying the HVSR and multichannel surface wave analysis (MASW). The predominant frequencies determined for the investigation area from microtremor data collected at a single station vary between 1.21-13.40 Hz, dominant periods between 0.07-0.82 sec, amplification potential values between 1.12-9.76 and VS30 values between 300.2-677.2 m/sec. Additionally, using the calculated VS30 values, soil classification was defined for the investigation area according to TBDY (2018), NEHRP (2020) and Eurocode-8 (2004). Using the measurement parameters obtained from HVSR and MASW methods, microzonation maps of the predominant frequency, predominant period, amplification potential risk and VS30 values of the study area were created. According to these maps, it was seen that the high predominant frequency and low predominant period regions in the central district of Gümüşhane province had low magnification potential and high VS30 values. With this study, it has been concluded that the ground parameters obtained from different geophysical methods for the central district of Gümüşhane province are in good harmony with each other and with the geological structure of the region. With this study, it has been concluded that the site effect parameters obtained from different geophysical methods for the central district of Gümüşhane province are in good harmony with each other and with the geological structure of the region. ing that pending at employer. please check into it and confirm my request [ABSTRACT FROM AUTHOR]

Two large earthquakes (Mw = 7.7 and Mw = 7.6) that occurred in Turkey on February 6, 2023, affected a very extent region and caused a lot of loss of life and property. This paper presents preliminary results from geophysical measurements (Seismic Refraction Tomography-SRT, Multi-Channel Surface Wave Analysis-MASW and Microtremor-MT) on eight profiles in four provinces (Kahramanmaraş, Hatay, Malatya, Gaziantep) to understand the relationship between subsurface properties and the destruction that occurs immediately after earthquakes. By analyzing the geophysical data, the dynamic-elastic properties of ground and the soil classification according to Vs30 were determined. It is generally understood that the near-surface (< ~ 10–15 m) units in the measurement areas are very loose, and the deeper ones (≥ ~ 15–20 m) have a very porous/fractured structure. Soil classes were defined as ZD (Malatya-1, Hatay-1 and Kahramanmaraş-1) and ZC (Malatya-2, Hatay-2, Gaziantep-1,2 and Kahramanmaraş-2). In addition, by evaluating the information of strong ground motion station closest to the measurement profiles, it is observed that the PGA values versus epicenter distances are higher at stations in the zone parallel to the direction of both faults than those in the perpendicular zones. This leads directivity effect in the propagation of earthquake waves. The results indicate that one of the basic reasons for the damages is that the earthquake-ground-structure relationship has not been fully and accurately reflected in building designs. Therefore, future researches involving more geophysical data and PGA values will provide more information about the structural, physical and geotechnical properties of subsurface and definitive results. [ABSTRACT FROM AUTHOR]

The presented investigation focused on site effect estimations, specifically resonance frequency and amplification. These estimations were carried out for both rotational and translational signals, using waveforms from mining-induced seismic events. Site effect parameters were calculated using the horizontal-to-vertical spectral ratio (HVSR) technique, which is commonly applied to translational records by comparing the spectral ratio between horizontal and vertical components. In this study, we also applied the horizontal-to-vertical (H/V) ratio to rotational records. However, due to the different orientations of motion propagation, we introduced the spectral H/V ratio for rotational motion as the torsion-to-rocking spectral ratio (TRSR). Furthermore, we analyzed these signals according to two approaches. First, we estimated the site effect parameters for directly registered signals, and secondly, we considered rotated components by varying the angle from 0° to 180° in 5-degree increments. Generally, the H/V curves indicated two peaks for translational motions and four peaks for rotational motions. The averaged H/V spectra and spectra obtained for different angles of component rotation showed insignificant fluctuation in amplification values for both rotational and translational motions. However, when comparing each component's spectrum for all angles, we observed changes in the site effect parameter values for both motion types. Radar plots depicting amplification values versus rotation angles for separated components revealed characteristic fluctuations, suggesting local anisotropy. Moreover, when comparing the radar plots between rotational and translational results, it was evident that rotational resonance frequencies shifted to higher frequency values, potentially indicating shallower geological layers as their source. [ABSTRACT FROM AUTHOR]

Abstract Background The Suban area of Curup Rejang Lebong is a tourist region in Bengkulu Province, Indonesia, close to the active Ketaun and Musi faults, which are segments of the Sumatra Fault System (SFS). However, no studies have been conducted in this area to assess how geological structures affect seismic ground motions and contribute to seismic hazard and risk assessment. Methods The first study of seismic microzonation in the Suban area of Curup City by ambient noise measurements was conducted at 100 sites, spaced ~ 1 km apart, with 60 min of data acquisition for each site. All microseismic data were processed using the Horizontal to Vertical Spectral Ratios (HVSR) method. Results The HVSR method revealed the amplification factors (A 0) ranging from 1.23 to 8.26 times, corresponding to natural frequency (f 0) variations between 1.24 and 9.67 Hz. About 13% and 55% of the sites show high (6 ≤ A 0 ≤ 9) and medium (3 ≤ A 0 ≤ 6) amplifications, respectively, predominantly in the western parts of the study area, consistent with a high seismic vulnerability index (K g). Furthermore, we also estimated the ground shear strain (GSS) of the region using the Kanai method with two large historical earthquakes at the Ketahun segment in 1943 (Mw 7.4) and the Musi segment in 1979 (Mw 6.0). The K g value is consistent with the GSS values and indicates areas of severe damage during the historic earthquakes. Conclusions Thus, the western parts of the Suban region are vulnerable to severe damage from an earthquake. These findings could provide valuable insights for future planning and risk management efforts aimed at minimizing the impact of earthquakes in the Suban region.

