Search Results (107)

This study presents a compact controlled urban geophysics test site developed at the University of Malta to evaluate the response of complementary near-surface sensing methods under known shallow subsurface conditions. The experimental setup is designed to investigate buried target detection and the response to a simulated shallow leak, used here as a controlled water-release experiment in a shallow carbonate setting characterized by thin, laterally variable soil cover and anthropogenic disturbance. A preliminary passive seismic survey based on the horizontal-to-vertical spectral ratio (HVSR) method was used to compare candidate sectors and select the most suitable area for installation. The test site includes a buried iron plate and a perforated PVC pipe, the latter used to release water under controlled shallow conditions. Ground-penetrating radar (GPR), smartphone magnetometry, electrical resistivity tomography (ERT), and UAV-based thermal imaging were applied to assess target detectability and leak-related surface–subsurface responses. Results show that GPR provides the clearest response for static target detection, while smartphone magnetometry identifies the buried ferrous target under favourable conditions. For the simulated leak experiment, ERT provides the most robust subsurface evidence of moisture redistribution after water injection. UAV thermal imaging captures a complementary surface thermal response influenced by both moisture dynamics and local surface disturbance. The results show that a compact controlled test site can support the comparison of professional and low-cost sensing methods for shallow target detection and simulated leak assessment. In this configuration, the controlled water-release experiment provides a practical basis for evaluating leak-related surface–subsurface responses under known shallow conditions. The proposed setup has implications for methodological assessment, training, and near-surface environmental monitoring in heterogeneous urban settings. Full article

This study investigates the comparative effectiveness of Lead Rubber Bearing (LRB) and Friction Pendulum System (FPS) isolation units under varying seismic hazard levels and soil classes, within the framework of the Turkish Building Earthquake Code (TBEC 2018). The assessment was conducted in two stages. First, keeping the site class constant, multiple locations characterized by different seismic hazard levels are examined. Second, a fixed geographical location is considered to evaluate the influence of different site classes on isolator response. The performance of the isolation systems is evaluated in terms of displacement demand, base shear ratio, and code-based verification criteria. Additional sensitivity checks were performed using selected limit values to better understand the response trends under changing hazard and soil parameters. The findings highlight how soil amplification effects and seismic intensity levels influence the relative advantages of LRB and FPSs. The results provide practical insight for the selection of seismic isolation systems in hazard-prone regions, contributing to improved performance-based decision-making in earthquake-resistant design. The isolator parameter choices were set based on average catalogue values provided by manufacturers to make this research an example. As a result of the analysis of the isolators’ performance, it was concluded that the FPS-type isolator performed better as acceleration values increased. Full article

Housner’s classical rocking model assumes a rigid base, which often leads to inaccurate seismic assessments under real–world soil conditions. This study quantitatively establishes the applicability limits of the rigid–base assumption and defines a reference range for its validity. To address these limitations, a novel soil–structure interaction (SSI) rocking model was developed using Lagrange’s formulation, incorporating an event–driven spring–dashpot mechanism to characterize contact forces. Validation against LS–DYNA simulations and existing compliant base models confirms high predictive accuracy across diverse geometries and ground motions. Crucially, an empirical formulation for the interface stiffness of rocking structures was derived to ensure the alignment of the proposed analytical model with numerical observations, thereby enhancing its practical utility in industrial design. Our findings reveal that rocking behavior depends not only on soil stiffness but also on the inherent stiffness of the structure. Specifically, soft soils significantly alter rocking initiation thresholds and amplify peak angles. The proposed SSI–rocking model provides a computationally efficient and FE–compatible tool for optimizing the seismic stability of unanchored structures on flexible foundations. Full article

Remote-sensing land surface deformation (LSD) is a powerful and effective approach for investigating regional alpine permafrost variations. However, alpine permafrost is often distributed in areas characterized by earthquakes, and the LSD of alpine permafrost is potentially contaminated or diminished by earthquake-related LSD. Therefore, this study aimed to derive the effective LSD in the alpine permafrost of the Source Area Yellow River (SAYR) by removing LSD originating from the M_w 7.4 Maduo earthquake in 2021-05-22 and analyzing the spatiotemporal variations in LSD during 2017–2024. Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) was used to obtain the initial LSD time series from Sentinel-1 images acquired during 2017–2024. The LSD of the M_w 7.4 Maduo earthquake, its aftershocks and the post-seismic relaxation in SAYR was simulated separately by considering its temporal process and removed from the LSD time series in SAYR. The final LSD was validated against in situ Global Navigation Satellite System (GNSS) measurements, and the spatiotemporal variations in LSD in SAYAR were subsequently analyzed. The study found the following: (1) the removal of the earthquake-related LSD was successful both spatially and temporally and the final LSD has mean absolute error (MAE) of 3.22 mm and root mean squared error (RMSE) of 3.92 mm; (2) during 2017–2024, the vertical LSD in SAYR was mostly −8–8 mm/y; (3) soil moisture determined the spatial distribution of the LSD direction in SAYR as a result of local drainage conditions, air temperature, precipitation and snow melt. This study demonstrated the necessity of removing the earthquake-related LSD when investigating the alpine permafrost LSD in tectonically active areas. The strategy adopted in this study serves as a technical reference for future investigations of this kind. The findings in this study provide insight for a thorough understanding of permafrost evolution on the Tibetan Plateau in the context of climate change. Full article