Ground liquefaction potential analysis is a fundamental characterization in areas with continuous seismic activity, such as Ecuador. Geotechnical liquefaction studies are usually approached from dynamic penetration tests, which pose problems both in their correct execution and in their evaluation. Our research involves analyzing dynamic penetration tests and microtremor geophysical surveys (horizontal-to-vertical spectral ratio technique, HVSR) for analyzing the liquefaction potential at the base of the San Marcos dam, a reservoir located in Cayambe canton (Ecuador). Based on the investigations performed at the time of construction of the dam (drilling and geophysical refraction profiles) and the application of 20 microtremor observation stations via the HVSR technique, an analysis of the safety factor of liquefaction (SFliq) was conducted using the 2001 Youd and Idriss formulation and the values of the standard penetration test (SPT) applied in granular materials (sands). In addition, the vulnerability index (Kg) proposed by Nakamura in 1989 was analyzed through the HVSR records related to the ground shear strain (GSS). The results obtained in the HVSR analysis indicate the presence of a zone of about 100 m length in the central part of the foot of the dam, whose GSS values identified a condition of susceptibility to liquefaction. In the same area, the SPT essays analysis in the P-8A drill hole also shows a potential susceptibility to liquefaction in earthquake conditions greater than a moment magnitude (Mw) of 4.5. That seismic event could occur in the area, for example, with a new activity condition of the nearby Cayambe volcano or even from an earthquake from the vicinity of the fractured zone.

This study uses integrated geological, geodesy, and seismology data to assess the potential tsunami and Probabilistic Seismic Hazard Function (PSHF) near Sumatra's coastal cities. It focuses on estimating the possible level of ground shaking due to the seismic activity within the Sumatran Fault Zone (SFZ) and subduction zone. It uses the Peak Ground Acceleration (PGA) as a measure. An amplification factor that is based on the previous study is used. It is calculated through the Horizontal-Vertical Spectral Ratio (HVSR), which measures possible surface ground shaking. The Seismic Hazard Function (SHF) is calculated considering magnitudes 6.5 to 9.0 for subduction sources and 6.5 to 7.8 for SFZ sources. Also, the PGA based on the Maximum Possible Earthquake (MPE) magnitude is estimated, and tsunami heights are simulated to assess the possible hazard risk. The tsunami source model in this study is characterized by considering the possibility of the long-term perspectives on giant earthquakes and tsunamis that might occur in subduction zones around the off-coast of southern Sumatra Island. The potentiality source zone is characterized based on the utilization of the cross-correlation of correlation dimension (D[sub C]) based on the shallow earthquake catalog of 2010 to 2022 and the SHmax-rate of surface strain rate. Based on the MPE, the relatively high estimated PGA at the base rock was found around Mentawai and Pagai Utara islands at about 0.224 g and 0.328 g, with the largest estimated PGA based on the MPE at the surface with values of about 0.5 g and 0.6 g. The possible maximum tsunami height (Hmax) estimated based on source scenarios position around the west coast of Sumatera Island, such as for Kota Padang and Kota Bungus, reaches up to 12.0 m and 22.0 m, respectively. The findings provide valuable insight into seismic and tsunami hazards, benefiting future mitigation strategies. [ABSTRACT FROM AUTHOR]

Background: The Suban area of Curup Rejang Lebong is a tourist region in Bengkulu Province, Indonesia, close to the active Ketaun and Musi faults, which are segments of the Sumatra Fault System (SFS). However, no studies have been conducted in this area to assess how geological structures affect seismic ground motions and contribute to seismic hazard and risk assessment. Methods: The first study of seismic microzonation in the Suban area of Curup City by ambient noise measurements was conducted at 100 sites, spaced ~ 1 km apart, with 60 min of data acquisition for each site. All microseismic data were processed using the Horizontal to Vertical Spectral Ratios (HVSR) method. Results: The HVSR method revealed the amplification factors (A0) ranging from 1.23 to 8.26 times, corresponding to natural frequency (f0) variations between 1.24 and 9.67 Hz. About 13% and 55% of the sites show high (6 ≤ A0 ≤ 9) and medium (3 ≤ A0 ≤ 6) amplifications, respectively, predominantly in the western parts of the study area, consistent with a high seismic vulnerability index (Kg). Furthermore, we also estimated the ground shear strain (GSS) of the region using the Kanai method with two large historical earthquakes at the Ketahun segment in 1943 (Mw 7.4) and the Musi segment in 1979 (Mw 6.0). The Kg value is consistent with the GSS values and indicates areas of severe damage during the historic earthquakes. Conclusions: Thus, the western parts of the Suban region are vulnerable to severe damage from an earthquake. These findings could provide valuable insights for future planning and risk management efforts aimed at minimizing the impact of earthquakes in the Suban region. [ABSTRACT FROM AUTHOR]

In the last decades, the concern for infrastructure damage and collapse due to natural hazards has globally increased. Highways, railways, bridges, and tunnels, worldwide, have faced consistent damage or destruction from landslides and floods, exacerbated by the ongoing climate change and population growth. In Italy, significant examples of these events are the recent failures of the Polcevera and Magra bridges, impacting people and the local economy. Especially, after the Polcevera bridge collapse, the Italian government has considered the need for specific practices of bridge/viaduct risk assessment. In response to this requirement, governmental agencies have developed specific projects oriented to the development of specific guidelines. This work is part of one of these projects, entrusted specifically to the ReLuis consortium, aimed at contributing to the application and optimization of an experimental protocol for bridge/viaduct classification in natural-hazard related risk assessment perspective. In this context, this work describes the results of an initial-level analysis of the interaction condition of a slowmoving landslide with the “Villa Ilii” Viaduct located along the A24 highway at Colledara, in the Teramo Province. The analysis aims to evaluate landslide characteristics, including landslide anatomy and kinematics, and their potential impact, contributing to define and identify viaduct classification in landslide risk perspective. The study area is characterized by the presence of the Laga Formation, mainly represented by sandstones and marls, overlaid by sandy Quaternary deposits. In fact the formation of the Laga (Ricci Lucchi, 1975) represents the filling of one of the many foreland basins currently exposed in a wide area between southern Marche and northern Abruzzo, developed at the forefront of the Apennines during its migration eastward and northeastward, as a result of the collision between the European lithospheric plate and the Adriatic plate, a likely protrusion of the African continent.), Methods including existing data collection, field surveys, numerical chartography analysis, geophysical surveys and PS InSAR technique were used to reconstruct the geological setting of the slope affected by the landslide, its anatomy and kinematics. Especially, multiple field surveys and numerical cartography analysis revealed landslide extent over a surface of 78,000 m², geophysical survey indicated a landslide thickness of around 15 m, comparable with the thickness of Quaternary deposits, and SAR-interferometric data, processed by SUBSIDENCE software, indicated persistent slow movement typically accelerating in spring. These data are crucial for understanding the landslide’s potential impact on the “Villa Ilii” viaduct’s structural conditions, already exhibiting local deformation and cracking, similar to surrounding settlements. [ABSTRACT FROM AUTHOR]

The occurrence of sinkhole phenomena in Italy is a prevalent and very uncertain class of geological hazards that pose a significant threat to human infrastructure and individuals. These events are characterized by their unpredictability and the challenges associated with their accurate forecasting. Both natural and anthropic factors influence the occurrence of these events; therefore, accurate identification of the above factors is critical for effective proactive and predictive efforts. The work presented in this paper refers to a collapse that occurred in a volcanic region in northern Latium (central Italy) on 31 January 2023. The area has been monitored using drones since the early stages of the sinkhole's formation and has continued to date. Then, the collapse and the neighboring area were examined via geophysical and geochemical investigations to identify potential underlying factors. Geophysical and geochemical data were combined to provide a preliminary hypothesis on the collapse's genesis. The obtained data indicate that the structural collapse can be attributable to the fluctuation in groundwater levels as well as the development of instabilities along its banks, leading to a growth in its dimensions. [ABSTRACT FROM AUTHOR]

Laterite weathering profile (LWP) thicknesses are functions of precipitation rate and time, but their exact dependence on them is uncertain. We investigate LWP development on ground surfaces in Hawai'i that are neither aggrading nor eroding across substrates from 0.01 to 4 Ma and rainfall rates of <250 to >3000 mm/a. The Hawaiian Islands provide an excellent opportunity for LWP studies across climates and over millions of years on a single rock type, basalt. LWP weathering rates are usually determined by geochemical approaches. We present a geophysical method once bedrock ages and precipitation rates are known. We employed multichannel analysis of surface waves and horizontal‐to‐vertical spectral ratio methods. Results indicate that >70% of the variability in LWP thickness is due to precipitation and bedrock age. The remainder is attributed to measurement uncertainty and heterogeneity in the permeability of basalt. LWPs develop by two paths. Dry (<1000 mm/a) areas have a negative water balance with evapotranspiration exceeding rainfall. LWPs thicken until they reach a steady state where the storage capacity of the saprolite precludes the percolation of water into subjacent lava. In wetter areas, downslope interflow produces thick laterite wedges near coastlines that migrate upslope over ~1 Ma. Subsequently, they thicken and reach a steady state where precipitation cannot deliver water through the vadose zone. LWPs' thickness (T) increases as a function of time (t) and precipitation (P) according to the expression (95% confidence): T=log10t+10.934±0.126×log10P+13.890±0.085. The first partial derivative, or weathering rate, is ∂T∂tP=0.406t+1×log10P+13.890. Weathering rates decrease with time and are strong functions of t and P. These expressions add considerable insight into the rates and processes driving weathering at large scales and can also be solved for t, giving a rough estimate of the time of landscape formation of eroded surfaces. [ABSTRACT FROM AUTHOR]

The Mandalika Circuit, now one of the icons of Indonesian pride, is located on the south coast of Lombok Island. The south coast of Lombok Island is an area where the Indo-Australian plate subducts into the Eurasian plate, known as the subduction zone. Coastal areas dominated by sediment deposits (alluvial) and adjacent to subduction zones are disaster-prone areas, such as damage from earthquakes and liquefaction. The objective of this research is centered on the analysis of the potential damage due to geological conditions and liquefaction caused by the earthquake. This microseismic method with a total of 51 measuring points scattered around the Mandalika circuit was employed in this research. The microseismic data were measured using a portable three-component seismograph and processed using the horizontal-to-vertical spectral ratio (HVSR) method. HVSR analysis results are presented in terms of natural frequency (f0), amplification factor (A0), seismic vulnerability index (Kg), shear wave velocity profile at 30m depth (Vs30), and sediment thickness. Groundwater level data was used to support the potential liquefaction analysis. Based on the Vs30 soil type classification, soft and medium soils dominate the Mandalika International Circuit. Estimates of sediment thickness range from 5 to 90 meters. The Mandalika Circuit and its surrounding area are vulnerable to earthquakes and liquefaction hazards that may potentially decrease to the north or away from the coastline. [ABSTRACT FROM AUTHOR]

Surface wave exploration plays a vital role in obtaining target detection information by analyzing and retrieving the dispersion curve of surface waves. Although surface wave exploration technology originated in the 1960s, it has experienced significant advancements in recent decades and has found widespread applications in earthquake disaster and volcanic activity prediction, deep geological structure analysis, engineering construction, mining area and goaf assessment, subsidence area detection, and near-surface structure investigation, including celestial bodies such as stars. This paper aims to provide a comprehensive overview of surface wave exploration technology. It begins by discussing two types of data sources, namely active source and passive source, and proceeds to review the fundamental theory of surface wave exploration based on dispersion curve analysis and observations of horizontal and vertical amplitude ratios. This paper also provides a brief introduction to the surface wave inversion method. Additionally, it highlights the various application domains of surface wave exploration, outlines the current development trend, and presents future prospects for this technology.