This study presents a comprehensive analysis of a landslide that occurred in February 2024 in the Tau-Samal district of Almaty, Kazakhstan. Characterized by rapid onset and anthropogenic influence, this event resulted from a complex interaction of environmental and anthropogenic factors. Specifically, the landslide was triggered by seasonal temperature fluctuations leading to multiple freeze–thaw cycles, localized microseismicity (magnitude 3.5 on 4 February 2024), and a major water main break resulting in localized flooding of loess soils. The study utilizes an integrated landslide susceptibility index (LSI) model, which combines the analytic hierarchy process (AHP) for factor weighting. Validation was conducted by comparing the spatial distribution of high-susceptibility zones derived from the LSI model with the actual location of the landslide. Geotechnical studies highlight the susceptibility of Almaty loess, focusing on parameters such as cohesion, internal friction angle, and liquefaction potential. The findings highlight the need for climate-adapted urban policies and improved geotechnical monitoring in high-risk loess areas. This study contributes to a regional understanding of Tien Shan geohazards by placing the Tau-Samal event within the broader context of seismically and hydrologically driven slope processes. Full article

Seismic damage has been observed not only in liquefiable sandy soil layers but also in thick deposits of soft clayey soils, which are characterized by the destruction of the soil structure, leading to strain softening. Previous studies conducted numerical simulations and defined this phenomenon as soil disturbance, which refers to the simultaneous reduction in stiffness and peak shear strength. To fill the research gap, this study systematically compares the post-cyclic degradation behavior of stiffness and peak shear strength of UDS and REC specimens derived from the same material. Based on the experimental results, the peak shear strength and rigidity of the UDS specimens simultaneously decrease, as the number of cycles increases. In contrast, the peak shear strength degradation effect is absent in the REC samples; both specimens exhibited loss in stiffness. The reduction in stiffness of UDS specimens was slower than that of REC specimens due to aging effects. Nevertheless, both effects on UDS and REC specimens are due to soil disturbance, which is defined in the numerical simulations of previous studies. Hence, the effects of soil disturbance can be summarized as (1) a reduction in the initial stiffness of soft clay and (2) a reduction in the mean effective stress during cyclic loading. Full article

Reliable assessment of small-strain soil stiffness is essential for geotechnical site characterization and for analysing the behaviour of embankments and other earth structures. Surface-wave methods provide an efficient non-destructive means of estimating shear-wave velocity profiles; however, their application is limited by the non-uniqueness of the inversion process. This paper implements and evaluates a PSO-based multimodal inversion framework for Rayleigh-wave dispersion curves in the context of geotechnical characterization of layered soil profiles. The procedure involves the calculation of theoretical dispersion curves for a horizontally layered medium and their matching with experimental data through a global search scheme. The implemented framework was first evaluated using two synthetic soil profiles, and its robustness was further assessed by considering perturbations of the theoretical dispersion curve of up to 10%. Particular attention was given to the influence of higher modes on the inversion results. The results indicate that including higher modes can improve the determination of shear-wave velocity profiles for the analysed cases compared with an inversion based solely on the fundamental mode. The procedure was subsequently validated on a transverse embankment profile using an experimental dispersion curve obtained by multichannel analysis of surface waves (MASW), with comparison against seismic cone penetration test (SCPT) results. Good agreement was obtained, and the eight-layer model proved to be a good compromise between accuracy and model complexity. The results indicate that the implemented PSO-based multimodal inversion framework can support the geotechnical characterization of layered soil profiles for the analysed synthetic and field cases, particularly when modal branches are clearly identified and appropriately included in the inversion. Full article