Abstract Background The Bangkok Basin has been known from non-instrumental observations of the local population to be subject to ground motion amplification due to the deep alluvial sediments and basin geometry. This study analyzes available seismic data to confirm that basin effects are significant in the Bangkok Basin. The paper contributes to the evaluation of basin effects by characterizing the engineering ground motion parameters and HVSR curves for the Bangkok basin which produce lengthening of ground motion duration with respect to nearby rock sites, albeit with very low ground motions. For this purpose, we analyzed ground motion records from seismic stations located within the Bangkok alluvial basin from 2007 to 2021. Recorded peak horizontal ground acceleration (PGA) for seismic stations inside the basin always exceeded 1 cm/s2 during eight earthquakes with Mw ≥ 5.5. Of these, two were intraslab events and six were shallow crustal earthquakes. These recorded ground motions shook high-rise buildings in Bangkok even though their epicentral distance exceeded 600 km. Methods Several time and frequency domain analyses (such as analysis of residual, HVSR, Hodogram plots, etc.) are used on the ground motion records in the Bangkok basin to determine the frequency content of recorded ground motion and to demonstrate the significance of surface waves induced by the deep basin in altering the engineering ground motion amplitudes. In addition, centerless circular array microtremor analysis is used to determine the depth of sedimentary basin to the bedrock. Results Based on comparisons from those stations located outside the Bangkok basin, we observed the capability of alluvial deposits in the Bangkok basin to amplify ground motion records by about 3 times. We observed that there is a unique site amplification effect between 0.3 and 0.1 Hz due to local surface waves and other moderate amplifications between 2 and 0.5 Hz due to a soft layer like other deep alluvial basins in other metropolitan areas. Conclusion We noticed that there is a unique site amplification effect between 0.1 and 0.3 Hz and smaller peaks around 2 and 0.5 Hz consistent with expectations for site amplification effects associated with deep basins. Moreover, we noticed the presence of low frequencies content of the surface wave generated within the basin which deserved further studies using the 2D/3D ground motion modelling through basin topography and velocity models.

This paper describes the relationship between bedrock depth (D) and site fundamental frequency (f0) in the Nakdonggang delta region in the southeastern part of the Korean peninsula. We collected borehole logs to confirm the thickness of the sediments and estimated the f0 at over 200 locations across the delta using the horizontal-to-vertical spectral ratio (HVSR) method. We developed an f0 map of the study area by spatially interpolating the f0 values using the Ordinary Kriging method. The bedrock depth in the main delta showed a power-law dependence on the f0. The derived f0–D model predicted much shallower bedrock depths compared with similar studies from other parts of the world. This was attributed to the fact that the Nakdonggang delta region is composed of relatively low Vs Holocene sediments. With an f0 map, the derived model could enable a quick estimation of the bedrock depth, which could help to determine the site class in the Nakdonggang delta region according to the Korean Seismic Design Standard (KDS 17 10 00).

This study uses integrated geological, geodesy, and seismology data to assess the potential tsunami and Probabilistic Seismic Hazard Function (PSHF) near Sumatra’s coastal cities. It focuses on estimating the possible level of ground shaking due to the seismic activity within the Sumatran Fault Zone (SFZ) and subduction zone. It uses the Peak Ground Acceleration (PGA) as a measure. An amplification factor that is based on the previous study is used. It is calculated through the Horizontal-Vertical Spectral Ratio (HVSR), which measures possible surface ground shaking. The Seismic Hazard Function (SHF) is calculated considering magnitudes 6.5 to 9.0 for subduction sources and 6.5 to 7.8 for SFZ sources. Also, the PGA based on the Maximum Possible Earthquake (MPE) magnitude is estimated, and tsunami heights are simulated to assess the possible hazard risk. The tsunami source model in this study is characterized by considering the possibility of the long-term perspectives on giant earthquakes and tsunamis that might occur in subduction zones around the off-coast of southern Sumatra Island. The potentiality source zone is characterized based on the utilization of the cross-correlation of correlation dimension (DC) based on the shallow earthquake catalog of 2010 to 2022 and the SHmax-rate of surface strain rate. Based on the MPE, the relatively high estimated PGA at the base rock was found around Mentawai and Pagai Utara islands at about 0.224 g and 0.328 g, with the largest estimated PGA based on the MPE at the surface with values of about 0.5 g and 0.6 g. The possible maximum tsunami height (Hmax) estimated based on source scenarios position around the west coast of Sumatera Island, such as for Kota Padang and Kota Bungus, reaches up to 12.0 m and 22.0 m, respectively. The findings provide valuable insight into seismic and tsunami hazards, benefiting future mitigation strategies.

Background: The Bangkok Basin has been known from non-instrumental observations of the local population to be subject to ground motion amplification due to the deep alluvial sediments and basin geometry. This study analyzes available seismic data to confirm that basin effects are significant in the Bangkok Basin. The paper contributes to the evaluation of basin effects by characterizing the engineering ground motion parameters and HVSR curves for the Bangkok basin which produce lengthening of ground motion duration with respect to nearby rock sites, albeit with very low ground motions. For this purpose, we analyzed ground motion records from seismic stations located within the Bangkok alluvial basin from 2007 to 2021. Recorded peak horizontal ground acceleration (PGA) for seismic stations inside the basin always exceeded 1 cm/s2 during eight earthquakes with Mw ≥ 5.5. Of these, two were intraslab events and six were shallow crustal earthquakes. These recorded ground motions shook high-rise buildings in Bangkok even though their epicentral distance exceeded 600 km. Methods: Several time and frequency domain analyses (such as analysis of residual, HVSR, Hodogram plots, etc.) are used on the ground motion records in the Bangkok basin to determine the frequency content of recorded ground motion and to demonstrate the significance of surface waves induced by the deep basin in altering the engineering ground motion amplitudes. In addition, centerless circular array microtremor analysis is used to determine the depth of sedimentary basin to the bedrock. Results: Based on comparisons from those stations located outside the Bangkok basin, we observed the capability of alluvial deposits in the Bangkok basin to amplify ground motion records by about 3 times. We observed that there is a unique site amplification effect between 0.3 and 0.1 Hz due to local surface waves and other moderate amplifications between 2 and 0.5 Hz due to a soft layer like other deep alluvial basins in other metropolitan areas. Conclusion: We noticed that there is a unique site amplification effect between 0.1 and 0.3 Hz and smaller peaks around 2 and 0.5 Hz consistent with expectations for site amplification effects associated with deep basins. Moreover, we noticed the presence of low frequencies content of the surface wave generated within the basin which deserved further studies using the 2D/3D ground motion modelling through basin topography and velocity models. [ABSTRACT FROM AUTHOR]

Horizontal to vertical spectral ratio (HVSR) based on seismic ground motion is an important index to study site conditions and dynamic characteristics (seismic effect). Due to the influence of the vertical dynamic amplification effect of the site, the Fourier spectral ratio calculated according to the surface motion and downhole motion is quite different from that of the horizontal and vertical ground motion in the case of strong vibration input. However, our recent research shows that when considering the time-varying characteristics of ground motion, the time-varying surface-downhole spectral ratio and time-varying HVSR are almost the same. Based on this discovery, the time-varying HVSR is used to study the dynamic characteristics of the site (site effect). First, a new method for calculating the natural period and damping ratio of the site is proposed. Secondly, based on tremendous strong motion records, the prediction formulas of natural period and damping ratio are studied. Finally, the effects of various influencing factors on the natural period and damping ratio are compared. The results of this paper can provide a basis for selecting and synthesizing appropriate ground motions in structural seismic design. [ABSTRACT FROM AUTHOR]

The urban area of Albuñuelas, a small town located to the south of Granada (S Spain), has been developed in terrain affected by a large-scale rotational landslide with very slow rate of movement. Despite this situation, the internal structure of the landslide and how it has evolved to its present state has not been analyzed in depth up to now. In this paper, we present the first study performed on this landslide to define its configuration and characteristics. For this purpose, ambient noise single-station and array measurements were carried out along several cross-sections of the landslide. The inversion of the measurements has allowed for the estimation of the soil stratigraphy at each site of measurement. These geophysical results have been constrained by data from a borehole drilled in the zone and from field observations of the local geology, allowing for the reduction in uncertainties in the results. A geological–geophysical model of the landslide has been built from these data, showing that the landslide thicknesses is greater than 50 m in its central parts and above 60 m in the upper ones. This model reveals that the evolution of the landslide was complex, with several dislodged elements (blocks) that moved in sequence (retrogression) and were partially eroded in order to explain present morphology. The future evolution of this landslide will be controlled by the composition of the materials surveyed along the foot of the valley, being the western part where there are more erodible materials according to the obtained results. [ABSTRACT FROM AUTHOR]

We present a novel strategy for joint modelling to estimate shear wave velocities at ten sites in Dhanbad City, India. The joint modelling technique utilizes the complementary sensitivities of disparate datasets, such as horizontal-to-vertical spectral ratios (HVSR) and Rayleigh wave phase velocity dispersion curves, obtained from passive and active seismic surveys, respectively. The model search space is explored rigorously via the very fast simulated annealing (VFSA) global optimization technique and uncertainties are quantified with estimates of marginal posterior probability distributions (PPDs) and parameter correlation matrices (PCMs). These tools help us identify the portions of acceptable models that are well, or poorly, constrained. A confirmatory test is conducted to demonstrate the effectiveness of the modelling scheme by synthetic data as well as field data recorded in Dhanbad City. The depth to engineering bedrock is found to reach its maximum (~ 42 m) and minimum (~ 9.5 m) in the southwestern and northeastern parts of the city, respectively, while dominant frequencies range between 2 and 14.6 Hz. The largest Vs30 value found is 562 m/s at Dhanbad's southern border and 351 m/s in south-central neighbourhoods. Shear wave velocity profiles are consistent with borehole lithology data. The seismic characterization of Dhanbad City presented here will aid in seismic hazard mitigation efforts and facilitate infrastructure that can sustain the dynamic load imposed by earthquakes. [ABSTRACT FROM AUTHOR]

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Deep sedimentary valleys entrap and amplify seismic waves, which is further responsible for site-specific amplification over the allied region. Kashmir valley is a deep and active sedimentary basin in the northwest portion of the Himalayan lap. To characterize the site response for the intermountain Kashmir valley for the first time, we acquire single station microtremor measurements using Lennartz (three components/5s seismometer) at 141 sites with a grid of (5 km × 5 km) and two-dimensional (2D) array measurements using seven units of recording station of different geometry pattern at 38 sites across different lithological setup within the basin. We present here (1) a first-order predominant fundamental frequency (0.21–10.19 Hz) and subsequent sedimentary thickness maps for the entire valley, reflecting deep deposition with spatial heterogeneity in the area using the horizontal-to-vertical spectral ratio (HVSR) technique; (2) spatial classification of generated HVSR curves linking subsurface geomorphology and post strong ground-motion scenario in the valley; (3) extraction of the best dispersion characteristics of Rayleigh waves (fundamental mode) from all recorded vertical signals at each array site using frequency–wavenumber (F-K) method with an emphasis on signal synchronicity; and (4) retrieval of one-dimensional (1D) shear wave velocity (VS) profiles across the valley from the inversion of dispersion curves using the neighborhood algorithm. Distinct model parameterizations were tested for the inversion to achieve the optimal inversion misfit. The collocated 1D VS profiles are consistent with newly drilled borehole logs information. Besides, the presented first-ever ambient noise survey–based site response study meets the objectives of site-specific seismic hazard and risk analysis of the Kashmir valley at the regional scale. [ABSTRACT FROM AUTHOR]