Ground failure during major seismic events associated with soil liquefaction can lead to major structural damage to both the columns and the bridge upper deck due to large seismic-induced displacements in the support foundation. Liquefaction-driven ground motion incoherence during the dynamic event and permanent soil deformations are key variables in the observed damage. This paper summarizes a numerical study of an alternative bridge foundation design proposed to reduce support displacements and bearing capacity failure during and after an earthquake, as well as relative settlement associated with partial loss of bearing capacity when the bridge column is founded on a potential liquefiable layer. Three-dimensional numerical models were developed using FLAC^3D. The seismic environment was characterized by a uniform hazard spectrum, UHS, for intraplate and interplate earthquakes, as presented in the current construction Mexico City regulations. Initially, a one-dimensional analysis was performed using SHAKE to evaluate liquefaction susceptibility. Results show that the structured cell foundation reduces excess pore-pressure generation by up to 42% compared to shallow foundations and 25% compared to pile systems. This improvement is associated with (i) restriction of cyclic shear strain, (ii) modification of deformation patterns, (iii) partial confinement of pore-pressure development within the enclosed soil mass, and (iv) preservation of effective stresses during shaking. Additionally, the system reduces shear strain localization and decreases acceleration transmitted to the superstructure by up to 14–33%. The findings demonstrate that structured confinement systems can significantly influence the mechanisms governing liquefaction, offering a promising alternative for bridge foundations in seismic regions. Full article

Ottoman mosques represent a unique synthesis of architectural elegance and structural ingenuity, where massive masonry domes are balanced on slender supports through carefully engineered load transfer systems. These monumental buildings, constructed centuries ago without modern analytical tools, continue to challenge contemporary engineers seeking to understand their behavior under seismic loading. This study presents an integrated evaluation of the structural and geotechnical performance of the 16th-century Sultan Selim Mosque in Konya, Türkiye, one of the most prominent examples of Classical Ottoman architecture. The research combines ambient vibration testing (AVT), geotechnical investigations, and finite element modeling (FEM) to assess the existing structural condition and soil–structure interaction (SSI) effects. Dynamic identification through AVT provided the modal characteristics of the mosque, which were used to calibrate a detailed three-dimensional FEM developed in ANSYS Workbench using a macro-modeling approach. The numerical analyses showed that observed deformation patterns and stress concentrations are consistent with field damage observations, indicating that differential settlements and heterogeneous subsoil stiffness are the primary factors influencing the structural response. The findings enhance understanding of the seismic behavior of monumental masonry domed structures and offer a solid basis for the evaluation and conservation of Ottoman-era architectural heritage. Full article

The construction sector is a major user of natural materials and a key contributor to global carbon emissions. To tackle these environmental challenges, the use of recycled products has become increasingly important in modern engineering. Cellular glass aggregate (CGA), made from recycled glass, is a material with potential as a sustainable alternative to natural aggregates. This study characterizes the cyclic behavior of CGA using a large-scale triaxial apparatus, focusing on seismic-relevant properties such as the damping ratio and Young’s modulus. Local displacement transducers (LDTs) were implemented to improve measurement at small strains. The results show that CGA exhibits strain-dependent stiffness and damping behavior comparable to natural aggregates at moderate strains (10⁻⁴–10⁻³). The Young’s modulus ranges from approximately 300 to 600 MPa, while damping ratios remain at approximately 2–3% for low values of strains (10⁻⁵). As strain increases to moderate levels (10⁻⁴–10⁻³), the Young’s modulus decreases to approximately 80–250 MPa, accompanied by an increase in damping ratio to approximately 4–6%. At higher strain levels ≥ 10⁻³, the Young’s modulus further reduces to approximately 40–80 MPa, while damping ratios increase to approximately 7–10%. These stiffness degradation and damping trends fall within the ranges reported for sands and gravelly soils in the literature, indicating that CGA can reproduce the cyclic mechanical behavior of natural aggregates under well-defined strain conditions. Full article

The study focuses on the results of the analysis of data recorded during Ambient Vibration Tests (AVT) conducted on a portion of the Medieval Walls of Verona (Northern Italy). Seismometric stations were installed both at the top and at the base of the walls, recording the free vibrations of the structure. Spectral analyses provide information about the principal modal frequencies, which are compared with the results obtained through Operational Modal Analysis (OMA) techniques. Numerical models were developed to describe the elastic behavior of the walls and to support the interpretation of the experimentally identified modes. Seismic noise measurements were also performed on the ground to characterize the spectral response of the soil and to estimate the soil–structure interaction. The combined use of AVT data, OMA procedures, and numerical modeling allowed for a robust identification of the fundamental dynamic properties of the walls, highlighting the predominance of out-of-plane modes and the limited dynamic coupling with the underlying soil. The study demonstrates the effectiveness of this non-invasive approach for improving the knowledge of structural assessment, reducing uncertainties in mechanical parameter calibration, and supporting informed conservation, maintenance, and risk-mitigation strategies for historic defensive masonry structures. Full article