The characterization of a groundwater body involves the construction of a conceptual model that constitutes the base knowledge for monitoring programs, hydrogeological risk assessment, and correct management of water resources. In particular, a detailed geological and geophysical approach was applied to define the alluvial Caronia Groundwater Body (CGWB) and to reconstruct a hydrogeological flow model. The analysis of the CGWB, located in north-eastern Sicily, was initially approached through a reanalysis of previous stratigraphic (boreholes) and geophysical (vertical electrical soundings and seismic refraction profiles) data, subsequently integrated by new seismic acquisitions, such as Multichannel Analysis of Surface Waves (MASW) and horizontal-to-vertical seismic ratio (HVSR). The analysis and reinterpretation of geoelectrical data allowed the construction of a preliminary 3D resistivity model. This initial modeling was subsequently integrated by a geophysical data campaign in order to define the depth of the bottom of the shallow CGWB and the thickness of alluvial deposits. Finally, a preliminary mathematical model flow was generated in order to reconstruct the dynamics of underground water. The results show that integration of multidisciplinary data represent an indispensable tool for the characterization of complex physical systems. [ABSTRACT FROM AUTHOR]

Conventional geophysical methods are suitable for estimating the thicknesses of subsoil layers. By combining several geophysical methods, the uncertainties can be assessed. Hence, the reliability of the results increases with a more accurate engineering solution. To estimate the base of an abandoned landfill, we collected data using classical approaches: high-resolution seismic reflection and refraction, with more modern methods including passive surface wave analysis and horizontal-to-vertical spectral ratio (HVSR) measurements. To evaluate the thickness of the landfill, three different datasets were acquired along each of the two seismic lines, and five different processing methods were applied for each of the two arrays. The results of all the classical methods indicate very consistent correlations and mostly converge to clear outcomes. However, since the shear wave velocity of the landfill is relatively low (<150 (m/s)), the uncertainty of the HVSR results is significant. All these methods are engineering-oriented, environmentally friendly, and relatively low-cost. They may be jointly interpreted to better assess uncertainties and therefore enable an efficient solution for environmental or engineering purposes. [ABSTRACT FROM AUTHOR]

This paper describes the relationship between bedrock depth (D) and site fundamental frequency (f0) in the Nakdonggang delta region in the southeastern part of the Korean peninsula. We collected borehole logs to confirm the thickness of the sediments and estimated the f0 at over 200 locations across the delta using the horizontal-to-vertical spectral ratio (HVSR) method. We developed an f0 map of the study area by spatially interpolating the f0 values using the Ordinary Kriging method. The bedrock depth in the main delta showed a power-law dependence on the f0. The derived f0–D model predicted much shallower bedrock depths compared with similar studies from other parts of the world. This was attributed to the fact that the Nakdonggang delta region is composed of relatively low Vs Holocene sediments. With an f0 map, the derived model could enable a quick estimation of the bedrock depth, which could help to determine the site class in the Nakdonggang delta region according to the Korean Seismic Design Standard (KDS 17 10 00). [ABSTRACT FROM AUTHOR]

In Northern Morocco, seismic site-effects in general and liquefaction hazard in particular can occur in the event of a major earthquake due to the thick sedimentary cover characterizing the peripheral Neogene basins of the Alboran Sea. An example is Martil plain, which was the subject of important economic development during the last two decades. In this regard, we present in this study an assessment of seismic site-effect hazard through the horizontal-to-vertical spectral ratio (HVSR) method and the vulnerability index (Kg). Multiple Analysis of Surface Waves (MASW) method and core-drilling data are also used to complete our analysis and interpret the spatial distribution of Kg maps. Our findings suggest more vulnerability to liquefaction in the Southern segment of the basin, which can be explained by the asymmetrical geometry of Quaternary sedimentation, due to tectonic uplift that influences also the surface and subsurface hydrology processes. However, in this study, the main difficulties and the challenges that we faced were related to data acquisition during windy days and in the areas near industrial zones or near high traffic roads, which have significant effects on the accuracy of the HVSR analysis. In this study, HVSR microtremor measurements are recorded at 197 stations in the Martil floodplain to generate a seismic vulnerability index (Kg) map. According to the analysis results, the predominant frequency (F0) values range from about 0.2 to 10.6 Hz and the peak amplitudes (A0) values are in the range of 0.39–10.4. As a result, some districts, especially those classified as economically disadvantaged, are found to be the most exposed to this hazard (with a Kg > 10), which must be taken into consideration in future risk reduction and mitigation plans. We conclude the existence of significant seismic effects potential despite the moderate seismicity of the area. Therefore, our research needs to be completed by scenario-based seismic hazard modeling to investigate the capacity of seismic events at the region to produce the above-suggested amplifications. [ABSTRACT FROM AUTHOR]

Frequency-dependent horizontal-to-vertical spectral ratios (HVSR) can provide information on one or more site resonant frequencies and relative levels of amplification at those frequencies. Such information is potentially useful for predicting site amplification but is not present in site databases that have been developed over the last 15–20 years for the Next-Generation Attenuation (NGA) projects, which instead use the time-averaged shear-wave velocity (VS) in the upper 30 m of the site (VS30) as the primary site parameter and are supplemented with basin depth terms where available. In order for HVSR-based parameters to be used in future versions of site databases, a publicly accessible repository of this information is needed. We adapt a relational database developed to archive and disseminate VS data to also include HVSR. Our intent with the database is to provide relevant HVSR data and supporting metadata, but not parameters derived from the data. We consider the relevant data to be the frequency-dependent HVSR, where the horizontal is taken as the median component and as a function of horizontal azimuth (referred to as polar plots). Relevant metadata includes site location information, details about the equipment used to make the measurements, and processing details related to windowing, anti-trigger routines, and filtering. We describe the database schema developed to organize and present this information. The relational database stores HVSR data, but not site parameters derived from the data. Site parameters of potential interest for modeling purposes include: (1) a binary variable indicating whether an HVSR plot contains a peak; (2) one or more peak frequencies; (3) peak amplitudes; and (4) peak widths. We describe and illustrate analysis routines to derive these parameters that are implemented in Python on a Jupyter Notebook enabled by DesignSafe-CI. These routines interact with the database via cloud computing, but are not directly part of the database.

This study simulates the strong ground motion of an earthquake having magnitude 6.4 occurred on 4 February 2011 in Indo-Burmese Arc (IBA). This earthquake recorded on seven seismic recording stations namely Jowai, Jorhat, Sibsagar, Nagaon, Guwahati, Cooch Bihar and Kokhrajhar. Also, estimation of site class performed to observe the site effects of recording stations in this study. The simulation performed on the basis of revised stochastic finite fault model with dynamic corner frequency and site class for the seismic recording station where the earthquake recorded has been estimated by using Horizontal to Vertical Spectral Ratio (HVSR) technique because modeling and simulation of ground motion majorly depend upon the recorded ground motion as well as site effects, where earthquake has been recorded. The revised well known finite source simulation program (EXSIM) used in this study becomes efficient in providing the results for small magnitude earthquake occurred at large distance. The average HVSR curves plotted for all the recording stations, providing peak frequency for all 7 sites. It is observed from the present work that simulated time histories as far as primary attributes, for example, Fourier spectra, Peak ground acceleration (PGA), Response spectra, Predominant frequency are in close concurrence with the recorded ones. The predominant frequency (fpeak) obtained from HVSR technique has been validated from existing literature for the estimation of site class for seismic recording stations. The fpeak determines the average shear wave velocity (Vs30) at depth of 30 ​m of overburden thickness which varies from 200 ​m/s to 1600 ​m/s according to Program for Excellence in Strong Motion Studies (PESMOS). Whereas, National Earthquake Hazard Reduction Program (NEHRP) provision consider the site class for Vs30 below 180 ​m/s. Due its wide range of site characterization, it has been adopted globally. Therefore, in this study, the site class obtained has been compared with the site classification scheme recommended by PESMOS, NEHRP provisions and previous literature. However, the ground motion parameters and the soil classification of the earthquake recording stations for the IBA region has not been explored yet even after seeing its severity in the past decades. Productive representation of present earthquake gives the confidence to understand and evaluate seismic danger at various parts of Indo- Burmese region from tremors of various sizes. In this study it is proposed that PESMOS site classification data should be revised because it covers wide range of soil types just into three (A, B and C type) class.

Earthquake S waves can become trapped, or resonate, between the free surface and high-impedance basal layers, strongly contributing to site response at specific frequencies. Strong S-wave resonances have been observed in the central and eastern U.S., where many sites sit on unlithified sediments underlain by stiff bedrock. To evaluate S-wave resonances in this region, we calculated 1D linear site-responses at 89 seismic stations with developed S-wave velocity profiles into bedrock. We found that S-wave resonances at the fundamental and strongest (peak) modes occur across large ranges of frequencies, each spanning more than two orders of magnitude — 0.21–54.0 Hz and 0.29–71.5 Hz, respectively. Amplifications of ∼5 and ∼6 are common at the fundamental frequency and peak modes, respectively; the largest amplification calculated was 13.2. Using simple regression analyses, we evaluated the skills of six proxies derived from the S-wave velocity profiles to predict the frequencies and corresponding amplifications of the fundamental and peak modes. We found that the depths to the 1.0 km/s and 2.5 km/s horizons, consistent with other studies, and to the maximum impedance contrasts strongly correlate with the resonance frequencies and that the fundamental-mode and peak amplifications correlate with the maximum impedance ratios. Correlations improved for data subsets based on the number and magnitude of impedance ratios underlying the sites and are the strongest at sites underlain by a single impedance ratio of 3.0 or greater. Finally, we calculated the S-wave horizontal-to-vertical spectral ratios (HVSR) at each possible seismic station and found, consistent with other studies, that the first peak can be used to estimate fundamental-mode frequencies and the corresponding amplifications. Thus, S-wave HVSR, can provide useful estimates of the fundamental-mode linear site response parameters at sites lacking S-wave velocity profiles. Furthermore, S-wave HVSR curves appear to be useful to broadly categorize impedance-ratio profiles.

In the municipality of Enna, 80 HVSR measurements were performed, and some of these were combined with MASW seismic measurements, which made it possible to constrain the data inversion and obtain significant shear wave velocity models. A reconstruction of the depth of the seismic bedrock was performed for the whole territory, showing different depths for the higher and lower areas, as evidenced also by the Vseq parameter map. The frequency peaks identified in the H/V curve were analyzed through a cluster analysis algorithm to evaluate similarities that allow these peaks to be divided according to their stratigraphic origin. A non-hierarchical analysis algorithm modified in such a way as to avoid any a priori choice that could influence the partition has been used. The cluster analysis made it possible to divide the frequency peaks into five groupings, each of which was then associated with a seismic discontinuity, according to the geological contacts expected in the subsoil. Finally, the inversion of the data made it possible to reconstruct the geometries of these geological contact surfaces and to reconstruct a 3D model of the subsoil, which agrees well with the surface geology of the area. [ABSTRACT FROM AUTHOR]

The Anninghe fault is a major left-lateral strike-slip fault in southwest China and a seismic gap with a potential earthquake larger than MW 7.0 lies in the Mianning-Xichang segment according to recent observations. The shallow structure of this region can offer a glimpse into the geometry of the fault, which plays an important role in earthquake hazard mitigation. To further investigate the sedimentary structure of the Anninghe fault zone, two dense linear arrays with a station spacing of around 80 m were deployed across the fault. In this study, the H/V spectral ratio (HVSR), together with its peak frequency at each station site, was obtained by applying the Nakamura method. Our findings demonstrate that the peak frequency behaves in high correlation with lithology and is controlled by topography. HVSR in foothills or regions with magmatic intrusion shows a single peak at about 2–3 Hz. In locations with abundant Quaternary sedimentation, such as Anninghe valleys and fracture zones, another low-frequency peak around 0.4 Hz can be noticed in HVSR. By using the empirical relationship, the thickness of the sedimentary layer around the fault fracture zone is estimated to be 300–600 m. Furthermore, the sedimentary interface shows a downward dip to the east, possibly influenced by the east-west extrusion stress. Considering the resonance effect, buildings with 6–9 stories in the valley area of the Anninghe require additional attention in earthquake hazard prevention. [ABSTRACT FROM AUTHOR]