Liquefaction is a critical mechanism amplifying earthquake-induced damage, necessitating systematic hazard assessment through spatially distributed mapping. This study presents a nationwide liquefaction hazard assessment framework for South Korea, integrating site classification, liquefaction potential index (LPI) computation, and probabilistic damage evaluation. Sites across the Korean Peninsula were stratified into five geotechnical categories (S1–S5) based on soil characteristics. LPI values were computed incorporating site-specific amplification coefficients for nine bedrock acceleration levels corresponding to seismic recurrence intervals of 500, 1000, 2400, and 4800 years per Korean seismic design specifications. Subsurface characterization utilized standard penetration test (SPT) data from 121,821 boreholes, with an R-based analytical program enabling statistical processing and spatial visualization. Damage probability assessment employed Iwasaki’s LPI severity classification across site categories. Results indicate that at 0.10 g peak ground acceleration (500-year event), four regions exhibit severe liquefaction susceptibility. This geographic footprint expands to seven regions at 0.14 g (1000-year event) and eight regions at 0.18 g. For the 2400-year design basis earthquake (0.22 g), all eight identified high-risk zones reach critical thresholds simultaneously. Site-specific analysis reveals stark contrasts in vulnerability: S2 sites demonstrate 99% very low to low damage probability, whereas S3, S4, and S5 sites face 33%, 51%, and 99% severe damage risk, respectively. This study establishes a scalable, evidence-based framework enabling efficient large-scale liquefaction hazard assessment for governmental risk management applications. Full article

The dynamic characterization of historical buildings located in a complex geological and seismological context is essential to assess seismic vulnerability and to guide conservation strategies. This study presents a non-invasive, ambient vibration-based, investigation of the Norman Castle of Aci Castello (Sicily, Italy), applying Horizontal to Vertical Spectral Ratio (HVSR), Horizontal to Horizontal Spectral Ratio (HHSR), and Random Decrement Method (RDM) to evaluate the structure’s dynamic behavior and potential Soil–Structure Interaction (SSI) effects. The fundamental site frequency, estimated within a broad plateau in the range 2.05–2.70 Hz, does not overlap with the structural frequencies of the castle, which range approximately from 6.30 Hz to 9.00 Hz in the N–S structural direction and from 3.50 Hz to 8.50 Hz in the E–W direction, indicating absence of global SSI resonance. However, the structure exhibits a complex multimodal response, with direction-dependent behavior evident both in spectral peaks and in damping ratios, ranging from 2.10–7.73% along N–S and 0.90–5.84% along E–W. These behaviors can be interpreted as possibly linked to structural complexity and the interaction with the fractured volcanic substrate, characterized by shallow cavities, as well as to the material degradation of the masonry. In particular, the localized presence of subsurface voids may induce a perturbation of the low-frequency ambient vibration wavefield (e.g., microseisms), producing a localized increase in spectral amplitude observed at Level I. The analysis indicates the absence of global SSI resonance due to the lack of overlap between site and structural fundamental frequencies, while significant local SSI effects, mainly related to cavity-induced wavefield perturbation, are observed and may represent a potential vulnerability factor. These findings highlight the relevance of vibration-based diagnostics for heritage vulnerability assessment and conservation strategies. Full article

Geological surveys provide important information for many sectors, from construction project planning to mineral exploration and environmental protection. The seismic cone penetration test with pore water pressure measurement (SCPTu) is a truly valuable tool in geological surveys. It provides detailed information on the subsurface conditions and geological characteristics of the area. The manuscript describes the methodology used to characterize the geological layers at the construction site and quantify the characteristics obtained from SCPT probing. The aim of the scientific study was to identify soft layers in the subsoil and to focus on the impact of pile driving technology on the foundation environment and SCPT probing results. The driving technology involved the implementation of 4.0 m long pyramidal precast concrete piles with pile head dimensions of 0.5 × 0.5 m and tip dimensions of 0.12 × 0.12 m. Probing of the SCPT before and after driving showed that the pile driving led to a significant increase in the velocity of shear waves in the soil at a distance of 0.5 m from the edge of the pile head, which was also reflected in the evaluation of the shear modulus G_max derived directly from shear wave velocity. Full article

Seismic risk assessment in megacities requires a high-resolution spatial framework that can capture the intrinsic heterogeneity of local geology, building distribution, and population characteristics beyond conventional administrative boundaries. This study develops a hazard-independent seismic susceptibility framework for the Seoul Metropolitan Area, a megacity of approximately 9.5 million residents (as of 2024), where historical and instrumental earthquake records are limited. The proposed framework integrates nine standardized indicators across geotechnical, structural, and social domains within a vulnerability–exposure model, analyzed on a 250 m grid—approximately 300 times finer than district-level assessments. Domain-specific indices and the integrated Seismic Susceptibility Index (SSI) were derived using Analytic Hierarchy Process (AHP)-based weighting to quantify the relative importance of indicators. Results show a highly concentrated spatial pattern of susceptibility: only 2.2% of Seoul (229 grids, 14.3 km²) falls within the high-to-very-high categories, primarily in northern and southwestern residential zones characterized by soft soils, aging buildings, and vulnerable populations. The proposed framework supports targeted risk-reduction strategies by providing a practical basis for pre-disaster decision-making and efficient allocation of mitigation resources in data-scarce urban environments. Full article