We performed one dimensional equivalent linear site response analysis for 11 soil profiles of Dhanbad city. To explore the effect of subsoil on the induced effect of earthquakes at the ground surface, the site response analyses is complemented with shear wave velocity models found from destructive geotechnical as well as non-destructive geophysical surveys, such as standard penetration test (SPT) and horizontal-to-vertical spectral ratio (HVSR). The bedrock depths obtained from shear wave velocity models, constructed from HVSR method, are validated using electrical resistivity tomography (ERT). Our results reveal that Dhanbad city consists of alluvium deposits, such as silty sand, sandy clay, silt + sand and sand + clay mixture. We used the 2015 Nepal (MHA = 0.15 g), 2016 Imphal (MHA = 0.18 g) and 2022 Nepal (MHA = 0.10 g) earthquakes as input motions at the bedrock level. Predominant frequency, soil thickness, surface PGA and Vs30 are found to follow a consistent trend relative to each other. The soil's transfer function, obtained from site response analysis (SRA), correlates generally well with the peak's predominant frequency of HVSR curves at all sites. The influence of input ground seismic motions on soil profiles is discussed, which shows that the soil deposit of Dhanbad city lies in a short period region. Our results would play an important role for Indian government agencies such as the Central Public Works Department (CPWD), Geological Survey of India (GSI) and National Disaster Management Authority (NDMA) to mitigate earthquake effects and to plan better to build an earthquake resilient society. [ABSTRACT FROM AUTHOR]

Seismic microzoning is the process of mapping out and comprehending the differences in ground motion due to earthquakes in a certain location. Accurate seismic microzoning is vital for the development and safety of buildings and infrastructure in earthquake-prone locations. In this work, we present the application of microtremors, multichannel analysis of surface and machine learning approaches for seismic microzoning at Benban Solar Park in Aswan, Egypt. The findings of the investigation indicated that the ground at Benban Solar Park was generally stiff, with certain regions having stronger stiffness and damping qualities than others. The data also indicated variances in the ground conditions at various sites inside the solar park, with certain regions having a greater risk of ground motion due to earthquakes. Overall, the combination of microtremors, multichannel analysis, and machine learning has shown to be an excellent strategy for correctly and effectively mapping out the ground conditions at Benban Solar Park and assuring the safety and structural integrity of the solar power plants at the park. Moreover, the results of the research could be used to guide the design and construction of the future solar power plants at the park and to examine the safety and structural integrity of the solar park. Furthermore, the application of these techniques not only ensures the safety and structural integrity of the solar power plants at Benban Solar Park, but also promotes sustainable development by providing valuable information for the design and construction of future solar power plants at the park, in line with the principles of environmentally-conscious and responsible development. [ABSTRACT FROM AUTHOR]

Frequency-dependent horizontal-to-vertical spectral ratios (HVSR) can provide information on one or more site resonant frequencies and relative levels of amplification at those frequencies. Such information is potentially useful for predicting site amplification but is not present in site databases that have been developed over the last 15–20 years for the Next-Generation Attenuation (NGA) projects, which instead use the time-averaged shear-wave velocity (VS) in the upper 30 m of the site (VS30) as the primary site parameter and are supplemented with basin depth terms where available. In order for HVSR-based parameters to be used in future versions of site databases, a publicly accessible repository of this information is needed. We adapt a relational database developed to archive and disseminate VS data to also include HVSR. Our intent with the database is to provide relevant HVSR data and supporting metadata, but not parameters derived from the data. We consider the relevant data to be the frequency-dependent HVSR, where the horizontal is taken as the median component and as a function of horizontal azimuth (referred to as polar plots). Relevant metadata includes site location information, details about the equipment used to make the measurements, and processing details related to windowing, anti-trigger routines, and filtering. We describe the database schema developed to organize and present this information. The relational database stores HVSR data, but not site parameters derived from the data. Site parameters of potential interest for modeling purposes include: (1) a binary variable indicating whether an HVSR plot contains a peak; (2) one or more peak frequencies; (3) peak amplitudes; and (4) peak widths. We describe and illustrate analysis routines to derive these parameters that are implemented in Python on a Jupyter Notebook enabled by DesignSafe-CI. These routines interact with the database via cloud computing, but are not directly part of the database.

The seismic site effect is critical in designing structures and the estimation of earthquake damage to existing structures, particularly in seismically active regions. To assess site-specific earthquake risks and design earthquake-resistant structures, it is necessary to classify a site according to its class. Here, the seismic site characterization (SSC) attributes have been generated using a topography gradient-based approach as the geophysical and geotechnical attributes are limited and insufficient for regional site classification in Northeast India. We attempted to quantify the dynamic properties of subsurface materials in terms of time average shear wave velocity (Vs30), frequency-dependent amplification factor (Af), predominant period (Ts), and vulnerability index (Kg). Subsequently, a holistic GIS model has been developed to classify the region into three microzones, viz. Low Susceptible, Moderate Susceptible, and High Susceptible by the integration of all the SSC attributes. The generic site response curve for various SSC zones has been developed through Horizontal-to-Vertical Spectral Ratio (HVSR) analysis of recorded strong ground motion. The present results show that SSC attributes corroborated with the geological, tectonic, geomorphological, and topographic settings of Northeast India. It is exhibited that the site classes E, D1, D2, and D3 are mostly associated with the Lower Brahmaputra Basin. The weak zone that failed during the earthquake in the basin areas has also been identified based on the highest Kg value (>10). This study has resulted in a map of seismically vulnerable regions. The developed SSC maps and generic site response curves may be used for surface consistent ground motion synthesis, seismic microzonation, risk mapping, and in developing earthquake mitigation strategies in Northeast India.